SOLAR BIOMASS POWER PLANT IN INDIA

Aditya Tiwari B.E., Gujarat University, India, 2007

PROJECT

Submitted in partial fulfillment of the requirements for the degree of

MASTER OF SCIENCE

in

ELECTRICAL AND ELECTRONIC ENGINEERING

at

CALIFORNIA STATE UNIVERSITY, SACRAMENTO

FALL 2010

ii

SOLAR BIOMASS POWER PLANT IN INDIA

A Project

by

Aditya Tiwari

Approved by: ______________________________, Committee Chair John C. Balachandra, Ph.D.

______________________________, Second Reader Preetham B. Kumar, Ph.D.

____________________________ Date

iii

Student: Aditya Tiwari

I certify that this student has met the requirements for format contained in the University

format manual, and that this project is suitable for shelving in the Library and credit is to

be awarded for the project.

______________________________, Graduate Coordinator __________________ Preetham B. Kumar, Ph.D. Date Department of Electrical and Electronic Engineering

iv

Abstract

of

SOLAR BIOMASS POWER PLANT IN INDIA

by

Aditya Tiwari

Developing countries have an abundance of renewable energy sources but the implementation of

cost effective projects, to harness this energy and provide a support system to the ever-increasing

demand from the conventional sources, are rare. Rapid depletion of fossil fuel resources and the

environmental concerns associated with them make electricity generation from certain alternate

sources increasingly important for the future. This project presents a system running solely on

renewable energy sources. It utilizes solar energy and biomass as fuels in a combined cycle power

plant to provide clean energy to the rapidly developing city of Maninagar in India.

The solar and biomass parts of the plant will share turbines and connecting infrastructure,

reducing the project cost and allowing continuous power generation. The plant can provide

peaking power using a combination of the two, regardless of the time or weather. Operating

strategy is designed to maximize solar energy use. The biomass is used to provide fuel during

cloudy periods. The turbine-generator efficiency is optimal at full load, therefore the use of

biomass supplement to allow full load operation maximizes plant output. The cost assessment of

the project remains the most crucial part in planning of a non-conventional energy based power

generation system. Different approaches to energy conversion from solar and biomass sources,

v

the financial risks involved and the future aspects are presented with the anticipated costs for the

planned project.

, Committee Chair John C. Balachandra, Ph.D.

______________________ Date

vi

TABLE OF CONTENTS

Page

List of Tables.……………………………………………………………………………......vii

List of Figures……………………………………………………………………………….viii

Chapter

1. INTRODUCTION ……………..……………………………………………………….....1

1.1 Energy…….…….....…………..…………………………………….……………..…..1

1.2 Energy Situation in India...……………………………………….….......…….……....3

2. SOLAR POWER …….……………...………………………..……………………..…….6

2.1 Solar Energy as a Resource for Power Generation………………………………….....6

2.2 Photo - Thermoelectricity.……….………………………………….……....................6

2.3 What are Solar Thermal Power Systems?.……………………………..……….….......9

2.4 Methods of Solar Energy Conversion …………………………..……………………11

3. BIOMASS POWER ……………..……………………………………………………….18

3.1 Biomass as an Alternative Source of Energy………………………………..………..18

3.2 Properties Influencing the Use of Biomass as a Fuel for Electricity Generation.…....19

3.3 Combustion ……………………………………………………………………….......23

3.4 Electricity from Biomass ………………………………………………………....…..24

4. SOLAR TROUGH BIOMASS HYBRID POWER PLANT IN INDIA……………….…27

4.1 Modeling of the Hybrid Solar Trough Biomass Power Plant……………………....…27

4.2 Layout and Working of the Proposed Power Plant…………………………...…….....30

4.3 Cost Estimation…………………………………………………………………….….34

4.4 Cash Flow Report Generated from the RETFinance Tool………………...…...…...…38

5. CONCLUSION ………………………………..……………………………………….…..40

References ………………………...………………………………………………………….42

vii

LIST OF TABLES

Page 1. Table 2.1 Typical solar collectors characteristics…………………………….……......9

2. Table 2.2 Solar thermal cost…………………………………………..........................11

3. Table 3.1 Quantitative comparison of technologies for energy conversion of biomass…………………………………………………………...……...19

4. Table 3.2 Elemental composition of typical biomass material…………….………….21

5. Table 3.3 Typical characteristics of different biomass fuel types used commercially…………………………………………………….……22

viii

LIST OF FIGURES

Page 1. Figure 1.1 Solar radiation in India………………………………………………………4

2. Figure 2.1 Photo-thermoelectric generator based on concentrating solar collectors………………………………………........…..7

3. Figure 2.2 Temperature behavior in heat exchanger………………………….......…….8

4. Figure 2.3 Schematic of a solar-thermal conversion system………………..…….…....10

5. Figure 2.4 Layout of a solar tower system……………………………………….….....13

6. Figure 2.5 Layout of a solar dish system……………………………………..….…….14

7. Figure 2.6 Parabolic trough concentrator………………………………………....……16

8. Figure 2.7 Electricity generation from distributed parabolic collectors at Kramer Junction, California……………………………………………...17

9. Figure 3.1 Process flow for biomass combustion………………………………………24

10. Figure 3.2 Energy transformations in steam cycle……………………………………...25

11. Figure 3.3 Schematic of a steam system………………………………………………..26

12. Figure 4.1 Hybrid power plant model with two PCUs………………………………....27

13. Figure 4.2 Hybrid power plant model with single PCU………………………………..28

14. Figure 4.3 Solar trough model………………………………………………………….28

15. Figure 4.4 Biomass model……………………………………………………………...29

16. Figure 4.5 Overall system model……………………………………………………….30

17. Figure 4.6 General layout of the plant………………………………………………….31 18. Figure 4.6 RETFinance tool project selection screen…………………………………..35 19. Figure 4.8 Project cash flow results…………………………………………………….37

1

Chapter 1

INTRODUCTION

1.1 Energy

Energy is the most important resource in the economic development of a country.

The development of techniques aimed at harnessing and utilization of its various forms

for a better quality of life have been the essence of continuous advancement of the

civilization as a whole. The invention of electrical machines and the establishment of

facilities to supply electrical power as a basic commodity for industrial as well as

household usage have led to the increase in its demand by leaps and bound.

The increased consumption of electricity has led to industrial and agricultural

expansion, better comfort at our homes and better transportation facilities that imply an

increase in the overall quality of life. The conventional methods of electricity generation

are experiencing mounting pressure from the ever-increasing demand rate. This trend has

led to the growth of other non-conventional methods of electricity generation with the

purpose of supporting and eventually replacing the conventional methods used today by

evolving into an improved form.

Fossil fuel resources have become increasingly scarce and environmental

concerns accompanying them have accentuated the requirement for fresh sustainable

2

energy providing options that utilize renewable energy. Accordingly, energy plans in

most of the countries include four fundamental factors for enhancing and preserving the

public gain from energy:

1. Better channeling of sustainable energy supply.

2. Improved efficiency at the end-use as well as the supply.

3. Pollution drop.

4. Importance of lifestyle

Among other renewable energy sources, solar and biomass have lately

encountered a prompt growth in most parts of the world. Geographically, the extensive

stretch they cover and ability of these forms to be generated close to the load centers

eliminates the high voltage transmission lines, which pass through the landscape of the

city. Biomass and solar power bring the following advantages to the utilities supply

business:

1. Modularity, in a sense that it allow the size to be incremented with the

demand in load.

2. The lead-time to build is smaller compared to the conventional plants, which

allows the reduction in regulatory and monetary based threats.

3. The detrimental effects of pollution due to fuel are eliminated and price of

fuel is also very low because of the assortment of sources these provide.

3

This project aims at setting up a solar thermal and biomass energy based hybrid

power plant in the town of Maninagar located in western India. It is a major town in the

southern part of the city of Ahmedabad. Currently a coal-fired thermal power plant

located in the western part of the city provides power to the entire city as well as some

small rural areas around the city. A renewable energy based plant will not only augment

the total power supply of this expanding city but also provide support to the thermal

power plant.

1.2 Energy Situation in India

The per capita energy consumption is 1/5th of the global average. The energy

consumption in the year 2000 was approximately 200 MtOE (million tons of oil

equivalent). Coal is the most important energy production fuel with a total of 309 Mt in

local supply and 20 Mt from foreign imports. Seventy percent of the total energy was

supplied by these two sources. Imported oil was solely used with figures in the year 2000

crossing 32 crude Mt local supplies and 57Mt from imports. 28.5 billion Cubic meters of

natural gas were consumed with all of it supplied and produced locally.

4

The electricity usage in the year 2000 was 101 GW(Primary fuels used Coal 60%,

Other thermal 11% , Hydro 25%, Nuclear 3 %, Wind 1 % ) and the real production came

up to the 500 Billion kWh. Energy production for non-commercial usage from traditional

fuels like firewood, dung cake, vegetable wastes, wood chips, animal/ human muscle

power etc forms a sizeable part, especially in the rural domestic sector. The total

approximation is in the range of 10 – 50 % of commercial energy consumption and is

divisive and undergoing immense changes [4].

Figure 1.1 Solar radiation in India[8]

The model predictions for the year 2100, are a population of 1.65 billion people,

an economy with a GNP of US$ 22000 billion dollars and an electric power generation

5

capacity of 1000 GW. The primary fuels are coal at 50 %, natural gas at 25 % and nuclear

and renewable energies sharing the last 25%.

The critical energy technologies for India therefore are clean coal technology,

exploration and exploitation of natural gas / gas hydrate resources, nuclear technologies

(especially those involving utilization of thorium), replacement of petroleum products in

the transport sector by fuel cells, hydrogen, electricity etc and the development of

improved solar photovoltaic, thermal systems and biomass energy[4].

6

Chapter 2

SOLAR POWER

2.1 Solar Energy as a Resource for Power Generation

A collection of solar thermal based power projects were made in california in the

late 1980s and early 1990s. Their design was based mainly an approximated solar energy

input of 2725 kWh/m2 /year which is equivalent to 22.75 GWh per hectare per year.

Based on this design data and assuming a conversion efficiency of 10%(which is now

about 20%) 100.000 square km (316km x316 km), would be enough for energy

generation to supply whole USA[1]. This seems to be an incredibly large area but such an

area of unused land with abundant solar energy can be foud very easily especially in

deserts. Even with such a huge prospective for energy production, the overall generation

throughout the world is lower than 800 MW of installed facilities in 1995 as depicted by

the European Union. This capacity has increased from 800 MW to 2600 MW at the end

of year 2003 and to 3400 MW at the end of 2004[1].

2.2 Photo-Thermoelectricity

Electricity may be derived from solar radiation by two methods: Firstly, by

following a two – step approach that includes deriving heat from radiation and then

7

converting that heat into electricity. Secondly, by using photovoltaic conversion systems

for directly obtaining electricity from the solar radiation. This project concerns mainly

with the first method of conversion mentioned above.

The two-step approach in a device form may be indicated by the figure 2.1. The

collector may require partial or complete tracking of sun to facilitate concentration in the

collector , or a flat-plate type solar collector may also be used. A thermodynamic engine

cycle, like the Rankine cycle, follows, causing expansion in a turbine as indicated in the

figure 2.1.

Figure 2.1 Photo-thermoelectric generator based on concentrating solar collectors[1]

In this process, the heat exchanger behaves in a pattern depicted by the figure 2.2.

As a result of path covered in the heat exchanger , from x1 to x2 , the collector circuit fluid

8

sees a uniform decrease in temperature. The working fluid going in the heat exchanger at

x2 experiences a temperature increase to boiling point. The heat exchange occurring after

that is for evaporating the working fluid or to superheat the gas, to a point so that the

temperature curve is flat after that point.

Figure 2.2 Temperature behavior in heat exchanger[1]

This shows the fundamental process involved in changing solar energy to electricity in

this project. Furthermore, solar to mechanical and electrical conversion has had

experimental significance for the greater part of the century. The inspiration here is to

9

utilize collectors with concentrating capacity to generate as well as deliver steam. The

following section further elaborates the processes involved.

Table 2.1 Typical solar collector characteristics[5]

2.3 What are Solar Thermal Power Systems?

The main objective of this section is to explain the production of mechanical and

electrical energy from solar energy with the help of methods involving collectors using

concentration and various heat engines. The only difference between the processes

discussed in this section from traditional thermal ones is the fact that these occur at very

high temperatures. The key process involved in this conversion from solar to mechanical

energy is depicted in figure 2.3. The heat engine is either a steam turbine where the heat

10

Figure 2.3 Schematic of a solar-thermal conversion system[1]

is used in the generation of steam, however it could as well be a gas turbine or a sterling

engine. The collector efficiency decreases with rise in its working temperature while the

efficiency of the heat engine rises with the rise of its working temperature. This is one of

the major issues associated with these systems. Even though solar thermal plants are

complicated, they utilize already existing power plant technology and are relatively

cheaper. Another issue associated with solar-based power plants is the fact that they can

only produce electricity during the day. In order to produce power during the night, either

a fuel based conventional backup system is required or some form of energy storage must

be used.

This project uses biomass as the fuel based system integrate with the solar thermal

11

part of the plant to support the plant during the nights as well as provide peaking power

during the day. This is discussed in a later part of the report.

2.4 Methods of Solar Energy Conversion

All the research until now has been concentrated mainly on three distinct methods

of conversion from solar to electrical energy based mainly upon collection and

concentration of solar energy to generate an energy abundant supply. These are listed

below and the table __ presents the costs associated with each type of technology :

Table 2.2 Solar thermal costs[1]

12

1. Solar towers

Solar tower technology uses a single central tower to concentrate and collect

energy. The tower located at the centre of the entire facility has a powerful receiver and

collection unit at the top which receives sunlight from a field of mirrors(called heliostats)

positioned all round the tower and controlled in such a way so that they focus all the

received sunlight onto the receiver. The mirrors used are parabolic in shape seem flat

because of the fact that their focal length is quite extensive.

They are also capable of tracking the sun independently and focusing the energy

to the central receiver, which allows them the advantage of being placed at longer

expanses. This is shown in the figure 2.4 below :

The fluid that passes through tubes at the top of the tower transfers the collected

heat energy into the heat exchange system. Here heat is used to produce steam for a

steam turbine

13

Figure 2.4 Layout of a solar tower system[8]

2. Solar dish

The second type is the solar dish system, which essentially uses a parabolic mirror

for sun tracking and a central unit consisting of a collector as well as small generator.

The main components are the reflector and the heat engine. The tracking system is also

an important part of the assembly, as the reflector must be tracking the sun at all times.

The heat engine is mostly a sterling engine. This is an engine consisting of pistons

with a closed system configuration where the energy in the form of heat has external

application. This form of solar thermal electricity generation is not used for large-scale

applications and is the most efficient of all technologies. It reduces the overall area per

megawatt of production ability because of the integrated sterling engine and its increased

efficiency. This technology is comparatively expensive and therefore its main

14

applications might be for detached and distant generation where the added efficiency and

dependability are important.

Figure 2.5 Layout of a solar dish system[8]

3. Parabolic trough

The dish receiver system is larger in size as it uses a full parabola that is a circle.

For extensive solar concentration, an effective configuration is the trough based reflector

system. A trough shaped in the form of parabola provides optimal efficiency for

concentrating the sunlight over a line running along the longitudinal axis of the trough

shaped receiver. Solar tracking allows it to attain superior efficiency and the mirrored

glass material used in the reflector surface help in getting better concentration on the

collector.

15

The system allows a sturdy weight support system for the mirror panels as well as

tracking along the horizontal and longitudinal axes. The concentrated heat energy is

collected by heat absorbing oil that is used mainly for collecting and transmitting the heat

energy from the troughs to the heat exchanger. This oil is elevated to a temperature of

about 400̊ C and heats water to produce steam that operates a steam turbine to generate

power.

The power plant planned in this project uses this form of solar thermal electricity

production. The plant discussed here uses secondary fuel from biomass-based processes

so that the output remains uniform in the shortage of solar input. The biomass energy

output would account for 25% of production. This is discussed elaborately in the

following section.

16

Figure 2.6 Parabolic trough concentrator. (a) General view (b) End view[6]

17

Figure 2.7 Electricity generation from distributed parabolic collectors at Kramer Junction, California (Working fluid is heated in the pipe at the focus of each parabolic trough)[6]

18

Chapter 3

BIOMASS POWER

3.1 Biomass as an Alternative Source of Energy

Different types of biomass and wood have become increasingly important for use

as fuels to generate electrical power and heating purposes around many parts of the

world. It is a low cost, local and completely restorable form of fuel. The advancement in

technology for effective usage and with less pollution coupled with widespread

accessibility of biomass is making it a more than suitable alternative to the existing

choice of fuels. This project deals with electricity produced as a result of biomass

combustion process and its utilization in combination with solar energy.

Wood is among the most significant of biomass-based fuels and very precious to

burn. Wood residues provide a much economical alternative to the whole wood that is

usually used for construction matter by processing it into a useful form. Residues from

trees include bark, sawdust, and ill shaped fragments of wood [2]. Residues from

agricultural products which include straw; rice ,coconuts, or coffee husks; cotton or

maize stalks; sugar cane bagasse; and forest conservation products like verge grass and

thinning can also be used for biomass fuels[2]. Energy cropping for biomass production

19

with farming of trees like miscanthus, willow, poplar, sugar cane, sorghum, etc., is also a

very useful option of farming for biomass products.

Process Technology Economics Environment Market

Potential

Present

Deployment

Combustion-

heat

+++ $ +++ +++ +++

Combustion

- electricity

++(+) $$ ++(+) +++ ++

Gasification +(+) $$$ +(++) +++ (+)

Pyrolysis (+) $$$$ (+++) ++(+) (+)

+,low; +++,high; $,cheap; $$$$,expensive.

Table 3.1 Quantitative comparison of technologies for energy conversion of biomass[6]

3.2 Properties Influencing the Use of Biomass as a Fuel for Electricity Generation.

The various forms of biomass have certain important properties that influence its

functioning as a fuel. Thermal properties are the most important while studying the

nature of a matter to be used as fuel for combustion. These are listed below :

20

1. Moisture content

The amount of water in the matter stated in percentage of its weight is known

as the moisture content of biomass. The moisture content is crucial in

conveying the importance of biomass as a fuel and the terms that it is stated

must be made known at all times. It may be stated in dry weight, wet weight,

or dry-and-ash-free weight basis [2]. This draws its significance from the fact

that a wide variety of moisture content is shown by biomass-based matter.

2. Ash content

The amount of ash in the biomass as well as the chemical makeup of the ash

influences the use of biomass as a fuel. Biomass combustion under high

temperatures is also influenced by the ash composition.

3. Volatile matter content

When heated to high temperatures the matter that is released from biomass

material is called volatile matter content. The biomass provides a high level of

volatile matter content that is about 80 percent ,in comparison with coal that

has about 20 percent.

4. Elemental composition

21

Biomass usually has varying quantities of carbon, hydrogen and oxygen with

traces of nitrogen present in some forms. This makes the elemental

composition consistent in all forms of the biomass energy sources.

Table 3.2 Elemental composition of typical biomass material[2]

5. Heating value

The heating value indicates the proportion of energy present in the fuel in

chemical form in accordance to standard conditions. The chemical energy of

the fuel is the heating value of the fuel measured in terms of the amount of

energy(J) per quantity of matter(kg)[2].

6. Bulk density

It is the weight of the material per unit volume. In simple words, it can be

expressed with or without the moisture content of the biomass material being

used.

22

The heating value and bulk density are combined to find the energy density that is

the potential energy present per unit volume of biomass. The energy density of

fossil fuels are much more than biomass, in fact it is about ten times that of

biomass-based fuels.

Biomass forms used in commercial production of energy, in combination with

their natural moisture content (MCw), ash content (ACd), and lower heating values

(LHVs) are listed in the table below.

Table 3.3 Typical characteristics of different biomass fuel types used commercially[2]

23

3.3 Combustion

Many applications using biomass energy require combustion to obtain useful

energy from biomass material. Igniting the biomass is the hardest part of the entire

combustion process as it requires high temperatures but when ignited with continuous

supply of air, the process will go on until the entire material is used up. The combustion

process occurs in a series of steps. At first, the water evaporates from the wood, followed

by the thermal breaking up of the fuel into volatile gas and solidified char. These

processes are known as drying and pyrolysis respectively. Then the combustion of the

gases takes place over the fuel bed with yellow flames, followed by the combustion of

char in the grates with blue flames or glowing of the char chunks .

Combustion process can be studied by making a clear separation between the

place of burning the fuel known as the furnace and the area where heat exchange between

energy carriers takes place, known as the heat exchanger. This is depicted in the figure __

below. The furnace is a place where the chemical energy in the fuel is converted into

thermal energy, which is the flue gases, in this case. The furnaces present in combustion

schemes are usually fixed-bed or fluidized bed types. Fixed-bed furnaces are manual-fed,

spreader-stoker , underscrew, through-screw, static, and inclined types. Fluidized –bed

schemes are either circulating or bubbling types [2].

24

Figure 3.1 Process flow for biomass combustion[2]

3.4 Electricity from Biomass

The steam cycle is used to generate electricity from the thermal energy derived

from the combustion process. The figure 3.5 below shows the order of energy change in a

steam cycle and figure 3.6 shows a simpler form of the process. The main parts can be

studied as

1. furnace and boiler(usually combined into one unit) known as the boiler

2. the turbine

3. Condenser

4. Feed water pump

25

The feed water undergoes pressurization from the feed-water pump and goes into

where it gets evaporated. The steam thus produced is superheated and passed on to the

steam turbine. It expands in the turbine to a lower pressure and temperature, governed by

the condenser. The saturated steam containing some water is then fed from the condenser

unit to the deaerator where the dissolved gases in the feed water are separated from it to

check its gathering further in the process.

Figure 3.2 Energy transformations in a steam cycle[2]

The efficiency of the cycle is dependent on the following aspects :

1. Efficiency of the boiler.

2. Temperature and pressure condition of the inlet steam to the turbine(should be

high).

3. Turbine efficiency.

26

4. Temperature and pressure condition inside the condenser(should be low).

5. Heating system of the feed-water.

Figure 3.3 Schematic of a steam system[2]

This turbine-generator arrangement produces electrical energy from

mechanical energy at typical efficiency range of 85 to 98 percent and the overall

efficiency ranges from 5 to 40 percent[2].

27

Chapter 4

SOLAR TROUGH BIOMASS HYBRID POWER PLANT IN INDIA

4.1 Modeling of the Hybrid Solar Trough Biomass Power Plant

This hybrid power plant can be designed with two formats. A single Power

Conversion Unit (PCU) or a separate PCU, for each of the solar trough and the biomass

technologies. The latter option provides a custom-made approach to the overall system.

Figure 4.1 Hybrid power plant model with two PCUs[7]

The two systems connected separately with a sole PCU (as shown in figure 1) is

much simpler than the one where they are both connected together to a single PCU unit

(as shown in figure 2). The overall efficiency is also better but the drawback is that the

system experiences a large increment in costs due to separate PCU installations for each

technologies.

28

Figure 4.2 Hybrid power plant model with single PCU[7]

Solar trough model - The model for the solar trough can be as shown in the figure

4.3. Only direct radiation incident on the solar trough is taken into account as the diffused

radiation is not viable for the system. The heat transfer fluid transfers the energy to the

end of the solar trough.

Figure 4.3 Solar trough model[7]

Biomass system model- The biomass system model uses a boiler and a directly-

fired biomass system as shown in the figure. The energy input is the energy from the

29

biomass fuel (High Heating Value) and the heat transfer fluid takes the output thermal

energy to the PCU[7].

Figure 4.4 Biomass model[7]

Overall system model- The energy input of the PCU model takes into account the

combined thermal energy from the solar trough and the biomass systems. The output is

the power produced by the hybrid solar trough biomass power plant as shown in the

figure below[7]

30

Figure 4.5 Overall system model

4.2 Layout and Working of the Proposed Power Plant

Parabolic trough solar thermal systems have been build and operated throughout

the world but a majority of these systems supply processed steam to industry. They

displace conventional fossil fuels like oil or natural gas as the energy source for

producing steam. These systems incorporate fields of parabolic trough collectors having

aperture areas from 500 to 5000 m2[1].

A bulk of these systems, provide industrial process steam from 150 to 200˚C. The

most current example of power production using parabolic trough is the nine commercial

solar energy-producing systems (SEGS). The total installed capacity of SEGS is 354 MW

and they are designed, installed and operated in the Mojave Desert of Southern

31

Figure 4.6 General layout of the plant[1]

California. These plants are based on large parabolic trough concentrators providing

steam to Rankine power plants. The first of these plants is a 14MWelectric (MWe) plant,

the next six are 30 MWe plants, and the two latest are 80MWe [1].

The proposed plant for this project can supply peaking power using solar, biomass

generated flue gases supplied to the boiler furnace, or a combination of the two,

regardless of the time and weather within the limits of supply of the biomass for

32

combustion. Operational design allows maximum solar energy usage and the biomass

generated steam from the boiler provides power during the cloudy intervals. The

efficiency of the turbine-generator is maximum at full-load so the supplemental energy

offered from the biomass increases plant output.

The basic arrangement of the plant is shown above in figure 4.1.

As observed, the solar and biomass loops are in parallel to allow operation with

one or both of the energy resources. The do not contain energy storage installations. The

major components in the scheme happen to be the collectors, the fluid transfer pumps, the

power generation system, the steam (biomass based) auxiliary subsystem, and the

controls. A synthetic heat transfer fluid is heated in the collectors and is piped to the solar

steam generator and superheater where it generates the steam, which drives the

turbine[1].

Reliable high-temperature circulating pumps are critical to the success of the

plants, and significant engineering effort has gone into assuring that pumps will stand the

high fluid temperatures and temperature cycling. The normal temperature of the fluid

returned to the collector field is 304˚C and that leaving the field is 390˚C. Experience

indicates that availability of the collector fields is about 99% [1].

33

A conventional Rankine cycle consisting of reheating steam turbine equipped

with feedwater heaters, deaerators, etc, constitutes the power generation system. Forced

draft cooling towers are used to cool the condenser cooling water . Black-silvered, low-

iron float-glass panels are used to make the reflectors, which are further molded to

parabolic shapes. The rear portion of the silver surface is covered with metallic and

lacquer coatings for protection and a considerable increase in the degradation resistance

is observed as a result of this process.

“The glass is mounted on truss structures, with the position of large arrays of

modules adjusted by hydraulic drive motors. The reflectance of the mirrors is 0.94 when

clean. Maintenance of high reflectance is critical to plant operation. With 2.32 x 106 m2

of mirror area, mechanized equipment has to be developed for cleaning the reflectors,

which is done regularly at intervals of about 2 weeks. The receivers are 70 mm diameter

steel tubes with cement selective surfaces surrounded by a vacuum glass jacket in order

to minimize heat losses. The selective surfaces have an absorptance of 0.96 and an

emittance of 0.19 at 350˚C”[1].

“The collectors rotate about horizontal north–south axes, an arrangement which

results in slightly less energy incident on them over the year but favors summertime

operation when peak power is needed and its sale brings the greatest revenue. Tracking of

the collectors is controlled by a system that utilizes an optical system to focus radiation

34

on two light-sensitive sensors. Any imbalance of radiation falling on the sensors causes

corrections in the positioning of the collectors. There is a sensor and controller on each

collector assembly; the resolution of the sensor is 0.5˚”[1].

4.3 Cost Estimation

The RETFinance tool from the NREL website is used to assess the financial needs

of the plant. “RETFinance is a levelized cost-of-energy model, which simulates a detailed

20-year nominal dollar cash flow for renewable energy projects power projects including

project earnings, cash flows, and debt payment to calculate a project's levelized cost-of-

electricity, after-tax nominal Internal Rate of Return, and annual Debt-Service-Coverage-

Ratios”[3].

35

Figure 4.7 RETFinance tool project selection screen[9]

Assumptions

Capital Structure Assumptions Non-Cost-Share Debt Percentage (%) 70 % Debt Interest Rate (%) 8 % Debt Repayment Period (Years) 15 Years

Tax/Economic Assumptions

Federal Income Tax Rate (%) 35 %

State Income Tax Rate (%) 7.7 %

Sales Tax Rate (%) 7.25 %

Can the project's tax benefits be used to offset other income? Yes

36

Expected Annual Inflation Rate (%) 3 % Investment Tax Credit (% of depreciable capital costs) 10 %

10-year Production Tax Credit (cents/kWh escalated at the rate of inflation) 0 $/kWh

Project Assumptions Plant Size (kW) 30000 kW Average Annual Capacity Factor (%) 25 % Power Plant Cost ($/kW) 2800 $/kW Taxable Amount (for Sales Tax) 1545 $/kW Transmission & Interconnect 0 $/kW Other Capital Costs 0 $/kW Interest Rate During Construction (%) 10 % Debt Service Reserve 0 $/kW Debt-Related Fees 0 $/kW Equity-Related Fees (like tax advice) 0 $/kW Equity-Related Fees (like organizational fee) 0 $/kW Equity-Related Fees (other) 0 $/kW Contingency 0 $/kW

Annual Costs Annual Fixed O&M ($/kW) 64 $/kW Annual Variable Costs ($/kWh) 0 $/kW Annual General & Admin Expense ($) 0 $

Annual Property Tax Rate (%) 1 % of Total Project Cost

Insurance Expense (%) 1 % of Total Project Cost

Annual Nominal Escalation Rates Annual Fixed O&M ($/kW) 3 % Annual Variable Costs ($/kWh) 3 % Annual General & Admin Expense ($) 3 % Annual Property Tax Rate (%) 0 %

37

Annual Mines Tax Rate (%) 0 % Insurance Expense (%) 3 %

Analysis Parameters Annual Nominal Electricity Sales Price Escalation Rate 2.5 %/year

Is the 'Average DSCR' constraint binding? Yes

Average DSCR (lender imposed) 1.8

Is the 'Minimum DSCR' constraint binding? Yes

Minimum DSCR (lender imposed) 1.4

Is the equity investor's hurdle rate binding? Yes

Minimum Acceptable Nominal After-Tax IRR (%) 17 % Are negative after-tax cash flows acceptable? No

Figure 4.8 Project cash flow results[9]

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4.4 Cashflow Report Generated from the RETFinance Tool[8] :

Calendar Year 2010 2011 2015 2020 2025 2030

Project Year Construction 1 5 10 15 20

Electricity Production (kWhs) 65,700,000 65,700,000 65,700,000 65,700,000 65,700,000

Electricity Sales Price (cents/kWh) 22.97 25.36 28.69 32.46 36.73

Operating Revenue 1,509,374,390 1,666,066,908 1,885,001,783 2,132,706,498 2,412,961,648

Fixed O&M $1,978 $2,226 $2,580 $2,991 $3,468

Variable Costs $0 $0 $0 $0 $0

Royalties $0 $0 $0 $0 $0

Insurance Expense $945 $1,063 $1,233 $1,429 $1,657

Property Tax $917 $917 $917 $917 $917

Mining Tax $0 $0 $0 $0 $0

Administration Expense $0 $0 $0 $0 $0

Operating Expenses $3,840 $4,206 $4,730 $5,338 $6,042

Operating Income $11,254 $12,454 $14,120 $15,989 $18,088

5-Year Depreciation Factor 20.00% 11.52% 0.00% 0.00% 0.00%

5-Year Depreciation $16,790 $9,671 $0 $0 $0

Debt Interest Payment $5,137 $4,284 $2,774 $556 $0

Amortization $0 $0 $0 $0 $0

First Year Expense $3,360 $0 $0 $0 $0

Loss Forward $0 $0 $0 $0 $0

Taxable Income ($14,033) ($1,501) $11,345 $15,434 $18,088

Income Tax ($5,614) ($601) $4,539 $6,174 $7,236

Investment Tax Credit $8,837 $0 $0 $0 $0

Production Tax Credit $0 $0 $0 $0 $0

Total Tax Taken ($14,451) ($601) $4,539 $6,174 $7,236

Net Operating Income $418 ($901) $6,807 $9,259 $10,852

Depreciation $16,790 $9,671 $0 $0 $0

Amortization $0 $0 $0 $0 $0

First Year Expense $3,360 $0 $0 $0 $0

Loss Forward $0 $0 $0 $0 $0

Debt Principal ($2,365) ($3,217) ($4,727) ($6,946) $0

Net Equity Cash Flow ($27,519) $18,203 $5,553 $2,079 $2,314 $10,852

Cumulative Net Equity Cash Flow ($27,519) ($9,315) $21,798 $33,385 $44,569 $96,252

Debt Funds $64,210

Beginning Balance $64,210 $53,554 $34,679 $6,946 $0

Debt Interest Payment $5,137 $4,284 $2,774 $556 $0

Debt Principal Payment $2,365 $3,217 $4,727 $6,946 $0

39

Total Debt Payment $7,502 $7,502 $7,502 $7,502 $0

Debt-Service Coverage Ratio 1.50 1.66 1.88 2.13

40

Chapter 5

CONCLUSION

The report presented here provides a technological insight into renewable

technologies and their potential in developing countries like India. The idea of a hybrid

power plant based totally on renewable technologies like solar and biomass needs

continuous research and financial support from the local government. This report presents

a biased solution for small to medium scale power generation using renewable solar and

biomass energy in developing nations.

The various forms of solar and biomass forms of generation that have

significantly affected the production of electricity with minimal dependence on fossil

fuels are discussed at length. This is followed by the operational details and the method

best suited for production in the area of concern. The financial investment in a facility

involving a non-conventional technology is of major concern and a Computer-aided

design tool is used to present a plan for necessary investments.

The tool gives a modeling environment for the cost assessment of the proposed

plant. An effort has been made to provide ample technical details for the proposed

scheme of the plant. Manufactured parts and installation details are much more complex

than the simplified models presented herein. A planned approach for the future based on

41

these models and future advances in technology may provide total renewable energy

based systems the investment opportunities that have stopped its progress and

commercial viability.

42

REFERENCES

[1] Dr. Paul Breeze, Professor Aldo Vieira da Rosa, Dr Mukesh Doble, Dr. Harsh Gupta,

Dr. Soteris Kalogirou, Dr. Truman Storvick, Shang-Tian Yang, Preben Maegaard,

Gianfranco Pistoia, Sukanta Roy, Dr. Bent Sørensen and Dr. Anil Kumar Kruthiventi,

“Renewable energy focus handbook” , Academic Press -Elsevier Ltd, San Diego, 2009

[2] Energy from biomass - A review of combustion and gasification technologies -

http://www-wds.worldbank.org/external/default/WDSContentServer/WDSP

/IB/2000/07/08/000094946_99033105581764/Rendered/PDF/multi_page.pdf”

[3] Solar technology analysis models and tools -

http://www.nrel.gov/analysis/analysis_tools_tech_sol.html

[4] Report on research and development of energy technologies -

http://www.iupap.org/wg/energy/annexb.pdf

[5] Barney L. Capehart, “Encyclopedia of energy engineering and technology”, CRC

press- Taylor and Francis group, 2007

[6] John Twidell and Tony Weir, “Renewable energy resources” , Taylor and Francis

group, NY, 2006

[7] Feasibility Study of a Small-Scale Grid-Connected Solar Parabolic Biomass Hybrid

Power Plant in Thailand - http://e-nett.sut.ac.th/download/ RE/RE17

43

[8] Making solar thermal power generation in India a reality – Overview of technologies,

opportunities and challenges -

http://www.cognizance.org.in/main/pages/technovision/Dr_Garud_Teri.pdf

[9] RETFinanace – Renewable energy technologies Financial model -

http://analysis.nrel.gov/retfinance/default.asp

[10] The Status of Biomass Power Generation in California -

http://www.fs.fed.us/psw/biomass2energy/documents/Morris 2003 Status of Bm Pwr Gen

in CA.pdf

[11] Cost and Performance Analysis of Biomass-Based Integrated Gasification

Combined-Cycle (BIGCC) Power Systems -

http://www.nrel.gov/docs/legosti/fy97/21657.pdf

[12] Design and implementatation of a solar power system in rural Haiti -

http://dspace.mit.edu/bitstream/handle/1721.1/32807/57587915.pdf