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
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
ii
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
iii
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,
iv
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
v
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
vi
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
vii
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
viii
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 400˚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
Combustion-
Technology
Economics
Environment
Market
Present
Potential
Deployment
+++
$
+++
+++
+++
++(+)
$$
++(+)
+++
++
Gasification
+(+)
$$$
+(++)
+++
(+)
Pyrolysis
(+)
$$$$
(+++)
++(+)
(+)
heat
Combustion
- electricity
+,low; +++,high; $,cheap; $$$$,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 directlyfired 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, lowiron 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-ofelectricity, after-tax nominal Internal Rate of Return, and annual Debt-Service-CoverageRatios”[3].
35
Figure 4.7 RETFinance tool project selection screen[9]
Assumptions
Capital Structure Assumptions
Non-Cost-Share Debt Percentage (%)
Debt Interest Rate (%)
Debt Repayment Period (Years)
70 %
8%
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
10 %
costs)
10-year Production Tax Credit (cents/kWh escalated
0 $/kWh
at the rate of inflation)
Project Assumptions
Plant Size (kW)
Average Annual Capacity Factor (%)
Power Plant Cost ($/kW)
Taxable Amount (for Sales Tax)
Transmission & Interconnect
Other Capital Costs
Interest Rate During Construction (%)
Debt Service Reserve
Debt-Related Fees
Equity-Related Fees (like tax advice)
Equity-Related Fees (like organizational fee)
Equity-Related Fees (other)
Contingency
30000 kW
25 %
2800 $/kW
1545 $/kW
0 $/kW
0 $/kW
10 %
0 $/kW
0 $/kW
0 $/kW
0 $/kW
0 $/kW
0 $/kW
Annual Costs
Annual Fixed O&M ($/kW)
Annual Variable Costs ($/kWh)
Annual General & Admin Expense ($)
Annual Property Tax Rate (%)
Insurance Expense (%)
Annual Nominal Escalation Rates
Annual Fixed O&M ($/kW)
Annual Variable Costs ($/kWh)
Annual General & Admin Expense ($)
Annual Property Tax Rate (%)
64 $/kW
0 $/kW
0$
1 % of Total
Project Cost
1 % of Total
Project Cost
3%
3%
3%
0%
37
Annual Mines Tax Rate (%)
Insurance Expense (%)
0%
3%
Analysis Parameters
Annual Nominal Electricity Sales Price Escalation
Rate
Is the 'Average DSCR' constraint binding?
Average DSCR (lender imposed)
Is the 'Minimum DSCR' constraint binding?
Minimum DSCR (lender imposed)
Is the equity investor's hurdle rate binding?
Minimum Acceptable Nominal After-Tax IRR (%)
Are negative after-tax cash flows acceptable?
2.5 %/year
Yes
1.8
Yes
1.4
Yes
17 %
No
Figure 4.8 Project cash flow results[9]
38
4.4 Cashflow Report Generated from the RETFinance Tool[8] :
Calendar Year
Project Year
2010
2011
2015
2020
2025
2030
Construction
1
5
10
15
20
65,700,000
65,700,000
65,700,000
65,700,000
65,700,000
22.97
25.36
28.69
32.46
36.73
1,509,374,390
1,666,066,908
1,885,001,783
2,132,706,498
2,412,961,648
Electricity Production (kWhs)
Electricity Sales Price (cents/kWh)
Operating Revenue
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
$3,840
$4,206
$4,730
$5,338
$6,042
$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
$5,137
$4,284
$2,774
$556
$0
$0
$0
$0
$0
$0
$3,360
$0
$0
$0
$0
Operating Expenses
Operating Income
Debt Interest Payment
Amortization
First Year Expense
Loss Forward
Taxable Income
Income Tax
Investment Tax Credit
Production Tax Credit
Total Tax Taken
Net Operating Income
Depreciation
Amortization
First Year Expense
Loss Forward
Debt Principal
$0
$0
$0
$0
$0
($14,033)
($1,501)
$11,345
$15,434
$18,088
($5,614)
($601)
$4,539
$6,174
$7,236
$8,837
$0
$0
$0
$0
$0
$0
$0
$0
$0
($14,451)
($601)
$4,539
$6,174
$7,236
$418
($901)
$6,807
$9,259
$10,852
$16,790
$9,671
$0
$0
$0
$0
$0
$0
$0
$0
$3,360
$0
$0
$0
$0
$0
$0
$0
$0
$0
($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
$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
Debt Funds
Beginning Balance
$64,210
39
Total Debt Payment
Debt-Service Coverage Ratio
$7,502
$7,502
$7,502
$7,502
1.50
1.66
1.88
2.13
$0
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