Hydropower water conveyance systam

GAZIANTEP UNIVERSITY FACULTY OF ENGINEERING

DEPARTMENT OF CIVIL ENGINEERING

HYDROPOWER ENGINEERINGWATER CONVEYANCE SYSTEM

Submitted by: KHABAT STAR MOHAMMED MARIF MAHMOOD KARIM

ISRAA NAJAT JABBARYASIR SHAKIR MAHMOOD

Submitted to :Doç.Dr.Aytaç Güven

Water Conveyance system

Introduction

Any structure that conveys water from one location to another.

Hydropower Block Diagram

Plan ( 1 )

Plan ( 2 )

Intake

Definition of diversion head work

A structure constructed across a river to raise the normal water level and drive the required supply in to main canal or power canal

Diversion Head work

Fig. ( 1 )

Components of diversion head work

1. Barrage or weir 2. Canal head regulator3. Divide wall4. Fish ladder 5. Under sluice portion 6. Silt excluder 7. Marginal bunds 8. Guide bank

Weir Barrage

Canal head regulator

Function of head work 1. A head work raises the water level in the

river.2. It regulates the intake of water into the canal.3. It also controls the entry of silt into the canal.4. A headwork can also store water for small

periods of time.5. Reduces fluctuations in the level of supply in

river.

What is intake

A hydraulic-engineering installation for obtaining water from a source of supply (river, lake, reservoir, and so on) for purposes of hydroelectric power engineering, water supply, or irrigation.

Intake

Elements of intake

1. Trash rack and supporting structure.2. Smolt screens. 3. Bell mouth entrance. 4. Gate slot closing devices with air vents.5. Ice, log trash boom.6. Silt excluders and silt ejectors. 7. Under sluices.

1- Trash rack 2- screen

• A trash rack is a wooden or metal structure, that prevents water-borne debris (such as logs, boats, animals, masses of cut waterweed, etc.) from entering the intake of a water mill, pumping station or water conveyance. This protects penstock, and sluice gates from destruction during floods..

• Usually positioned in forebay or intake structure.

Trash Rack

Trash rack Trash rack

Removing or cleaning process to trash rack

Smolt Screen

3- Bell mouth entrance .

4 – gate slot closing It is control regulates the entry of water into the intake.

Gates

5- ICE,LOG,AND TRASH BOOMS

Floating boom use to perform one or more of the following functions

1. Deflection of logs and trash from the intake screens.

2. Deflection of ice away from the intake.3. Prevention of the boats form being carried into

the intake

Trash Boom .

6- silt excluders and silt ejectors

• Silt Control Devices A. Silt Excluder: The silt excluder is located on

the u/s of diversion weir and in front of the head regulator and the object is to remove silt that has entered in the stilling basin through scouring sluices.

B.Silt Ejector: Silt Ejector is located in the canal take off from the diversion weir it ejects the silt that has entered in the canal

Silt control

Silt excluder Silt Ejector

LOCATION OF INTAKE The various factors influencing the choice of location of intake structure are:1- Type of storage reservoir2- Location and type of dam/weir3- Type of water conductor system that is canal or tunnel4- Topographical features of the river.5- should not be located on curves or at least on shape curves 6- should remain easily accessible during floods.7- located at place from where can draw water even during the driest period of the year

TYPE OF INTAKE

•Depending on the function served and the range in reservoir head under which it is to operate, •The discharging capacity and frequency of the reservoir drawdown, intake for hydroelectric projects or more elaborate structure raised as a tower above maximum reservoir level.

Type of Intake

PLAN ( 3 )

A- According to source

1- River Intake

River intake

2- Reservoir intake

3- Lake intake

4 - Canal intake

B- According to position of intake

• An Intake structure which remains entirely under water during its operation is termed as submerged intake.

• It is provided where the structure serves only as an entrance to the outlet required.

• The conduct intake may be inclined, vertical or horizontal in accordingly with the intake requirements.

• An inclined intake may be provided with gates and operated on the upstream slopes of a low dam.

1-submerged intake

submerged intake

2- Exposed intake

• Is in the form of well or tower constructed near the bank of river or in some cases even away from the bank of river, they are more common due to ease in operation and maintenance .

Exposed intake

C – According to presence of water in the tower

• In dry intake tower the entry ports are directly connected with the withdrawal conduit and water inside the tower when gates are in a closed position.

• Dry Intake tower has a merit that the intake tower being dry is made accessible for inspection and operation besides that the water can be withdrawn from any level by opening the port at that level.

1- Dry intake tower

2- Wet Intake Tower

• A wet intake tower has entry ports at various levels and the vertical shaft is filled with water up to reservoir level.

• It differs from the dry intake tower is that the water enters from the ports into the tower and then into the withdrawal conduct through separate gated openings.

Wet intake tower

QUALITY WATER

1- Location of intake is required to be such as to draw the best quality of water from the reservoir.

2- Depth of water at intake is important.

3- Quality of water varies at different levels in the reservoir and it is necessary to draw water fromdifferent elevation of the reservoir at different seasons of the Year for which multi-level intakes are frequently provided.

Water conveyance systemThe main components are :A. Open channel flow systemB. Pressure flow system

Open channel flow and pressure flow systems

What is Open channel?A covered or uncovered conduit in which liquid (usually water) flows with its top surface bounded by the atmosphere. Typical open channels are rivers, streams, canals, flumes, or sewers, and water-supply or hydropower aqueducts

Classification of open channel

Based on : 1. shape 2. natural / artificial (man made) 3. change in cross section and slope 4. boundary characteristic

Classification based on a shape

1.Rectangular2.Trapezoidal 3. Triangular4. semi-Circular5.Parabolic6.Compound

Trapezoidal open channel

Rectangularopen channel

semi-circular open channel

Triangularopen channel

Compound open channel

Parabolic open channel

Open channel geometric relationships for varies cross-section

Classification based on

• Natural channel All watercourses that exist naturally on the

earth like Brooke ,creeks , tidal• Artificial channel Those constructed to perform various project

requirements and termed canals Flumes , culverts

Natural channel Artificial channel

Classification based on change in slope and cross section

Prismatic : a channel in which cross section shape and size also the bottom slope are constant , most of man-made channels(artificial) are prismatic channels like rectangular ,trapezoidal , triangular ,circular channels

• Non – prismatic : slope or cross section changes, all natural channels generally have varying in cross section and consequently are non- prismatic.

Classification based on boundary characteristic

Mobile boundary channel Rigid boundary channel

Forebay

• A forebay is an artificial pool of water in which located before and connected with penstocks

• Provided in case of run-off- river plants • The major use of forebay was to distribution Flow of water in to penstocks , store water

which is rejected by hydropower plant , Containing a trash rack and bye-pass channel.

Forebay connecting with penstock and Containing a trash rack and bye-pass channel

Forebay in nature

Trashrack that which used to prevent undesirable material (planate , dead animals) for entering to penstock that may choke the system

BANK AND CHANNEL PROTECTIVE LINING

Lining are Protective layer artificial or natural material which placed in a channel bottom and banks that may be used to: • prevent erosion resulting from high velocities of water • breaking down resulting from entering water in Cracks and gaps• shapely appearance and proper

Lining classification The main classifications of open channel linings are based on the material which that covered the channel and we have two items :

• Rigid Linings

• Flexible linings

Rigid LiningsRigid linings are generally constructed of concrete, pvc, or concrete blocks pavement they are more expensive , prevent infiltration and Require periodic maintenancewhose smoothness offers a higher capacity for a given cross-sectional area and Higher VelocitiesThe following are examples of Rigid Linings:

Pri –cast concrete channel

concrete blocks channel Pvc channel

Flexible liningsFlexible linings have several advantages compared to rigid linings They are generally less expensive, permit infiltration and exhilaration and can be vegetated to have a natural appearance, have self-healing qualities which reduce maintenance In many cases flexible linings are designed to provide only transitional protection against erosion

The following are examples of Flexible linings:

Grasses or natural vegetation

Grass linings are suitable for applications where they will be exposed to periodic relatively slow flow of water This type of lining has a pleasing appearance, is economical and is not subject to damage as a result of undermining or settlement of the supporting soils

Rubble riprap

Wire-enclosed riprap

B:Pressure flow system1- Low-pressure conduits and tunnels2- High-pressure conduits, commonly called the

penstocks

TunnelsTunnels can be designed as underground passages made without removing the overlying rock or soil.

TBM: also known as a "mole", is a machine used to excavate tunnels with a circular cross section through a variety of soil and rock strata. They may also be used for micro tunneling. They can bore through anything from hard rock to sand.

Layout of a tunnel alignmentThe first aspect that needs to be decided for a tunnel is the alignment .

Hydropower tunnel•

Hydraulic tunnels can be divided into the following categories:

1- Pressure tunnels2- Free flowing tunnelsDepending on their shape, tunnels may be classified as:1- D-shaped2- Horse-shoe shaped 3- Circular shaped4- Egg Shaped and Egglipse Sections

Tunnel section

Cross – section of a tunnel depends on the following factors:1- Geological conditions prevailing along the alignment,2- Structural considerations, and3- Hydraulic requirements,4- Functional requirements.

D-SHAPED SECTION:• D-shaped section is found to be suitable in tunnels located

in good quality, intact sedimentary rocks and massive external igneous, hard ,compacted , metamorphic rocks where the external or internal pressures.

Horse-Shoe sectionThis sections are strong in their resistance to external pressure. Quality of rock and adequate rock cover in terms of the internal pressure to which the tunnel is subjected govern the use of these sections. This section offers the advantage of flat base for constructional ease and change over to circular section with minimum additional expenditure in reaches of inadequate rock cover and poor rock formation.

Note: For tunnel excavated to horse -shoe section and concreted to circular section.

Modify horse shoe section

Egg Shaped and Egglipse Sections• Where the rock is stratified soft and very closely laminated (as

laminated sand stones, slates, micaceous schists , etc) and where the external pressure and tensile forces in the crown are likely to be high so as to cause serious rock falls, those sections should be considered.

Circular sectionThe circular section is most suitable from structural consideration. It is difficult to excavation where cross-sectional area is small. In case where the tunnel is subjected to high internal pressure, but does not have good quality of rock and/or adequate rock cover around it. circular section is considered to be most suitable.

Steel supports These are built of steel sections, usually I-sections, either shaped or welded in pieces in the form of a curve or a straight section

Installing steel supports

ROOF BOLTS OF ROCK• Rock bolts were used to support the roof and walls of major structures

such as tunnels and power stations• These steel bolts, of different length and spacing, were inserted into the

rock where they were found to be an excellent anchorage for the rock.

Tunnel Lining• Tunnel linings: main types. Tunnel linings are grouped into three

main forms some or all of which may be used in the construction of a tunnel.

• Temporary ground support• Primary lining• Secondary lining • Temporary ground support: In rock tunnels where the ground has

insufficient stand-up time to allow the construction of the primary lining some distance behind the face.

• Primary lining. A primary lining is the main structural component of the tunnel support system which is required to sustain the loads and deformations that the ground may induce during the tunnel's intended working life.

• Secondary lining. Various tunnels require smooth bore profiles for their intended use, eg sewer and water tunnels or aesthetic finishes for public usage, eg highway and pedestrian tunnels.

Arch steel support

Shotcrete in tunnel

Tunnel Grouting: This is a cement mortar with proportion of cement, sand and water in the ratio 1:1:1 by weight usually, though it may be modified suitably according to site

conditions.types of grouting:• Back-fill grouting :to fill spaces between initial lining and

rock.• − Contact grouting: to fill gaps between initial lining and plug

concrete.• − Consolidation grouting: to improve the quality of the

surrounding rock.• − Curtain grouting: To preventing water seepage from the

waterway end portion.

• Grouting

• Grouting process

• Pattern of Holes for Grouting• Backfill or Contact Grouting - Backfill grouting is limited to

the arch portion of the tunnel. The number of holes normally three in each section, the pattern being staggered in each subsequent sections located 3 m center to center.

Consolidation or Pressure Grouting -• Consolidation grouting is done to consolidate the shattered rock

all around the cavity. The pattern of holes is such that these are distributed all along the periphery but staggered in alternate sections space 3 m center to center. The number of holes may be four for smaller tunnels six for bigger tunnels.

Consolidation or Pressure Grouting 6 holes

What is surge tankSurge tank is located between the headrace pressure conduit and the steeply sloping penstock pipe and is designed either as a chamber excavated in the mountain or as a tower raising high above the surrounding terrain.

The main functions of a surge tank are:• Reduces the amplitude of pressure

fluctuations by reflecting the incoming pressure waves.

• Improves the regulating characteristics of a hydraulic turbine because; it reduces the water starting time of a hydropower scheme.

• Surge tanks, which are used to dissipate water hammer pressure

Water Hammer

• Water Hammer is a pressure surge or wave that occurs when there is a sudden momentum change of a fluid (the motion of a fluid is abruptly forced to stop or change direction) within an enclosed space (Water Hammer).

• This commonly occurs in pipelines when a valve is closed suddenly at the end of a pipeline where the velocity of the fluid is high. The pressure wave created will propagate within the pipeline.

Depending upon its configuration, a surge tank may be classified as follows;

• 1- Simple surge tank: A simple surge tank is a shaft connected to pressure tunnel directly or by a short connection of cross-sectional area not less than the area of the head race tunnel.

2- Orifice surge tank: if the entrance to the surge tank is restricted by means of an orifice, it is called an orifice tank.

3- Differential surge tank: an orifice tank having a riser is called differential tank.

4-Closed surge tank:If the top of the tank is closed and there is compressed air between the water surface and the top of the tank, then the tank is called closed surge tank, a tank with air cushion.

5-Surge Tank with Spilling Chamber

PENSTOCK

What is penstock ?•A penstock is one of the parts of conveyance system that construct from a steel or reinforced concrete to resist high pressure in the water conveyance system

• What is the Function of penstock?

• It’s function is conveying water from for bay or surge tank to the turbine in the power hous and it’s help to increase the kinetic energy of water that comes from the end of head race.

Type of penstock

1. Buried penstocks 2. Exposed penstocks

Buried penstocks:

are supported continuously on the soil at the bottom of a trench backfilled after placing the pipe. The thickness of the cover over the pipe should be about 1.o to 1.2 m.

Advantage:• The soil cover protects the penstock against effect of

temperature variations,• It protects the conveyed water against freezing.• Buried pipes do not spoil the landscape.• They are safer against rock slides, avalanches and falling

trees.

Disadvantage:

• the inspection and faults cannot be determined easily.• It’s installation expensive Especially For large diameters and

rocky soils.• On steep hillsides, especially if the friction coefficient of the

soil is low, such pipes may slide.• Maintenance and repair of the pipe is difficult.

are installed above the terrain surface and supported on piers (briefly called supports or saddles). Consequently, there is no

contact between the terrain and the pipe itself, and the support is not continuous but confined piers.

Advantage:•The possibility of continuous and adequate inspection during operation.•Its installation is less expensive in case of large diameters of rocky terrain.•Safety against sliding may be ensured by properly designed anchorages.•Such pipes are readily accessible and maintenance and repair operations can be carried out easily

Exposed penstocks:

Disadvantage:

• Full exposure to external variations in temperature.• The water conveyed may freeze.• Owing to the spacing of supports and anchorages

significant longitudinal stresses may develop especially in pipes of large diameters designed for low internal pressures

Design of penstock:

• According to the Bureau of Indian Standards code IS: 11625-1986 “Criteria for hydraulic design of penstocks” The determination of penstock diameter based on the following losses may be expected for a penstock:

a. Head loss at trash rock .b. Head loss at intake entrance .c. Friction losses, and .d. Other losses as at bends, bifurcations, transitions,

values, etc.

Bends Depending on topography, the alignment of the penstock is often

required to be changed, in direction, to obtain the most economical profile.

Reducer piece:In the case of very long penstocks, it is often necessary to reduce the diameter

of the pipe as the head on the pipe increases. This reduction from one diameter to another should be effected gradually by introducing a special pipe piece called reducer piece.

Branch pipe: Depending upon the number of units a single penstock feeds.

Expansion joints :are installed in exposed penstocks to prevent longitudinal expansion or contraction when changes in temperature occur.

Manholes: Manholes are provided in the course of the penstock length to provide access to the pipe interior for inspection, maintenance and repair.

Air vents and valves: These are provided on the immediate downstream side of the control gate or valve to facilitate connection with the atmosphere.

How hydropower system work ?

• Tailraces: After passing through the turbine the water

returns to the river trough a short canal called a tailrace.

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