Manual of Mini-hydropower Design Aids

Version 2006.05

Micro-hydropower Design Aids Manual (v 2006.05) SHPP/GTZ

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NOTICE The earlier version of these hydropower Design Aids had been prepared to provide a basis for micro-hydropower consultants to undertake calculations and prepare drawings as per the requirements of Alternative Energy promotion Centre (AEPC) of the Government of Nepal. The tools in this version (version 2006.05) were amended to fulfill the minimum requirements of standard micro and mini hydropower project feasibility studies. It is expected that the use of these Design Aids will result in a standard methodology for calculating and presenting MHP designs. This manual and any examples contained herein are provided “as is” and are subject to change without notice. Small Hydropower Promotion Project (SHPP/GTZ) shall not be liable for any errors or for incidental or consequential damages in connection with the furnishing, performance, or use of this manual or the examples herein. © Small Hydropower Promotion Project (SHPP/GTZ). All rights reserved. All rights are reserved to the programs and drawings that are included in the MHP Design Aids. Reproduction, adaptation or translation of those programs and drawings without prior written permission of SHPP/GTZ is also prohibited. Micro-hydropower Design Aids (v 2006.05) is a shareware and can also be downloaded from www.entec.com.np . Permission is granted to any individual or institution to use, copy, or redistribute the MHP Design Aids so long as it is not sold for profit. Reproduction, adaptation or translation of those programs and drawings without prior written permission of SHPP/GTZ is prohibited. Published by: Small Hydropower Promotion Project (SHPP/GTZ) Pulchowk, Lalitpur, Nepal PO Box 1457, Kathmandu, Nepal Tel: 977 1 5009067/8/9 Fax: 977 1 5521425 Web: http://www.entec.com.np Email: [email protected] Author: Mr. Pushpa Chitrakar Engineering Advisor SHPP/GTZ Printed by: Hisi Offset Printing Press, Jamal, Kathmandu, Nepal This Edition: May 2006 First Edition 1000 copies Price: : NRs. 300 (for Nepal and SAARC countries) : US$ 15 (for other countries)

http://www.entec.com.np


mailto:[email protected]


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PREFACE This set of hydropower design tools is an updated version of Micro-hydropower Design Aids which was prepared by Small Hydropower Promotion Project (SHPP/GTZ) during its collaboration with Alternative Energy Promotion Centre (AEPC/ESAP) from 2002 to 2004. It is a complete set of tools consisting of typical AutoCad drawings, typical Microsoft Excel spreadsheets and a users’ manual. An electronic version of earlier tools was officially distributed by AEPC/ESAP for using up to feasibility study levels of its subsidized micro-hydropower schemes up to 100kW. German Development Cooperation (GTZ) has been cooperating with the Kingdom of Nepal for more than four decades. During this period its bilateral Technical Cooperation covered a broad range of sectors including agriculture, livestock, rural development, forestry, energy, credit, industry, vocational training, urban development, education and health. Small Hydropower Promotion Project was established in 1999 as its bilateral Technical Cooperation on energy sector. Since then this project has been providing technical and logistic services to small hydropower stakeholders within Nepal through Entec AG of Switzerland as an implementing consultant of this project. Since its establishment in 1999, SHPP/GTZ has been providing its services to hydropower stakeholders. Although its main mandate is to provide technical and logistic supports to small hydropower projects in Nepal within the range of 100kW to 10MW, SHPP/GTZ has also been backstopping hydropower project below 100kW. The overwhelming positive feedbacks from micro and small hydropower stakeholders on these tools and continuous update and distribution of these tools are the examples of its concern on the holistic approach of sectorial development of hydropower in Nepal. This version of the design aids includes three additional spreadsheets and enhanced utilities especially useful for mini hydropower project component designs. Since these tools were verified with real project studies, I personally found them very useful for the stated design works. Irrespective of the sizes and locations, all hydropower schemes have a common feature using potential energy of water for generating electricity. Therefore, use of all the tools except the spreadsheet on hydrology can also be used for micro and mini hydropower projects outside Nepal. Moreover, some spreadsheets and drawings can also be small and even large hydropower project designs. These tools have also been used in some small hydropower projects in Vietnam and micro hydropower projects in Afghanistan. I would like to thank Entec AG, Switzerland and German Development Cooperation, Nepal for their support to make this publication happen. My special thank goes to Mr. Pushpa Chitrakar, Engineering Advisor of SHPP/GTZ, for his devotion of making such a useful complete set of utility package for micro and mini hydropower project designs. I would also like to extend my sincere thanks to AEPC/ESAP for their contributions to the development of these Design Aids. The contribution of all SHPP/GTZ team members for their continuous support on the development of these design aids is highly appreciated. I do hope that this Micro-hydropower Design Aids would fill the gap that has been felt by all the micro and mini hydropower stakeholders and will be able to contribute to the hydropower sector. Sridhar Devkota Project Manager SHPP/GTZ


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ACKNOWLEDGEMENTS Thanks for using the Micro-hydropower Design Aids (version 2006.05). Micro-hydropower Design Aids is a complete set of tools consisting of typical AutoCad drawings, typical Microsoft Excel spreadsheets (a workbook) and a users’ manual (this manual) recommended for use in the feasibility study of micro and mini hydropower schemes. Although these tools were mainly prepared based on the prudent practices of Nepali micro and mini hydropower scheme designs, it is expected that the use of these Design Aids helps enhancing the overall quality of hydropower sector within Nepal and abroad. All spreadsheets except “Hydrology” can also be used for mini and small hydropower projects outside Nepal. However, the title of these tools in this version is not changed. Why I Prepared the Design Aids I approached this project with one goal in mind. To write a one-step Micro-hydropower Design Aids that would appeal to all Nepali micro-hydropower stakeholders. That is a fairly ambitious goal. But based on the feedback I received from all the stakeholders, I think I have been successful. In addition to updating the existing tools for use in mini, micro and small hydropower projects, spreadsheets for calculating anchor block calculation and design, machine foundation design, loan payback cash flow, etc, are added in this version. These additional tools are especially useful for mini and small hydropower projects. Interactive diagrams to most of the spreadsheets are added in this version. Microsoft Excel is the present market leader, by a long shot, and it is truly the best spreadsheet available. Excel lets you do things with formulas and macros (Visual Basic for Application) that are impossible with other spreadsheets. Similarly, Autodesk AutoCad has been the best and suitable tool for creating digital drawings. Since most of the hydropower stakeholders are familiar with these application software, I have prepared these tools on these application software platforms. Although the above mentioned software are popular amongst all the micro-hydropower stakeholders, it is a safe bet that only about five percent of Excel and AutoCad users in Nepali hydropower sector really understand how to get the most out of these software. With the help of these Design Aids, I attempt to illustrate the fascinating features of these software (especially Excel) and nudge you into that elite group. I have noticed that there are very few complete technical tools and books related to micro and small hydropower design available in the market. A single set of tools for all the calculations is not yet available. Moreover, the outcome of most of these tools are not adequately tested and verified. Most of the good software have none or only poorly illustrated manuals. The combined outcome may produce poor quality feasibility studies which lead to improper implementation decision. To overcome these dangers, I have prepared the Design Aids along with this manual. Electronic version of the Design Aids (an Excel workbook), 15 AutoCad drawings and this manual in Acrobat PDF format are presented on the attached CD ROM. This set of Design Aids (v 2006.05) is a shareware. It would not have been possible for me to write this Design Aids package without the encouragement from German Development Cooperation, Nepal; Entec AG, Switzerland and of course, Mr. Sridhar Devkota, the Project Manager, Small Hydropower Promotion Project. I would also like to thank my colleague Mr. Girish Kharel for his tireless assistance and valued suggestions on composition and presentation.


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What You Should Know The Design Aids are prepared for practicing technical designers who have basic knowledge of hydropower, technical calculation skills and who are familiar with Excel and AutoCad. I attempt to elaborate these Design Aids in such a way that the users will learn to use these Design Aids quite comfortably. The calculations in the spreadsheets are intended to mimic manual calculations as far as possible. Stepwise calculations are also presented in this manual. What You Should Have To make the best use of the Design Aids, you need a copy of Microsoft Excel (XP or later), Autodesk AutoCad (2000 or later) and Adobe Acrobat Reader (5.0 or later). The latest version of a free copy of Adobe Acrobat Reader can be downloaded from www.adobe.com. A downloaded copy of Adobe Acrobat Reader is included in the bundled CD. The minimum system requirements are: Operating system : Windows 98/2000/NT/XP CPU : 486/333MHz RAM : 128MB Display : 640 x 480 pixels, 256 colours CD ROM : Double-speed (for installation only) HD : 10 MB (approximately) How These Design Aids Are Organized There are many ways to organize these Design Aids materials, but I settled on a scheme that divides them into three main parts. Part I A: Micro-hydropower Drawings The section of this part consists of fifteen typical drawings useful for project elements from intake to transmission line. Since they are only typical drawings, additions of drawings and the level of details may be amended to fulfill specific needs of a particular project. Special efforts were made to maintain the level of consistency, compatibility and the extent of information in the drawings. It is expected that the presented feasibility drawings by consultants are complete and appropriate for micro hydropower plants and all the concerned stakeholders should be able to understand and implement the presented content. Part I B: Mini/Small-hydropower Drawings Part I B consists of fifteen selected typical drawings of an actual feasibility study of a 1500kW Lipin Small Hydropower Project, Sindhupalchowk District, Central Nepal. I used most of the spreadsheets presented in the Design Aids for designing and detailing project elements of this project. Hard copies and soft copies in Acrobat PDF format are presented in this version of Design Aids. The difference between the levels of details of these drawings prepared for a 1500kW project and micro-hydropower projects up to 100kW are quite noticeable. Therefore, it is obvious that higher levels of details with the help of more drawings are expected for larger small hydropower projects. Part II: Spreadsheets This part consists of twenty-five typical spreadsheets covering all calculations recommended by AEPC guidelines for subsidy approval of micro-hydropower schemes, Practical Action Nepal (formerly ITDG, Nepal) guidelines and requirement recommended by small hydropower designers. An earlier version the Design Aids prepared especially for micro-hydropower

http://www.adobe.com


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schemes had thirteen typical spreadsheets. Some additional spreadsheets have been presented to cater mini and small hydropower design needs. These spreadsheets provide users to estimate hydrological parameters; design civil, mechanical and electrical components and analyze financial robustness of the perspective micro and mini hydropower schemes in Nepal. Part III: Users’ Manual This manual (also in Adobe Acrobat PDF format) illustrates aspects of using the presented drawings and spreadsheets; and stepwise calculations covering all technical and non technical (costing and financial) components of hydropower schemes. Download and Reach Out Electronic files included on the attached CD can also be downloaded from www.entec.com.np. Updates will also be posted on this site. Preparation of the Design Aids is a continuous process. I am always interested in getting feedback on these Design Aids. Therefore, valuable suggestions and feedbacks are expected from all the stakeholders/users so that the overall quality of the hydropower sector is enhanced. Any suggestion and feedback can directly be sent to my email [email protected]. Sharing of hydropower related information regarding advanced options beyond this design aids is also expected. Pushpa Chitrakar Engineering Advisor SHPP/GTZ




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TABLE OF CONTENTS

Page No.

NOTICE II

PREFACE III

ACKNOWLEDGEMENTS IV

TABLE OF CONTENTS VII

1. INTRODUCTION 1 1.1 GENERAL 1 1.2 OBJECTIVES OF THE DESIGN AIDS 2 1.3 SOURCES OF THE DESIGN AIDS 2 1.4 DESIGN AIDS: TYPICAL MICRO-HYDRO DRAWINGS 2 1.5 DESIGN AIDS: TYPICAL MINI/SMALL HYDRO DRAWINGS 3 1.6 DESIGN AIDS: SPREADSHEETS 5

1.6.1 Flow chart notations 5 1.6.2 Iterative Processes 6 1.6.3 Macro Security 6 1.6.4 Individual vs. linked spreadsheets 7 1.6.5 User specific inputs 7 1.6.6 Interpolated computations 7 1.6.7 Errors 7 1.6.8 Cell notes 7 1.6.9 Cell Text Conventions 8 1.6.10 Types of inputs 8 1.6.11 Pull Down menus and data validation 9 1.6.12 Design Aids Menus and Toolbars 10 1.6.13 Interactive Diagrams 11

1.7 INSTALLATION DIRECTORY 11

2 DISCHARGE MEASUREMENT 12 2.1 GENERAL 12 2.2 PROGRAM BRIEFING & EXAMPLES 12 2.3 CALCULATION AT SITE 13

3 HYDROLOGY 15 3.1 GENERAL 15 3.2 HYDROLOGICAL DATA 15 3.3 MEDIUM IRRIGATION PROJECT (MIP) METHOD: MEAN MONTHLY FLOWS 16 3.4 WECS/DHM (HYDEST) METHOD: FLOOD FLOWS 18 3.5 GENERAL RECOMMENDATIONS 19


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3.6 PROGRAM BRIEFING & EXAMPLES 20

4 HEADWORKS 23 4.1 INTRODUCTION AND DEFINITIONS 23 4.2 GENERAL RECOMMENDATIONS 24

4.2.1 Weir 24 4.2.2 Intake 24 4.2.3 Intake Trashrack 24

4.3 PROGRAM BRIEFINGS AND EXAMPLES 24 4.2.4 Side Intake calculations 26 4.2.5 Drop Intake calculations 29

5 HEADRACE/TAILRACE 32 5.1 GENERAL 32 5.2 GENERAL RECOMMENDATIONS 32

5.2.1 Canal 32 5.2.2 Pipe 32

5.3 PROGRAM BRIEFING AND EXAMPLES 33 5.3.1 Canal 33 5.3.2 Canal 33 5.3.3 Pipe 36

6 SETTLING BASINS 39 6.1 SEDIMENT SETTLING BASINS 39 6.2 SETTLING BASIN THEORY 40 6.3 GENERAL RECOMMENDATIONS 40

6.3.1 Gravel Trap 40 6.3.2 Settling Basin 41 6.3.3 Forebay 41

6.4 PROGRAM BRIEFING AND EXAMPLES 42 6.4.1 Features of the spreadsheet 42 6.4.2 Vertical flushing pipe 43 6.4.3 Spillway at intake 43 6.4.4 Gate 43

7 PENSTOCK AND POWER CALCULATIONS 47 7.1 GENERAL 47 7.2 GENERAL RECOMMENDATIONS 47 7.3 PROGRAM BRIEFING AND EXAMPLE 47

7.3.1 Program Briefing 47 7.3.2 Typical example of a penstock pipe 48

7.4 FORCES ON ANCHOR BLOCKS 51 7.4.1 Program example 51

7.5 ANCHOR BLOCK DESIGN 55 7.5.1 Program example 55

8 TURBINE SELECTION 59


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8.1 GENERAL 59 8.2 GENERAL RECOMMENDATIONS 59 8.3 PROGRAM BRIEFING AND EXAMPLE 60

9 ELECTRICAL EQUIPMENT SELECTION 61 9.1 GENERAL 61 9.2 SELECTION OF GENERATOR SIZE AND TYPE 61

9.2.1 Single Phase versus Three Phase System 61 9.2.2 Induction versus Synchronous Generators 61

9.3 GENERAL RECOMMENDATIONS 62 9.3.1 Sizing and RPM of a Synchronous Generator: 62 9.3.2 Sizing and RPM of an Induction Generator: 63

9.4 PROGRAM BRIEFING AND EXAMPLES 63 9.4.1 Program Briefing 63 9.4.2 Typical example of a 3-phase 60kW synchronous generator 64 9.4.3 Typical example of a single phase 20kW induction generator 66

10 MACHINE FOUNDATION 68 10.1 INTRODUCTION AND DEFINITIONS 68 10.2 EXAMPLE 68

11 TRANSMISSION AND DISTRIBUTION 72 11.1 INTRODUCTION AND DEFINITIONS 72 11.2 GENERAL RECOMMENDATIONS 72 11.3 PROGRAM BRIEFING AND EXAMPLES 72

11.3.1 Program Briefing 72

12 LOADS AND BENEFITS 77 12.1 GENERAL 77 12.2 GENERAL RECOMMENDATIONS / AEPC GUIDELINES 77 12.3 PROGRAM BRIEFING AND EXAMPLE 77

12.3.1 Program Briefing 77

13 COSTING AND FINANCIAL ANALYSES 80 13.1 INTRODUCTION AND DEFINITIONS 80 13.2 GENERAL RECOMMENDATIONS / AEPC GUIDELINES 80 13.3 PROGRAM BRIEFING AND EXAMPLE 80

13.3.1 Program Briefing 80 13.3.2 Typical example of costing and financial analyses 81

14 UTILITIES 83 14.1 INTRODUCTION 83

14.1.1 Uniform depth of a rectangular or trapezoidal canal 83 14.1.2 Payment of loan for different periods (monthly, quarterly and yearly) 83 14.1.3 Power calculations 84


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14.1.4 Spillway sizing. 85 14.1.5 Voltage drops of transmission line. 85 14.1.6 Pipe friction factor. 86

15 REFERENCES 87

DRAWINGS I TYPICAL MICROHYDROPOWER DRAWINGS I TYPICAL DRAWINGS OF 1500KW LIPIN SMALL HYDROPOWER PROJECT XVII

LIST OF FIGURES Figure 1.1: A typical Micro Hydro Settling Basin Drawing .................................................................4 Figure 1.2: A typical Small Hydro Settling Basin Drawing .................................................................4 Figure 1.3: Iterative process .................................................................................................................6 Figure 1.4: Activation of iteration (Tools => Option =>Calculations..................................................6 Figure 1.5: Enabling macros and macro security ...............................................................................6 Figure 1.6: Cell formula incorporated in a cell note............................................................................7 Figure 1.7: A cell note presenting typical values of Manning’s n for different surfaces ..................8 Figure 1.8: Colour coding of cell texts.................................................................................................8 Figure 1.9: Different categories of inputs. ...........................................................................................9 Figure 1.10: Different categories of inputs. .........................................................................................9 Figure 1.11: Design Aids Menu and Toolbar .....................................................................................10 Figure 1.12: Typical interactive diagram of Side Intake....................................................................11 Figure 2.1: Discharge calculations by salt dilution method .............................................................14 Figure 3.1: Hydrology..........................................................................................................................15 Figure 3.2: Hydrological Data and MHP .............................................................................................15 Figure 3.3: MIP Regions ......................................................................................................................16 Figure 3.4: MIP model .........................................................................................................................17 Figure 3.5: Need of interpolation for calculating mean monthly coefficient ...................................17 Figure 3.6: Effect of interpolation on mean monthly flows ..............................................................18 Figure 3.7: Hydest Model ....................................................................................................................19 Figure 3.8: Flow chart of Hydrology spreadsheet .............................................................................20 Figure 3.9: Typical example of a hydrological parameters calculation spreadsheet “Hydrology”22 Figure 4.1: Trashrack parameters ......................................................................................................25 Figure 4.2: Flow chart for trashrack calculations..............................................................................25 Figure 4.3: Side intake parameters ....................................................................................................26 Figure 4.4: Flow chart for side intake calculations ...........................................................................27 Figure 4.5: An example of side intake calculations ..........................................................................28 Figure 4.6: Parameters and flow chart of drop intake design ..........................................................29 Figure 4.7: An example of drop intake ...............................................................................................31 Figure 5.1: Flow chart for canal design .............................................................................................34 Figure 5.2: An example of canal design.............................................................................................35 Figure 5.3: Illustrated canal type and their dimensions....................................................................36 Figure 5.4: Flow chart for pipe design ...............................................................................................37 Figure 5.5: An example of headrace pipe design ..............................................................................38 Figure 6.1: Typical section of a settling basin...................................................................................39 Figure 6.2: An ideal setting basin.......................................................................................................40 Figure 6.3: Flushing pipe details ........................................................................................................43 Figure 6.4: Typical example of a settling basin (Settling basin, spilling and flushing). .................45 Figure 6.5: Typical example of a settling basin (Gate and rating curve). ........................................46 Figure 6.6: Typical example of a settling basin (forebay and dimensioning)..................................46 Figure 7.1: Flow diagram of penstock design ...................................................................................48 Figure 7.2: Input required for penstock and power calculations .....................................................49 Figure 7.3: Output of penstock and power calculation spreadsheet. ..............................................50


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Figure 7.4: Output of anchor block force calculation spreadsheet..................................................55 Figure 7.5: Anchor Block Considered................................................................................................55 Figure 7.6: Anchor Block force diagram............................................................................................57 Figure 7.7: Anchor Block force diagram............................................................................................58 Figure 8.1: Pelton and Crossflow Turbines .......................................................................................59 Figure 8.2: A Typical turbine example. ..............................................................................................60 Figure 9.1: Electrical components of a 20kW 3-phase synchronous generator. ............................65 Figure 9.2: Electrical components of a 20kW 1-phase induction generator....................................67 Figure 10.1: Layout of MachineFoundation Spreadsheet.................................................................71 Figure 11.1: Flow chart of transmission and distribution line computation. ..................................73 Figure 11.2: Transmission line and load used for the example. ......................................................73 Figure 11.3: Typical example of a low voltage transmission line. ...................................................76 Figure 12.1: Flow chart of the load and benefits calculation spreadsheet......................................77 Figure 12.2: Load duration chart ........................................................................................................78 Figure 12.3: An example of load and benefits calculation................................................................79 Figure 13.1: Flow chart for Project costing and financial analyses. ................................................81 Figure 13.2: A typical example of project costing and financial analyses. .....................................82 Figure 14.1: A typical example of uniform depth calculation of a trapezoidal section...................83 Figure 14.2: A typical example EMI calculation.................................................................................84 Figure 14.3: Generated Schedule of EMI calculation ........................................................................84 Figure 14.4: A typical example of power calculation ........................................................................84 Figure 14.5: A typical example of spillway sizing .............................................................................85 Figure 14.6: A typical example of transmission line calculation......................................................85 Figure 14.7: A typical example of pipe friction calculation ..............................................................86 LIST OF TABLES Table 1.1: Summary of Micro Hydropower Drawings ........................................................................3 Table 1.2: Summary of Small Hydropower Drawings ........................................................................3 Table 1.3: Summary of Spreadsheets ..................................................................................................5 Table 2.1: Input parameters for Salt Dilution Method .......................................................................12 Table 2.2: First set conductivity reading for Salt Dilution Method (Example).................................12 Table 2.3: Data Input (partial) .............................................................................................................13 Table 3.1: MIP regional monthly coefficients ....................................................................................16 Table 3.2: Standard normal variants for floods.................................................................................19 Table 4.1: Drop intake and upstream flow .........................................................................................29 Table 6.1: Settling diameter, trap efficiency and gross head ...........................................................41 Table 7.1: Summary of penstock thickness and corresponding maximum permissible static head

.......................................................................................................................................................50 Table 7.2: Summary of forces.............................................................................................................53 Table 8.1: Turbine specifications .......................................................................................................59 Table 8.2: Turbine type vs. ns .............................................................................................................59 Table 9.1: Selection of Generator Type.............................................................................................62 Table 9.2: Generator rating factors ....................................................................................................62 Table 11.1: ASCR specifications ........................................................................................................72 Table 11.2: Rated current and voltage drop calculation ...................................................................72 Table 13.1: Per kilowatt subsidy and cost ceiling as per AEPC.......................................................80


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LIST OF MICRO-HYDROPOWER DRAWINGS Drawing Name Page 01 General Layout ……………………………………….................................... D-ii 02A Side Intake Plan ……………………………………….................................... D-iii 02B Side Intake Sections ……………………………………….................................... D-iv 03 Drop Intake Plan ……………………………………….................................... D-v 04 Headrace ……………………………………….................................... D-vi 05A Gravel Trap …...………………………………….................................... D-vii 05B Settling Basin ……………………………………..................................... D-viii 06 Headrace Canal ……………………………………….................................... D-ix 07 Forebay ……………………………………….................................... D-x 08 Penstock Alignment ……………………………………….................................... D-xi 09 Anchor & Saddle Blocks …...…………………………………..................................... D-xii 10 Powerhouse ..……………………………………...................................... D-xiii 11 Machine foundation ..……………………………………...................................... D-xiv 12 Transmission …..…………………………………...................................... D-xv 13 Single line diagram ..……………………………………...................................... D-xvi LIST OF SMALL-HYDROPOWER DRAWINGS Drawing no 7.D.np.5133/01/ Title / Remarks

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10A01 Project Location, District Map & Catchment Area D-xviii 10A02 Project Layout, sheet 1 of 2, Plan D-xix 10A03 Project Layout, sheet 2 of 2, Profiles D-xx 20A01 Weir, Intake and Gravel Trap, sheet 1 of 3, plan and sections D-xxi 20A02 Weir, Intake and Gravel Trap, sheet 2 of 3, plan and sections D-xxii 20A03 Weir, Intake and Gravel Trap, sheet 3 of 3, plan and sections D-xxiii 20A04 Settling Basin, sheet 1 of 2, plan and sections D-xxiv 20A05 Settling Basin, sheet 2 of 2, plan and sections D-xxv 30A01 Plan and Profile and Typical Sections/Similar for penstock alignment D-xxvi 40A10 Anchor Blocks, sheet 1 of 2 D-xxvii 40A11 Anchor Blocks, sheet 2 of 2 D-xxviii 40A12 Saddle Support D-xxix 50A02 Powerhouse Plan and Sections D-xxx 60A04 Geological Mapping, sheet 4 of 4 D-xxxi 70A01 Single line diagram D-xxxii


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1. INTRODUCTION

1.1 GENERAL This set of Micro-hydropower1 Design Aids is a complete set of feasibility level hydropower design tools consisting of typical AutoCad drawings, typical Microsoft Excel spreadsheets and a users’ manual recommended for micro and mini hydropower schemes. An earlier digital version of the set was published as a part the publication of Alternative Energy promotion Centre (AEPC) of The Government of Nepal2 (ISBN 99933-705-5-X) and has officially been recommended for its subsidized micro-hydropower schemes in Nepal up to 100kW. The micro-hydropower Design Aids were prepared to provide a basis for consultants to undertake calculations and prepare drawings as per the requirements set aside by the procedural guidelines of AEPC-the Government of Nepal. Since most of the stakeholders are familiar with Autodesk AutoCad (2000 or later) and Microsoft Excel (XP or later) application software, the Design Aids were prepared based on these software to make them simple and user friendly. During the preparation of these Design Aids, special efforts were made so that the skills and knowledge of practicing stakeholders such as consultants, manufacturers and inspectors are further enhanced by this Design Aids. This design aids are updated version of the previous design aids and suitable for designing mini and small hydropower schemes. Update, addition and publication of the design aids are the symbols of Small Hydropower Promotion Project(SHPP/GTZ)3 SHPP’s continuous assistance and support to the Nepali hydropower sector. The Design Aids consist of a set of fifteen typical drawings, a workbook with twenty-five typical spreadsheets and a users’ manual for procedural guidance. This set of design aids also covers all aspects recommended by AEPC guidelines for its subsidized micro-hydropower schemes. The Design Aids provide users to estimate hydrological parameters; design civil, mechanical and electrical components and analyze financial robustness of the prospective micro hydropower schemes in Nepal. Procedural guidelines, detailed step by step calculations and guidelines for using the presented spreadsheets are presented in this users’ manual. A copy of this manual in Acrobat PDF file format is included in the bundled CD. The Design Aids are distributed in template/read-only formats so that the original copy is always preserved even when the users modify them. The Design Aids were originally prepared for micro hydropower schemes up to 100kW. Since there are many common approaches and features in all hydropower projects, these spreadsheets were modified to suit mini and small hydropower design requirements as well. Spreadsheets on Hydrology are intended for Nepali micro hydropower schemes only. Spreadsheets on Cost&Benefits and FinancialAnalyses are intended to serve micro-hydropower schemes outside Nepal too (refer to Table 1.2). Preparation and use of the Design Aids is a continuous process. SHPP/GTZ has been continuously enhancing the Design Aids and this update (version 2006.05) is the outcome of SHPP’s efforts in hydropower sector development in Nepal. Therefore, valuable suggestions and feedbacks are expected from all the stakeholders/users so that the overall quality of the micro hydro sector is enhanced. Any suggestion and feedback can directly be sent to [email protected] .

1 In Nepal, hydropower projects up to 100kW are termed as micro hydropower projects. Projects within 100kW to 1000kW are termed as mini hydropower projects. 1000kW to 10,,000kW are termed as small hydropower projects. Beyond this, they are termed as large hydropower projects. 2 Alternative Energy Promotion Centre (AEPC) is a Nepal Government organization established to promote alternative sources of energy in Nepali rural areas. MGSP of AEPC-ESAP is promoting Nepali micro-hydropower schemes up to 100kW. 3 Small Hydropower Promotion Project is a joint project of the Government of Nepal, Department of Energy Development (DoED) and German Technical Cooperation (GTZ). Since its establishment in 1999, this project has been providing its services to sustainable development of small hydropower projects in Nepal (100kW to 10MW) leading to public private participation and overall rural development. It has also been providing technical support and backstopping to Nepali micro-hydropower stakeholders including AEPC. Entec AG of Switzerland is the implementing consultant of this project.



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1.2 OBJECTIVES OF THE DESIGN AIDS The main objective of the Design Aids is to enhance the quality of the micro and mini hydropower sector in Nepal. Use of these Design Aids helps fulfilling the main objective because:

1. The Design Aids function as a set of “Time Saver Kit” for precision and speed (e.g. hydrological calculations based on exact flow measurement date, Q flood off-take, friction factor of penstock pipes, etc.).

2. They provide relevant references to micro and mini hydro sector stakeholders for using and upgrading their skills and creativities. Useful information is incorporated within the design aids so that external references are minimized. Cell notes, tables, figures, etc., in the spreadsheets and information in this manual are some of the examples that will greatly reduce external references.

3. The depth of the study and presented reports by different consultants are uniform and their data presentations are consistent and to the required depth.

4. The Design Aids serve as templates so that there is sufficient room for further creativity and improvement and tailoring to include specific needs of particular projects.

5. In addition, the Design Aids are handy and user friendly. The user familiar AutoCad 2000 and MS Excel XP software platforms have been used to develop the Design Aids.

1.3 SOURCES OF THE DESIGN AIDS The Design Aids were prepared aiming to enhance the overall quality of the micro and mini hydro sector. Reviews of following sources were carried out during the preparation of the Design Aids:

1. Review and assessment of more than 60 small hydropower projects which have been assisted by SHPP/GTZ.

2. Review, assessment and appraisal of more than 300 preliminary feasibility, 200 feasibility and 50 Peltric set feasibility study reports during the SHPP-AEPC collaboration.

3. Review of AEPC micro hydropower guidelines and standards for Peltric and micro-hydropower schemes. These guidelines and standards were updated by SHPP during SHPP-AEPC collaboration.

4. Feedbacks from all stakeholders such as Independent power producers (IPPs), lending agencies, in-house colleagues, AEPC, Consultants, Manufacturers and Installers.

5. Experience from other micro, small and large hydropower projects within Nepal and abroad.

6. Standard textbooks, guidelines and other standards.

1.4 DESIGN AIDS: TYPICAL MICRO-HYDRO DRAWINGS As stated earlier, fifteen micro-hydropower related AutoCad drawings were prepared and incorporated in the Design Aids. The presented drawings cover from intake to transmission line. Since they are only typical drawings, additions of drawings and the level of details may be changed to fulfill specific needs of a particular project. The level of consistency, compatibility and the extent of information in the drawings are complete and appropriate for micro hydropower plants and all the concerned stakeholders should be able to understand and implement the presented content. The main features of the presented drawings are:

1. These drawings are recommended only for micro-hydro schemes.

2. Minimum required details such as plans and adequate cross sections are provided.

3. Recommended values of elements such as the minimum thickness of a stone masonry wall, the longitudinal slope of a settling basin, etc, are presented in the drawings.

4. Standard line types and symbols are presented.


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5. Basic drawing elements such as a title box with adequate information and controlling signatories; scale; etc are presented.

6. All drawings with standard layouts for printing. The dimensions and geometries of the presented drawings should be amended according to the project details. A set of all the drawings are presented in the appendix. For an example, a typical drawing of a settling basin is presented in Figure 1.1. The MHP drawings that are presented are listed in Table 1.1.

1.5 DESIGN AIDS: TYPICAL MINI/SMALL HYDRO DRAWINGS A total of fifteen selected typical drawings of an actual feasibility study of a 1500kW Lipin Small Hydropower Project, Sindhupalchowk District, Central Nepal are presented in appendix. The difference between the levels of details of micro and small hydropower drawings are quite noticeable. A typical settling basin drawing is presented in Figure 1.2. All the presented drawings listed in Table 1.2 are recommended for mini and small hydropower projects within 2000kW. Table 1.1: Summary of Micro Hydropower Drawings SN Drawing Name (*.dwg) Remarks 1 01 General Layout General layout of project components except the transmission and

distribution components. 2 02A Side Intake Plan A general plan of headworks including river training, trashrack, intake,

gravel trap and spillway. 3 02B Side Intake Sections A longitudinal section along water conveyance system from intake to

headrace, two cross sections of weir for temporary and permanent weirs respectively and a cross section of a spillway.

4 03 Drop Intake Plan A general plan, a cross section across a permanent weir and a cross section of a drop intake.

5 04 Headrace A longitudinal headrace profile showing different levels along it. 6 05A Gravel Trap A plan, a longitudinal section and two cross sections. 7 05B Settling Basin A plan, a longitudinal section and two cross sections. 8 06 Headrace Canal Two cross sections for permanent lined canal and one for temporary

unlined canal. 9 07 Forebay A plan, a longitudinal section, two cross sections and penstock inlet

details. 10 08 Penstock Alignment A longitudinal section of penstock alignment. 11 09 Anchor & Saddle

Blocks Plans and sections of concave and convex anchor blocks and a saddle.

12 10 Powerhouse A plan and a section of a typical powerhouse. 13 11 Machine foundation A plan and three sections of a typical machine foundation. 14 12 Transmission A single line diagram if a transmission/distribution system. 15 13 Single line diagram A single line diagram showing different electrical components. Table 1.2: Summary of Small Hydropower Drawings

SN Drawing no 7.D.np.5133/01/ Title / Remarks

1 10A01 Project Location, District Map & Catchment Area 2 10A02 Project Layout, sheet 1 of 2, Plan 3 10A03 Project Layout, sheet 2 of 2, Profiles 4 20A01 Weir, Intake and Gravel Trap, sheet 1 of 3, plan and sections 5 20A02 Weir, Intake and Gravel Trap, sheet 2 of 3, plan and sections 6 20A03 Weir, Intake and Gravel Trap, sheet 3 of 3, plan and sections 7 20A04 Settling Basin, sheet 1 of 2, plan and sections 8 20A05 Settling Basin, sheet 2 of 2, plan and sections 9 30A01 Plan and Profile and Typical Sections/Similar for penstock alignment 10 40A10 Anchor Blocks, sheet 1 of 2 11 40A11 Anchor Blocks, sheet 2 of 2 12 40A12 Saddle Support 13 50A02 Powerhouse Plan and Sections 14 60A04 Geological Mapping, sheet 4 of 4 15 70A01 Single line diagram


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Figure 1.1: A typical Micro Hydro Settling Basin Drawing

Figure 1.2: A typical Small Hydro Settling Basin Drawing


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1.6 DESIGN AIDS: SPREADSHEETS As stated earlier, MS Excel XP has been used to develop the presented twenty-five spreadsheets. General as well as special features of Excel XP have been utilized while developing the spreadsheets. There are sixteen main spreadsheets each covering a tool required for covering computations for an element of hydropower schemes. The “Utility” spreadsheets presented at the end of the workbook covers minor calculations such as uniform depth of water in a canal, loan payback calculations, etc. The list of the presented spreadsheets and their areas of coverage are presented in Table 1.3. Table 1.3: Summary of Spreadsheets SN Name Area of coverage Uses 1 Discharge Chapter 2: Computation of river discharge from Salt dilution method. Micro/small 2 Hydrology Chapter 3: Hydrological parameters calculations based on MIP and

Hydest methods (Regression Methods) Micro/ small in Nepal

3 Side Intake Chapter 4: Design of side intakes including coarse trashrack, flood discharge and spillways.

All sizes

4 Bottom Intake Chapter 4: Design of bottom intake including flood discharges. All sizes 6 Canal Chapter 5: Design of user defined and optimum conveyance canals with

multiple profiles and sections. All sizes

7 Pipe Chapter 5: Design of mild steel/HDPE/PVC conveyance pipes. All sizes 5 Settling Basin Chapter 6: Design of settling basins, gravel traps and forebays with

spilling and flushing systems with spillways, cones and gates. All sizes

8 Penstock Chapter 7: Design of penstocks with fine trashrack, expansion joints and power calculations.

All sizes

9 AnchorLoad Chapter 7: Calculations of forces on anchor blocks. All sizes (2D) 10 AnchorBlock Chapter 7: Design of anchor block. All sizes (2D) 11 Turbine Chapter 8: Selection of turbines based on specific speed and gearing

ratios. Micro

12 Electrical Chapter 9: Selection of electrical equipment such as different types of generators, cable and other accessories sizing.

Micro

13 Machine Foundation

Chapter 10: Design of machine foundation. Micro

14 Transmission Chapter 11: Transmission / Distribution line calculations with cable estimation.

Micro/small

15 Load Benefit Chapter 12: Loads and benefit calculations for the first three years and after the first three years of operation.

Micro

16 Costing & Financial

Chapter 13: Costing and financial analyses based on the project cost, annual costs and benefits.

Micro

17-24

Utilities Chapter 14: Utilities such as uniform depth, loan payment calculations, etc.

All sizes

Design of anchor blocks and saddles are site and project specific. The presented anchor block spreadsheets are based on two-dimensional calculations and are useful for penstock aligned in straight lines without any horizontal deflection. Background information and main features of the presented spreadsheets are: 1.6.1 Flow chart notations Standard flow chart notations are used to describe program execution flows. Following notations are mostly used: Start and End Input Processing formulas and output Processing and output from other sub routine


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Conditional branching Flow direction 1.6.2 Iterative Processes The spreadsheets are designed to save tedious and long iterative/repetitive processes required for calculations. Manual repetitive processes are the main source error generating and they are also time consuming factors. A typical repetitive process is presented in Figure 1.3.

Figure 1.3: Iterative process As shown in the figure, the initial assumed value of X0 is amended until an acceptable error limit is reached. By default, Excel does not activate this features and generates Circular Reference Error. The iterative features in Excel can be activated by selecting Calculations tab (Tools->Options->Calculations>Tick Iteration (cycles & h)) and checking the iteration box. The Excel dialogue box with this features activated is presented in Figure 1.4.

Figure 1.4: Activation of iteration (Tools => Option =>Calculations 1.6.3 Macro Security The spreadsheets contain Visual Basic for Application (VBA) functions and procedures. Because of the safety reasons against possible virus threats, MS Excel disables such VBA functions and procedures by default. Setting security level to medium (Tools => Macros => Security => Medium) and enabling the macros during the opening of the Design Aids are required for the proper execution of the Design Aids. Dialogue boxes for setting security level to medium and enabling the macros are presented in Figure 1.5. Figure 1.5: Enabling macros and macro security

EndY =f(X): X=f`(Y)

X=X+h

Is e=<|Yn+1 –Yn|

No

YesAssume Xo


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1.6.4 Individual vs. linked spreadsheets By default, common inputs such as the project name, etc., in all the spreadsheets are linked to the first design spreadsheet “Conductivity”. The objective of linking such common inputs is to have consistent input with minimal user effort. Some of the other processed data such as the design discharge or flood discharge are also linked by default. However, the users may change these values for specific calculations i.e., the spreadsheets can also be used as individual spreadsheets for independent calculations that are not linked to a single project. It is recommended to save an extra copy of the workbook before manipulating such linked cell so that the saved copy can be used as a workbook with linked spreadsheets for a single project. 1.6.5 User specific inputs Some parameters such as canal freeboards, width of a canal, factor of safety for a mild steel penstock, etc., have their standard optimum values. By default, the standard optimum values are computed or presented. However, users are allowed to enter non-standard specific values under special circumstances. 1.6.6 Interpolated computations Some of the parameters such as frictional coefficient of a bend, coefficient of gate discharge, etc., have standard proven values for standard conditions. In case the condition is of a non-standard type, interpolated values with the help of curve fittings are estimated and used. The users are cautioned to check the validity of such values whenever they encounter them. 1.6.7 Errors Mainly three types of errors are known in the presented design aids. One of them is the NAME# error which is caused by not executing custom functions and procedures because of the macro security level set to high or very high level. In case such an error occurs, close the workbook, activate the macro security level to medium and enable the macros when opening the workbook again. Typical NAME# errors occur for the depth of water during flushing yfi (m) and d50f during flushing (mm) in the settling basin spreadsheet. VALUE# error is the other error that is generated by the malfunctioning of circular references. When such an error occurs, select the error cell, press F2 and press Enter. Q intake Qf cumec in the side intake spreadsheet is an example of such an error. A REF# error in transmission line computation occurs due to the deletion of unnecessary rows in a branch. In such an instance, copy the second cell from the second line of any branch. 1.6.8 Cell notes Cell notes are comments attached to cells. They are useful for providing, information related to computational procedures. Adequate cell notes are provided in the presented spreadsheets so that external references are minimized.

Figure 1.6: Cell formula incorporated in a cell note. For example, a cell note with a cell formula for calculating specific speed of a turbine is presented in Figure 1.6. Similarly, the cell note in Figure 1.7 presents a basic table for selecting Manning’s coefficient of roughness of a canal. Other information such as mandatory requirements set by AEPC for its subsidized micro hydropower projects are also presented. For hydropower projects that are not subsidized by AEPC, these mandatory requirements may be amended.


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Figure 1.7: A cell note presenting typical values of Manning’s n for different surfaces 1.6.9 Cell Text Conventions Three different colour codes are used to distinguish three different cell categories. A typical example of colour coding of cells is presented in Figure 1.8. The colours and categories of these cells are:

Blue cells: These cells represent mandatory input cells. These cells are project dependant cells and project related actual inputs are expected in these cells for correct outputs. The mandatory input includes the name of project, head, discharge, etc. Some of these cells are linked.

Figure 1.8: Colour coding of cell texts Red cells: These cells are optional input cells. Standard values are presented in these cells. Values in this type of cells can be amended provided that there are adequate sufficient grounds to do so. It is worth noting that care should be taken while changing these values. Typical optional values / inputs are the density of sediment, sediment swelling factor, temperature of water, etc. Black cells: The black cells represent information and or output of the computations. For the sake of protecting accidental and deliberate amendment or change leading to wrong outputs, these cells are protected from editing.

1.6.10 Types of inputs According to the nature of inputs, the inputs are further categorized into the following three groups:


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1. User or project specific inputs: The input variables that totally depend on the user and or

the project are categorized as the user or project specific inputs. The programs do not restrict on or validate the values of such inputs. The name and gross head of the project are some of the examples that fall on this category. The velocity through orifice (Vo) in the example presented in Figure 1.9 can have any value hence it is a user specific input.

2. Prescribed Input: Some of the inputs have some standard values for standard conditions.

The programs list using such values and give choices for the user to select. However, the programs do not restrict on or validate such variables. These inputs are termed as prescribed inputs. For example in Figure 1.9, with the help of a pull-down menu, Manning’s coefficients for different types of surfaces are listed for selection. This will greatly reduce the need for referring external references. However, any specific values for specific need can be entered into this type of cells.

Figure 1.9: Different categories of inputs.

3. Mandatory Input: Some inputs can only have specific values and the programs need to validate such values for proper computations. These values are termed as mandatory inputs. Since Nepal is divided into seven MIP regions, the value for a MIP region can have an integer ranging from 1 to 7 only. In the example presented in Figure 1.10, the MIP region can have values from 1 to 7. In case the user enters different values (for example 8 as presented in the figure), the program generates an error prompting for the correct input of 1 to 7. The proper value between 1 and 7 can be entered after clicking “Retry” button.

Figure 1.10: Different categories of inputs. 1.6.11 Pull Down menus and data validation As demonstrated earlier, some input cells are equipped with pull down menus to facilitate the users to input standard values related to the input cell. Cells related to pull down menus can have any user specific values than the stated standard values if the data cells are not of mandatory type. In Figure 1.9, the pull down menu for Manning’s roughness coefficient (n) in cell B42 is activated. Different surface materials are listed in the pull down menu, stone masonry surface type is selected and the corresponding standard value of the Manning’s coefficient of roughness of 0.02 is substituted in the corresponding cell. Since the value in this cell is not restricted, users can enter any values for this cell. Some inputs such as the name of the month, MIP hydrological region and dates in Hydrology spreadsheet can have specific values in their respective cells. Since the outcome of the computation will be erroneous if the input data does not match with the desired values, the spreadsheets are designed to reject such an invalid value and flag an error message with suggestions. This example is demonstrated in Figure 1.10.


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1.6.12 Design Aids Menus and Toolbars A menu and a toolbar are added to the workbook to facilitate users’ access all the design tools including online manual, drawings and feedback to the Design Aids. They are set to active only when the workbook is active. The toolbar has to be dragged to either on top or side of the screen (as presented in Figure 1.11) for convenience.

Figure 1.11: Design Aids Menu and Toolbar


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1.6.13 Interactive Diagrams Most of the design spreadsheets are equipped with dynamically linked interactive diagrams which change according to the changes in the design parameters. A typical example of an interactive diagram for a side intake is presented in Figure 1.12. Interactive diagrams are provided for the following designs:

1. Side Intake.

2. Bottom Intake.

3. Settling Basin.

4. Anchor Block.

5. Machine Foundation and

6. Canal (utility)

Figure 1.12: Typical interactive diagram of Side Intake

1.7 INSTALLATION DIRECTORY It is recommended to install the design aids under “C:\Design Aids\” directory for the full functioning of these tools. In case it is installed elsewhere, the external links for online manual and drawings will not work. Run “Install.bat” on the root directory of the bundled CD for installing to the default location. It is also recommended that the working copy of project specific spreadsheet be saved on “C:\Design Aids\Design Aids”.

Wall Geometry

Orif ic =0.2x0.32

Top =501.91

HFL =501.41

Crest =500.66

NWL =500.56 NWL =500.45

HFL =500.49

Canal =500


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2 DISCHARGE MEASUREMENT

2.1 GENERAL Almost all potential hydropower project sites in Nepal are located in remote areas where there is a complete lack of hydrological information. For micro-hydropower projects in Nepal, MGSP guidelines requires at least one set of discharge measurement at the proposed intake site to be carried out in the dry season, between November and May. Regular (such as monthly measurements) measurements during dry seasons are recommended for mini and small hydropower projects. Bucket method for flow up to 10 l/s, weir method for a flow from 10 to 30 l/s and for flows larger than 30 l/s salt dilution method (conductivity meter method) are recommended by MGSP. This chapter deals with spreadsheet calculations based on the salt dilution method. Since the salt dilution method is quick (generally less than 10minutes per set of measurement), easier to accomplish and reliable, its accuracy level is relatively higher (less than 7%) than other methods. This is suitable for smaller fast flowing streams (up to 2000 l/s), easier for carrying the instrument in remote places. Consultants have been using mainly this method even though AEPC and other guidelines have proposed different methods for different flows at the river. In this method, the change of conductivity levels of the stream due to pouring of known quantity of predefined diluted salt (50-300gm per 100 l/s) are measured with a standardized conductivity meter (with known salt constant, k) at a regular interval (e.g., 5 seconds). For more information, please refer to MGSP Flow Verification Guidelines or Micro Hydro Design Manual (A Harvey) or other standard textbooks.

2.2 PROGRAM BRIEFING & EXAMPLES “Hydrology” spreadsheet presented in the Design Aids can handle up to four sets of data. The input parameters required for the discharge calculation are presented in Table 2.1. Discharge measurement carried out in a small river in Eastern Nepal with an average gradient of 10% is considered as an example. The typical input parameters considered in the example are presented in the adjacent column. The first set of field readings are presented in Table 2.2. Partial inputs of three sets of reading are presented in Table 2.3.

Table 2.1: Input parameters for Salt Dilution Method SN Input parameters Input for the cited (Example) 1 River Mai Khola 2 Conductivity Meter HANNA Instruments HI 933000 3 Date 12-Jan-04 4 Type of Salt Iyoo Nun 5 Conductivity Constant (µ Siemens) 1.8 at 15oC 6 Water temp 15oC 7 Time Intervals (dt) 5sec 8 Weights of salt for sets 1 to 4 (M in g) 400g, 1580g and 1795g 9 Readings (µ & µbaseline) for sets 1 to 4 Presented in Table 2.2

Table 2.2: First set conductivity reading for Salt Dilution Method (Example)

Time(sec) 5 10 15 20 25 30 35 40 45 50 55 60 Sum

25 26 27 28 29 30 31 32 32 33 34 34 361 34 35 35 35 35 34 34 34 33 33 33 32 407 32 32 32 31 31 31 31 31 31 30 30 30 372 30 29 29 29 29 29 29 28 28 28 28 28 344 28 28 27 27 27 27 27 26 26 26 26 26 321

Water Conductivity in

µS

26 26 26 26 26 26 26 25 25 25 257 Total (µS) = Σµ 2062 Total readings (nr) 70


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Table 2.3: Data Input (partial)

Time Reading 1 Reading 2 Reading 3 Reading 4 25 24 24

5 26 24 25

10 27 24 25

15 28 24 26

………………. ………………….. ……………….. ………………………

With these input parameters, discharge at the stream can be calculated by the following procedures:

Stream Flow, Q = M x k/A Where,

Q = flow in litre/sec M = mass of dry salt in mg (i.e.10-6 kg) k = salt constant in (µS)/(mg/litre) A = effective area under the graph of conductivity versus time, after excluding

the area due to base conductivity. The units for the area under the graph is sec x µS. The area is determined as follows: Area (A) = (Σµ– nr x µbaseline) * dt

Weighted averages of the individual flows thus calculated are computed. A typical spreadsheet is presented in Figure 2.1. The average estimated discharge will further be used by Medium Irrigation Project Method (MIP) to calculate long term average monthly flows. The calculation procedures for the first set of measurement (Set 1) are:

Area (A) = (Σµ– nr x µbaseline) * dt = (2062-70*25)*5 = 1560 sec x µS Discharge (Q) = M x k/A = 400000*1.8/1560 = 461.54 l/s = 461 l/s

2.3 CALCULATION AT SITE Calculation of measured flows and plotting of graphs of the corresponding data are always recommended at site for verification. This saves critical time of revisiting the intake site in case the measured discharge is not within acceptable limits. It is recommended to carry out a number of measurements until at least three consistent results (within 10%) are obtained. Procedural steps for checking flow with the help of a scientific calculator (Casio Fx 78 or equivalent) are presented in this section. This procedure uses inbuilt standard deviation functions.

INV MODE => starts standard deviation mode (STD)

INV SAC => standard deviation all memory clear

25x, 26x….=> input data (readings)

Σx-n* (xbase) = *(dt) = (Area) =>2062-70*25=*5=1560 => gives area (A)

INV MODE – exits STD MODE

1/x* (M)* (K)=Q => 1/x of 1560*400000*1.8=461.54 (Q in l/s)

Note Italic & Underlined letters are individual calculator keys


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Discharge Measurement by Conductivity MeterSmall Hydropower Promotion Project (SHPP)/GTZ Spreadsheet by Mr Pushpa ChitrakarReferances: 6,12,13,15,16 Date 24-May-2006SMALL HYDROPOWER PROMOTION PROJECT/GTZ Revision 2006.05Project Upper Jogmai, IlamDeveloper Kankaimai Hydropower P LtdConsultant EPC ConsultDesigned Pushpa ChitrakarCheckedMeter HANNA Instruments (HI 933000)Salt Iyoo Noon 11 deg CGiven k 1.8 5 sec

Salt Const. (k)Wt. of Salt 400 gm 1580 gm 1795 gmNr of data 70 91 106 1Baseline conductivity 25 24 24Sum of readings 2062 3433 3997Effective Area 1560 6245 7265Discharge 462 l/s 455 l/s 445 l/s

454 l/s

Discharge Measurement by Conductivity Meter: Upper Jogmai, IlamDate= 2006/5/24, 11deg C, HANNA Instruments (HI 933000), Iyoo Noon, k=1.8, Ave. Discharge = 453.89 l/sSalt =400gm, A eff =1560Salt =1580gm, A eff =6245Salt =1795gm, A eff =7265Salt =0gm, A eff =0

Water temp:Time intervals

1.8000

Average Discharge

Discharge Measurement by Conductivity Meter: Upper Jogmai, Ilam

0

10

20

30

40

50

60

70

80

0 50 100 150 200 250 300 350 400 450 500 550 600Time(sec)

Con

duct

ivity

µS

Salt =400gm, A eff =1560Salt =1580gm, A eff =6245Salt =1795gm, A eff =7265Salt =0gm, A eff =0

Date= 2006/5/24, 11deg C, HANNA Instruments (HI 933000), Iyoo Noon, k=1.8, Ave. Discharge = 453.89 l/s

Figure 2.1: Discharge calculations by salt dilution method


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3 HYDROLOGY

3.1 GENERAL Hydrology is the science that deals with space-time characteristics of the quantity and quality of the waters of the earth. It is the intricate relationship of water, earth and atmosphere. Tools developed for estimating hydrological parameters for un-gauged catchment areas are mainly based on regional correlations. The outputs of these tools are quite comparable to the actual hydrological parameters for rivers having bigger catchment areas (100km2 or more). Almost all potential micro and mini hydropower scheme sites in Nepal have relatively small catchment areas and are located in remote areas where there is a complete lack small of hydrological information. It is recommended that at least one set of actual measurement in dry season (November-May) for estimating reasonably reliable long term mean monthly flows. Long term mean monthly flows are estimated by the use of a regional regression methods called Medium Irrigation Project (MIP) method developed by M. Mac Donald in 1990. For hydropower schemes having a design discharge more than 100 l/s, flood hazards are generally critical and flood flows should be calculated. Long term mean monthly flows based on MIP method and flood flows based on ‘methodologies for estimating hydrologic characteristics of engaged locations in Nepal, WECS/DHM 1990 Study (Hydest)” are incorporated in “Hydrology” spreadsheet. Brief introduction of these two methods are presented in the subsequent sub-sections. It is worth noting that MIP and HYDEST are only applicable for Nepal.

Figure 3.1: Hydrology

3.2 HYDROLOGICAL DATA As presented in Figure 3.2, the hydrological data constitute of stream flow records, precipitation and climatological data, topographical maps, groundwater data, evaporation and transpiration data, soil maps and geologic maps. Large projects may need all the hydrological data. However, only the first three data are sufficient for the estimation of MIP monthly flows and Hydest floods in micro and mini hydropower projects.

Hydrological DataHydrological Data

Precipitation and Climatological DataPrecipitation and Climatological DataTopographic MapsTopographic MapsGroundwater DataGroundwater Data

Evaporation and Transpiration DataEvaporation and Transpiration DataSoil MapsSoil Maps

Geologic MapsGeologic Maps

Streamflow RecordsStreamflow RecordsMHP

Hydrological DataMHP

Hydrological Data

Figure 3.2: Hydrological Data and MHP

Hydrology

AtmosphereAtmosphere

EarthEarthWaterWater

Hydrology

AtmosphereAtmosphere

EarthEarthWaterWater


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3.3 MEDIUM IRRIGATION PROJECT (MIP) METHOD: MEAN MONTHLY FLOWS As stated earlier, this method is developed by M. Mac Donald in 1990. According to this method, Nepal is divided into 7 regions. Based on wading measurements by the Department of Hydrology and Meteorology, Government of Nepal, non-dimensional regional hydrographs were developed for each region. The month of April was used for non-dimensionalizing. Seven sets of average monthly coefficients for the seven regions for each month were prepared. The seven regions are graphically shown in Figure 3.3 and the corresponding seven sets of mean monthly coefficients are presented in Table 3.1. It is worth noting that these monthly coefficients have to be interpolated to get the actual monthly coefficients if the flow measurement is not on the 15th of the measured month.

Figure 3.3: MIP Regions Table 3.1: MIP regional monthly coefficients

Regions Month 1 2 3 4 5 6 7 January 2.40 2.24 2.71 2.59 2.42 2.03 3.30 February 1.80 1.70 1.88 1.88 1.82 1.62 2.20 March 1.30 1.33 1.38 1.38 1.36 1.27 1.40 April 1.00 1.00 1.00 1.00 1.00 1.00 1.00 May 2.60 1.21 1.88 2.19 0.91 2.57 3.50 June 6.00 7.27 3.13 3.75 2.73 6.08 6.00 July 14.50 18.18 13.54 6.89 11.21 24.32 14.00 August 25.00 27.27 25.00 27.27 13.94 33.78 35.00 September 16.50 20.91 20.83 20.91 10.00 27.03 24.00 October 8.00 9.09 10.42 6.89 6.52 6.08 12.00 November 4.10 3.94 5.00 5.00 4.55 3.38 7.50 December 3.10 3.03 3.75 3.44 3.33 2.57 5.00 Figure 3.4 represents a flow chart of the MIP model for calculating mean monthly flows based on a set of low flow measurement. As shown in the figure, this model takes low flow measurement, its date and MIP region number as inputs and processes them for estimating mean monthly flows for that point on the catchment area. As stated earlier, the actual measurement date plays an important role in computing more realistic mean monthly flows. This critical factor is often ignored by micro-hydropower Consultants resulting in highly unlikely flow estimation.


Page: 17

Figure 3.4: MIP model These mean monthly flows are calculated as:

Mean Coeff. for this month by interpolation if the date is not on 15th April coeff = 1/coeff this month (interpolated) April flow = April coeff * Q Monthly flows = April flow * coeffs (Qi = QApril * Ci)

Interpolation of April 1, 15 and 30 dataQ measured =54 l/s

0, 1.38

15, 1.19

30, 1

45, 1.44

60, 1.88

11.11.21.31.41.51.61.71.81.9

2

0 15 30 45 60March 15 April 1 April 15 April 30 May 15April 15 Q corr 45.38 54.00 37.50

Q corr for mid month = Q measured * Average Coeff/Actual Coeff

Figure 3.5: Need of interpolation for calculating mean monthly coefficient The importance of considering actual date of measurement and the need of calculating actual mean monthly flows are further explained in Figure 3.5. The measured flow is 54 l/s and the project lies in region 3. The corrected flows for April are 45.38 l/s, 54 l/s and 37.5l /s corresponding to the measurement dates as April 1, 15 and 30 respectively. This important factor is incorporated in the spreadsheet. The fact that the mean monthly coefficient calculation plays a major role in AEPC acceptance criteria is illustrated further by the following example.

Measured flow (m3/s): 1 MIP region (1 -7): 3 Area of basin below 3000m elevation A3000 (km2): 65 Turbine discharge (m3/s): 1.173 Water losses due to evaporation/flushing (%): 15%

Mean monthly flowsMean monthly flowsLow flow measurementLow flow measurement

MIP region numberMIP region numberMeasurement dateMeasurement date

OUTPUTOUTPUTINPUTINPUT

MIPMIP

Days If measured on

Q calculated


Page: 18

Figure 3.6 is the graphical representation of the outcome of the MIP method. Interpolated MIP flows corresponding to the measurement dates of April 1, 15 and 30 are presented. The design flow exceeds 11 months and fulfills AEPC criteria if it is measured on April 15th. However, the design flow exceeds only 10 months and does not meet AEPC criteria if it is measured on either 1st or 30th of April.

Figure 3.6: Effect of interpolation on mean monthly flows

3.4 WECS/DHM (HYDEST) METHOD: FLOOD FLOWS The WECS/DHM (Hydest) Method, which is also known as “Methodologies for estimating hydrologic characteristics of un-gauged locations in Nepal”, was developed by WECS/DHM in 1990. Long term flow records of DHM stations (33 for floods and 44 for low flows) were used to derive various hydrological parameters such as the monsoon wetness index (June-September precipitation in mm). The entire country is considered as a single homogenous region. This method generally estimates reliable results if the basin area is more than 100 km2 or if the project does not lie within Siwalik or Tarai regions. Annual, 20-year and 100-year floods based on Hydest method are presented in the spreadsheet. It is recommended to use instantaneous floods of 20-year return period while designing Nepali micro hydro intake structures. In case of mini and small hydropower projects, it is recommended that the headworks structures should be able to bypass 100-year instantaneous flood. The catchment area below 3000 m contour line is used for the estimation of floods of various return periods. 3000m elevation is believed to be the upper elevation that is influenced by the monsoon precipitation. This method has to be used with caution for catchments having significant areas above snowline. The 2-year and 100-year flood can be calculated using the following equations:

Q2 daily = 0.8154 x (A3000 +1) 0.9527 Q2 inst = 1.8767 x (A3000 +1)0.8783

Q100 daily =4.144 x (A3000 +1)0.8448

Q100 inst = 14.630 x (A3000 +1)0.7343

Errors G e ne rate d by using mid monthly flows

0

5

10

15

20

25

30

1 2 3 4 5 6 7 8 9 10 11 12

M O NTH

Dis

char

ge (m

3 /s)

1-A pr15-A pr30-A prQ diverted


Page: 19

Flood peak discharge, QF, for any other return periods can be calculated using:

Where, S is the standard normal variant for the chosen return period, from Table 3.2, and

Table 3.2: Standard normal variants for floods

Return period (T) (yrs) Standard normal variant (S) 2 0 5 0.842 10 1.282 20 1.645 50 2.054 100 2.326

As shown in Figure 3.7, the Hydest method requires different catchment areas and monsoon wetness index as inputs to estimate hydrological parameters such as the mean monthly flows, floods, low flows and flow duration curve.

Figure 3.7: Hydest Model

3.5 GENERAL RECOMMENDATIONS General recommendations on estimating hydrological parameters for hydropower projects in Nepal are summarised as:

1. Discharge measurement at the proposed intake site should be between November and May.

2. The recommended discharge measurement methods for different discharges are: Method Discharge (l/s)

Bucket collection <10

Weir 10-30

Salt dilution >30

3. Since MIP method utilizes actual measured flow data, mean monthly flows should be computed by using this method. Alternatively, HYDEST method may be used for catchment area equal to or more than 100 km2.

4. The design flow for AEPC subsidized micro hydropower projects should be available at least 11 months in a year (i.e., the probability of exceedance should be 11 months or more). The

( )lnQFSlnQeQ

2F

σ⋅+=

2.326Q

Qln2

100

lnQF

σ =

Total catchment area (MMF & FDC)Total catchment area (MMF & FDC)

Area below 5000m (LF)Area below 5000m (LF)Area below 3000m (FF)Area below 3000m (FF)

INPUTINPUT

HydestHydest

*Monsoon wetness index (MMF & FDC)*Monsoon wetness index (MMF & FDC)

*Mean monthly flows*Mean monthly flowsFlood flows (2-100 yrs)Flood flows (2-100 yrs)

Low flows(1,7,30 & monthly)Low flows(1,7,30 & monthly)

OUTPUTOUTPUT

Flow duration (0-100%)Flow duration (0-100%)

* Area =>100km2* Area =>100km2Monsoon wetness index=(Jun-Sept) mmMonsoon wetness index=(Jun-Sept) mm


Page: 20

design flow corresponding to the installed capacity (Qd) should not be more than 85% of the 11-month exceedance flow. Loses and environmental releases should also be considered if it exceeds 15% of the 11-month exceedance. There is a provision of ±10% tolerance on Qd at the time of commissioning a scheme.

5. The design flow for other projects should be based on the prudent practices of the stakeholders and project optimization. For example for a small hydropower project with an installed capacity of more than 1MW, the design flows should not exceed 65% probability of exceedance. For projects less than or equal to 1MW, the design flows are estimated by optimizing project installed capacities.

6. Construction of flood wall against annual flood is recommended if the design flow exceeds 100 l/s.

3.6 PROGRAM BRIEFING & EXAMPLES As per the standards and guidelines, the presented spreadsheet is designed to compute MIP mean monthly flows and exceedance of the design flow, Hydest floods and design discharges for different components of a hydropower scheme. For simplicity, the program considers 30 days a month for all the months. The flow chart for the proposed hydrological calculations is presented in Figure 3.8.

Start

Project name, location,river, Qd, % losses

IsA3000Given?

Q measured, date measured,

MIP region from the attached map

MIPQ monthly

EndA3000 Hydest

Flood flows

No

Yes

Q designed & MGSP

Q divertedQ losses

Q releaseQ available

Q exceedance

MonthlyHydrograph Q

Figure 3.8: Flow chart of Hydrology spreadsheet A typical example of the spreadsheet including inputs and outputs are presented in Figure 3.9. The considered project is 55kW Chhotya Khola Micro-Hydropower Project in Dhading. The information required for computations such as the MIP regions and the corresponding coefficients are presented in the spreadsheet. The project lies in MIP region 3. The measured discharge of 80 l/s on March 23 shows that the project is proposed to utilize a small stream. Although the floods are not critical to the project, they are calculated for sizing floodwall and other structures. The design discharge of 80 l/s has a probability of exceedance of 10 months only and hence does not qualify AEPC acceptance criteria. For AEPC to qualify this project, the turbine design discharge should not exceed 73.389 l/s. The detailed calculations are: MIP mean flows:

Corrected coefficient and mid month discharges (Kc December) for Region 3: Since the measured date of March 23 lies in between March 15th and April 15th, K March = 1.38 K April = 1.00 Kc March = K March+ (K April -K March)*(Date -15)/30 = 1.38 + (1.00-1.38)*(23-15)/30 = 1.2787 Q March = Q measured *K March /Kc April = 80 *1.38/1.2787 = 86.34 l/s


Page: 21

Q April = Q March /K March = 86.34/1.38 = 62.57 l/s Q May = Q April *K May = 62.57 * 1.88 = 117.62 l/s Other mean monthly discharges are calculated similar to the discharge calculation for the month of May. Hydest flood flows: The 2-year and 100-year floods are: Q2 daily = 0.8154 x (A3000 +1) 0.9527 = 0.8154 * (1.5+1) 0.9527 = 1.952 m3/s Q2 inst = 1.8767 x (A3000)0.8783 = 1.8767 x (1.5+1)0.8783 = 4.197 m3/s

Q100 daily =4.144 x (A3000 +1)0.8448 =4.144 x (1.5 +1)0.8448 = 8.987 m3/s

Q100 inst = 14.630 x (A3000 +1)0.7343 = 14.630 x (1.5+1)0.7343 = 28.669 m3/s Peak discharges for other return periods are calculated by using these formulas: Q20 daily = EXP(LN(1.952 )+ 1.645*(LN(8.987/1.952)/2.326)) = 5.747 m3/s

Q20 inst = EXP(LN(4.197 )+ 1.645*(LN(28.669/4.197)/2.326)) = 16.334 m3/s

Different discharge calculations (as per AEPC criteria): Qturbine = 85% of the 11 month flow exceedance from the MIP flow if the designed flow is

higher or the design flow. = 73.389 l/s (since the design flow is higher and has 10 months exceedance only) Qdiverted = Qturbine / (1-%losses) = 73.389 / (0.95) = 77.252 l/s Qlosses = Qdiverted -Qturbine = 77.252-73.389 = 3.863 l/s Qrelease = Qmin MIP *%release = 62.57 * 0.05 = 3.128 l/s Qrequired at river = Qdiverted + Qrelease = 77.252+3.128 = 80.380 l/s A hydrograph including the design flow, exceedance of the proposed design flow and the flow acceptable for AEPC is presented in Figure 3.9.

( )lnQFSlnQeQ

2F

σ⋅+=

2.326Q

Qln

2

100

=nQFlσ


Page: 22

Small Hydropower Promotion Project (SHPP)/GTZ Spreadsheet by Mr Pushpa ChitrakarReferances:2,2,4, 6,12,13,15,16 Date 24-May-2006SMALL HYDROPOWER PROMOTION PROJECT/GTZ Revision 2006.05Project: Chhyota Khola MHPDeveloper Kankai Hydropower P LtdConsultant EPC ConsultDesigned Pushpa ChitrakarChecked

INPUT River name : Chhyota Khola Location : Barand, Sertung VDC 2, Dhading Measured flow for MIP method l/s: 80 Month and day of flow measurement: March 23 MIP region (1 -7) : 3 Area of basin below 3000m elevation A3000 km2 : 1.5 Turbine discharge Qd l/s: 80 Water losses due to evaporation/flushing/seepage % of Qd : 5% Downstream water release due to environmental reasons % of Q lowest : 10%

OUTPUTMIP monthly average discharge Hydest Flood Flows Month @ river To plant Return Period (yrs)January 169.55 77.25 Daily InstantaneousFebruary 117.62 77.25 2 1.952 4.197March 86.34 77.25 20 5.747 16.334April 62.57 56.31 100 8.987 28.669May 117.62 77.25June 195.83 77.25 Discharges (l/s) Designed As per MGSPJuly 847.13 77.25 Qturbine (Qd) 80.000 73.389August 1564.13 77.25 Q diverted Qd+Qlosses 84.211 77.252September 1303.23 77.25 Q losses 5% of Qd 4.211 3.863October 651.93 77.25 Q release 10% of Qlow 6.257 6.257November 312.83 77.25 Q min required @ river 90.467 83.508

December 234.62 77.25 Q exceedence (month) 10 11Annual av 471.950 75.506 Q turbine for 11m 73.821

Flood Discharge (m3/s)

HYDROLOGICAL CALCULATIONS FOR UNGAUGED MHP RIVERS

Long Term Average Annual Hydrograph of Chhyota Khola river, Chhyota Khola MHP

0

200

400

600

800

1000

1200

1400

1600

1800

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Months

Dis

char

ge (l

/s)

MIP Flows

Q design =80 l/s with 10-month exceedence

Q as per MGSP =73.389 l/s with 11-month exceedence

Figure 3.9: Typical example of a hydrological parameters calculation spreadsheet “Hydrology”


Page: 23

4 HEADWORKS

4.1 INTRODUCTION AND DEFINITIONS

Headworks A headworks consists of all structural components required for safe withdrawal of desired water from a source river into a canal/conduit. Intake, weir, protection works, etc., are the main structural components. Indicators of an ideal headworks can be summarized as:

1. Withdrawal of desired flows (i.e., Qdiverted and spilling in case of flood).

2. Sediment bypass of diversion structure (Continued sediment transportation along the river).

3. Debris bypass (Continued debris bypass without any accumulation).

4. Hazard flood bypass with minimum detrimental effects.

5. Sediment control at intake by blocking/reducing sediment intake into the system.

6. Settling basin control (settling and flushing of finer sediments entered into the system through intakes or open canals).

Intake An intake can be defined as a structure that diverts water from river or other water course to a conveyance system downstream of the intake. Side intake and bottom intake are the common types of river intakes that are used in Nepali hydropower schemes. Conveyance Intake is an intake which supplies water to a conveyance other than the pressure conduit to the turbine. Power Intake is an intake which supplies water to the pressure conduit to the turbine. Side Intake A structure built along a river bank and in front of a canal / conduit end for diverting the required water safely is known as a side intake. Side intakes are simple, less expensive, easy to build and maintain. Bottom/Drop/Tyrolean/Trench Intake A structure built across and beneath a river for capturing water from the bed of a river and drops it directly in to a headrace is known as a bottom intake. They are mainly useful for areas having less sediment movement, steeper gradient, and surplus flow for continual flushing. Inaccessibility of trashrack throughout the monsoon season and exposure of the system to all the bed load even though only a small part of the water is drawn are the common drawbacks of drop intakes. Weir A weir is a structure built across a river to raise the river water and store it for diverting a required flow towards the intake. Protection Works Protection works are the river protection and river training works to safeguard the headworks against floods, debris and sediments. Trashrack A trashrack is a structure placed at an intake mouth to prevent floating logs and boulders entering into headrace. Coarse trashracks and fine trashracks are provided at the river intake and penstock intake respectively.


Page: 24

4.2 GENERAL RECOMMENDATIONS General recommendations and requirements for headworks components such as weirs, intakes and trashracks are briefly outlines in this section. 4.2.1 Weir

• Type: A weir can be either temporary or permanent in nature. A dry stone or gabion or mud stone masonry can be termed as a temporary weir whereas a cement masonry or concrete weir can be termed as a permanent weir.

• Location: It is recommended that the weir should be 5m to 20m d/s of side intake. This will assure that water is always available and there is no sediment deposition in front of the intake. A narrow river width with boulders is preferable for weir location.

• Height: The weir should be sufficiently high to create enough submergence and driving head.

• Stability: Permanent weir should be stable against sinking, overturning and sliding even during the designed floods.

4.2.2 Intake

• Type: Side intakes are suitable for all types of river categories whereas the drop intake is recommended for rivers having longitudinal slopes more than 10% with relatively less sediment and excess flushing discharge. The side intake is generally is of rectangular orifice type with a minimum submergence of 50mm. The side intake should be at:

o Straight river u/s & d/s of the intake.

o Alternatively, on the outer side of the bend to minimize sediment problems and maximise the assured supply of water.

o Relatively permanent river course.

o By the side of rock outcrops or large boulders for stability and strength.

• Capacity: According to the flushing requirement and tentative losses the intake has to be oversized to allocate an excess flow of 10% to 20% (or Qdiverted).

• A coarse trashrack should be provided to prevent big boulders and floating logs from entering into the headrace system.

• A gate/stop log should be provided to regulate flow (adjust/ close) during operation and maintenance.

• To optimize downstream canal and other structures, a spillway should be provided close to the intake.

4.2.3 Intake Trashrack

The recommended intake coarse trashrack is made of vertical mild steel strips of 5mm*40mm to 5mm*75mm with a clear spacing not exceeding 75mm. The approach velocity should be less than 1.0m/s. For transportation by porters in remote areas, the weight of a piece of trashrack should not exceed 60 kg. Placing of trashrack at 3V:1H is considered to be the optimum option considering the combined effect of racking and hydraulic purposes.

4.3 PROGRAM BRIEFINGS AND EXAMPLES There are two spreadsheets for designing intake structures, They are “sideIntake” and “BottomIntake” for designing side and bottom intakes respectively. The first part of the side intake calculates trashrack parameters while the second part of it calculates side intake parameters including spillways for load rejection and flood discharge off-take. The second spreadsheet calculates all the design parameters for a drop intake.


Page: 25

Since most of the program flow chart in this section is self explanatory, only critical points are explained. Figures 4.1 to 4.7 present the assumptions, flow charts and typical examples for calculating trashrack parameters, side intake and drop intake dimensioning.

Figure 4.1: Trashrack parameters

Start

Project name, location,river, Trashrack coefficient kt

Bar thickness t mmClear spacing of bars b mmApproach velocity Vo m/s

End

h friction = kt * (t/b)^(4/3) * (Vo^2/2/g) * sin φ

K = (hf + hb)/(Vo^2/2g)

h bend = Vo^2 /2/g * sin βhl= hf + hb

Angle of inclination from hor φ degHt of trashrack bot from river bed ht

Flow deviation β deg Design Discharge Qd cumec

K1=0.8K1 MHP = 0.55

A surface= 1/K1 * (t+b)/b * Q/Vo * 1/sin φh submerged = hr –ht, hr from intake cal

B = S/(h/sinφ)

Is cleaningmanual

K1=0.3

No

Yes

Figure 4.2: Flow chart for trashrack calculations The trashrack coefficients for different cross section of the bars are presented in the pull down menu. Typical bar thickness, clear spacing and approach velocity are suggested in the respective cell notes. According to the flow chart presented in Figure 4.2, the trashrack losses consist of frictional and bend losses. The frictional losses depend on the geometry of trashrack such as the trashrack coefficient, thickness and clear spacing of bars, inclination of the trashrack and the approach velocity. The bend loss depends on the hydraulics of the approaching flow such as the approach velocity and its deviated direction with respect to the normal of the trashrack surface.


Page: 26

The trashrack surface area coefficient K1 for automatic raking is 0.8 whereas it is 0.3 for manual raking suggesting that the raking area for manual operation to recommended surface area is 3.33 times more than the theoretical area. Manual racking is recommended for Nepali micro and mini hydropower. Since the consequence of temporary reduced trashrack area in micro and mini hydro is not severe and the trashrack sites are generally accessible to operators all the year, the average of automatic and manual racking coefficient of 0.55 (i.e., 80% more than the theoretical area) is recommended for practical and economic reason.

FloodFlood

ht

FloodFlood

ht

Figure 4.3: Side intake parameters Typical side intake parameters considered in the spreadsheet are presented in Figure 4.3. The procedures for designing a side intake parameters are presented in Figure 4.4. An example is presented in Figure 4.5. The calculation processes for designing a typical side intake are also presented in the following section. 4.2.4 Side Intake calculations

Trashrack Design: h friction = kt * (t/b) (4/3) * (Vo 2/2g)* sin φ = 2.4*(4/25) (4/3) * (0. 5 2/2/9.81)* sin 60o = 0.0023m h bend = (Vo 2/2g)* sin β = (0. 5 2/2/9.81)* sin 20o = 0.0044m h total = h friction + h bend = 0.00232 + 0.0044 = 0.0067m A surface S = 1/k1*(t+b)/b * Q/Vo * 1/ sin φ = 1/0.55*(4+25)/25*0.077*1/ sin 60o = 0.3763 m2 Width B = S/(h/ sin φ) = 0.3763/(.3/ sin 60o) = 1.09 m

Normal condition: Depth @ canal (hc) = h submergence + height of orifice + height of orifice sill from bottom of the canal

= 0.05+0.2+0.2 = 0.45m Driving head (dh) = (Vo/c)2/2/g = (1.2/0.8)2/2/9.81 = 0.115 m Head at river (hr) = hc+dh (this value can be provided) = 0.45+0.115 = 0.565 Height of weir (hw) = hr +0.1 = 0.565+0.1 = 0.665 m


Page: 27

Start Orifice

V coeff c, Vo, n,d/s submergence hsub,

H from canal bed h bot, height H

IsWc provided?

hc=hsub+H+hbotdh = (Vo/c)^2 / 2g

hr = hc + dhhw = hr+0.1

End

Canal & SpillwaySpillway above NWL

Cd spillway

Freeboard h fb1canal width d/s of orifice

RiverCrest length L

Qf flood

Wc=2*hc

Wc=Wc

No

Yes

1/S = 1/Q * n * P^2/3 /A^5/3 ^2A = Q/V, B = A /HFB = FB if provided

Or else Min(300, 0.5*hc))

Circular references (flood):dhf = hrf -hcf

Qo = A * C * (2*g*dhf)^0.5hcf = (Qo*n/2^(1/3)/SQRT(1/S))^(3/8)

Vof =c*SQRT(2*g*dhf)

ycf = (Qf^2/L^2/g)^(1/3)hrf = hw+yc

h overtop = 50% (FB - spillway crest height above NWL)

Ls100%=Qf/C/(2*h overtop)^1.5,Ls=max(Ls1 =Qf/C/h overtop^1.5,Ls2 =2*(Qf-Qd)/C/h overtop^1.5)Ls1=>obstruction d/s=> h ot const

Figure 4.4: Flow chart for side intake calculations

Orifice area (A) = Q/V = 0.77/1.2 = 0.064 m2

Orifice width (B) = A/H = 0.064/.2 = 0.322 m Flood: Critical depth at crest (yc) = (Qf2/L2/g)1/3 = (102/52/9.81)1/3 = 0.742 m Head at river (hf r) = hw+yc = 0.665+0.742 = 1.407 m Water depth at canal during flood is calculated by equating and iterating flow coming from orifice to that of canal flow. Since this iterative process is tedious and erroneous, most of the micro-hydropower consultants do not calculate it precisely. This iterative process is introduced in the presented spreadsheet. In case this cell generates VALUE# error, select the cell, press F2 and press Enter. The final canal depth is (hcf) = 0.490m Q intake (Qf) = 0.218 m3/s Spillway overtopping height (h overtop) = 50%(Free board –h nwl) = 0.5*(.3-.05) = 0.125 m Spillway length 100% (Ls for Qf) = Qf/C/(2*h ot)1.5 = 0.218/1.6/(2*0.125)1.5 = 1.525 m Spillway length 50% = Qf/C/(h ot)1.5 = 0.218/1.6/(0.125)1.5 = 3.078 m Care should be taken while designing spillway lengths. Ls for Gfm (d/s Obs & 100% hot -50) is only applicable when full downstream obstruction for flood off-take is provided with the help of stop logs or gates. Otherwise, the gradually varying water profile at the spillway has to be considered.


Page: 28

Spreadsheet developed by Mr. Pushpa Chitrakar, Engineering Advisor, SHPP/GTZReferances: 6,12,13,15,16 Date 24-May-2006SMALL HYDROPOWER PROMOTION PROJECT/GTZ Revision 2006.05Project Chhyota Khola MHPDeveloper Kankaimai Hydropower P LtdConsultant EPC ConsultDesigned Pushpa ChitrakarChecked

Trashrack calculationsInput Output

Trashrack coeffieient kt 2.4Bar thickness t mm 4.00 Headloss due to friction hf m 0.0023

Clear spacing of bars b mm 25.00 Headloss due to bends hb m 0.0044Approach velocity Vo m/s 0.50 Headloss coeff K 0.5226

Angle of inclination from horizontal φ deg 60.00 Total headloss ht m 0.0067Flow deviation β deg 20.00 Surface area A surface m2 0.3750

Design Discharge Qd cumec 0.077 Vertical height h m 0.3647Height of trashrack bottom from river bed ht 0.200 Trashrack width B m 0.8906

Canal invert level (m) 500.00

Orifice Calculations for (B = 2H or provided) rectangular canal downstream of orificeInputOrifice River

Velocity coeff of orifice c 0.8 Crest length L m 5.000Velocity through orifice Vo m/s 1.2 Provided Q flood m3/s 10.000

Manning's coeff of roughness 0.02 Q flood m3/s (Q20 for MHP with Qd>100) 16.334Downstream submergence depth hsub m 0.050 Used Q flood 10.000

Orifice height H m 0.200 Canal & SpillwayHeight of orifice from canal bed h bot m 0.200 Spillway crest height above NWL m 0.050Provided water depth in the river hr (m) Spillway discharge coeff 1.6

Provided canal width (m) 0.500 Provided Freeboard h fb1 m 0.300

OutputNormal Condition Flood

Canal witdth d/s of orifice 0.500 Critical depth of water at crest yc m 0.7421/Slope of canal immediately d/s of orifice 1865 Flood head at river hf r = hw+yc m 1.406

Depth of water in canal hc m 0.450 Head difference dhf 0.916Free board in canal h fb m 0.300 Velocity through orifice Vof m/s 3.392

Area of orifice A m2 0.064 Q intake Qf cumec 0.218Width of orifice B m 0.321 Depth of water at canal (hc f) m 0.490

Actual velocity through orifice Vo act m/s 1.200Canal width Wc m 0.500 Spillway

Water level difference dh m 0.115 Ls for Qf m (d/s Obs & 100% hot -50) 1.521Water depth in the river hr = hc + dh m 0.565 Length of spillway Ls1 for Qf m (d/s Obs) 3.078

Height of weir (hw = hr+0.1) m 0.665 Length of spillway Ls2 for Qf-Qd m 3.978Spillway overtopping height h overtop m 0.125 Designed spillway length Ls m 3.978

Design of Orifice Side Intake

1.6

2.4

0.02

0.8

Wall Geometry

Orific =0.2x0.32

Top =501.91

HFL =501.41

Crest =500.66

NWL =500.56 NWL =500.45

HFL =500.49

Canal =500

-hhrh

c

ch LSCanal

Weir Crest

sub

bot.

H

River bed

rfh

Normalriver level

.hr

13

1:30

Coarse TrashrackDesignFlood Level

Orifice (H*B)

h

h cf

Fb

Compacted earth/200mm stone soling

Gravel Flushing Gate

Gravel trap (if needed)

.

. ..

Min 100 thick & 1000 wide walkway Rcc slab

Figure 4.5: An example of side intake calculations


Page: 29

4.2.5 Drop Intake calculations The example presented in Figure 4.7 follows the procedures presented in Figure 4.6. This example is taken from a 4500kW Sarbari Small Hydropower Project, Kullu, India. Although the calculation procedures for the drop intake are relatively straightforward and simple, it has more restrictions and limitations regarding the stream geometry and operational conditions. Based on the flow conditions and the slope of rack, flow immediately upstream of the rack may be either critical or sub-critical. Critical depth at the entrance of the rack has to be considered if the rack is steeper (more than 15o). For more details, please refer to EWI UNIDO Standard. The main differences between considering critical flow and normal flow conditions are presented in the Table 4.1. In the presented spreadsheet, critical depth of upstream flow of the intake is calculated and presented if normal flow (sub-critical) is considered.

Start RiverRiver Width (Br)

Head of u/s water (ho)U/s water velocity (vo)

River gradient (i) degreeshof, vof

d = t + a, he = ho = vo^2/2gX = =0.00008*b^2 - 0.0097*b + 0.9992

c =0.6*a/d*(COSβ)^1.5

End

TrashrackAspect ratio (L across river/B along river)

Design Discharge (Q)Gradient (β) deg, Contraction coeff (µ)

Witdth/diameter (t), Clearance (a)

Yc Considered?

h =2/3*c*he Qo u/s = Br * ho * vo

Qof u/s = Br * hof * vof

h = ¾*YcQo u/s = v (9.81 * ho3 * Br2)

Qof u/s = v (9.81 * hof3 * Br2)

Yes

No

L =SQRT(3*Q/(2*c*m*L/B ratio*SQRT(2*9.81*h)))L' = 120% of L, b = L/B ratio * L”, A=L'*b

Qu u/s = Qo u/s – Qdesignh f = 2/3*χ*(ho + vo f^2/2g)

Q in f= 2/3*c*m*b*L'*SQRT(2*9.81*h f)Quf d/s = Qof u/s of intake -Q in f

Figure 4.6: Parameters and flow chart of drop intake design Table 4.1: Drop intake and upstream flow Parameters Normal flow Critical Depth considered Velocity head (h) = 2/3 * χ * he = ¾ * Yc Qo u/s of intake (m3/s) normal = Br * Ho * Vo = SQRT(9.81*ho 3*Br 2) Qo u/s of intake (m3/s) flood = Br * Ho f * Vo = SQRT(9.81*ho f 3*Br 2)

The calculations presented in Figure 4.7 are verified in the following section. In this example the flow upstream of the intake is considered to be of critical.

Normal condition: c/c distance of trashrack bars d (mm) = t + a = 60+30 = 90mm Kappa (χ) = 0.00008*β^2 - 0.0097*β + 0.9992 (by curve fitting) = 0.00008*36^2 - 0.0097*36 + 0.9992 = 0.749 Velocity head (h) m = ¾ * of Yc = ¾ * 0.226 = 0.170 m Correction factor (c) = 0.6*a/d*(COSβ)^1.5 = 0.6*30/90*(Cos 36)^1.5 = 0.146


Page: 30

Length of Intake (L) m = SQRT(3*Q/(2*c*µ*L/B ratio*SQRT(2*9.81*h))) = SQRT(3*2.7/(2*c*0.85*3.546468*SQRT(2*9.81*.170))) = 2.249 m Length (L’) m = L*COS(β) = 2.249*cos (36) = 1.819 m Intake length across the river (b) m = L/B ration * L = 3.546468*2.249 = 7.975m Area of intake (A) m2 = L * b = 2.249 * 7.975 = 17.935 m2 Qo u/s of intake (m3/s) = SQRT(9.81*ho 3*Br 2) = SQRT(9.81*.226 3*8 2) = 2.7 m3/s Qu d/s of intake (m3/s) = Qo u/s –Qd = 2.7-2.7 = 0 m3/s Intake length across the river (b) m = L/B ration * L = 3.546468*2.249 = 7.975m Flood: h flood (hf) m = 2/3*χ*(ho flood+vo flood^2/2g) = 2/3*0.749*(3+4^2/2/9.81) = 1.906 m Qo u/s of intake (m3/s) = SQRT(9.81*hof 3*Br 2) = SQRT(9.81*1.9063*20 2) = 325.497 m3/s Qo in (off-take) (m3/s) = 2/3*c*µ*b*L *SQRT(2*9.81*h flood) = 2/3*0.146*0.85*7.975*2.249*SQRT(2*9.81*1.906) = 7.318 m3/s (this discharge can be reduced by introducing a throttling pipe

d/s of the intake) Qu d/s of intake (m3/s) = Qo u/s –Qd = 315.497-7.318 = 318.178 m3/s


Page: 31

Spreadsheet developed by Mr. Pushpa Chitrakar, Engineering Advisor, SHPP/GTZReferances: 6,7,8,12,13 Date 24-May-2006SMALL HYDROPOWER PROMOTION PROJECT/GTZ Revision 2006.05Project Sarbari SHPDeveloper Kullu, Himanchal Pradesh, IndiaConsultantDesigned Pushpa ChitrakarChecked

Input 1River Width flood (Brf) m = 20

River Width (Br) m = 8 ho flood m = 3.000Head/Critical Depth of u/s water (ho)m = 0.226 vo flood m/s = 4

Upstream water velocity (vo) m/s = 1.494 Design Discharge (Qd), m3/s = 2.7River gradient (i) degrees = 9.462 Trashrack witdth/diameter (t) mm = 60

Trashrack gradient (β) deg = 36 Trashrack clearance (a) mm = 30Contraction coeff (µ) = 0.85 Invert level of crest (masl) 500

3.546468

Outputc/c distance of trash rack bars d mm = 90 Qo u/s of intake (m3/s) normal = 2.700

Total head (he) m = 0.340 Qu d/s of intake (m3/s) normal = 0.000kappa (χ) = 0.749 h d/s normal (m)

velocity head (h) m = 0.170 h flood u/s= 1.906Correction factor ( c) = 0.146 h d/s flood (m) 1.864

Length of intake (L) m = 2.249 Qof u/s of intake = Br * hof * vof (m3/s) = 325.497Length (L' ) m = 1.819 Q in flood m3/s = 7.318

Intake length across the river (b) m = 7.975 Quf d/s of intake (m3/s) = 318.178Area of intake (A=L' *b) m2 = 17.935

Aspect ratio (Length across the river/Breadth along the river) =

Design of Bottom/Drop Intake

Critical Depth Considered

Weir Geometry

Top =500

Top =498.68

HFL =501.91

NWL =500.23

Trashrack

Width =1.82

Figure 4.7: An example of drop intake


Page: 32

5 HEADRACE/TAILRACE

5.1 GENERAL A headrace or a tailrace can be defined as a conveyance system that conveys designed discharge from one point (e.g. intake) to another (e.g. forebay). Generally canal systems are used in all micro hydropower schemes whereas pipe systems are used for specific e.g. difficult terrain. A canal can be unlined (earthen) or lined (stone masonry or concrete). Rectangular and trapezoidal canal cross sections are mostly used profiles. Pipes used in MHP can be of HDPE or mild steel and it can be either open or buried. Mild steel and glass reinforced pipe (GRP) headrace-cum-penstock pipes are getting popularity in mini and small hydropower schemes in Nepal. Because of the easier sediment handling facility and better financial parameters, a layout with headrace-cum-penstock pipe has been adopted in many micro, mini and small hydropower projects in Nepal. For computing head losses, Manning’s equation is used for canal whereas Darcy-Weisbach equation is used for pipe.

5.2 GENERAL RECOMMENDATIONS General recommendations and requirements for designing canal and pipe headrace systems are outlined here. 5.2.1 Canal

a) Capacity: The canal should be able to carry the design flow with adequate freeboard and escapes to spill excess flow. A canal should generally be designed to carry 110 to 120 % of the design discharge.

b) Velocity: Self cleaning but non erosive (≥ 0.3m/s).

c) Unlined canal: In stable ground for Q ≤ 30 l/s

d) Lined canal: For higher discharge and unstable ground. Canals with 1:4 stone masonry or concrete are recommended. Care should be taken to minimize seepage loss and hence minimize the subsequent landslides.

e) Sufficient spillways and escapes as required.

f) Freeboard: Minimum of 300mm or half of water depth.

g) Stability and Safety against rock fall, landslide & storm runoff. A catch drain running along the conveyance canal is recommended for mini and small hydropower projects.

h) Optimum Canal Geometry: Rectangular or trapezoidal section for lined canal and trapezoidal section for unlined canal are recommended. Unequal settlement of lined trapezoidal canal should be prevented.

5.2.2 Pipe

a) PVC/HDPE/GRP: Buried at least 1m into ground.

b) Steel/Cast Iron: As pipe bridge at short crossings/landslides. They are also used for low pressure headrace and headrace-cum-penstock alignments.

c) Pipe inlet with trashracks for a pipe length of more than 50m.

d) Minimum submergence depth of 1.5*v2/2g at upstream end.

e) Provision of air valves and wash outs where necessary.


Page: 33

5.3 PROGRAM BRIEFING AND EXAMPLES 5.3.1 Canal

a) Permissible erosion free velocities for different soil conditions: Fine sand =0.3-0.4 Sandy loam =0.4-0.6 Clayey loam =0.6-0.8 Clay =0.8-2.0 Stone masonry =0.8-2.0 Concrete = 1.0-3.0

b) Sectional profiles considered in the program are:

1) Semicircular (not popular because of the construction difficulty) 2) Rectangular 3) Triangular (not popular because it is not financially attractive) 4) Trapezoidal

c) Two parts of calculations for canals are provided for:

1) Evaluation of the design parameters based on user specified inputs. 2) Optimum canal parameters based on MHP Sourcebook by Allen R Iversin.

d) Two spreadsheets are included in the Design Aids for:

1) Canal calculations: Calculations procedures are presented in Figure 5.1 with the help of a flow chart and a typical spreadsheet with an illustration is presented in Figure 5.2.

2) Pipe calculations: Pipe calculation flow chart is presented in Figure 5.4. The calculation procedures are further illustrated in Figure 5.5.

5.3.2 Canal Calculations for a rectangular stone masonry headrace canal for 185 l/s flow presented in Figure 5.2 (Intake Canal in second column) are briefly described in the following section. This example is taken from a 750kW Sisne Small Hydropower Project, Palpa, Nepal.

Present Canal: Area A m2 = D*B = 0.3*0.5 = 0.15 m2 Top Width T (m) = B+2*H*N = 0.5+2*0.3*0 = 0.5m Wetted Perimeter (m) = 2*D+B = 2*0.3+.5 = 1.1m Hydraulic Radius r (m) = A/P = 0.15/1.1 = 0.136 m Calculated flow (m3/s) = A*r2/3*S0.5/n = 0.15*0.1362/3*0.012990.5/n = 0.226 m3/s Critical Velocity Vc m/s = sqrt(A*g/T) = sqrt(0.15*9.81/.5) = 1.72 m/s Velocity V m/s = Q/A = 0.185/0.15 = 1.233 m (Okay since it is less than 80% of Vc) Headloss hl (m) = S*L + di (drops) = 0.01299*20+0 = 0.260m Critical dia of sediment d crit (mm) = 11000*r*S = 11000*0.136*0.01299 = 19.48mm (i.e., the canal can transport sediments of diameter 19.48mm

or less during its normal operation) Optimum Canal: Area A m2 = Q/v desired = 0.185/1 = 0.185 m2 Hydraulic Radius ro (m) = 0.35*SQRT(A) = 0.35*SQRT(0.185) = 0.1505 m


Page: 34

Depth Do (m) = 2*ro = 2*0.1505 = 0.301m Top Width Bo (m) = 4*ro = 4*0.1505 = 0.602m Critical Velocity Vc m/s = sqrt(A*g/T) = sqrt(0.185*9.81/.602) = 1.74 m/s (Okay since the desired

velocity of 1m/s is less than 80% of Vc)

Headloss hl (m) = S*L + di (drops) = 0.0050*20+0 = 0.100m Critical dia of sediment d crit (mm) = 11000*r*S = 11000*0.136*0.0050 = 8.271mm (i.e., the canal

can tranport (self clean) sediments of diameter 8.271mm or less during its normal operation)

Ho = Do + FBo

ro for optimum canalSemicircular = 0.4*SQRT(A)

Trapezoidal=0.5*SQRT(Sin(N)*A/(2-COS(N))Rectangular/Traingular = 0.35*SQRT(A)))

Ao = Qd/Vo,T=B+2*D*N (trapezoidal) or =B

Vcrit = sqrt(9.81*Ao/T) V desired=80% of Vcrit,

Depth Do for optimum canalSemicircular = 4*roTraingular = 2.8*ro

Rectangular/Trapezoidal = 2*ro

Channel width BoSemicircular = 2*DoRectangular = 4*roTraingular = 5.7*ro

Trapezoidal = 4*ro/Sin(N)

hl =S*L+diHl =hl previous + hld crit =11000*r*S

End

Start

Project name, Reach name,Design discharge (Qd)

Roughness coefficient (n)Side slope (N)

Sectional profile

Canal length (L)1/canal slope (1/S)

Canal depth/diameter (D)Freeboard (FB)Canal width (B)

Desired velocity (Vo)Canal drop di (V) & hi(H)

Flow area (A) semicircular = PI()* D^2/4/2

Trapezoidal = (B+N*D)*DRectangular = D*BTriangular = D*B/2

Wetted perimeter (P)Semicircular = PI()* D/2

Trapezoidal = B+2*D*sqrt(1+N^2)Rectangular =2* D+B

Triangular = 2*D*sqrt(1+N^2)

r = A/P, Qc = A*r^(2/3)*S^0.5/nFB=min(0.3,0.5*D) V = Q/A, hl =S*L+di

hl =hl previous + hl (continuous)d crit =11000*r*S

Figure 5.1: Flow chart for canal design


Page: 35

Canal Design: Proposed design and optimum canal sectionsSmall Hydropower Promotion Project (SHPP)/GTZ Spreadsheet by Mr Pushpa Chitrakar

Referances: 6,12,13,15,16 Date 24-May-2006SMALL HYDROPOWER PROMOTION PROJECT/GTZ Revision 2006.05Project Sisne Small Hydropower ProjectDeveloper Gautam Buddha Hydropower P LtdConsultant EPC ConsultDesigned Pushpa ChitrakarCheckedInputType and Name Intake Canal Tailrace Main2 Main3Flow (m3/s) 0.185 0.145 0.145 0.145Roughness coefficient (n) 0.02 0.017 0.02 0.02Sectional Profile Rectangular Trapezoidal Semicircular TriangularSide slope N (1V:NHorizontal) 0 0.5 0 0.5Length of the canal (m) 20 40 150 1201/Canal slope (s) 77 200 30 72Channel Depth/diameter D (m) 0.300 0.525 0.300 0.300Freeboard FB (m) 0.300 0.250 0.150 0.150Channel Width (B) m 0.500 1.000 0.400 0.400Channel Drops di mChannel Drops Horizontal length hi mDesired velocity Vo (m/s) 1.000 1.500 1.500 1.500

OutputSide slope d (degrees) 63.435 63.435Canal slope S 0.01299 0.00500 0.03333 0.01389Total depth H (m) 0.600 0.775 0.450 0.450Chainage L (m) 20.000 60.000 210.000 330.000

Present canalArea A m2 0.150 0.663 0.035 0.060Top Width T (m) 0.500 1.525 0.400 0.400Wetted Perimeter P (m) 1.100 2.174 0.471 0.671Hydraulic Radius r (m) 0.136 0.305 0.075 0.089Calculated flow (m3/s) & remarks 0.226 high 1.249 high 0.057 low 0.071 lowComment on freeboard ok low ok okVelocity V m/s 1.233 0.219 4.103 2.417Critical Velocity Vc m/s & Remarks 1.72 Ok 2.06 Ok 0.93 Not Ok 1.21 Not OkHeadloss hl (m) 0.260 0.200 5.000 1.667Total headloss Hl(m) 0.260 0.460 5.460 7.126Critical dia of sediment d crit (mm) 19.481 16.769 27.500 13.665

Optimum canalArea Ao m2 0.1850 0.0967 0.0967 0.0967Top Width T (m) 0.6022 0.7636 0.9949 0.4867Critical Velocity Vc m/s & Remarks 1.74 Ok 1.11 Not Ok 0.98 Not Ok 1.4 Not OkHydraulic Radius ro (m) 0.1505 0.1180 0.1244 0.1088Channel Depth/diameter Do (m) 0.301 0.236 0.497 0.218Freeboard Fbo (m) 0.150 0.263 0.150 0.150Total depth Ho (m) 0.451 0.498 0.647 0.368Channel Width Bo (m) 0.602 0.528 0.995 0.487Canal Slope 0.0050 0.0112 0.0145 0.0173Headloss hlo (m) 0.100 0.449 2.175 2.079Total headloss Hlo(m) 0.100 0.549 2.724 4.803Critical dia of sediment d crito (mm) 8.271 14.584 19.834 20.736

0.500.50

0.02 0.017 0.02 0.02

Figure 5.2: An example of canal design.


Page: 36

B = 0.5 & 0.602

D = 0.6 & 0.451d & FB (0.3 & 0.3) & (0.301 & 0.15)

B = 1 & 0.764

D = 0.775 & 0.498

d & FB (0.525 & 0.25) & (0.236 &

0.263)

B = 0.4 & 0.995

D = 0.45 & 0.647

d & FB (0.3 & 0.15) & (0.497 & 0.15)

B = 0.4 & 0.487

D = 0.45 & 0.368

Figure 5.3: Illustrated canal type and their dimensions. 5.3.3 Pipe Calculations for a headrace pipe presented in Figure 5.5 are briefly described in the following section. The trashrack calculations are similar to the trashrack calculations presented earlier in the intake design, hence it is not presented in this section. Trashrack loss of 0.02m is taken in this example. In this example, one 140m long HDPE pipe with 260mm internal diameter is considered for a design flow of 160 l/s each.

Sizing of headrace pipe Headloss HDPE pipe roughness, k =0.06 mm From Moody chart (Appendix), f=0.0153. Based on an iterative method presented in Layman’s Guidebook on How to Develop a Small Hydro Site, European Small Hydropower Association (ESHA), the presented spreadsheet calculates this friction factor and greatly speeds up the pipe selection decision for consultants by iterating following equations: Friction loss Turbulent losses considering, K entrance for inward projecting pipe= 0.8, Kexit=1.0 and Kbends based on the bending angles (see Table in the Appendix) Total head loss= 3.82 m + 0.02+1.10 m = 4.94 m

000231.0260

06.0==

mmmm

dk

73846.0260.0

160.02.12.1==

xdQ

( )

mx

gVKKKKKh exitothersvalvebendsentranceossesturbulentl

10.181.92

01.3*)10057.08.0(

22

2

=++++=

++++=∴

52

2

**0826.02 d

lfQg

Vdlf ==

mh losswall 82.326.0

140*0153.0*160.0*0826.0 52 ==


Page: 37

Water level difference between intake and storage reservoir is 7m and 95% of this head is allowed for total headloss. Only 70.56% is estimated as the total headloss. Although the exiting water has some residual head, it is recommended to provide some marginal residual head for safety. The HDPE pipe does not need expansion joints and therefore not calculated.

Start

Pipe #, Material, FabricationIf steel, Laying, Valve,

t, L, θ(upto 10)

Trashrackhl, Surface Area,

Width, h submerge

End

HydraulicsQd, Hg, RL us,%hl, Entrance,

Exit, R/d

ProjectName,

Location,Life

Hydraulicshl(friction, turbulent)

Other criteria checking

TrashrackBar type,t,b, Vo,Φ, β,H

Exp JointTmax, Tinst,Tmin, Group

L (5)

Exp JointDimensions, Positionduring installation

Figure 5.4: Flow chart for pipe design


Page: 38

HEADRACE PIPE CALCULATIONSSmall Hydropower Promotion Project (SHPP)/GTZ Spreadsheet by Mr Pushpa ChitrakarReferances: 2,4, 6,12,13,15,16 Date 24-May-2006SMALL HYDROPOWER PROMOTION PROJECT/GTZ Revision 2006.05Project: MHP in Jumla Location: JogmaiDeveloperConsultantDesigned Pushpa ChitrakarChecked

INPUT

Economic life (years) 15

Hydraulics:Diversion flow Qd (m3/s) 0.160 U/S Invert Level (m) 1950.00Flow in each pipe Qi (m3/s) 0.160 % head available or headloss hlt (m) 95.00%Gross headHg (m) 7.000 Entrance Type 0.8

Bending radius (r/d) 0.3

Headrace pipePipe Material HDPE Exit (Yes/No) Yes

Welded / Flat rolled if steel NA No of pipes 1.00

Rolled if steel NA Bending angle 01 20.00Type if steel NA Bending angle 02 4.00Burried or exposed Burried Bending angle 03 6.00Type of valve Bending angle 04 20.00Non standard ultimate tensile strength (UTS) N/mm2 Bending angle 05Estimated pipe diameter d(mm) 282 Bending angle 06Provided pipe diameter d(mm) 260 Bending angle 07Min pipe thickness t (mm) NA Bending angle 08

Provided pipe thickness t (mm) 3.0 Bending angle 09Pipe Length L (m) 140.000 Bending angle 10

Trashrackk t b Vo φ β Q H

2.40 6.00 20.00 1.00 60.00 0.160 3.00

Expansion JointsTmax (deg) T installation Tmin 1st Pipe length(m) 2nd Pipe L (m) 3rd Pipe L (m) 4th Pipe L (m) 5th Pipe L (m)

40 20 4 50.00 100.00 150.00 200.00 250.00

OUTPUTTrashrack

hf hb H coeff H S B Min Submergence CGL=1.5v 2/2g

0.0213 0.4174 0.0213 0.8006 0.23 1.39 0.69

Turbulent loss coefficientsK inlet 0.80 K bend 05 K bend 10K bend 01 0.16 K bend 06 K valveK bend 02 0.13 K bend 07 K exit 1.00K bend 03 0.13 K bend 08 K othersK bend 04 0.16 K bend 09 K Total 2.37

HydraulicsPipe Area A (m2) 0.053 U/S Invert Level (mAOD) 1950.000Hydraulic Radius R (m) 0.07 D/S Invert Level (mAOD) 1943.000Velocity V (m/s) 3.01 Is HL tot < HL available OKAYPipe Roughness ks (mm) 0.06 Friction Losses hf (m) 3.82Relative Roughness ks/d 0.00023 Fitting Losses hfit (m) 1.10Reynolds Number Re = d V /Vk 687032 Trashracks and intake loss (m) 0.02Type of Flow Turbulent Total Head Loss htot individual (m) 4.94Friction Factor f 0.0153 % of H.Loss of individual pipe 70.56% OkExpansion Joints (mm)EJ number 1 2 2 4 5dL theoreticaldL recommendeddL for expansiondL for contraction

Inward project5

Flat

Figure 5.5: An example of headrace pipe design


Page: 39

6 SETTLING BASINS

6.1 SEDIMENT SETTLING BASINS A settling basin traps sediment (gravel/sand/silt) from water and settles down in the basin for periodical flushing back to natural rivers. Since sediment is detrimental to civil and mechanical structures and elements, the specific size of specified percentage sediment has to be trapped, settled, stored and flushed. This can only be achieved by reducing turbulence of the sediment carrying water. The turbulence can be reduced by constructing settling basins along the conveyance system. Since the settling basins are straight and have bigger flow areas, the transit velocity and turbulence are significantly reduced allowing the desired sediments to settle. The sediment thus settled has to be properly flushed back to the natural rivers. Thus a settling basin:

1. Prevents blocking of headrace system assuring desired capacity of the system.

2. Prevents severe wearing of turbine runner and other parts.

3. Reduces the failure rate and O&M costs. According to the location and function, a settling basin can be of following types:

1. Gravel Traps for settling particles of 2mm or bigger diameter.

2. Settling Basins for settling particles of 0.2mm or bigger diameter.

3. Forebays for settling similar to settling basin (optional) and smooth flow transition from open flow to closed flow.

Micro hydro settling basins are generally made of stone masonry or concrete with spillways, flushing gates, trashracks, other accessories as and when necessary. Most of the mini and small hydropower settling basins are of concrete (M20 or higher). However, for functionality, all settling basins should have following components:

1. Inlet Zone: An inlet zone upstream of the main settling zone is provided for gradual expansion of cross section from turbulent flow to smooth/laminar flow..

2. Settling Zone: A settling zone is the main part of a settling basin for settling, deposition, spilling flushing and trash removal.

3. Outlet Zone: An outlet zone facilitates gradual contraction of flow to normal condition. A typical section of a settling basin with all the components (inlet, transition, settling and outlet zones) and accessories (spillway, gate) is presented in Figure 6.1.

Figure 6.1: Typical section of a settling basin


Page: 40

6.2 SETTLING BASIN THEORY An ideal settling basin is a basin having a flow flowing in a straight line (no turbulence, no eddy current). In practice, no single basin is ideal. For an ideal basin shown in figure 6.2:

H/W = L/V Or, B *H /W = B*L/V Or, Ax/W = As/V Or, Q/W = As = Surface area (i.e., the surface area is directly proportional to the discharge and inversely proportional to the settling velocity/sediment diameter/temperature).

Figure 6.2: An ideal setting basin Efficiency of a real basin is generally 50 % or less than that of an ideal basin. This is mainly because of the following factors:

1. Presence of water turbulence in basin.

2. Imperfect flow distribution at entrance.

3. Flow convergence towards exit.

Vetter’s equation takes care of the factors stated above and hence recommended for use in settling basin design. According to Vetter’s equation, trap efficiency (η) for a given discharge (Q), surface area (As) and falling velocity of critical sediment diameter (w) is:

6.3 GENERAL RECOMMENDATIONS 6.3.1 Gravel Trap General recommendations and requirements for designing a gravel trap are outlined in the following sections:

1. Location: Close to intake and safe.

2. Dimensions: Sufficient to settle and flush gravel passing through upstream coarse trashrack.

3. Spilling: Sufficient spillway/vertical flushing pipe.

4. Spilling and flushing: back to the river.

5. Material: 1:4 cement stone masonry with 12mm thick 1:2 cement plastering on the waterside or structural concrete.

6. Recommended settling diameter and trap efficiency are 2mm and 90% respectively.


Page: 41

7. Sediment storage zone: Adequate storage for 12 hours minimum (flushing interval).

8. Drawdown: Drawdown discharge capacity should be at least 150% of the design discharge.

9. Aspect ratio (straight length to width ratio): 1.5 to 2 for micro-hydropower gravel trap. The recommended aspect ratio of mini and small hydropower gravel trap is 4.

6.3.2 Settling Basin General recommendations for designing a settling basin are outlined below:

1. Location: Close to gravel trap/Intake.

2. Dimensions: Sufficient to settle and flush the designed sediment size.

3. Spilling: Sufficient spillway/vertical flushing pipe (layout dependent).

4. Spilling and flushing: back to the river.

5. Material: 1:4 cement stone masonry with 12mm thick 1:2 plastering on the waterside or structural concrete.

6. Recommended settling diameter (trap efficiency) and head are presented in Table 6.1

Table 6.1: Settling diameter, trap efficiency and gross head Gross Head (m) Settling diameter (mm) Trap efficiency (%)

Micro Hydro Mini/Small Hydro

0.3-0.5 90% 10m 10m

0.3 90% 10 to 100m 10 to 50m

0.2 90% More than 100m 50 to 100m

0.2 95% More than 100m

7. Sediment storage zone: Adequate storage for 12 hours (flushing interval)

8. Drawdown: Drawdown discharge capacity should be at least 150% of the design discharge.

9. Aspect ratio (straight length to width ratio): 4 to 10. 6.3.3 Forebay Following criteria have been outlined for designing a forebay:

1. Dimensions and functions: Similar to settling basin if upstream system is of open type or the forebay functions as a combined settling basin cum forebay.

2. Submergence: Sufficient to prevent vortex (i.e. 1.5 * v2/2g).

3. Active Storage: At least 15 sec * Qd. Active storage capacity should be based on closing time of turbines.

4. Freeboard: 300mm or half the water depth whichever is less.

5. Drawdown: A drain pipe/Gate.

6. Spilling capacity: Minimum of spilling Qd during load rejection.

7. Fine Trashrack:

a. At the entrance of the penstock

b. Inclination: 3V:1H

c. Bars: Placed along vertical direction for ease of racking.


Page: 42

d. Clearance: 0.5 * nozzle diameter in case of Pelton or half the distance between runner blade in case of Crossflow/Francis.

e. Velocity: 0.6 to 1 m/s

f. Weight: =< 60kg (porter load) for transportation by porters.

6.4 PROGRAM BRIEFING AND EXAMPLES 6.4.1 Features of the spreadsheet The spreadsheet is designed to cater for all types of settling basins and with all possible spilling and flushing mechanisms. Some of the main features are listed below:

1. A single spreadsheet for:

a. Gravel Trap

b. Settling Basin (Desilting)

c. Forebay-cum-Settling Basin

2. Settling of sediment using:

a. Ideal settling equation

b. Vetter’s equation

3. Flushing of deposited sediment during:

a. Normal operational

b. Drawn-down condition

4. Sediment flushing with:

a. Vertical flushing pipe

b. Gate

c. Combination of both

5. Spilling of excess flow due to:

a. Incoming flood

b. Load rejection

6. Spilling of excess flow with

a. Spillway

b. Vertical flushing pipe

c. Combination of both

7. Drawdown / Dewatering with:

a. Vertical flushing pipe

b. Gate

8. Rating curve for the gate: According to Norwegian Rules and Regulations of Dam Construction, a gate rating curve for the designed parameters is computed. According to this manual, the flow through gate is of free flow type until the gate opening is two third of the water depth behind the gate. Beyond this level (i.e., the gate opening higher than 2/3 of the water depth behind the gate), the flow through gate is a pressure flow.

9. Multiple basins

10. Combination of approach canal / pipe options


Page: 43

6.4.2 Vertical flushing pipe Vertical flushing pipes (used in micro hydropower projects) are used for spilling of excess water and flushing of the basin. The diameter of vertical flushing pipe is estimated based on the critical parameter of these two functions.

1. Overflow: Acts as a sharp crested weir. Discharge through the flushing pipe having a diameter d1 is: Qf =π*d1*Cw*hf 2/3 for Cw = 1.6 d1 = Qf/(1.6*π*hf2/3)

2. Drawdown / Dewatering through the vertical flushing pipe:

1.5*Qd =C*A*(hb+fflush) 0.5: A=π*d212/4: C=2.76 for L=<6m d21=(6*Qd/( π *C *( hb+fflush)0.5 )0.5 @ full d22=(4*Qd/( π *C *( fflush)0.5 )0.5 @ empty

3. Design diameter: Maximum of above (d1, d21,d22)

Figure 6.3: Flushing pipe details 6.4.3 Spillway at intake Length of a spillway is the function of spilling discharge, freeboard and downstream obstruction. In case there is not downstream obstruction such as a gate the cross section area of flow is of a triangular shape. For a downstream obstructed condition, the flow is rectangular in section across the spillway. According the conditions, the spillway length is calculated as:

hovertop = 50% of (FB – spillway crest height above NWL) Ls1 =Qf/C/hovertop

1.5: for downstream obstruction and constant h overtop. Ls2 =2*Abs(Qf-Qd)/C/ hovertop

1.5) for no downstream obstruction and average h overtop. Ls3=Qf/C/(2* hovertop -0.05)1.5: for downstream obstruction and constant h overtop (100%-0.05).

6.4.4 Gate

Lifting force F(kg)=W buoyant + 1000*m*Asub*hcg


Page: 44

Gate opening dh=h1-h2 dh<2/3*h1 :=> Pressure flow (as a gate): Q=C*L*(H11.5-H21.5) dh=>2/3*h1 :=> Open flow (as a spillway ): Q=C*L*H11.5 Enter the maximum gate opening in the lowest gate opening cell and press the Calculate Gate Rating Curve button for computing rating curve.

An example of a settling basin design is presented in figure 6.6. The procedures for designing the settling basin are briefly described in the following section.

Sizing of settling basin

1. Settling of sediment using: a. Vetter’s equation Surface area of basin = -(Qtotal)/w*LN(1-neff) Asi = -(0.455)/.035* LN(1-neff) = 25 m2

Max section width for hydraulic flushing = 4.83*Q^0.5 = 4.83*.455^0.5 = 3.258m Provided Width B = 2.5m Length of basin L = Asi/B = 25/2.5 = 10m, which is 4 times the width hence, satisfies the requirement.

Basin transit velocity vt = 0.44* sqrt(d) = 0.44*sqrt(0.2) = 0.241m/s Water depth Hi = Qi/B/vt = 0.455/2.5/0.241 = 0.755m Sediment storage volume assuming 100% trap efficiency (conservative side) V = (Qtotal)*(Flushing intensity in sec)*Concentration max in kg/Bulk Sed.

Density in kg/m3/Sed Swelling factor = (Qtotal)*(FI*3600)*Cmax/G*S = 0.455*(8*3600)*2/2.6*1.5 = 15.12m3

Sediment depth Hs = V/Asi = 15.12/25 = 0.6m b. Ideal settling equation Length of an Ideal Basin= Maximum of (4xB and Q/B/w) = MAX(4*2.5, 0.455/2.5/0.035) = MAX(10, 5.2) = 10 m 2. Spilling of excess flow due to load rejection: A combination of a 0.3m diameter vertical pipe

and spillway of 1.0m length is used. H overtopping = h ot =(Q1/(1.9*PI()*n1*d1+Cd*Ls))^(2/3) = (0.455/(1.9*pi()*1*.3+1.6*1))^(2/3) = 0.262 m Q pipe = 1.9*PI()*n1*d1*h ot ^1.5 = 1.9*pi()*1*.3*0.262^1.5 = 0.240 m3/s Q spillway = Cd*Ls*h ot ^1.5 = 1.6*1*0.262^1.5 = 0.215 m3/s 3. Flushing of deposited sediment through the flushing pipe: The pipe diameter will be the biggest

of : a. For incoming flow and draw down: D1 = (Qflushing%*4*Qi/(PI()*Cd*SQRT(h NWL+h flush)))^0.5


Page: 45

= (100%*4*0.455/(pi()**2.76*SQRT(1.36+1.7)))^0.5 = 0.35m b. For incoming flow only: D2 =(4*Qi/(PI()*Cd*SQRT(hflush)))^0.5 = (4*0.455/(pi()**2.76*SQRT(1.7)))^0.5 = 0.4m

Settling Basin DesignSmall Hydropower Promotion Project (SHPP)/GTZ Spreadsheet by Mr Pushpa ChitrakarReferances: 2,4, 6,9,12,13,15,16 Date 24-May-2006

SMALL HYDROPOWER PROMOTION PROJECT/GTZ Revision 2006.05Project: Upper Jogmai SHP Location: JogmaiDeveloper Kankaimai Hydropower P LtdConsultant EPC ConsultDesigned Pushpa ChitrakarChecked Pushpa Chitrakar

Q flood Sediment swelling factor S = 1.50Manning's number M (m1/3/s) 1/n= 50.000 Volume of sediment storage V (m3) = 15.12Design discharge Qdesign (m3/s) = 0.421 Sediment depth Hs (m) = V/Asi 0.63Flushing discharge Qf lush (m3/s) = 0.034 Inlet approach conveyance Canal/Pipe = Canal

Total discharge Qbasins (m3/s) = 0.455 1/Bottom slope of SB Sf (1:50 to 1:20) = 50.00Particles to settle d (mm) = 0.300 Outlet approach conveyance Canal/Pipe = PipeTrapping efficiency n (%) = 85% Water level at inlet NWL (m) = 1950.00water temperature t (oC) = 15 h flush below the base slab (L<6m) 1.70

Fall velocity w at 15 deg C (m/s) = 0.037 Number of basins N 1.00Sediment concentration Cmax (kg/m3) = 2 Spillway crest height above NWL m 0.05

Flushing Frequency FI (hours) = 8 Spillway discharge coeff 1.60Surface area / basin Asi (m2) 85 % = 24.000 Provided Freeboard h fb1 m 0.30

Basin transit velocity Vt (m/s) = 0.241 Discharge coeff for pipe as orifice (2.76 if L <6 m) 2.76Bulk Sed density G (kg/m3) = 2600 Drawdown discharge % of design discharge 1.00

Discharge per basin Qbasin (m3/s) = 0.455 Water depth of inlet canal hc1 (m) = 0.50Max section width for hydraulic flushing B (m) = 3.258 Outlet canal width /canal diameter Bc2 (m) = 0.50

Width used B (m) = 2.500 Water depth of outlet canal hc2 (m) = 0.30Inlet canal width /canal diameter Bc1 (m) = 1.000 Provided Length of the basin Lact (m)=

Length of basin L (m) (Idel L = 9.6) = 10.000 Pipe does not need a straight approach! ***Aspect ratio (4<=AR<=10) 4.000 Head over outlet weir h overtop (m) = 0.23Min. water depth Hi (m) = 0.755 Approach inlet velocity vi1 (m/s) = 0.91

X-sectional area / basin Ai (m2) = 1.888 Approach outlet velocity vi2 (m/s) = 3.03Wetted perimeter / basin Pi (m) = 4.010 1/Energy gradient during operation So = 15763.86

Hydraulic radius Ri (m) = 0.471 d 50 during operation (mm) = 0.33Normal WL @ basin h b m = 1.385 Depth of water during flushing yfi (m) = 0.12

Straight inlet transition length at 1:5 (m) = 3.750 d 50f during flushing (mm) = 49.32Straight approach canal length (m) = 10.000 Length of an Ideal Basin (m) = 10.00

Spilling of excess waterVertical Flushing pipe

Diameter for flood d1 m = Diameter for load rejection (u/s flood bypass) d1 m = 2 x 0.43

SpillwayFreeboard m 0.300 Spillway length for Qd (under operation) 6.43

Spillway overtopping height h overtop m 0.125 Spillway length for Qd (load rejection & u/s flood bypass) 6.43Spillway length for Qf (flood and non operational) Spillway length for Qd (d/s obstruction & full hovertop-50) 3.18

Combination of vertical flushing pipe and spillway Flood and non operational (Qf)Vertical flushing pipe diameter d1 m 0.30 Flood discharge passing through vertical pipe

No of vertical flushing pipe 1.00 Spillway length for the remaining discharge m 1.00Spillway length used (m) 1.00

Flood and Under Operation (Qf- Qd) Load Rejection (Qd)H overtopping H overtopping 0.262

Discharge passing through vertical pipe Discharge passing through vertical pipe 0.240Discharge passing over spillway Discharge passing over spillway 0.215

Figure 6.4: Typical example of a settling basin (Settling basin, spilling and flushing).


Page: 46

In the second case, the depth of water during flushing (yfi) may be added to h flush for higher precision. This is not considered here. The recommended minimum diameter of the flushing pipe diameter is 0.4 m. Use of flushing pipe should be restricted to micro-hydropower projects. For larger projects, use of gates is recommended. The gate curve in the example presented in Figure 6.5 includes the gate dimensions, forces and the rating curve. The rating curve of the gate versus different gate opening can be computed by entering allowable gate opening at the lowest input cell and clicking “Calculate Gate Rating Curve” button.

Flushing of water and sedimentFlushing pipe and orifice diameter Gate Relative Discharge

d for incoming flow and draw down m 0.35 Opening Gate Openinig One basind for incoming flow only (empty state) m 0.40 Hg Hg/H1 Q

d for incoming flow only (empty state & with y flushing) m 0.39 0.000 0.000 0.0000.033 0.025 0.127

Gate 0.067 0.049 0.249Buoyance weight of the gate W kgf 300.00 0.100 0.074 0.366

Gate Opening B, (m) 1.00 0.133 0.098 0.479Gate Opening H (m) 0.50 0.167 0.123 0.591

Submerged area of th gate A m2 0.50 0.200 0.147 0.700Water surface to cg of submerged area h m 1.11 0.233 0.172 0.807

Coeff of static friction mu 0.90 0.267 0.196 0.912Lifting force F kgf 799.50 0.300 0.221 1.016

H. of water (H1) 1.36 0.333 0.245 1.1170.367 0.270 1.2160.400 0.294 1.3120.433 0.319 1.4060.467 0.343 1.4970.500 0.368 1.586

Calculate Gate Rating Curves

Figure 6.5: Typical example of a settling basin (Gate and rating curve). The last part the spreadsheet can be used if the considered basin is a settling basin cum forebay. The basic penstock inlet geometry is computed in this section. An example is presented in Figure 6.6.

0.367 0.265 1.2300.400 0.289 1.3280.433 0.313 1.4230.467 0.337 1.5160.500 0.361 1.606

Forebay cum settling basin (one basin)Penstock diameter m 0.41Penstock velocity m/s 3.45Submergence depth of penstock pipe m 0.91Height of pipe above the base slab m 0.30Min. pond depth m 1.62Effective thickness of penstock mm 3FS for air vent (5 burried, 10 exposed) 10Young's modulus of elasticity E N/mm2 200000Penstock inlet gate (Yes/No) NoAir vent diameter mm Nominal

Gradual Expansion of 1:5 half of Gr expansion0.500

1.000 Width 2.5m Flushing cone/spillway O

Gradual Expansion 1 in 10 (1:2 for MHP) L =10Spillway 0.300

0.500 Water depth 0.76mSediment depth 0.63m Slope 1:50

Designed Cross Section

Width 2.5m

Water depth 0.76m

Sediment depth 0.63m

Av. H ot =0.125m

0.000

0.200

0.400

0.600

0.800

1.000

1.200

1.400

1.600

1.800

Figure 6.6: Typical example of a settling basin (forebay and dimensioning).


Page: 47

7 PENSTOCK AND POWER CALCULATIONS

7.1 GENERAL A penstock pipe conveys water from free flow state (at a settling basin or a forebay) to pressure flow state to the powerhouse and converts the potential energy of the flow at the settling basin or forebay to kinetic energy at the turbine.

7.2 GENERAL RECOMMENDATIONS 1. Material: Mild steel (exposed and buried) and HDPE/GRP (buried) pipes should be used as

penstock pipes. For mild steel pipes, flanged connections are recommended for low head (up to 60m) micro-hydropower projects. In other cases, site welding is recommended. A combination of HDPE/GRP and mild steel can also be used.

2. For exposed (i.e., above ground) mild steel penstock alignment, a minimum clearance of 300 mm between the pipe and the ground should be provided for ease of maintenance and minimising corrosion effects.

3. GRP/HDPE pipes should be buried to a minimum depth of 1 m. Similarly, if mild steel penstock pipes have to be buried, a minimum of 1 m burial depth should be maintained and corrosion protection measures such as high quality bituminous/epoxy paints should be applied. Due to higher risks of leakage, flange connected penstocks are not recommended to be buried.

4. The recommended initial trial internal diameter (D) can be calculated as: D = 41 x Q 0.38 mm

Where, Q = Design flow in l/s 5. Total penstock headloss should not be more than 10% of the penstock gross head. 6. Anchor / Thrust blocks at every horizontal and vertical bend are recommended. For micro

hydropower projects, these blocks are also recommended for every 30m of straight pipe stretch. 7. Expansion joints should be placed immediately downstream of every anchor block for exposed

mild steel penstock. 8. Instead of providing an expansion joint immediately upstream of turbine, a mechanical coupling is

recommended for ease of maintenance and reduced force transmitted to the turbine casing.

7.3 PROGRAM BRIEFING AND EXAMPLE 7.3.1 Program Briefing The design procedure of a penstock pipe is similar to that of a headrace pipe. In this spreadsheet, the penstock is checked for surge / water hammer head propagated due to various closures of the system. Sudden closure of one jet is considered as the maximum surge in case Pelton turbines are used. Both the installed capacities based on the AEPC criteria and actual cumulative efficiency of the electro-mechanical are presented. The installed capacity based on the given cumulative efficiency should be used in case it is provided by manufacturers. Since a provision of maximum of ten bends is generally sufficient for a typical micro and mini hydropower scheme, head losses due to ten bends are incorporated. However, users can add any cumulative values of bend constants (k) if there are more than ten bends and other losses due to turbulence in the “K others” cell.


Page: 48

A fine trashrack is always recommended upstream of penstock inlet. Therefore, a trashrack calculation and minimum submergence criteria by Gordon and AEPC criteria are also included. AEPC criterion of 150% of the velocity head is enough for micro and mini hydropower projects. User specific factor of safety and ultimate tensile strength for mild steel penstock are allowed in the spreadsheet in order to be able to use non standard values. The friction factor calculation is based on the iteration procedures described in the Layman’s Guidebook on How to Develop a Small Hydro Site by European Small Hydropower Association (ESHA). Design and installation criteria of expansion joints are presented at the end of the spreadsheet.

Start

Pipe #, Material, FabricationIf steel,Laying, Valve,

t, L, θ(upto 10)

Trashrackhl, Surface Area,

Width, h submerge

End

HydraulicsQd, Hg, RL us,%hl, Entrance,

Exit, R/d

ProjectName,

Location,Life

Hydraulicshl(friction, turbulent)

Other criteria checking

TrashrackBar type,t,b, Vo,Φ, β,H

Exp JointTmax, Tinst,Tmin, Group

L (5)

PowerPturbine,PMGSP,

P hnetPCUM

Exp JointDimensions, Positionduring installation

Figure 7.1: Flow diagram of penstock design 7.3.2 Typical example of a penstock pipe Figure 7.1 presents calculation procedures applied in the example presented in Figures 7.2 and 7.3. The presented example is taken from the 500kW Jhakre Mini Hydropower Project, Dolakha. For the given head of 180m and discharge of 450 l/s, three units of two-nozzle Pelton turbines are selected. Since trashrack and pipe hydraulics are similar to headrace pipe presented earlier, the detailed calculations are not presented in this section. The steel pipe thickness, expansion joints and power calculations are presented in this section. It is assumed that the valve closing is of slow type. The minimum factor of safety for penstock is chosen to be 2.5.

Pipe thickness: It is worth noting that in reality the diameter of penstock pipe is optimized by calculating marginal costs and benefit method. In this method, the incremental benefit of annual energy by increasing the pipe diameters and corresponding increase of costs are plotted. The intersecting point represents the cost of optimum diameter. Alternatively, net present values of these cash/cost flow can be calculated and the net present value (NPV) of marginal benefit from energy gain should be higher than that of the marginal cost of that diameter. Let’s consider 4mm thick 300mm diameter pipe, the wave velocity

sm

xx

xxxtEdxx

a /454.1071

1000610200

300.0101.21

1440

101.21

1440

9

9

9=

+

=

+

=


Page: 49

hsurge = a * V/(g*njet) = 1071.454*2.83/(9.81*6) = 51.484m htotal = hgross + hsurge = 180+51.484 = 231.484 m t effective = t/(welding factor*rolling) – thickness for corrosion taken as Life span/10 = 6/(1.1*1.2) – 1.0 = 3.55mm Factor of safety (allowable FS = 3.0) = 2.79 which does not exceed the allowable FS of 2.5, hence OK. This factor of

safety should be used for thinner penstock.

PENSTOCK AND POWER CALCULATIONSSpreadsheet developed by Mr. Pushpa Chitrakar, Engineering Advisor, SHPP/GTZReferances:2,4, 5,6,12,13,15,16 Date 10-Nov-2005SMALL HYDROPOWER PROMOTION PROJECT/GTZ Revision 2005.10Project: Jhankre mini-hydropower Location: Barand, Sertung VDC 2, DhadingDeveloper Himal Power LimitedConsultant BPC HydroconsultDesigned Pushpa ChitrakarChecked Pushpa Chitrakar

INPUTGeneral:Project: Jogmai ILocation: Ilam Economic life (years) 10Hydraulics:Diversion flow Qd (m3/s) 0.450 WL @ forebay or U/S Invert Level (m) 1213.90Flow in each pipe Qi (m3/s) 0.450 % head allowable headloss hlt (m) 16.00%Gross head (from forebay) Hg (m) 180.00 Cumulative knowm efficiency (g,t,tr,others) 79.38%Power:Turbine type (CROSSFLOW/PELTON) Pelton Valves (Sperical/Gate/Butterfly) 0.3No of total jets (nj) 6 Taper (Yes/No) No

Direct Coupling (Yes/No) Yes Exit (Yes/No) NoClosure time T sec 30.00 Non standard ult. tensile strength (UTS) N/mm2 0Number of units 3Penstock pipe:Pipe Material (STEEL/HDPE/PVC) Steel Safety factor for lower pipes (0 for default) 2.5Welded / Flat rolled if steel Welded Entrance Type 0.5Rolled if steel Rolled Entrance with gate and air-vent (Yes/No) NoType if steel (UNGRAGED/IS) IS Bending radius (r/d) (1/2/3/5/1.5) 0.45Burried or exposed Exposed Bending angle 05 22No of pipes 1.00 Bending angle 06 14.00Bending angle 01(degrees) 2.00 Bending angle 07 0.00Bending angle 02 11.00 Bending angle 08 0.00Bending angle 03 4.00 Bending angle 09 0.00Bending angle 04 11.00 Bending angle 10 0.00Penstock diameter d=>d estd, d act (mm) 418 450 Pipe thickness t=>t min, t act (mm) 3.0 6.0Pipe Length L (m) 550.000 Roughness coefficient (ks) 0.060Trashrack

k t b Vo φ β Q H2.40 6.00 20.00 1.00 71.56 0.00 0.450 0.70

Expansion JointsTmax (deg) T installation Tmin 1st Pipe length(m) 2nd Pipe L (m) 3rd Pipe L (m) 4th Pipe L (m) 5th Pipe L (m)

40 20 4 10.00 15.00 20.00 25.00 30.00

Sharp cornered

1.5

Flat

Butterfly

Figure 7.2: Input required for penstock and power calculations

450.010484.231510410)100055.3(

105.. 3

6

3 xxxxx

dxxhxSxt

FStotal

effective ==


Page: 50

OUTPUTTrashrack

hf hb H coeff H S B Min Submergence CGL=1.5v 2/2g

0.0233 0.0000 0.4572 0.0233 2.0555 2.79 1.84 0.61

Turbulent loss coefficients K Total 2.06K inlet 0.50 K bend 05 0.24 K bend 10 0.00K bend 01 0.18 K bend 06 0.22 K valve 0.30K bend 02 0.21 K bend 07 0.00 K taper 0.00K bend 03 0.19 K bend 08 0.00 K exit 0.00K bend 04 0.21 K bend 09 0.00 K others 0.00

HydraulicsPipe Area A (m2) 0.159 U/S Invert Level (mAOD) 1213.90Hydraulic Radius R (m) 0.11 D/S Invert Level (mAOD) 1033.90Velocity V (m/s) 2.83 Is HLtot < HL available OKAYPipe Roughness ks (mm) 0.060 Friction Losses hf (m) 6.87Relative Roughness ks/d 1.333E-04 Fitting Losses hfit (m) 0.84Reynolds Number Re = d V /Vk 1116427 Trashracks and intake loss (m) 0.02Type of Flow Turbulent Total Head Loss htot individual (m) 7.73Friction Factor f 0.0138 % of H.Loss of individual pipe 4.3% Ok

Factor of SafetyYoung's modulus of elasticity E N/mm2 200000 Ultimate tensile strength (UTS) N/mm2 410Thickness 6.000 H total for one jet closure of Pelton(m) 231.48Diameter (mm) 450.000 t effective (mm) 3.55Net Head (m) 172.268 Minimum t effictive for negative pressure (mm) 4.71Wave Velocity a (m/s) 1071.454 Comment on thickness NA, No gateCritical time Tc (sec) *2 = Closing time T 1.03 Ok Safety Factor (S) 2.79K if crossflow turbine Kcf 0.00000 Check on Safety Factor OkHsurge for one jet closure of Pelton(m) 51.484 Air vent diameter d vent (mm) 67.45Hsurge for instanteneous closure of all unit closure of Pelton (m) 308.907 H total capacity of the specified pipe (m) 258.42Lengths (max & actual) of the specified pipe (m) & Ok 613.998 550.000 H static capacity of the specified pipe (m) 206.94

PowerTurbine efficiency as per MGSP 75.00% Electrical Power as per MGSP GL (kW) 397.31Available shaft power(kW) 570.36 Electrical Power based on Hnet (kW) 456.29Reqd.'Turbine Capacity (+10%) (kW) 627.39 Power for known cumulative eff (kW) 603.67

Expansion Joints (mm) Coeff of linear expansion /deg C 1.2E-05EJ number 1 2 2 4 5dL theoretical 4 6 9 11 13dL recommended 9 13 17 22 26dL for expansion 5 7 10 12 14dL for contraction 4 6 8 10 12

Figure 7.3: Output of penstock and power calculation spreadsheet.

Based on the American Society of Mechanical Engineers (ASME) recommendations, the allowable minimum thickness is 3.00 mm. Therefore, optimum penstock thickness can vary from 3mm to 6mm. The summary of the penstock thickness corresponding to static head is presented in Table 7.1. The static heads for different thickness of pipes are calculated by applying different thickness of the pipe and noting the thickness and the corresponding to the calculated values of H static capacity of the specified pipe (m) cell. Table 7.1: Summary of penstock thickness and corresponding maximum permissible static head

Penstock thickness (mm) Static Head (m) 3 40 4 86 5 132 6 180


Page: 51

7.4 FORCES ON ANCHOR BLOCKS An anchor block is a gravity retaining structure placed at every sharp change along the penstock pipe and is designed to retain penstock pipe movement in all directions. It should be stable against overturning, sliding and sinking/bearing. Although the design of anchor blocks and saddles are site and user specific and the rules of thumb are valid for micro-hydropower schemes, care should be taken while using these rules of thumbs even for micro-hydropower projects. The spreadsheet “AnchorLoads” is useful for calculating static and dynamic forces on an anchor block. In case the penstock pipes upstream and downstream of an anchor block are not on a single plane (i.e., 3 dimensional forces), the resultant forces act on three dimensions and the block has to be stable in all three dimensions. Calculation and design of anchor blocks for three dimensions is a complex process and beyond the scope of this book and most of micro and mini hydropower projects have penstock in single planes, therefore, a spreadsheet useful for calculating forces in a single plane parallel to longitudinal section of the anchor block is presented. Moreover, the designers are strongly advised to align penstock in a single plane. AEPC/ESAP does not have any mandatory procedures for designing anchor blocks. Therefore, standard procedures for calculating forces on anchor blocks are considered in this spreadsheet. The possible forces acting on anchor blocks are presented in the spreadsheet. Since the calculation of anchor forces consists of single line formula calculations without many conditions, the spreadsheet is designed to present simple definitions of these forces along with sketches, their formulae and the calculated results. An example of 500kW Jhankre mini-hydropower project anchor block presented in “Civil Works Guidelines for Micro-Hydropower in Nepal” has been taken as an example. Some additional forces are added and some of the formulae based on analytical method are used. 7.4.1 Program example

Input for the cited example are presented in Figure 7.4. Elevations are used to calculate vertical angles ( α and β ) in case these angles are not entered as inputs. As always, care should be taken to verify inputs in red colour. Total head, Static head h gross = forebay water level – pipe centre line = 650.50 – 636.750 = 13.750m htotal = h gross + hsurge = 13.750 m + 48 m = 108 m Unit weight of pipe and water, Wp =∏ (d + t) t γsteel = ∏ x 0.454 x 0.004 x 77 = 0.448 kN/m

Ww =∏ (d )2/4* γwater = ( )Π 0 450

49 8

2..× = 1.560 kN/m

Total weight per unit length WT=Wp+Ww = 2.008 kN/m Velocity, v = Q/A = 4*Q/(∏*d2) = 4*0.45/(∏*.452) = 2.829 m/s 1. Perpendicular component of weight of pipe and water acting perpendicular to the pipe centre line along

the anchor faces F1u = WT L1u cos α = 2.008 * 2 * cos 13° = 3.913 kN F1d = WT L1d cos β = 2.008 * 2 * cos 25° = 3.640 kN The axial components of these forces can be calculated as: F1u axial = - WT L1u sin α = 2.008 * 2 * sin 13° = - 0.903 kN F1d axial = - WT L1d sin β = 2.008 * 2 * sin 25° = - 1.697 kN FEMu = WT L1u

2 /8 = 2.008 * 22/8 = 2.677 kN-m FEMd = - WT L1d

2 /8 = 2.008 * 22/8 = - 2.677 kN-m


Page: 52

2. Axial frictional force of pipe on saddle supports transferred to anchor block considering f = 0.25 for steel

on steel (greased) saddle top. Frictional force per support pier = ± f *WT*L2u cos α = ± 0.25*2.00 * 4 cos 13°= ± 1.95 kN Total frictional force for 8 piers (F2u ) = ± 1.95 x 8 = ± 15.653 kN Note that F2d is zero since an expansion joint is located immediately downstream of the anchor block. 3. Hydrostatic pressure at bend due to the vector difference of static pressure and acting towards IP (F3)

and total force along the pipe (P). Since upstream and downstream penstock diameter are the same. Pu (kN) = ∏/4*d2*Ht*γ = ∏/4*.452*108*9.81 = 168.50

F3 = 2*P*sin((β-α)/2) = 2 x 168.50 x sin

°−°2

1325 = 35.227 kN

4. Component of weight of pipe along the pipe (L4u = 34.89 – 4 = 30.894) F4u = L4u = 0.448 x 30.894 x sin 13° = 3.112 kN F4d = WpL4d sin β = 0.448 x 4.0 x sin 25° = 0.757 kN 5. Since expansion joints both upstream and downstream are provided, F5 = 0. Typical temperature ranges

are presented in the example. Since the temperatures (dt) are different for expansion and contraction, F5 for both the cases are presented.

6. Axial friction within expansion joint seal due to the movement against the circumferential pressure (F6)

can be calculated using either of the formulas: F6 = ±100 x d or F6 = ±∏*D*W*H*γ*µ Since the second formula is based on analytical method, it is recommended to use it. H is the total head

at the considered expansion joint. For a seal width (W) of 0.16m and a friction factor (m) of 0.25, F6 is F6u= ±∏*0.454*0.16*98.512*9.81*0.25 = 55.666 kN F6d= ±∏*0.454*0.16*109.888*9.81*0.25 = 60.959 kN 7. Axial hydrostatic pressure on exposed end of pipe in expansion joint (F7): F7=∏*(d + t)*t*H*g

F7u = ∏* 0.454*0.004*98.512*9.81= 5.518 kN F7d = ∏* 0.454*0.004*109.888*9.81= 6.042 kN

8. Dynamic pressure at the bend due to the vector difference of momentum (F8): P8 (kN) = F8 = Q*ρ ∗v= 0.45*1*2.829 = 1.273 kN

F8 = 2.5Qd

2

2 2

−

sin β α= 2.5

°−°

21325sin

450.0450.0

2

2 = 0.261 kN

9. No reducer is provided in this case. Therefore axial force on reduce (F9 = 0). In case there is a reducer,

total head at the specified reducer location is calculated for calculating F9. 10. Axial drag of flowing water (friction of flowing water) is generally not considered in micro and mini

hydropower scheme penstock design. Therefore F10 =0 is considered in this example. 11. Force due to soil pressure (F11):

F11= 2h 2

1soilγ cos i x Ka x w

For γsoil = 20 kN/m3, φ = 30° and Ka = φ−+

φ−−22

22

cosicosicos

cosicosicos=0.371

F11 = 20 182

2× . cos 13° x 0.371 x 2 = 23.455 kN

This force acts at 1/3 of the buried depth at upstream face of anchor block, which is (1/3 x 1.8) = 0.6 m.


Page: 53

Summary of forces are presented in Figure 7.4. The forces calculated above are further resolved in mutually perpendicular directions to get the summary. A typical calculation is presented in Table 7.2. Forces acting at the bend and the total forces for both the expansion and contraction are presented in the table. The total forces will further be utilized in anchor block design. These forces are calculated for vertical angles of α = 13°, β = 25°. Table 7.2: Summary of forces Forces (kN) X - component (kN) →+ Y- component (kN) ↓+ F1u = 3.90 = - F1u sin α = - 0.880 = F1u cos α = 3.813 F1d = 3.63 = - F1d sin β = - 1.538 = F1d cos β = 3.299 F2u = ± 15.6 = F2u cos α = 15.252 = F2u sin α = 3.521 F3 = 35.20

= F3 sinβ α+

2

= 11.469 = - F3 cos β α+

2

= - 33.308

F4u = 2.97 = F4u cos α = 3.033 = F4u sin α = 0.700 F4d = 2.97 = F4u cos β = 0.686 = F4u sin β = 0.320 F5u = 0.000 = F5u cos α = 0.000 = F5u sin α = 0.000 F5d = 0.000 = - F5d cos β = 0.000 = - F5d sin β = 0.000 F6u = 45 = F6u cos α = 54.239 = F6u sin α = 12.522 F6d = 45 = - F6d cos β = - 55.248 = -F6d sin β = -25.763 F7u = 5.70 = F7u cos α = 5.377 = F7u sin α = 1.241 F7d = 6.08 = - F7d cos β = - 5.476 = - F7d sin β = - 2.553 F8 = 0.26

= F8 sin β α+

2

= 0.085 = - F8 cos β α+

2

= - 0.247

F9u = 0.000 = F9u cos α = 0.000 = F9u sin α = 0.000 F9d = 0.000 = - F9d cos β = 0.000 = - F9d sin β = 0.000 F10u = 0.000 = F10u cos α = 0.000 = F10u sin α = 0.000 F10d = 0.000 = - F10d cos β = 0.000 = - F10d sin β = 0.000 F11 = 23.45 = F11 cos i = 22.853 = F11 sin i = 5.276 F12 = 354.64 0 = F12 = 354.640 SUM (expansion)

∑H @ bend exp = ∑H total exp - F11H = 26.997 kN ∑V @ bend exp = ∑V total exp - F11V - F12V = -36.454 kN

∑H total exp = 49.851 kN ∑V total exp = 323.460 kN SUM (contraction)

∑H @ bend c = ∑H total c – F11H = -1.488 kN ∑V @ bend = ∑V @ total c – F11V = -17.015 kN

∑H total c = ∑H @ bend expansion – 2(F2H +F6Hu+ F6Hd ) = 21.366 kN

∑V total c = ∑V @ bend contraction – 2(F2V +F6Vu+ F6Vd)=342.901 kN

Forces on Anchor Block Block # & type 2 Convex

Small Hydropower Promotion Project (SHPP)/GTZSpreadsheet by Mr Pushpa Chitrakar

Referances: 6,12,13,15,16 DateSMALL HYDROPOWER PROMOTION PROJECT/GTZ Revision 2006.05Project Jhankre mini-hydropowerDeveloper DesignedConsultant BPC Hydroconsult Checked

InputParticulars Upstream Central Downstream Design Discharge, Q (m3/s) 0.45Pipe dimensions Unit Weights (kN/m3)

Diameter (Di) 0.45 0.45 Mild Steel 78.5Thickness 0.004 0.004 Water 9.81Shaddle Spacing & number 4.00 8 4.00 RCC 25

Anchor Block 22Elevations 636.750 Soil

Bearing capacity (kN/m2) 200Horizontal Distance (m) 34.000 40.000 φ 30 0.5236

γs 20Vertical angles, a & b (deg) 13.0000 25.0000

Location of Expansion Joint 4 4 Heads (m)Forebay WL 696.750

D/S Expansion Joint : Yes Yes Tot.Transient Len 3277.753Sum of Pipe Len (forebay to Anchor Block)1074.814

Output Total Surge Head 146.381Weight of pipe, Wp (kN/m) 0.448 0.448 Static Head 60.000Weight of water, Ww (kN/m) 1.560 1.560 Surge Head ± 48.00Total weight, W (kN/m)) 2.008 2.008 Total (H) 108.000Velocity, v (m/s) 2.829 2.829 Youngs Modulus of Elasticity (E)2.1E+11Vertical angles, a & b (rad) 0.226893 0.436332 Coefficient of Linear Expansion (12E-06

24-May-2006


Page: 54

GENERAL FORCES1. Perpendicular component of Wt of pipe and water act perpendicular to the pipe CL along the anchor faces

F1=dead weight of half of anchor saddle pipe perp to pipe4.016 4.016

F1u (kN)=wu*lmu/2*COS(α): F1d (kN)=wd*lmd/2*COS(β)F1 perpendicular to pipe 3.913 3.640F1 axial -0.903 -1.697Fixed end moment = wl 2/8 for proped cantilever FEM.FEMu (kN-m)= Restoring moment: FEMd (kN-m)= Overturning moment

FEM 2.677 -2.677

2. Axial frictional force of pipe on saddle supports transferred to anchor F2 (kN)= ±µ*w*L'*cos α 0.25US Pipe Length, L' (m): 34.89

F2 (kN) = ± 15.653 +ve for expansion

3. Hydrostatic Pressure at Bend due to the vector difference of static pressure & acting towards IPPu (kN) = F3u =PI/4*dui 2*Ht*γ 168.50Pd (kN) = F3d =PI/4*ddi 2*Ht*γ 168.50F3 = 2*P*sin((β-α)/2) 35.227

4. Component of weight of pipe (wp) along the pipeF4u= wp*active arm L’*sin(α) F4d= wp*active arm L’*sin(β)

F4 3.112 0.757

5. Thermally (expansion/contraction) induced axial force ( if no EJ provided)F5 (kN)=pi()*Dmean*t*E*a*Dt + Expansion, - Contraction

Condition Tmax Tinstallation TminTemp at oC 40 20 4

F5 expansion 0.000 0.000

F5 contraction 0.000 0.000

6. Axial friction within Expansion joint seal due to the movement against the circumferential pressureF6=±PI()*D*W*H*g*m + Expansion, - Contraction

µ for rubber packing 0.25 Seal width, W (m)0.16

Static Pressure at Exp, Ps (m) 52.150 61.69

Dynamic Pressure at Exp, Pd (m) 46.442 48.20

Total (AH) 98.592 109.888F6 (kN) = ± 55.666 60.959

7. Axial hydrostatic pressure on exposed end of pipe in Expansion JointF7=PI*D*t*H*g

F7 5.518 6.042

8. Dynamic pressure at the bend due to the vector difference of momentumF8 = 2.5*(Q 2/d 2)*sin((β-α)/2) P8= mV =Q*ρ*Vi

P8 (kN) 1.273 1.273F8 0.261

9. Axial (small diameter) force on Reducer F9=PI()*(Dupi 2-Ddni 2)/4*g*HReducer: No NoLocation & Diameter: 3.00 0.40 4.00 0.40St. Head 59.33 61.69Dyn. Head 47.97 48.08F9 (kN) 0.000 0.000

p F7F7

Steel to (HDPVC) to Steel (greased) (m)

F5 F5

a

b

F1 d F1 u

F2

L'

FEMu FEMd

a

bpu

pd

F3

L'

W

F4=w sin a

F6

Pipe Movement

p

F6

W

F6

b

Q*r* Vi

Q*r*Vo

F8

Vector difference of momentum at bend (mvi -mvo)

- Q*r*Vo

Q*r* Vi

FH

Fv

p F9F9


Page: 55

10 Axial drag of flowing Water (friction of flowing water) (not considered in MHP)F10=g*PI()*Dupi 2/4*DH(Exp to block)

F10 (kN) 0.000 No 0.000 No

11 Axial (u/s slope) force due to soil pressure upstream of the block F11 =γs*hs 2/2*cos φ*ka*Bka= (cosi-sqrt(cosi^2-cosφ^2))/(cosi+sqrt(cosi^2-cosφ^2)) 0.371 Width, B(m) 2hs = soil depth = hu 1.8F11 23.455 Yes @ 1/3 of hs 0.6

12 Vertical force due to the weight of the block F12 =γblock*Vol of blockVol of block 16.12F12 354.640 Yes

SUMMARY OF CRITICAL FORCES@ bend Total @ bend Total

1 Summation of total horizontal forces ΣH (kN) 26.997 49.851 -1.49 21.372 Summation of total vertical forces ΣV (kN) -36.454 323.462 -17.02 342.903 Summation of total moment forces ΣM (kN-m) 0.000 0.00

Expansion Contraction

F11

F 1 2

Figure 7.4: Output of anchor block force calculation spreadsheet.

7.5 ANCHOR BLOCK DESIGN A design of one of the anchor blocks of 500kW Jhankre mini-hydropower project presented in “Civil Works Guidelines for Micro-Hydropower in Nepal” has been taken as an example for preparing the spreadsheet “AnchorBlock”. It is worth noting that the slight differences in calculated output in the guidelines are mainly due to the rounding off of processed data for secondary processing. A typical sketch of the considered anchor block is presented in Figure 7.5. Stepwise calculations of the considered example are also presented in this section. The inputs for the calculations are presented in the input section of the spreadsheet presented in Figure 7.7.

Figure 7.5: Anchor Block Considered The spreadsheet is also designed to accommodate forces due to the dead weight of anchor block and upstream earth pressure. In case forces at the pipe bend calculated as per section 7.4 are used, dead weight of anchor block and upstream earth pressure for a different anchor block (not similar to defined in “AnchorLoads”) can be used in this spreadsheet. 7.5.1 Program example

Concrete Block Centre of gravity of the block from the upstream face of the block taking the moment of mass.

2x)05.1x3x2/1()25.2x3( 2 x 3 x 1.05)1/3 x 3 x (1/2 2.25)3/2 x (3

++ = 1.405m

∴ the weight of the block WB acts 1.41 m from point O. Concrete volume (V) = Block volume excluding volume of the pipe and water if any

= (2.25 x 3) + 12

3 105× ×

. x 2 - 1 x Π x 0.4582/4 cos 13° - 2 x Π x 0.4582 /4 cos 25° = 16.191 m3

Unit weight of concrete, (γconcrete)= 22 kN /m3 Weight of block, WB = 16.12 x 22 = 356.199 kN


Page: 56

Soil

Ka = φ−+

φ−−22

22

cosicosicos

cosicosicos=0.3715

F11= 2h 2

1soilγ cos i x Ka x w = 20 182

2× . cos 13° x 0.3715 x 2 = 23.455 kN

This force acts at 1/3 of the buried depth at upstream face of anchor block from point O as shown in Figure 7.6, which is (1/3 x 1.8) = 0.6 m. Perpendicular components of this forces are: F11X= F11 *cos i = 23.455*cos 13° = 22.853 kN F11Y= F11 *sin i = 23.455*sin 13° = 5.276 kN Stability (refer to Figure 7.6) Overturning: Expansion case Sum of moments about point O with clockwise moments as positive: ∑M @ O = 30.327 x 2.15 + 22.853 x 0.6 + 356.199 x 1.405 – 16.215 x 1.0 = 563.303 kN-m

d = 26.345303.563

=

∑∑

VM

= 1.632 m

e = 632.123

− = 0.132 m

eallowable = m5.063

6Lbase ==

∴ e < eallowable OK Contraction case Sum of moments about point O with clockwise moments as positive: ∑M @ O = -6.19 x 2.15 + 22.85 x 0.6 + 356.199 x 1.405 – 41.03 x 1.0 = 473.281 kN –m

d = 44.320281.473

=

∑∑

VM

= 1.477 m

e = 477.123

− = 0.023 m

Recall that eallowable = 0.5 ∴ e < eallowable OK. Since e < eallowable for both cases, the structure is safe against overturning. Bearing capacity: Note that for stiff clay allowable bearing pressure is 200 kN/m2 (Table 7.3). Expansion case:

Pbase max =

+

∑

basebase Le61

AV =

×

+× 3

132.0612326.345

= 72.681 N/m2


Page: 57

Pbase min =

−

∑

basebase Le

AV 61 =

×

−× 3

132.0612326.345

= 42.406 N/m2

Contraction case:

Pbase max =

+

∑

basebase Le61

AV =

×

+× 3

023.0612344.320

= 55.866 N/m2

Pbase min =

−

∑

basebase Le

AV 61 =

×

−× 3

023.0612344.320

= 50.947 N/m2

In both cases Pbase < Pallowable = 200 kN/m2. ∴ the structure is safe against sinking. Sliding: Expansion case

∑ H < µ ∑ V µ = 0.5 for concrete/masonry on soil 53.18 kN < 0.5 x 345.26 kN 53.18 kN < 172.63 kN OK. Contraction case ∑ H < µ ∑ V 16.66 kN < 0.5 x 320.44 kN 16.66 kN < 160.22 kN OK. Since ∑ H < µ ∑ V in both cases the structure is safe against sliding. ∴The anchor block is stable.

Figure 7.6: Anchor Block force diagram


Page: 58

Anchor Block StabilitySmall Hydropower Promotion Project (SHPP)/GTZSpreadsheet by Mr Pushpa Chitrakar

Referances: 6,12,13,15,16 DateSMALL HYDROPOWER PROMOTION PROJECT/GTZ Revision 2006.05Project Jhankre mini-hydropowerDeveloperConsultant BPC HydroconsultDesignedChecked

Input OutputAnchor

Upstream depth, Hu (m) 3.3 Concrete volume of Anchor Block 16.191Downstream depth, Hd (m) 2.25 Weight of block, Wb (kN) 356.199Width, W (m) 2 Centre of gravity XX 1.405Length, L (m) 3γ anchor (kN/m3) 22µ 0.5

PenstockBend at (X), (m) 1Bend at (Y), (m) 2.15Diameter, d (m) 0.458Upstream angle, α (deg) 13Upstream angle, β (deg) 25

FoundationUpstream depth hfu (m) 1.8 Active earth pressure coeff, Ka 0.3715Soil friction φ, (deg) 30 F Pa Fx Fyγ soil (kN/m3) 20 Soil force 23.455 22.853 5.276Bearing Capacity, SBC (kN/m2) 200 Acting at (m) 0.6

Forces (with soil pressure and block weight)Forces with earthpressure & anchor Yes Overturning Bearing Sliding

ExpansionNet Forces @ bend SM @ O 563.303 P max 72.681 172.63

ΣH (kN) 53.180 30.327 d 1.632 P min 42.406 OkΣV (kN) 345.260 -16.215 eccentricity e, Ok 0.132 Ok

e allowable 0.500

Contraction SM @ O 473.281 P max 55.866 160.22ΣH (kN) 16.66 -6.19 d 1.477 P min 50.947 OkΣV (kN) 320.44 -41.03 eccentricity e, Ok 0.023 Ok

24-May-2006

Anchor Block Section

Pipe CL

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

-0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

Lengt h X (m) '

Figure 7.7: Anchor Block force diagram


Page: 59

8 TURBINE SELECTION

8.1 GENERAL A turbine converts potential energy of water to rotational mechanical energy. Cross-flow and Pelton turbines are the most commonly used turbines in Nepali micro hydropower plants. Pelton, Francis and Turgo turbines are used in mini and small hydropower projects. The size and type of turbine for a particular site depends on the net head and the design flow. Pelton turbines are suitable where the ratio of head to flow is high. For Cross-flow and Francis turbines, this ratio is lower than that of the Pelton turbines. Turgo turbines lie in between these two categories. It should be noted that for certain head and flow ranges, both Pelton (multi-jet) and other turbines may be appropriate. In such cases, the designer should consult with manufacturer and make a decision based on availability, efficiency and costs. On a horizontal shaft Pelton turbine the maximum number of jets should be limited to 3 for ease of manufacturing. The number of jets can be higher for vertical shaft Pelton turbines. However, these require higher precision work in mounting the generator vertically on the turbine shaft and furthermore, in case of varying rotational speeds (RPM of the turbine and the generator), the belt drive arrangements (including those for mechanically coupled end uses) will be difficult.

Figure 8.1: Pelton and Crossflow Turbines

8.2 GENERAL RECOMMENDATIONS The recommended net heads for maximum rotational speed (rpm) and efficiencies for different turbines and turbine specifications are presented in Table 8.1. Table 8.1: Turbine specifications Type Net head (m) Max RPM Efficiency (nt) Pelton More than 10m 1500 70 - 75% T12 Crossflow up to 50m 900 60 - 78% T15 Crossflow up to 80m 1500 60 - 78% The type of turbine can be determined by its specific speed given by the following equation: Sp Speed (no gear) ns = Turbine rpm*√(1.4*PkW/Nturbines)/Hn5/4 Sp Speed (gear) nsg = Sp Speed (no gear)* Turbine rpm / Generator rpm Table 8.2: Turbine type vs. ns

Turbine types ns Ranges Single Jet Pelton 10 – 30 Double Jet Pelton 30 – 40 Three Jet Pelton 40 – 50

Cross flow 20 – 80


Page: 60

8.3 PROGRAM BRIEFING AND EXAMPLE The “Turbine” spreadsheet is presented in Figure 8.2. The specific speeds (ns) with (gear ratio of 1:2) and without gear are calculated as:

Sp Speed (no gear) ns = Turbine rpm*√(1.4*PkW/Nturbines)/Hn5/4 = 750*SQRT(1.4*67.89/1)/58^(5/4) = 46 (Turgo/Crossflow/2-jet Pelton is suitable) Sp Speed (gear) nsg = Sp Speed (no gear)* Turbine rpm / Generator rpm = 46*1/2 = 23 (Single jet Pelton/Crossflow is suitable) If ns exceeds the range given in Table 8.2, multiple units should be used. Specific speed of multi-jet Pelton turbines is computed by multiplying the specific speed of runner by the square root of the number of the jets. The calculations show that for the given parameters, either a gearless Crossflow/Turgo turbine or a Pelton/Crossflow with a gear ratio of 1:2 is recommended.

Turbine SelectionSmall Hydropower Promotion Project (SHPP)/GTZ Spreadsheet by Mr Pushpa ChitrakarReferances: 6,7,8,12,13 Date 25-Apr-2006SMALL HYDROPOWER PROMOTION PROJECT/GTZRevision 2006.03ProjectDeveloperConsultantDesigned Pushpa ChitrakarChecked Pushpa Chitrakar

InputDischarge (l/s) 150 Gear ratio at turbine 1Gross head (m) 69 Gear ratio at generator 2Hydraulic losses 15.94% No of turbines/generators 1Max turbine output kW 67.89 Total number of jets if Pelton n 2Turbine rpm 750 Specified turbine PeltonCd 0.96 Cu 0.46

OutputNet head m 58.001 Generator with gearing rpm 1500

No Gearing With GearingSp speed of runner rpm (no gearing) 46 Sp speed of turbine 23Pelton (12-30) => (Ns 17-42) ** Pelton (12-30) => (Ns 17-42) PeltonTurgo (Ns 20-70) => (Ns 28-99) Turgo Turgo (Ns 20-70) => (Ns 28-99) **Crossflow (Ns 20-80) Crossflow Crossflow (Ns 20-80) CrossflowFracis (Ns 80-400) ** Fracis (Ns 80-400) **Propeller or Kaplan (Ns 340-1000) ** Propeller or Kaplan (Ns 340-1000) ** Figure 8.2: A Typical turbine example.


Page: 61

9 ELECTRICAL EQUIPMENT SELECTION

9.1 GENERAL A generator converts mechanical energy to electrical energy. There are two types of generators; namely, synchronous and asynchronous (induction). Generally, induction generators are inexpensive and appropriate for Nepali micro-hydro schemes up to about 15kW. For micro-hydro schemes ranging from 10kW to 100kW, synchronous generators are technically and economically more attractive. Both synchronous and asynchronous generators are available in single and three phases. Brushless synchronous generators are recommended for mini and small hydropower projects. Load controllers are generally used as the governing system in Nepali micro hydro schemes. An Electronic Load Controller (ELC) is used for controlling power output of a synchronous generator. To control an induction generator, an Induction Generator Controller (IGC) is used. Brushless synchronous generators with hydraulic controlling systems are recommended for mini and small hydropower projects.

9.2 SELECTION OF GENERATOR SIZE AND TYPE Selection of generator size mainly depends up on the loads of a proposed site. Selection of generator type depends on the size of the selected generator, nature of the proposed loads and costs and benefits of the scheme. As stated earlier, a generator type can be either synchronous or induction of either single or three phase. Some of the main features of all types of generator are outlined in the following sections: 9.2.1 Single Phase versus Three Phase System

Advantages of a Three - Phase System • Considerable saving of conductor and machine costs. • Cheaper above 5 kW. • Less weight by size ratio. Advantage of a Single – Phase System • Simple wiring. • Cheaper ELC. • No problem due to unbalanced load.

9.2.2 Induction versus Synchronous Generators

Induction Generators Advantages of Induction Generators: • Easily available • Cheap, rugged and simple in construction • Minimum Maintenance Drawbacks of Induction Generators: • Problem supplying large inductive loads. • Capacitor banks are generally not durable. • Poor voltage regulation compared to synchronous generators.

Synchronous Generators Advantages of Synchronous Generators: • High quality electrical output. • Higher efficiency. • Can start larger motors.


Page: 62

Drawbacks of Synchronous Generators: • The cost is higher than induction generator for small sizes. • Higher losses due to unbalanced load.

9.3 GENERAL RECOMMENDATIONS Based on the major features, general guidelines for selection of phase and type of generator are prepared and summarized in Table 9.1. Table 9.1: Selection of Generator Type

Size of scheme Up to 10 kW 10 to 15 kW More than 15 kW Generator Synchronous/Induction Synchronous/Induction Synchronous Phase Single or Three Phase Three Phase Three Phase Maximum ambient temperature, powerhouse altitude, electronic load controller correction factor and power factor of the proposed loads are the major factors affecting the size of a generator. De-rating coefficients to allow for these factors are presented in the Table 9.2. Table 9.2: Generator rating factors Max. Ambient temperature in oC => 20 25 30 35 40 45 50 55 Temperature Factor (A) 1.10 1.08 1.06 1.03 1.00 0.96 0.92 0.88 Altitudes 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000 4250 4500 Altitude Factor (B)

1.00 0.98 0.96 0.945 0.93 0.915 0.90 0.88 0.86 0.845 0.83 0.815 0.8 0.785 0.77

ELC Correction Factor (C) 0.83

For light bulb loads (inductive) only 1.0 Power Factor (D) For mixed loads of tube lights and other inductive loads 0.8 9.3.1 Sizing and RPM of a Synchronous Generator: The steps for selecting the size of a synchronous generator are as follows:

1 Power factor of 0.8.

2 The size of synchronous generator (kVA): Installed Capacity in kW

Generator (kVA) = 1.3*----------------------------- A x B x C x D

Where, A, B, C and D are correction factors from Table 9.2, and 1.3 is the 30% overrating factor (recommended) to allow for:

i) Unexpected higher power from turbine.

ii) Handling of starting current if large motors (> 10% of generator size) are supplied from the generator.

iii) The generator running at full load when using an ELC.

3 The synchronous rotational speed per minute:

PfrpmNspeedRotational 120))(( =

Where,


Page: 63

f = frequency of the system in Hertz (Hz) (50 Hz in Asia and Europe) P = number of poles of the generator (2, 4, 6, etc., in pairs). P for Nepali micro-hydropower

schemes is generally 4 so that the rotational speed is 1500 RPM. 9.3.2 Sizing and RPM of an Induction Generator: The steps for selecting the size of an induction generator are as follows:

1 The size of an induction generator (kW):

Installed Capacity in kW Induction Generator (kW) = 1.3* -----------------------------------------

A x B It is worth noting that an induction generator is basically a motor used as a generator. Similar to motor rating, the rating of an induction generato should be in kW. Therefore, ELC factor (C) and the power factor (D) corrections are not applicable for an induction generator. Other factors are applied similar to a sychronous generator. Generator voltage and current ratings should not exceed 80% of the electrical motor rating.

2 The rotational speed of an induction generator:

( )sP

fRPMNispeedRotational += 1120))((

Where, P and f are the same as for synchronous generator and s is the slip of the generator,

Where,

Ns is the synchronous speed, i.e. P

fRPMNs 120)( =

Nr is the rated rotor speed of the induction motor and Ni always exceeds Ns while acting as a generator.

9.4 PROGRAM BRIEFING AND EXAMPLES 9.4.1 Program Briefing In addition to calculating electrical parameters stated above, following electrical parameters are added to the presented “Electrical” spreadsheet:

1 Computation of excitation capacitance for an induction generator.

2 Sizing of electrical load controller (ELC) or induction generator controller (IGC) (equal to the installed capacity).

3 Sizing of ballast (20% higher than the installed capacity). In case the installed capacity exceeds or equal to 50kW, the ballast capacity of ELC-Extension is calculated as:

Ballast capacity of ELC extension (kW) = 60% * 1.2 * Pe (electrical power)

Fixed load = 40% * Pe (electrical power)

4 Sizing of MCCB/MCB.

5 Sizing of power cables.

NsNrNss −

=


Page: 64

1. Sizing of excitation capacitance of an Induction Generator Excitation capacitance for Delta connection C (цF) = 1/(2*pi()*f*Xc*ηm) 1000*Pe* sin (cos-1 (power factor)) Or, C (цF) = ----------------------------------------------------- 3*V2*pf*2*pi()*f*ηm Where,

Xc (Ω) = V / Im V (V) = Rated Voltage of the motor (V) (phase to phase voltage, 380/400/415) Im (A) = Magnetizing Current = I rated at full load current (A) * sin (cos-1 (power factor)) I rated at full load current = Rated power (kW) * 1000/(V*pf) ηm = rated efficiency of motor at full load For star connected capacitors, the excitation capacitance is three times that for the Delta connection.

2. Sizing of MCCB/MCB (A) = 1.25*Pe * 1000/(V*pf)

Where,

1.25 = overrating factor by 25%. Pe (kW)= Installed capacity V (V) = Rated phase to neutral Voltage (V) (V*√3 for 3-phase) pf = power factor if induction generator is used

3. Sizing of power cable (A) = 1.7*I

Where, 1.70 = overrating factor by 70%. I (A) = Current = Generator size/(V *pf if induction generator is used) V (V) = Rated phase to neutral Voltage (V) (V*√3 for 3-phase) pf = power factor

9.4.2 Typical example of a 3-phase 60kW synchronous generator Electrical component calculations for an example of a three-phase 60kW synchronous generator at an altitude of 1500m are presented in Figure 9.1. The detailed step-by-step calculations are:

The size of synchronous generator:

Installed Capacity in kW Generator kVA = 1.3*----------------------------- A x B x C x D = 1.3*60.04/(0.96*0.96*0.83*0.8) = 127.70 kVA The higher size available in the market of 45kVA is used.

RPMP

fNspeedRotational 120)( = =120*50/4

= 1500 rpm Since Pe > 50kW, the ballast capacity of ELC extension (kW) = 60% * 1.2 * Pe + 40% * Pe = 0.6*1.2*60.04 + 0.4*60.04 = 67.24 kW I rated for Cable & MCCB at Generator side = 1000/ V rated * Generator size /1.732 = 1000 / 400*140/1.732 = 202.08 Amp


Page: 65

Calculated size MCCB/MCB (A) = 1.25*Pe * 1000/(V*pf) = 1.25*60.04*1000/(400*1.732*0.8) = 135.40 Amp Power cable inside the powerhouse Rating current = 1.5*I rated = 1.5*202.08 = 303.12 Amp For this current a 4-core copper armoured cable of ASCR 185mm2 is chosen.

Selection of Electrical EquipmentSpreadsheet developed by Mr. Pushpa Chitrakar, Engineering Advisor, SHPP/GTZReferances: 6,7,8,12,13 Date 11-Nov-2005SMALL HYDROPOWER PROMOTION PROJECT/GTZRevision 2005.10Project Upper Jogmai, IlamDeveloper Kankaimai Hydropower P LtdConsultant EPC ConsultDesigned Pushpa ChitrakarChecked Pushpa Chitrakar

INPUTDischarge (m3/s) 0.204 Power factor 0.8Gross head (m) 60.000 Safety factor of generator 1.3Overall plant efficiency (%) 50% Phase 3Temperature (oC) 45 Type of Generator 1Altitude (m) 1500 Over rating factor of MCCB 1.25ELC correction factor 0.83 Over rating factor of cable 1.5Frequency of the system (Hz) 50 No. of poles 4Capacity of used generator (kVA) 0 Rated rotor speed if induction generator N (rpm)

Delta

OUTPUTPe Electrical output (active power) (kW) 60.04 Ok

GeneratorTemp.factor 0.96 Altitude factor 0.96Capacity (kVA) 127.70 Actual available capacity (kVA) 140.00Synchronous rotational speed Ns (rpm) 1500

ELC capacity (kW) 60.04 Calculated Ballast capacity 1.2*Pe (kW) 72.04Ballast capacity of ELC-Extention (kW) 67.24

Rated Voltage (V) 400 Irated for Cable & MCCB (A) at Generator side 202.08

Rating of MCCB (A) 108.32 Calculated size of MCCB (A) 135.40

Cable Rating (A) 303.12 Size of 4-core cupper armoured cables 185

3-phaseSynchronous

Figure 9.1: Electrical components of a 20kW 3-phase synchronous generator.


Page: 66

9.4.3 Typical example of a single phase 20kW induction generator Figure 9.2 gives electrical equipment sizing of the previous project with a single phase induction generator with a rotor speed of 1450rpm. Since the electrical output is more than 10kW, a reminder error is flagged in the adjacent cell. The electrical components presented in Figure 9.2 are computed as:

The size of the asynchronous generator:

Installed Capacity in kW Generator kW = 1.3*---------------------------------------- = 1.3*20/(0.96*0.96) A x B = 28.25 kW The higher size available in the market of 30kW is used.

PfNspeedRotational 120)( = =120*50/4

= 1500 rpm Rotational speed of a generator = Ns*(1+(Ns-N)/Ns) = 1500*(1+(1500-1450)/1500) = 1550 rpm Excitation capacitance 1000*Pe* sin (cos-1 (power factor)) C (цF) = ----------------------------------------------------- 3*V2*pf*2*pi()*f*ηm 1000*20* sin (cos-1 (0.8)) C (цF) = ----------------------------------------------------- 3*4002*0.8*2*pi()*50*0.89 =123.16 цF I rated for Cable & MCCB at Generator side = 1000/ V rated * Generator size /pf = 1000 / 220*30/0.8 = 170.45 Amp MCCB/MCB (A) = 1.25*Pe * 1000/(V) = 1.25*20*1000/(220) = 142.05 Amp Power cable inside the powerhouse Rating current = 1.5*I rated = 1.5*170.45 = 255.68 Amp For this current a 2-core copper armoured cable of ASCR 185mm2 is chosen.


Page: 67

Selection of Electrical EquipmentSpreadsheet developed by Mr. Pushpa Chitrakar, Engineering Advisor, SHPP/GTZReferances: 6,7,8,12,13 Date 11-Nov-2005SMALL HYDROPOWER PROMOTION PROJECT/GTZRevision 2005.10Project Upper Jogmai, IlamDeveloper Kankaimai Hydropower P LtdConsultant EPC ConsultDesigned Pushpa ChitrakarChecked Pushpa Chitrakar

INPUTDischarge (m3/s) 0.08 Power factor 0.8Gross head (m) 50.968 Safety factor of generator 1.3Overall plant efficiency (%) 50% Phase 1Temperature (oC) 45 Type of Generator 2Altitude (m) 1500 Over rating factor of MCCB 1.25ELC correction factor 0.83 Over rating factor of cable 1.5Frequency of the system (Hz) 50 No. of poles 4Capacity of used generator (kW) 0 Rated rotor speed if induction generator N (rpm) 1450Capacitor configuration Delta Efficiency of motor at full load 89%

OUTPUTPe Electrical output (active power) (kW) 20.00 Use of 3-phase generator is mandatory

GeneratorTemp.factor 0.96 Altitude factor 0.96Capacity (kW) 28.25 Actual available capacity (kW) 30.00Synchronous rotational speed Ns (rpm) 1500 Rotational speed of the generator (rpm) 1550

IGC capacity (kW) 20.00 Calculated Ballast capacity 1.2*Pe (kW) 24.00Excitation Capacitance (micro F) 123.16

Rated Voltage (V) 220 Irated for Cable & MCCB (A) at Generator side 170.45

Rating of MCCB (A) 113.64 Calculated size of MCCB (A) 142.04

Cable Rating (A) 255.68 Size of 2-core cupper armoured cables 150

1-phaseInduction

Figure 9.2: Electrical components of a 20kW 1-phase induction generator.


Page: 68

10 MACHINE FOUNDATION

10.1 INTRODUCTION AND DEFINITIONS A machine foundation of a hydropower scheme is a gravity structure designed to transfer hydraulic forces from penstock, torque from rotating machines and gravity loads from generator, turbines and the foundation itself. Similar to an anchor block, the machine foundation should be stable against overturning, sliding and sinking/bearing. Standard dimensions can be referred to while dimensioning micro-hydropower machine foundation. It is strongly recommended to refer to suppliers while dimensioning mini and small hydropower machine foundations. A machine foundation of 500kW Jhakre Mini-hydropower project cited in “Civil Works Guidelines for Micro-Hydropower in Nepal” has been taken as an example in the spreadsheet “MachineFoundation”. A plan and a section of the considered foundation are presented in Figure 10.1. These figures are part of the presented spreadsheet and are interactive diagrams. The considered machine foundation is designed to support a directly coupled Pelton turbine and a generator. It is worth noting that the critical plane of a machine foundation depends on turbine axis and coupling types. A turbine axis (shaft) is perpendicular to the incoming flow for Crossflow, Pelton and Spiral case Francis turbines whereas it is parallel to the incoming flow for open flume Francis and other axial flow turbines. Coupling type (direct or belt drive) also determine a critical plane (XX or YY as presented in the spreadsheet) with respect to its stability. Stability along both these mutually perpendicular axes are analysed in the presented spreadsheet. Stepwise calculations of the considered example are presented in the following sections. For input to these stepwise calculations, refer to the input section of the spreadsheet is presented in Figure 10.1.

10.2 EXAMPLE

General Calculations htotal = hgross + hsurge = 51 m + 50 m = 101 m:

Force due to htotal , (FH) = (Pipe area) x 101 m x unit weight of water = 322

m/kN8.9m101m4

3.0××

∏

= 70.036 kN Weight of the three sections W1, W2. W3 as presented in Figure 10.1 are: W1 = 3kN/m22m 2.5m 1.5m 0.4 ××× =33.00 kN W2 = [(0.45 x 1.5 x 2.5)-(0.45 x 1 x 0.5)-(0.45 x 0.5 x 1)] x 22 = 27.225 kN W3 = 2.35 x 1.5 x 2.5 x 22 = 193.875 kN Overturning: Take sum of moments about point B (counter clockwise moments as positive):

ΣM@B = W1 x ( )×+

T2 WW+2.35+0.45+

20.4 ( ) 1.8F

22.35WW2.35

20.45

H3G ×−

++

+


Page: 69

= 33.00(3.0) + (27.225+2.94)(2.575) + (3.43+193.875)(1.175) – 70.036 x 1.8 = 282.455 kNm Sum of vertical forces, ΣV = W1+W2+W3+WT+WG = 33.00 + 27.225 + 193.875 + 2.94 + 3.43 = 260.477 kN Equivalent distance at which ΣV acts from point B:

d = m1.084260.477282.455

VM

==∑∑

eccentricity, e = L

dBase

2−

=

− 084.1

22.3

= 0.516 m

eallowable = mLBase 533.062.3

6==

Since e is less than eallowable , eccentricity is in the middle third. ∴The structure is safe against overturning. Bearing pressure:

Pbase max = V

A1 6e

Lbase base

∑ +

=

×

+× 3.2

0.516612.53.2

260.477= 64.038 kN/m2

Pbase min =

−∑

basebase L6e1

AV

=

×

−× 3.2

0.516612.53.2

260.477= 1.081 kN/m2

Since both pressures are within zero and 180 kN/m2 (max. allowed for soil) the structure is safe against sinking. Sliding: Assume that the friction coefficient between block and soil, µ = 0.5 ΣH = FH = 70.036 kN µ ΣV = 0.5 x 260.5 = 130.2 kN Factor of safety against sliding:

= 1.8670.036

130.238HV

==∑∑µ

> 1.5 OK

∴ The structure is safe against sliding.

Stability along YY is analysed in similar manner. It is worth noting that the machine foundation is not stable (for the stated factor of safety) against overturning and bearing along YY axis and this is the real critical case for the presented example in the guidelines. However, this critical case is not considered and not illustrated in the guidelines. The mismatch between Photo 8.4 (the actual case) and Figures 8.2 to 8.4 is quite noticeable. The Pelton turbine axis in Photo 8.4 perpendicular to XX axis (longer) whereas it is considered parallel to XX axis in the illustrated calculations.


Page: 70

Turbine and Generator Machine FoundationSmall Hydropower Promotion Project (SHPP)/GTZ Spreadsheet by Mr Pushpa ChitrakarReferances: 6,12,13,15,16 Date 24-May-2006SMALL HYDROPOWER PROMOTION PROJECT/GTZRevision 2006.05Project Jhankre mini-hydropowerDeveloperConsultant BPC HydroconsultDesignedChecked

INPUTGross head hg (m) 51.00 Design Discharge Qd (m3/s) 0.150Surge head hs (m) 50.00

Foundation PenstockFoundation on Soil Diameter dp (m) 0.300

Allowable bearing capacity Pall (kN/m2) 180 Material mild steelFriction coeff between block and soil m 0.5 Centreline above PH floor hp (m) 0.300

Length L (m) 3.2 Turbine PitBredth B (m) 2.5 Length of opening Lo (m) 0.450Height H (m) 1.5 Bredth of opening Bo (m) 0.500

Material of foundation Concrete Height of opening Ho (m) 1.000Density of foundation (kM/m3) 22 Height of tailrace canal Htr (m) 0.500

Electro-mechanical XX (m) YY (m)Weight of turbine Wt (kN) & cl position 2.943 0.625 1.250Weight of generator Wg (kN) & cl position 3.434 2.025 1.250

OUTPUT

LA along XX LA along YYForce due to h total of 101 m, Fh (kN) 70.036 1.800Foundation

W1 33.000 3.000 1.25W2 27.225 2.575 1.25W3 193.875 1.175 1.25

Sum of moments ΣM (kN-m) 282.455 199.530Sum of vertical forces ΣM (kN) 260.477 260.477

Lever Arm LA (m)Forces

Weight Wi (kN)

Machine Foundation Section

W1 W2 W3

Turbine CL Generator CL

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

XX (m)

Hei

ght Z

Z (m

)

Machine Foundation Plan

Turbine CL Generator CL

0.00.20.40.60.81.01.21.41.61.82.02.22.42.62.8

XX (m)

YY (m

)


Page: 71

OverturningEquivalent distance at which SM acts from critical point LA along XX LA along YY

1.084 0.7660.516 0.4840.533 0.417

Ok Not Ok

BearingLA along XX LA along YY

64.038 70.3791.081 -5.260

Ok Not Ok

SlidingLA along XX LA along YY

1.860 1.860Ok Ok

d (m)Eccentricity e, (m)Allowable eccentricity e all (m)Comment on overturning moment

Pressure at base

Factor of safety against sliding, FS slComment of sliding

PmaxPminComments on bearing

Figure 10.1: Layout of MachineFoundation Spreadsheet.


Page: 72

11 TRANSMISSION AND DISTRIBUTION

11.1 INTRODUCTION AND DEFINITIONS Power generated at a powerhouse is evacuated to load centres or grids with the help of transmission and distribution lines. According to the Nepal Standards, 400/230V is the standard minimum voltage. 400/11000V system is used in micro-hydropower transmission system where as 11 kV/33 kV is used in mini and small hydropower transmission system. 11 kV and 33 kV are also considered to be distribution voltage by Nepal Electricity Authority (NEA). Use of standard voltages in micro hydropower projects is recommended so that the power can be easily synchronized and evacuated to grid in future.

11.2 GENERAL RECOMMENDATIONS AEPC MGSP/ESAP has formulated following guidelines regarding micro-hydropower transmission and distribution systems:

1 Cable configuration and poles: Buried or suspended on wooden or steel or concrete poles.

2 Permissible Voltage drop: 10% of nominal value at point of use.

3 Conductor: Aluminum conductor steel reinforced (ACSR) or Arial Bundled Cable (ABC)

4 The ASCR specifications are presented in Table 11.1. Table 11.1: ASCR specifications

ACSR Code

number Type of ACSR

Resistance Ohm/km

Current rating max

Amps

Equivalent Copper area

mm2

Inductive Reactance Ohm/km

Sp. Weight (kg/km)

Sp. Cost (Rs/km)

1 Squirrel 1.374 76 13 0.355 80 13000 2 Gopher 1.098 85 16 0.349 106 14500 3 Weasel 0.9116 95 20 0.345 128 15500 4 Rabbit 0.5449 135 30 0.335 214 25750 5 Otter 0.3434 185 50 0.328 6 Dog 0.2745 205 65 0.315 394 52000

Note: Sp. Costs are taken from the guidelines and are lower than the market price. It is recommended to refer to the actual market price in the design.

11.3 PROGRAM BRIEFING AND EXAMPLES 11.3.1 Program Briefing

1 The presented spreadsheet is designed to calculate transmission parameters for three phase 33kV, 11kV and 400V and single phase 230V transmission and distribution lines.

2 Balanced load is assumed, i.e., neutral conductor does not carry any current.

3 With a power factor of 0.8, the rated current and voltage drop are calculated as: Table 11.2: Rated current and voltage drop calculation

4 Impedance (Z) = √(Resistance2+Reactance2).

5 Voltage at node (Vi)

Phase Current (A) Voltage drop (dV) 3-phase Power*1000/(1.732*V* power factor) 1.732*IA*Z*Lkm 1-phase Power*1000/(V*power factor) 2*IA*Z*Lkm

Phase Voltage at node (Vi) Single to single phase or 3 to 3 phase Vprevious - dV


Page: 73

6 Spreadsheet protection: Transmission line networks is project specific and does not match each other. Therefore, this spreadsheet is not protected to match the transmission line networks of the considered project.

Start

CurrentResistanceReactanceImpedance

End

Node & reach names, reach lengths, phase, Power at node, ASCR code,

Remarks for repeated lengths

ProjectName,

Location,

Voltage dropVoltage at node

Length of cablesCost of cables

Lengthof

neutralcables

Figure 11.1: Flow chart of transmission and distribution line computation. The grid and load presented in Figure 11.2 are used for the calculations presented in Figure 11.3.

Figure 11.2: Transmission line and load used for the example.

Three to single phase (400V to 230V) Vprevious/1.732 - dV

Reach length (m)/Phase/Load (kW)

Transformer # 1

Node/Load (kW) at nodes

Legends


Page: 74

Transmission line calculations Reach: powerhouse to node A to B The installed capacity of the considered scheme is 36kW. Out of this, a total of 16kW of power is transmitted from the powerhouse to nodes A, B, C and D. The transmission line from the powerhouse to node A is 400V three phase four wires type. Power from node A to other load centres are transmitted using 230V single phase two wire systems. Lengths and other information of these reaches are presented in Figures 11.2 and 11.3. Reach PH-A By Trial and error to limit voltage drop at the end of last load centre, a dog is found to be suitable. For this cable, Z = √(I2 + L2) = √(0.2752 + 0.3152) = 0.418 Ohm /km Current, I PH-A = Power*1000/(√3*V* power factor) = 16*1000/(√3*400*0.8) = 28.87 A Voltage drop, dV = √3* I PH-A *Z*Lkm = √3* 28.87 *0.418 *0.300 = 6.3 V dV% = dV/VPH = 6.3/400 *100 = 1.58%, which is within the limit of 10%. A relatively lower value is recommended at this point because voltage drop at the end of either B or C or D has to be within 10%. Voltage @ node A, VA = VPH – dV = 400 – 6.3 = 393.70 V Reach A-B As stated, this is single phase line. By Trial and error to limit voltage drop at the end of last load centre, an otter is found to be suitable. For this cable, Z = √(I2 + L2) = √(0.5452 + 0.3352) = 0.640 Ohm /km Voltage at A for single phase, VA1 = 393.70/√3 = 227.30 V Current, I A-B = Power*1000/(VA* power factor) = 5*1000/(227.30 *0.8) = 27.50 A Voltage drop, dV = 2* I A-B *Z*Lkm = 2* 27.50 *0.640 *0.500 = 17.60 V Voltage at B for single phase, VB = 227.30 - 17.60 = 209.70 V dV% = dVtotal/VPH = (1-209.70 /230) *100 = 10.40%, which is slightly above the limit of 10%. Hence OK for micro-hydropower project. Calculations for other nodes C and D shall be calculated in similar manner. It is worth noting transmission line from A to C and D are constructed by splitting lines from A and therefore the voltage at A for these calculations should also be same (i.e., 227.30 V). It should also be noted that standard voltage should be used at the outlet of the transformers. The voltage at the outlet is standarised using tapping switch adjustment. The length of neutral wire depends on the configure of the transmission line network and user’s choice of type of the neutral wire. Therefore, the length and type of neutral wire is presented as an input parameter. Transmission line calculations for mini and small hydropower project shall be calculated similar to the calculations presented in Reach PH-A. Power from most of the mini and small hydropower projects in Nepal are evacuated to load centres or grids. Since the tariff for these projects is fixed on energy basis, energy losses while transmitting power to the load centres or grids should also be calculated and considered in the financial analyses. Power losses is not included in this spreadsheet but included in the Voltage Drop calculation under Utility. It is calculated using following equation: Ploss = √3*(V1-V2)/2/1000*I*pf


Page: 75

Transmission and Distribution System:

Small Hydropower Promotion Project (SHPP)/GTZ Spreadsheet by Mr Pushpa ChitrakarReferances:2,4, 6,12,13,15,16 Date 20-Apr-2006SMALL HYDROPOWER PROMOTION PROJECT/GTZ Revision 2006.03Project: Upper Jogmai, Ilam Cable SummaryDeveloper Kankaimai Hydropower P Ltd Type Length(km)Consultant EPC Consult Squirrel 7.02Designed Pushpa Chitrakar GopherChecked Pushpa Chitrakar Weasel 10.00

Rabbit 2.36Otter 1.55Dog 2.40

Total Cost(Rs) 486080.00Length of neutral cables (km)

Node nameReach name

Reach Length

(km)Phase 1,3,11

Power at next node

(kW)ACSR type

Vrated @ node & Current

(A) V @ prev node (V)

Rated Voltage d/s prev node

(V)

Reach Voltage drop (V)

Volt at node branch (V) % voltag drop

3 400.00 400.00 400.00 400.00PH A PHA 0.300 3 16 Dog 28.87 393.70 400.00 6.30 393.70 1.58A B AB 0.500 1 5 Rabbit 27.50 393.70 227.30 17.60 209.70 10.40

C AC 0.090 1 5 Rabbit 29.80 393.70 227.30 3.40 223.90 2.65D AD 0.090 1 6 Rabbit 33.50 393.70 227.30 3.90 223.40 2.87

3 400.00 400.00 400.00 400.00PH T1 PHT1 0.050 3 20 Otter 36.08 400.00 400.00 1.50 398.50 0.38

11 11000.00 11000.00 11000.00 11000.00T1 T2 T1 T2 1.500 11 20 Squirrel 1.31 11000.00 11000.00 4.70 10995.30 0.04

3 400.00 400.00 400.00 400.00T2 E T2 E 0.300 3 20 Dog 36.08 400.00 400.00 7.80 392.20 1.95

1 226.44 226.44 226.44 226.44T2 J T2 J 0.300 1 20 Dog 110.41 226.44 226.44 27.70 198.74 13.59

1 226.44 226.44 226.44 226.44E F EF 0.300 1 6 Otter 33.12 217.04 226.44 9.40 217.04 5.64F H FH 0.400 1 5 Otter 28.80 217.04 217.04 10.90 206.14 16.01

1 226.44 226.44 226.44 226.44E F E F 0.300 1 7 Rabbit 38.64 211.64 226.44 14.80 211.64 7.98F G FG 0.200 1 5 Rabbit 29.53 211.64 211.64 7.60 204.04 19.27

1 226.44 226.44 226.44 226.44E F EF 0.300 1 1 Squirrel 5.52 221.84 226.44 4.60 221.84 3.55F M FM 0.600 1 1 Squirrel 5.63 221.84 221.84 9.40 212.44 11.19

1 217.04 217.04 217.04 217.04F K F K 0.180 1 2 Squirrel 11.52 217.04 217.04 5.80 211.24 8.16

1 211.64 211.64 211.64 211.64F L F L 0.180 1 1 Squirrel 5.91 211.64 211.64 3.00 208.64 9.29

Intermediate Calculation

PH-A-B-C-D

T1-T2

T2-E

E-H (y)

PH-T1

E-J ( r )

E-G (b)

E-M ( r)

F-K (y)

F-L(b)


Page: 76

10

Squirrel Gopher Weasel Rabbiit Otter Dog

0.901.000.180.18

0.15

4.50

0.90

0.60

0.600.80

0.600.40

0.601.20

0.36

0.36 Figure 11.3: Typical example of a low voltage transmission line.


Page: 77

12 LOADS AND BENEFITS

12.1 GENERAL By optimising the use of available energy by allocating it in different time slots, benefit from a micro hydro scheme can be maximized. Based on the AEPC MGSP/ESAP guidelines, a spreadsheet on loads and benefits is presented for concerned stakeholders to arrive to the most optimum pre-construction decision.

12.2 GENERAL RECOMMENDATIONS / AEPC GUIDELINES 1. Average subscription wattage should not exceed 120W per household.

2. Minimum of 10% of total energy output as productive end use is mandatory.

3. Multipurpose scheme is preferable.

12.3 PROGRAM BRIEFING AND EXAMPLE 12.3.1 Program Briefing A flow chart of loads and benefits analyses used in the spreadsheet is presented in Figure 12.1. Based on this flow chart, an example is presented in Figure 12.2. The main features and assumptions are:

1. In case the guidelines are similar to that set by AEPC, this spreadsheet can also be used to all micro hydropower project. For the first three years of operation, one set of domestic and five different end uses can be defined in five different time slots in the 24-hour load duration curve.

2. Probable business load after three years of operation can defined based on the AEPC requirements.

3. Annual available energy, annual load, productive end use load factor and annual total income are calculated and subsequently used in the financial analyses.

4. A load duration chart for the first three years of operation is presented at the end of the spreadsheet. This chart is very helpful in planning and allocating different loads so that the benefits are maximized.

Start

Annual energy Yearly loads EU factors

Yearly income

End

Installed capacity, present loads & tariff (24 hr, 5 slots) Future EU load & tariff (1 time slot)

Project Name,

Location,

24 hr load Load duration

Graph (decision making)

Figure 12.1: Flow chart of the load and benefits calculation spreadsheet.


Page: 78

Loads and Benefits calculations Loads and benefits calculation in the presented spreadsheet are divided into two main parts. The first part covers existing or committed business loads while the second part covers probable business load after this period. This spreadsheet is prepared to mimic AEPC subsidy calculation format. A 96.1kW Gaddigadh MHP, Doti is used as an example in the spreadsheet. The stepwise calculations for the first three years of load and benefit calculations are presented. Domestic Loads Annual available energy, Ey = operating days * installed capacity * 24 = 330*96.1*24 = 761112 kWh Load P (kW) =Beneficiary households (HH) *Average HH load /(1-loss)/1000 = 471 * 85 /(1-0.1)/1000 = 44.483 kW Yearly load P y = operating days * daily load (D) = 330 * (5* 88 + 2*91.1) = 205326 kWh Average daily operating hours = Py/ D /P = 205326/330/44.483 = 13.987 hours/day Load factor = Py / Ey * 100 = 205326/761112*100 = 26.98% Annual Income By =tariff * HH * load*12 = Rs 1*471*85*12 = Rs 480,420 Existing/ Committed business loads Existing or committed business loads are calculated in similar manner. The calculated values are presented in Figure 12.3. As presented in the figure, the annual end use and productive end use load factor are 117060 kW and 15.38% respectively. Similarly the total plant factor and annual income are 42.36% and Rs 916,050 respectively. Since the committed end use is more than 10%, this project is recommended for implementation using AEPC subsidy. The presented load duration chart in Figure 12.2 suggests that the scheme is mainly dominated by domestic load. Other end uses can be incorporated even at subsidized rate during 5:00 to 17:00 and 20:00 to 24:00 hours. The available power varies from zero to 96.1kW during these periods. In case the scheme has to share water with other existing water utilities such as irrigation systems, this can be arranged during the non-operating hours or during partial load hours. Thus, this load duration curve can also be used to maximize benefits even at lower tariff during such hours.

Load Duration Chart for the first three years of operation of Gaddi Gad Khola

0

20

40

60

80

100

120

140

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Time (hrs)

Inst

alle

d Cap

acity

& L

oad

(kW

)

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Domestic Agro-processing Bakery Saw Mill Herbs Processing Load 5 Load 6 Installed Capacity Figure 12.2: Load duration chart


Page: 79

LOADS AND BENEFITSSmall Hydropower Promotion Project (SHPP)/GTZ Spreadsheet by Mr Pushpa ChitrakarReferances: 1,2,3,4, 6,12,13,15,16 Date 20-Apr-2006

SMALL HYDROPOWER PROMOTION PROJECT/GTZ Revision 2006.03Project: Gaddi Gad Khola Location: Ladagada VDC, DotiDeveloper Gaddi Gad Khola MHPConsultant PerinialDesigned Pushpa ChitrakarChecked Pushpa Chitrakar

INPUTGeneralPower Output (kW) 96.1 Domestic lightingName of the Source Gaddi Gad Khola Average subscription/household (W/HH) 85

System loss 10%Beneficiary HH (nos.) 471 time 5 8 18 20Plant's operating days 330 load 88 91.1

440 182.2Loads (kWh or W/m) Operating days/yearTariff (Rs) Probable Business Load Expected after 3 yearsDomestic 330 1.00 Operating d/y Tariff (Rs) Load From (hr) To (hr)Agro-processing 330 6.00 Metal Workshop 330 6.00 10 12 16Bakery 320 6.00 Photo Studio 320 6.00 1 8 20Saw Mill 300 5.00 Dairy Processing 320 6.00 8 8 18Herbs Processing 180 5.50 Cold Store 310 6.00 6 8 18Load 5 330 Load 5Load 6 330 Load 6

Proposed end uses and operting hourstime (hr) 4 12 16 22 Daily Energy Demand (Dd) kWh 1037Agro-processing 22.5 Yearly Energy Demand (Dy) kWh 378578time (hr) 8 14 18 22 Average Load Factor 49.97%Bakery 9time (hr) 3 16 18 22Saw Mill 10time (hr) 3 12 17 22Herbs Processing 25time (hr) 6 8 15 22Load 5 15time (hr) 3 5 10 22Load 6 12

36 36.00OUTPUT

SummaryAnnual Available kWh 761112

First 3 years After 3 yearsYearly end use load (kWh) 117060 147680Productive end use load factor (%) 15.38 19.40Total load plant factor 42.36 50.40Annual total (domestic + end uses) Income (Rs) 916,050 1,099,770

End Use Load Yearly Load(kW) Hours/day Days/year kWh LF (%)

Domestic Lighting 44.483 13.987 330 205326 26.98 480,420

Agro-processing 22.5 4 330 29700 3.90 178200Bakery 9 6 320 17280 2.27 103680Saw Mill 10 2 300 6000 0.79 30000Herbs Processing 25 5 180 22500 2.96 123750Load 5 15 6 330 29700 3.90Load 6 12 3 330 11880 1.56Total 117060 15.38 435,630 Total Annual Income from sales of electricity 916,050

Metal Workshop 10 4 330 13200 1.73 79200Photo Studio 1 12 320 3840 0.50 23040Dairy Processing 8 10 320 25600 3.36 153600Cold Store 6 10 310 18600 2.44 111600Load 5Load 6Total additional annual income after 3 years 61240 8.05 183,720 Productive End Use (%) 19.40

Annual Income (Rs)

Existing/Committed Business Load

Probable Business Load after 3 years

Operation Period

Figure 12.3: An example of load and benefits calculation.


Page: 80

13 COSTING AND FINANCIAL ANALYSES

13.1 INTRODUCTION AND DEFINITIONS As per the guidelines and standards set aside by AEPC, this spreadsheet tests financial viability of a micro-hydro scheme for the subsidy approval. The base of the robustness of the project is mainly its financial sustainability during its life span of 15 years. Positive Net Present Value (NPV) of project cost (equity) and benefit streams based on based on 4% of discount rate is expected for subsidy approval.

13.2 GENERAL RECOMMENDATIONS / AEPC GUIDELINES 1. 15 years as the economic life span of the project for calculating financial parameters. 2. Total cost of the project including subsidy should be limited to

Table 13.1: Per kilowatt subsidy and cost ceiling as per AEPC Walking distance from nearest road head Subsidy Ceiling less than 2 days walking distance 70000 170000 2-5 days walking distance 78750 178750 more than 5 days walking distance 91500 191500

3. Net present value of equity investment at a discount rate of 4% should be positive.

13.3 PROGRAM BRIEFING AND EXAMPLE 13.3.1 Program Briefing The spreadsheet presented requires the total costs including financing of the project and annual costs and benefits as inputs to calculate the financial parameters such as the net present value and cost per kilowatt. The flow chart on which the spreadsheet is based is presented in Figure 13.1. Annual cash flows for the stated planning horizon is presented and used to calculate different financial parameters. Present values of costs and benefit streams are calculated to estimate NPV of the scheme. The total capitalized cost of the project includes subsidy based on accessibility of the project site, loans from banking and other lending agencies, cash and kind equities and other sources such as donations, etc. Investment costs are presented in Figure 13.2. Costs required for the operation and maintenance of the project is calculated. Revenues with and without probable business loads are calculated (Refer to Chapter 11 for business loads). NPVs of the project on total investment, total cost excluding subsidy and equity only are calculated and compared. As stated earlier, the minimum criteria for subsidy approval is to have positive NPV for equity only consideration without probable business loads. Cost per kilowatt to be within the specified limits is another criteria for the subsidy approval. The subsidy policy came into effect because of the fact that implementation of micro-hydropower projects in Nepal is not financially feasible and sustainable without subsidies. Moreover, soft loans and relatively lower discount rate are applied to make them more sustainable. It is worth noting that the only loans and cash equity are considered as investments in the financial analyses. The loans shall be paid back within the stated payback periods.


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Start

NPV w & w/o probable business loadCost per kW

Subsidy per HHCash flows

End

Sources of investmentPayback of loanDiscount factor

Breakdown of investment costAnnual operating cost

ProjectName,

Location,

Figure 13.1: Flow chart for Project costing and financial analyses. 13.3.2 Typical example of costing and financial analyses A typical example of costing and financial analyses of a micro-hydro scheme based on projected cash flow is presented in Figure 13.2. Since the economic life span of mini and small hydropower is more than 15 years, use of the spreadsheet should be limited to micro-hydropower projects only. However, financial analyses of mini and small hydropower projects can be carried out using the stepwise calculations presented in the subsequent section.

Financial Analyses Project costs and benefit related are presented in Figure 13.2. The summary of costs and benefits are: Total project cost P = Rs 12,734,865 Total loan L = Rs 1,890,044 Cash equity = Rs 1,200,000 Operation and maintenance cost = Rs 305,004 Annual installment of bank loan (annuity) = Rs 303,364 Alternatively, an Excel built-in function PMT (interest rate, payback year, loan) can also be used to calculate the annual installment. If the installment mode is other than annual (such as monthly and quarterly), it is recommended to use Loan Payment module of the presented Utility spreadsheet. Based on the projected annual cash flows (CFs), NPV of the project can be calculated by using following equation.

1)1()1(

−++×

= n

n

iiiL

1%)31(%)31%(31890044

7

7

−++×

=

nn

iCF

iCF

iCFCFNPV

)1(.............

)1()1( 22

11

0 +++

++

++= ∑

= +=

n

tt

t

iCF

0 )1(


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An alternative equivalent Excel built-in function NPV(Discount Factor, Cash Flows)*(1+Discount Factor) is used in this spreadsheet. NPV of equity without probable business load is, NPV equity = NPV(Discount Factor, Cash Flows)*(1+Discount Factor) = NPV(4%, -1200000, 307682, …., 611046,…)*(1+4%) = Rs. 3,773,038 OK since it is positive. Cost per kilowatt = Total Project Cost / Project Size = 12,734,865/96.1 = Rs 132,517/kW OK since it is within the limit Rs 191,500/kW for projects located with an access of five days or more of walking distance. Based on above results, the project is financially viable for subsidy approval. Other similar financial parameters for different cases are calculated in similar manner.

Project Costing and Financial AnalysesSmall Hydropower Promotion Project (SHPP)/GTZ Spreadsheet by Mr Pushpa ChitrakarReferances: 1,2,3,4, 6,7,8,12,13 Date 23-Apr-2006SMALL HYDROPOWER PROMOTION PROJECT/GTZ Revision 2006.03Project Upper Jogmai, IlamDeveloper Kankaimai Hydropower P LtdConsultant EPC ConsultDesigned Pushpa ChitrakarChecked Pushpa Chitrakar

INPUTProject size (kW): 96.10Total Project Cost (Rs.) 12,734,865

Subsidy/kW Total subsidy Bank loan Other loan Cash equity Kind equity Others91500 Rs/kW x 96.1 = 8793150 1,890,044 1,200,000 851,671

3%7

Plant life N (yr) 15Discount Rate I (%) 4%

O & M (Rs) 305,004Investment Cost (Rs) 8,516,715 Salary 114000Mechanical components 999,040 Installation 232,500 SparesElectrical component 2,061,717 Commissioning Maintenance 171,000Civil component 1,363,497 VAT 623,611 Office expensesSpare parts & tools 57,550 Contingencies Miscellaneous 20,004Transport. 3,178,800 Others Others

Cost Summary NPV Based on Different Project CostsProject cost (Rs) 12,734,865 NPV Probable Business LoadAnnual Operation, Maintenance and other Costs (Rs) 305,004 Without WithAnnual Income without probable business loads (Rs) 916050 Total investment cost -3,543,677 -2,010,846Annual Income with probable business loads (Rs) 1099770 Total Inv Cost-Subsidy 5,249,473 6,782,304Annual installment for Bank loan 303364 Equity 3,773,038 5,305,869Annual installment for other loan NANPV on equity without probable business load (Rs)+ve 3,773,038NPV equity with probable business load (Rs)+ve 5,305,869Cost/Kw =>>Ok 132,517Subsidy/HH 18,669

Annual Cash Flows

Income Cash flow Income Cash flow1,200,000 -1,200,000 -1,200,000

1 305,004 303,364 916,050 307,682 916,050 307,6822 305,004 303,364 916,050 307,682 916,050 307,6823 305,004 303,364 916,050 307,682 916,050 307,6824 305,004 303,364 916,050 307,682 1,099,770 491,4025 305,004 303,364 916,050 307,682 1,099,770 491,4026 305,004 303,364 916,050 307,682 1,099,770 491,4027 305,004 303,364 916,050 307,682 1,099,770 491,4028 305,004 916,050 611,046 1,099,770 794,7669 305,004 916,050 611,046 1,099,770 794,766

10 305,004 916,050 611,046 1,099,770 794,76611 305,004 916,050 611,046 1,099,770 794,76612 305,004 916,050 611,046 1,099,770 794,76613 305,004 916,050 611,046 1,099,770 794,76614 305,004 916,050 611,046 1,099,770 794,76615 305,004 916,050 611,046 1,099,770 794,766

Interest rate i (%)Payback period n (yr)

Without Probable Business Loads With Probable Business LoadsYear Equity O & M costs Loan repayment

more than 5 days walking distance

Figure 13.2: A typical example of project costing and financial analyses.


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14 UTILITIES

14.1 INTRODUCTION In this spreadsheet tools for independent calculations are presented. These tools are especially helpful in case quick and handy independent computations are required. Some of the presented tools are: 14.1.1 Uniform depth of a rectangular or trapezoidal canal Calculation of uniform depths of an open channel is an iterative process. Manning’s equation is used for calculating uniform depth. VBA for Excel is used for this iterative process. A typical calculation for a trapezoidal section is presented in Figure 14.1. Uniform Depth of a Trapezoidal Canal (Y-m)Small Hydropower Promotion Project (SHPP)/GTZ Spreadsheet by Mr Pushpa Chitrakar

Upper Jogmai, Ilam Date 01-May-2006

Stone masonry canal Revision 2006.05

Design Discharge (l/s): 1,0001/Mannings Coeff (M): 50.00001/Canal Slope (S): 300Freeboard, FB (m) 0.2Wall Thickness, t (m) 0.3Width of Canal, b (m): 1.000

Z= 0.50Top width, T (m) 1.572Uniform Depth (Y-m) 0.572

Unlined fissured/disintegrated rock/tough hardpen cut

Canal Wall Geometry

WallNWL = 572 mm &

T = 1572 mm

Figure 14.1: A typical example of uniform depth calculation of a trapezoidal section 14.1.2 Payment of loan for different periods (monthly, quarterly and yearly) The tool presented in Figure 14.2 is useful for calculating equal installment payback (EMI) for a given loan at a specific interest rate and terms. Three modes namely monthly, quarterly and yearly payments are available in this tool.


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Payment of a loanSmall Hydropower Promotion Project (SHPP)/GTZ Spreadsheet by Mr Pushpa Chitrakar



Payback 1

Loan amount (NRs) : 1,800,000 Starting Month 2Interest rate (APR): 13.00% Starting Year 2006Yearly payment and No 10

Yearly Payment 331,721.20

Back to Utilities Print Generate Schedule

Figure 14.2: A typical example EMI calculation A full payment schedule can also be generated by clicking Generate Schedule button. A typical schedule is presented in Figure 14.3. Payment Schedule of Upper Jogmai, Ilam with Loan(1800000) & Interest(13%)

Month Pmt No. Pmt Principal Interest BalanceFeb-06 1 Rs 331,721 Rs 97,721 Rs 234,000 Rs 1,702,279Feb-07 2 Rs 331,721 Rs 110,425 Rs 221,296 Rs 1,591,854Feb-08 3 Rs 331,721 Rs 124,780 Rs 206,941 Rs 1,467,074Feb-09 4 Rs 331,721 Rs 141,002 Rs 190,720 Rs 1,326,072Feb-10 5 Rs 331,721 Rs 159,332 Rs 172,389 Rs 1,166,740Feb-11 6 Rs 331,721 Rs 180,045 Rs 151,676 Rs 986,695Feb-12 7 Rs 331,721 Rs 203,451 Rs 128,270 Rs 783,244Feb-13 8 Rs 331,721 Rs 229,899 Rs 101,822 Rs 553,345Feb-14 9 Rs 331,721 Rs 259,786 Rs 71,935 Rs 293,559Feb-15 10 Rs 331,721 Rs 293,559 Rs 38,163 (Rs 0)

Figure 14.3: Generated Schedule of EMI calculation 14.1.3 Power calculations This tool is useful for calculating power based on AEPC guidelines for subsidy criteria and actual power based on known cumulative efficiency. A typical example is presented in Figure 14.4 below: Actual vs AEPC Power (Pe-kW)Small Hydropower Promotion Project (SHPP)/GTZ Spreadsheet by Mr Pushpa Chitrakar



Discharge (l/s): 120Cumulative efficiency including head loss (n%) 80.00%Gross Head (H-m) 300.00Actual Power (Pact-kW) 282.53Power MGSP-ESAP (Pe-kW) 176.58 Figure 14.4: A typical example of power calculation


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14.1.4 Spillway sizing. The spillway sizing tool is useful for calculating spillway lengths for different spillway shapes with different downstream conditions (downstream obstructed or free). As presented in Figure 14.5, this tool calculates actual spillway length required for critical conditions of load rejection and off-take flood. Spillway Lengths (m)Small Hydropower Promotion Project (SHPP)/GTZ Spreadsheet by Mr Pushpa Chitrakar

Upper Jogmai, Ilam Date 15-Apr-2006


Flood discharge (l/s): 2,000

Design discharge (l/s): 500Overtopping height (ho) mm: 300Spillway discharge coeff 1.5L spillway min for Qf m & full height 8.11Length of spillway Ls1 for Qf m & half height 17.21

1.5

Figure 14.5: A typical example of spillway sizing

14.1.5 Voltage drops of transmission line. This tool calculates voltage drop, percentage voltage drop and voltage at a lower end of a transmission line segment for a given power. A typical example is presented in Figure 14.6. Voltage Drop

Small Hydropower Promotion Project (SHPP)/GTZ Spreadsheet by Mr Pushpa Chitrakar



Reach length, L (km) 1.000Voltage at 1st node, V1 (V) 230Power, P (kW) 20ASCR type 6.00Phase at 1st node, φ1 (1/3) 1Phase at 2nd node, φ2 (1/3) 1Current, I (A) 108.70Impedence, Z (Ω/km) 0.4178Voltage at 2nd node, V2 (V) 151.34Power loss P loss (kW) 3.42Voltage drop, dV (V) 78.66% Voltage drop 39.49

Dog

Figure 14.6: A typical example of transmission line calculation


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14.1.6 Pipe friction factor. This tool is useful for calculating friction factor. Manual friction factor calculation involves a long and tedious process and can easily go wrong. The tool presented in Figure 14.7 also calculates head losses in metres and percentage and net head for given inputs. Friction Factor (f) & Net headSmall Hydropower Promotion Project (SHPP)/GTZ Spreadsheet by Mr Pushpa ChitrakarUpper Jogmai, Ilam Date 01-May-2006Stone masonry canal Revision 2006.05

Discharge (m3/s) 0.500 FlowGross head (m) 63 Velocity, v(m/s) 2.546479089Pipe roughness ks (mm) 0.010 Reynold's nr, (R ) 1116876.794Pipe diameter (mm) 500.00 Laminar Flow 5.73027E-05Pipe Length (m) 100 9.170E+00Turbulent headloss factor (K) 1.50 9.170E+00Friction factor f 0.0119 Transitional Flow & Turbulent Flow0.011893135Headloss hl (m) 1.282Headloss hl (%) 2.03Net Head (m) 61.718 Figure 14.7: A typical example of pipe friction calculation


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15 REFERENCES

1. Mini-Grid Support Programme, Alternative Energy Promotion Centre, Kathmandu, Nepal (2002), Peltric Standards

2. Mini-Grid Support Programme, Alternative Energy Promotion Centre, Kathmandu, Nepal (2003),

Preliminary Feasibility Studies of Prospective Micro-hydro Projects 3. Mini-Grid Support Programme, Alternative Energy Promotion Centre , Kathmandu, Nepal(2001),

Technical Details and Cost Estimate 4. Mini-Grid Support Programme, Alternative Energy Promotion Centre , Kathmandu, Nepal(2003),

Guidelines for Detailed Feasibility Study of Micro-Hydro Projects

5. European Small Hydropower Association (1998), Layman's Guidebook on How to Develop a Small Hydro Site

6. BPC Hydroconsult, Intermediate Technology Development Group (ITDG), Kathmandu, Nepal

(2002), Civil Works Guidelines for Micro-Hydropower in Nepal. 7. United Nations Industrial Development Organization (UNIDO), Report on Standardization of Civil

Works for Small Hydropower Plants 8. GTZ/Department of Energy Development, Energy Division, Papua New Guinea, Micro Hydropower

Training Modules (1994), Modules 1-7, 10, 13, 14 & 18B. 9. American Society of Civil Engineer (ASCE), Sediment Transportation. 10. KB Raina & SK Bhattacharya, New Age International (P) Ltd (1999), Electrical Design Estimating

and Costing. 11. Badri Ram & DN Vishwakarma, Tata McGraw-Hill Publishing Company Limited, New Delhi 1995,

Power System Protection and Switchgear, 1995. 12. Adam Harvey et.al. (1993), Micro-Hydro Design Manual, A guide to small-scale water power

schemes, Intermediate Technology Publications, ISBN 1 85339 103 4. 13. Allen R. Inversin (1986), Micro-Hydropower Sourcebook, A Practical Guide to Design and

Implementation in Developing Countries, NRECA International Foundation, 1800 Massachusetts Avenue N. W., Washington, DC 20036.

14. Helmut Lauterjung/Gangolf Schmidt (1989), Planning of Intake Structures, GATE/GTZ, Vieweg. 15. HMG of Nepal, Ministry of Water Resources, Water and Energy Commission Secretariat,

Department of Hydrology and Meteorology, Methodologies for estimating hydrologic characteristics of un-gauged locations in Nepal (1990).

16. HMG/N, Medium Irrigation Project, Design Manuals, 1982 17. His Majesty's Government of Nepal, Ministry of Water Resources, Department of Irrigation,

Planning and Design Strengthening Project (PDSP), United Nations Development Programme (NEP/85/013) / World Bank, Design Manuals for Irrigation Projects in Nepal, 1990.

18. ITECO, DEH/SATA Salleri Chialsa Small Hydel Project (1983), Technical Report.


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19. P.N. Khanna (1996), Indian Practical Civil Engineer's Handbook, 15th Edition, Engineer's Publishers, Post Box 725, New Delhi - 110001.

20. ITDG, Electrical Guideline For Micro-Hydro Electric Installation.

21. REDP, REDP Publications, Environment Management Guidelines, 1997

22. ITDG, IT Nepal Publications, Financial Guidelines for Micro-hydro Projects, 1997

23. IT Nepal Publications, Management Guidelines For Isolated MH Plant In Nepal, 1999.

24. ITDG/ESAP, Guidelines relating to quality improvement of MH plants, 1999

25. ICIMOD, Manual for Survey and Layout Design of Private Micro Hydropower Plants.

26. Norwegian Water Resources and Energy Administration, The Norwegian Regulations for Planning,

Construction and Operation of Dams, Norwegian University Press, Oslo, Norway, 1994.

27. Various Consultants, AEPC subsidized Nepali micro-hydropower (up to 100kW) Pre-feasibility and Feasibility Study Reports (about 400 projects), 2002-2004.

28. Various Consultants, SHPP/GTZ assisted Nepali small hydropower (up to 10MW) study reports at

various levels (about 65 projects), 2001-2006.

29. Small Hydro Engineers Consultants P Ltd, Detailed Project Report (DPR) of 5MW Soldan Small Hydropower Project, Himachal Pradesh, India, 2001.

30. Small Hydro Engineers Consultants P Ltd, Detailed Project Report (DPR) of 4.5MW Sarbari Small

Hydropower Project, Himachal Pradesh, India, 2001.

31. Entec AG, Switzerland, 240 kW Dewata Tea State Mini Hydropower Scheme Feasibility Study, West Java, Indonesia, 2000.

32. Entec AG, Switzerland, 585 kW Jegu Village Mini Hydropower Plant Feasibility Study, East Java,

Indonesia, 2000.

33. Son Vu Energy Development Joint Stock Company, 3.2MW Nhap A Hydropower Project Final Feasibility Report, Hoa Binh, Vietnam, 2005.

34. Hanoi Construction Company, 3MW Sao Va Hydropower Project Feasibility Report, Nghe An

Province, Vietnam, 2005.


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DRAWINGS

TYPICAL MICROHYDROPOWER DRAWINGS


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TYPICAL DRAWINGS OF 1500KW LIPIN SMALL HYDROPOWER PROJECT


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Small Hydropower Promotion Project (SHPP/GTZ) Introduction: Small Hydropower Promotion Project (SHPP/GTZ) was established in 1999 as a joint project of the Ministry of Water Resources and German Development Cooperation. It provides technical and logistic supports to hydropower projects in Nepal within the range of 100kW to 10MW. Objectives: The objective of the project is to establish a market for small hydro power development, rehabilitation and operation which will in turn facilitate the expansion of rural electrification and leads to associated economic activities and rural development. Activities: 1. Strengthening of Policy Frame Work

SHPP provides input to the formulation of hydropower and other related policies, acts and regulations.

2. Technical and logistic support from desk studies to operation of small hydropower schemes on:

• Performance and optimization studies incorporating efficient technologies • Review of projects including financial analysis, hydrological studies, environmental

protection, civil works , metal works, electro-mechanical works, transmission lines, etc. • Preparation of model contracts on civil construction, mechanical works, etc. • Technical supports to under-construction small hydropower projects. • Operation, repair, maintenance and rehabilitation

3. Capacity building of stakeholders

Conducting seminars, workshops and forums for professionals and stakeholders in SHP. Facilitating Nepali developers to participate in seminars, workshops and forums organized by others.

4. Facilitating Investment

SHP facilitate on building up of financial set ups of small hydropower projects. It also helps share relevant information among developers and other stakeholders.

5. Assistance and advice to

SHPP provides assistance and advice to Independent Power Producers (IPPs) on the maximum use of electricity by increasing load factors and utilizing off-peak hours of isolated plants to increase revenue streams. It also assist prospectus leases on assessing inventories and requires repair & maintenance statements of NEA schemes

Approaches: In order to overcome the entrepreneur's hesitation and / or inability to engage in the small hydropower sector, the project offers a common platform for public and private stakeholders. The platform allows them to make each other aware of their specific constraints as well as their mutual interest in developing a partnership for satisfying the uncovered electricity demand of the rural areas. In this way, the project seeks to have the barriers to private sector's involvement in the small hydropower field reduced or eliminated. The projects also works directly with the developers assisting them to acquire services they require to implement and operate successful projects. Institutional Framework: The project has an Advisory Committee which has the representation from Ministry of Water Resources (MoWR), Department of Electricity (DoED) and German Technical Cooperation (GTZ). The committee meets, as and when required, to discuss and approve policies and directives for the execution of plans and programs. The implementing consultants of Small Hydropower Promotion Project are ENTEC, Switzerland and Winrock International, Nepal.

Documents

Manual of Mini-hydropower Design Aids