This document provides an overview of solar energy and solar collectors. It discusses the different types of solar collectors, including flat plate collectors, evacuated tube collectors, and concentrating collectors. Flat plate collectors are the most common for residential water heating, while evacuated tube collectors can achieve higher temperatures suitable for commercial or industrial applications. Concentrating collectors use mirrors to focus sunlight onto receivers to produce high temperatures for electricity generation. The key components and working principles of these different collector types are also explained.
3. 3
UNIT I PRINCIPLES OF SOLAR
RADIATION
Role and potential of new and renewable
source, the solar energy option,
Environmental impact of solar power, physics
of the sun, the solar constant, extra-terrestrial
and terrestrial solar radiation, solar radiation
on titled surface, instruments for measuring
solar radiation and sun shine, solar radiation
data.
8. 8
Energy
Energy is the branch of science
Energy is the capacity for doing work.
Energy may exist in potential, kinetic, thermal,
electrical, chemical, nuclear, or other various forms.
Energy can be neither created nor destroyed but only
changed from one form to another. This principle is
known as the conservation of energy or the first law of
thermodynamics.
9. 9
Energy Sources
Renewable Energy
Solar Energy
Wind Energy
Tidal Energy
Water Energy
Geothermal
Biomass and
Biofuels
Non Renewable
Energy
Coal
Oil
Gas
Nuclear Energy
13. 13
Solar Energy
Sun is the primary source of energy. Sunlight is a
clean, renewable source of energy. It is a sustainable
resource, meaning it doesn't run out, but can be
maintained because the sun shines almost every day.
Coal or gas are not sustainable or renewable: once
they are gone, there is none left. More and more
people are wanting to use clean, renewable energy
such as solar, wind, geothermal steam and others. It is
called 'Green Power'. It lights our houses by day,
dries our clothes and agricultural produce, keeps us
warm and lots more. Its potential is however much
larger
14. 14
Wind Energy
Wind is the natural movement of air across the land or
sea. The wind when used to turn the blades of a wind
mill turns the shaft to which they are attached. This
movement of shaft through a pump or generator produces
electricity. The Potential for wind power generation for
grid interaction has been estimated at about 1,02,788
MW taking sites having wind power density greater than
200 W/sq. m at 80 m hub-height with 2% land
availability in potential areas for setting up wind farms
@ 9 MW/sq. km. India now has the 4th largest wind
power installed capacity in the world which has
reached 36089.12 MWp (as on May, 2019). Private
agencies own 95 % of the wind farms in India.
15. 15
Tidal power
Tidal power or tidal energy is a form of
hydropower that converts
the energy obtained from tides into useful
forms of power, mainly electricity.
Although not yet widely used, tidal
energy has potential for
future electricity generation. Tides are more
predictable than the wind and the sun.
16. 16
Geothermal energy
Geothermal Energy is heat stored in earth crust and
being used for electric generation and also for direct
heat application. Geothermal literally means heat
generated by earth. Various resource assessment carried
out by agencies established the potential 10600 MWth
/1000MWe spread over 340 hot springs across seven
Geothermal provinces/11 states.
The availability of geothermal power is most
environment-friendly power, round the year 24x7 basis,
not affected by the severity of climate during 6 to 7
winter months like hydro and like dependence on sun in
solar PV.
17. 17
Water
The flowing water and the tides in the sea are
sources of energy. India is endowed with large
hydropower potential of 1,45,320 MW. Heavy
investments are made on large projects. In recent
years, hydel energy (through mini and small
hydel power plants) is also used to reach power
to remote villages which are unelectrified. The
estimated potential of Small Hydro Power is
about 15,000 MW in the country. As on May
2019, the installed capacity of Small hydro
projects (upto 3MW) amounts to 4603.75 MW.
18. 18
Biomass
The plants fix solar energy through the process of
photosynthesis to produce biomass. This biomass passes
through various cycles producing different forms of
energy sources. For example, fodder for animals that in
turn produce dung, agricultural waste for cooking, etc.
The current availability of biomass in India is estimated
at about 500 million MT per annum, with an estimated
surplus biomass availability of about 120 – 150 million
metric tones per annum covering agricultural and forestry
residues. This corresponds to a potential of about 18,000
MW. An additional 9131.50 MWp power was generated
through bagasse based cogeneration in the country’s
Sugar mills.
19. 19
Biofuels
Biofuels are predominantly produced from
biomass feed stocks or as a by-product from the
industrial processing of agricultural or food
products, or from the recovery and reprocessing
of products such as cooking and vegetable oil.
Biofuel contains no petroleum, but it can be
blended at any level with petroleum fuel to create
a biofuel blend. It can be used in conventional
healing equipment or diesel engine with no major
modification. Biofuel is simple to use,
biodegradable, non-toxic and essentially free of
Sulphur and aroma.
20. 20
Non Renewable energy
Coal, Oil and Natural gas are the non-renewable sources
of energy. They are also called fossil fuels as they are
products of plants that lived thousands of years ago. Fossil
fuels are the predominantly used energy sources today.
India is the third largest producer of coal in the world,
with estimated reserves of around 3,19,020.33 million
tonnes of Geological Resources of Coal (as of 1.4.2018).
Coal supplies more than 70.87% of the country's total
production of energy by commercial sources. India
consumes about 245 MT of crude oil annually, and more
than 70% of it is imported. Burning fossil fuels cause
great amount of environmental pollution.
21. 21
Environmental Impacts of Solar Power
1) The use of Land
2) The use of Water
3) The use of Natural Resources
4) The use of Hazardous Materials
5) The life-cycle Global Warming Emissions
6) The Visual Impact
24. 24
• The sun is a gaseous body composed mostly of
composed mostly of hydrogen
SUN
• Sun is a sphere of hot
gaseous matter with a
diameter of 1.39*10^9m.
Due to its temperature,
sun emits energy in the
form of electromagnetic
waves, which is called
radiation energy.
30. 30
Solar Constant
The solar constant is defined as the amount
of heat energy received per second per unit
area (J/s/m2, or W/m2 ) and completely
absorbed by a “perfect black body” at the
surface of the Earth.
33. 33
Direct Radiation or Beam Radiation:
Radiation from the sun that
reaches the earth without scattering
Diffuse Radiation:
Radiation that is
scattered by the
atmosphere and clouds
38. 38
Pyrheliometer
It is used to measure direct beam radiation at
normal incidence.
Pyranometer
It is used to measure total
hemispherical radiation - beam plus diffuse -
on a horizontal surface. ...
39. 39
Photoelectric sunshine recorder
The natural solar radiation is notoriously
intermittent and varying in intensity. The most
potent radiation that creates the highest potential
for concentration and conversion is the bright
sunshine, which has a large beam component. The
duration of the bright sunshine at a locale is
measured, for example, by a photoelectric
sunshine recorder.
53. 53
Measurement of Sunshine Duration
Sunshine duration is the length of time
that the sunlight reaching the earth's surface
directly from the sun.
World Meteorological Organization
(WMO) defined sunshine duration as 120
watts per square meter (W/m²).
56. 56
Working Principle of Sunshine Hours
A homogeneous transparent glass sphere L is
supported on an arc XY, and is focused so that an
image of the sun is formed on recording paper
placed in a metal bowl FF' attached to the arc.
The glass sphere is concentric to this bowl,
which has three partially overlapping grooves
into which recording cards for use in the summer,
winter or spring and autumn are set.
Three different recording cards are used
depending on the season. The focus shifts as the
sun moves, and a burn trace is left on the
recording card at the focal point.
57. 57
Working Principle of Sunshine Hours
A burn trace at a particular point indicates
the presence of sunshine at that time, and
the recording card is scaled with hour
marks so that the exact time of sunshine
occurrence can be ascertained.
Measuring the overall length of burn
traces reveals the sunshine duration for
that day.
58. 58
Solar Radiation on a Tilted
Surface
The amount of solar radiation
incident on a tilted module surface is
the component of the incident solar
radiation which is perpendicular to
the module surface.
65. 2
UNIT II
SOLAR ENERGY COLLECTION
Flat plate and concentrating collectors,
classification of concentrating collectors,
orientation and thermal analysis,
advanced collectors.
66. 3
Solar Energy Conversion
1. Solar Thermal Energy system
2. Solar Photovoltaic system
3. Solar Photosynthesis system
70. 7
1.Non-concentrating collectors
The aperture area (i.e., the area that
receives the solar radiation) is roughly the same
as the absorber area (i.e., the area absorbing the
radiation). This type has no extra parts except the
collector itself.
Non-concentrating collectors are typically
used in residential and commercial buildings for
space heating, while concentrating collectors in
concentrated solar power plants generate
electricity by heating a heat-transfer fluid to drive
a turbine connected to an electrical generator.
72. 9
2. Concentrating collectors
Concentrating collectors have a much bigger
aperture than absorber area (additional mirrors focus
sunlight on the absorber) and only harvest the direct
component of sunlight.
77. 14
Flat Plate Collector is a heat exchanger that
converts the radiant solar energy from the sun into
heat energy using the well known greenhouse effect.
It collects solar energy and uses that energy to
heat water in the home for bathing, washing and
heating, and can even be used to heat outdoor
swimming pools and hot tubs.
For most residential and small commercial hot
water applications, the solar flat plate collector tends
to be more cost effective due to their simple design,
low cost, and relatively easier installation compared
to other forms of hot water heating systems.
Flat-Plate Collector
78. 15
Flat-plate collectors are the most common solar collector for
solar water-heating systems in homes and solar space heating.
A typical flat-plate collector is an insulated metal box with a
glass or plastic cover (called the glazing) and a dark-colored
absorber plate.
These collectors heat liquid or air at temperatures less than
180°F.
Flat-plate collectors are used for residential water heating and
hydronic space-heating installations.
Flat-Plate Collector
81. 18
Glazing: One or more sheets of glass (radiation-
transmitting) material.
Tubes : To conduct or direct the heat transfer fluid
from the inlet to the outlet.
Absorber plates: Flat, corrugated, or grooved plates,
to which the tubes, fins, or passages are attached. The
plate may be integral with the tubes.
Headers: To admit and discharge the fluid.
Insulation: To minimise the heat loss from the back
and sides of the collector.
Casing: To surround the aforementioned components
and keep them free from dust, moisture, etc.
Components of Flat-Plate Collector
82. 19
Flat-Plate Collector
Flat plate collector absorbs both beam and diffuse
components of radiant energy. The absorber plate is a
specially treated blackened metal surface. Sun rays
striking the absorber plate are absorbed causing rise of
temperature of transport fluid.
Thermal insulation behind the absorber plate and
transparent cover sheets (glass or plastic) prevent loss of
heat to surroundings.
84. 21
Evacuated Tube Solar Collector
Evacuated-tube collectors can achieve extremely high
temperatures (170°F to 350°F), making them more
appropriate for cooling applications and commercial
and industrial application.
However, evacuated-tube collectors are more expensive
than flat-plate collectors, with unit area costs about
twicethat of flat-plate collectors.Evacuated-tube
collectors are efficient at high temperatures.
The collectors are usually made of parallel rows of
transparent glass tubes. Each tube contains a glass outer
tube and metal absorber tube attached to a fin.
85. 22
Evacuated Tube Solar Collector
The fin is covered with a coating that absorbs solar
energy well, but which inhibits radiative heat loss.
Air is removed, or evacuated, from the space
between the two glass tubes to form a vacuum,
which eliminates conductive and convective heat
loss.
Water is typically allowed to thermosyphon down
and back out the inner cavity to transfer the heat to
the storage tank.
There are no glass-to-metal seals. This type of
evacuated tube has the potential to become cost-
competitive with flat plates.
87. 24
Concentrating collector is a device to collect solar energy with
high intensity of solar radiation on the energy absorbing surface.
Concentrating solar collectors use mirrors and lenses to
concentrate and focus sunlight onto a thermal receiver, similar to
a boiler tube.
The receiver absorbs and converts sunlight into heat. The heat is
then transported to a steam generator or engine where it is
converted into electricity.
These technologies can be used to generate electricity for a
variety of applications, ranging from remote power systems as
small as a few kilowatts (kW) upto grid-connected applications
of 200-350 MW or more.
A concentrating solar power system that produces 350MW of
electricity displaces the energy equivalent of 2.3 million barrels
of oil.
Concentrating Collectors
88. 25
Types of Concentrating Solar Power Systems
Parabolic Trough Collector
Parabolic Dish Collector
Fresnel Lens Collector
Compound Parabolic Concentrator
Minor Strip Collector
Flat Plate Collector with Reflector
93. 30
Parabolic Trough Collectors
Parabolic trough with line focusing reflecting
surface provides concentration ratios from 30 to 50.
Hence, temperature as high as 300 central line of the
parabolic trough. The pipe located along the centre
line absorbs the heat and the working fluid is
circulated through the pipe.
96. 33
Parabolic Dish Collector
The beam radiation is reflected by paraboloid
dish surface. The point focus is obtained with
Central Receiver (above 1000) and temperatures
around 1000°C.
97. 34
Fresnel Lens Collector
A solar concentrator uses lenses, called Fresnel
lenses, which take a large area of sunlight and
direct it towards a specific spot by bending the rays
of light and focusing them.
100. 37
Fresnel lenses are shaped like a dart board, with
concentric rings of prisms around a lens that's a
magnifying glass. All of these features let them focus
scattered light from the Sun into a tight beam.
Solar concentrators put one of these lenses on top of every
solar cell. This makes much more focused light come to
each solar cell, making the cells vastly more efficient.
Concentrators work best when there is a single source of
light and the concentrator can be pointed right at it. This is
ideal in space, where the Sun is a single light source.
Fresnel Lens Collector-Working Principle
101. 38
Compound Parabolic Concentrator
These collectors are line focusing type.
The compound parabolic collectors have two
parabolic surfaces to concentrate the solar
radiation to the absorber placed at bottom.
These collectors have high concentration ratio.
106. 43
Mirror Strip Collector-Working Principle
In this system, the solar radiations falling on the earth
are focused to a vessel (boiler) mounted on a high
tower by using a large number of flat mirror reflectors
which are steerable about to axis known as heliostat.
The mirrors are installed on the ground and are
oriented such that to reflect the direct radiation beam
on vessels.
This produces high-temperature fluids. Radiation
falling on the vessel is heated by black pipes in which
working fluid is circulated.
The working fluid is used to drive a turbine to produce
mechanical energy.
109. 46
Flat Plate Collector with Reflector
In a flat plate collector, a blackened sheet of
metal is used to absorb all sunlight.
The solar collector consists of a glass cover and
an absorbing plate, and a flat plate bottom
reflector is assumed to be made of highly
reflective material.
Direct and diffuse solar radiation and also the
reflected solar radiation from the bottom
reflector are transmitted through the glass cover
and then absorbed onto the absorbing plate.
112. 49
Solar Power Tower
These collectors are used to collect the large
solar energy at one point. This system uses 100-
10000 of flat tracking mirror scaled heliostats to
reflect the solar energy to central receiver mounted
on tower.
The energy can be concentrated as much as
1,500 times than that of the energy coming in, from
the sun. The losses of energy from the system are
minimized as solar energy is being directly
transferred by reflection from the heliostats to a
single receiver where the sun’s rays heat a fluid to
produce steam.
115. 52
Solar Air Collector
Solar hot air collectors are mounted on
south-facing vertical walls or roofs.
Solar radiation reaching the collector heats
the absorber plate.
Air passing through the collector picks up
heat from the absorber plate.
116. 53
Orientation of Solar Collector
For obtaining the maximum productivity of a
solar Energy, solar collector should be
provided with the correct orientation and tilt
angle.
Factors to be considered for Optimum Orientation :
Latitude angle
An hour angle
Declination
A tilt angle
An Azimuth
117. 54
Latitude
The Latitude angle shows, the distance from
equator to the north or to the south and makes a
corner from 0º to 90º, counted from the equator
plane.
121. 58
An Hour Angle
An hour angle transfers local solar time to
number of the degrees which sun passes on the
sky. The hour angle is zero at mid-day.
122. 59
Declination
The declination of the sun depends on earth
rotation around the sun.
Earth turns on 15º for one hour.
In morning, declination is negative, in evening
declination is positive.
The declination becomes equal to zero at two
times per year.
127. 2
UNIT III
SOLAR ENERGY STORAGE
AND APPLICATIONS
Different methods, Sensible, latent heat
and stratified storage, solar ponds. Solar
Applications solar heating/cooling
technique, solar distillation and drying,
photovoltaic energy conversion.
130. 5
Solar Energy Storage Methods
1. Sensible heat storage
2. Latent heat storage
3. Stratified storage
131. 6
Sensible heat storage
In sensible heat storage, thermal
energy is stored by raising the
temperature of solid or liquid by using
its heat capacity.
Q=m𝐂𝒑𝝙T
133. 8
SHS system utilizes the heat capacity
and the change in temperature of the
material during the process of charging
and discharging.
The amount of heat stored depends on the
specific heat of the medium, the
temperature change and amount of
storage material
Sensible heat storage system
134. 9
Process involved :
Charging
Storage
Removal process
Sensible Heat Storage System
137. 12
Long service life
Non-corrosive
Non-toxic
Non-flammable
Long heat storage capacity.
High thermal diffusivity
Thermal conductivity and density.
Simple handling
Low cost
Requirement for
Effective storage of Sensible heat
138. 13
Latent heat is the amount of heat
absorbed or released during the change
of the material from one phase to
another phase.
Latent heat
The amount of heat stored in material in
form of Latent heat is
E=m 𝝙h
140. 15
Latent heat of fusion :
It is the amount of heat is absorbed or
released when the material changes from
solid phase to liquid phase.
Latent heat of vaporization :
It is the amount of heat is absorbed or
released when the material changes
from liquid phase to vapor phase.
Types of Latent heat
144. 19
Stratification is defined as the process
of exchanging the heat between hot
water (warm water) and cold water.
The warm water is always settle on the
top of cold water. This process takes
place in stratified thermal energy
storage tanks by two operations.
Stratified Heat Storage System
145. 20
Stratified Heat Storage System
Operations of Stratification :
i) Charging ii) Discharging
Amount of Heat during charging :
𝐐𝐜=𝐦𝐜𝐂𝐩𝐜(𝐓𝐜𝐢−𝐓𝐜𝐨)
Amount of Heat during discharging :
𝐐𝒅=𝐦𝒅𝐂𝐩𝒅(𝐓𝐝𝐨−𝐓𝐝𝐢)
146. 21
Stratified Heat Storage System
Charging :
Charging operation starts when the tank is
full of warm water. The warm water is
replaced by cold water through chiller
unit.
This replacement is carried out for several
hours upto there is no warm water in the
tank and cold water only left in the tank.
147. 22
Stratified Heat Storage System
Discharging :
Cold water is removed from the tank by
entering the warm water.
Warm water enters the tank through
diffuser which is placed at the top of the
tank to replace the cold water.
156. 31
1. Power generation
2. Space heating and cooling
3. Crop drying
4. Desalination
Applications of Solar Pond
157. 32
Applications of Solar Energy
1. Solar Heating technique
2. Solar Cooling technique
3. Solar Distillation and
4. Solar Drying
158. 33
1) Solar Heating
2) Solar Cooling
3) Solar Distillation
4) Solar Drying
5) Solar pumping
6) Solar furnaces
7) Solar cooking
8) Solar electric power generation
9) Solar thermal power production
10) Solar green houses
Applications of Solar Energy
161. 36
SOLAR WATER HEATING
Solar water heating system (SWHS) is a device
which supplies hot water at 60°C to 80°C using
only solar thermal energy without any other fuel.
Components :
1. Solar Collector
2. Insulated hot water storage tank and
3. Cold water tank with required insulated hot
water pipelines and accessories.
162. 37
SOLAR WATER HEATER TYPES
1.Flat Plate Collectors (FPC) based Solar
Water Heaters
2. Evacuated Tube Collectors (ETC) based
Solar Water Heaters
167. 42
Working Principle of Solar water heating
In a typical solar water heater, water is heated by
the solar thermal energy absorbed by the collectors.
The hot water with lower density moves upwards
and cold water with higher density moves down
from the tank due to gravity head.
A bank of collectors can be arranged in a series –
parallel combination to get higher quantity of hot
water.
A typical 100 litres insulated tank with a 2 m²
collector area, will supply water at a temperature of
60 - 80°C.
168. 43
Environmental benefits of
Solar Water Heating System
A SWH of 100 litres capacity can prevent
emission of 1.5 tonnes of carbondioxide per
year.
Life : 15-20 years
Cost: Rs.15000- 20,000 for a 100 litres
capacity system
Payback period:
3-4 years when electricity is replaced
4-5 years when furnace oil is replaced
5-6 years when coal is replaced
169. 44
Types of solar cookers:
(a) Solar panel cooker
(b) Solar box cooker and
(c) Solar parabolic cooker
SOLAR COOKER
Solar cooker uses the solar thermal energy for
cooking of rice, pulses, vegetables, meat, fish
and preparation of snacks, soups, cakes etc. by
directly from the sun.
171. 46
The panel cooker is the least expensive type of
solar cooker.
It is designed to reflect sunlight over the entire
surface of a lightweight cooking pot painted
black on the outside with non-toxic paint.
It can reach temperatures up to 120ºC.
The inexpensive cardboard and aluminum foil
are most widely used of all panel cookers.
(a) Solar panel cooker
174. 49
Box Solar Cookers have an insulated box,
topped with a transparent glass or plastic cover
and reflctors that help heat the box.
Temperatures inside the box can reach 400ºF.
The solar cooker box uses mylar on plastic flute
board for the refectors and the inside of the box
is aluminum sheet metal. This model can be
made at home.
(b) Solar box cooker
178. 53
Solar parabolic cooker
The Parabolic Solar Cooker (or Curved
Concentrator solar cooker) concentrates the sun’s
heat onto the bottom or the sides of a pot—similar
to a stovetop.
Temperatures can get so hot that you can fry food or
pop popcorn.
The advantages are speed and the potential to cook
when it is cool outside.
Temperatures can reach above 400ºF in the pot. The
parabolic cooker might also need adjustment to keep
it faced toward the sun.
182. 57
SOLAR WATER COOLING SYSTEM
In this system mechanical compression process of
vapor compression cycle is replaced by a thermal
compression process.
The thermal compression is achieved by the following
process:
Absorbing a fluid vapor (e.g., say: ammonia) into
another carrier liquid (e.g., say water).
Pumping this solution to a high pressure cycle by a
simple pump
Producing vapors from the solution by heating
183. 58
SOLAR WATER COOLING SYSTEM
◉ Dry ammonia vapor at low pressure passes in to the
absorber from the evaporator.
◉ In the absorber the dry ammonia vapor is dissolved
in cold water and strong solution of ammonia is
formed.
◉ Heat evolved (heat of absorption) during the
absorption of ammonia in water is removed by
circulating cold water through the coils kept in the
absorber.
◉ The highly concentrated ammonia solution (known
as Aqua Ammonia) is then pumped by a liquid pump
to the generator through a heat exchanger.
188. 63
SOLAR DISTILLATION
Distillation is one of water purification. This
requires an energy input, as heat, solar radiation can
be the source of energy.
In this process, water is evaporated,
thus separating water vapour from
dissolved matter, which is condensed
as pure water.
193. 68
SOLAR STILL-Working Principle
The incident solar radiation is transmitted
through the glass cover and is absorbed as heat
by a black surface in contact with the water to
be distilled.
The water is heated and gives off water
vapour.
The vapour condenses on the glass cover,
which is at a lower temperature because it is in
contact with the ambient air, and runs down
into a gutter from where it is fed to a storage
tank.
194. 69
Solar dryers are devices that use solar energy
to dry the substances, especially food.
Types of solar dryers:
i) Direct
ii) Indirect
SOLAR DRYING
Solar drying is one of the application of solar
energy. Drying means moisture removal from
the product. Drying is helpful in preserving
food product for long time; it prevent product
from contamination.
200. 75
Solar Drying-Working Principle
Direct solar dryers expose the substance to be
dehydrated to direct sunlight.
Food and clothing was dried in the sun by using
lines, or laying the items on rocks or on top of
tents.
In these systems the solar drying is assisted by
the movement of the air (wind) that removes the
more saturated air away from the items being
dried.
More recently, complex drying racks and solar
tents were constructed as solar dryers.
210. 2
UNIT IV
WIND ENERGY
Sources and potentials, horizontal and vertical
axis windmills, performance characteristics,
Betz criteria BIO-MASS: Principles of Bio-
Conversion, Anaerobic/aerobic digestion,
types of Bio-gas digesters, gas yield,
combustion characteristics of bio-gas,
utilization for cooking, I.C.Engine operation
and economic aspects.
212. 4
Wind Energy
Wind power or wind energy is the use
of air flow through wind turbines to
provide the mechanical power to
turn electric generators for generation of
electric power.
213. 5
Wind Energy-Principle
The energy in the wind turns the blades
around a rotor. The rotor is connected to the
shaft, which spins a generator to create
electricity.
214. 6
Potential of Wind Energy in India
STATE
DEMONSTRATION
PROJECTS (in MW)
ANDHRA PRADESH 5.4
GUJARAT 17.3
KARNATAKA 7.1
KERALA 2.0
MADHYA PRADESH 0.6
MAHARASHTRA 8.4
RAJASTHAN 6.4
TAMIL NADU 19.4
WEST BENGAL 1.1
OTHERS 3.3
TOTAL 71.0
215. 7
Wind Mills-Types
1. Horizontal Axis Wind Mill
(Axis of the rotation is parallel to air stream)
2.Vertical Axis Wind Mill
(Axis of the rotation is perpendicular to air stream)
226. 18
Components-Horizontal Wind Mill
1. Blades and rotor: Converts the wind power to a
rotational mechanical power.
2. Gear box: Wind turbines rotate typically between
40 rpm and 400 rpm. Generators typically rotates at
1,200 to 1,800 rpm. Most wind turbines require a
step-up gear-box for efficient electricity
production.
3. Generator: Converts the rotational mechanical
power to electrical power.
4. Rotor : The portion of the wind turbine that
collects energy from the wind is called the rotor.
The blades are attached to the hub, which in turn is
attached to the main shaft.
227. 19
Horizontal Wind Mill
All of the components (blades, shaft,
generator) are on top of a tall tower,
and the blades face into the wind.
The shaft is horizontal to the ground.
The wind hits the blades of the turbine
that are connected to a shaft causing
rotation.
The shaft has a gear on the end which
turns a generator.
228. 20
Horizontal Wind Mill
The generator produces electricity and
sends the electricity into the power
grid.
As the wind changes direction, a
motor turns the nacelle so the blades
are always facing the wind.
In case of extreme winds the turbine
has a break that can slow the shaft
speed.
235. 27
Biomass is plant or animal material used for
energy production (electricity or heat).
Biomass is biological organic matter derived
from living or recently-living organisms.
BIOMASS
237. 29
Forms of Biomass
1.Raw Products:
Materials that available from animal or
plant by naturally
2.Secondary Products:
Materials that undergone significant
changes from raw biomass.
238. 30
Forms of Biomass
1.Raw Products:
i) Forestry products
ii) Grasses
iii) Crops
iv) Animal manure and
v) Aquatic Products (seaweed)
239. 31
Forms of Biomass
2.Secondary Products:
i) Paper
ii) Cardboard
iii) Cotton
iv) Natural rubber products and
v) used cooking oils
260. 52
Gasification
Gasification is a process that converts solid
and carbonaceous materials into carbon
monoxide, hydrogen and carbon dioxide.
This is achieved by reacting the material at
high temperatures (>700 °C), without
combustion, with a controlled amount of
oxygen and/or steam.
The resulting gas mixture is called syngas
(from synthesis gas) or producer gas and is
itself a fuel.
263. 55
a) Ethanol Fermentation
It is a biological process in which sugar
is converted into cellular energy and
thereby produce ethanol and carbon
dioxide. Yeast perform this conversion in
the absence of oxygen.
264. 56
b) Anaerobic Digestion
In anaerobic digestion, biogas is produced by
the bacterial decomposition of wet sewage
sludge, animal dung or green plants in the
absence of oxygen.
The final product is a mixture of methane,
carbon dioxide and some other gases are known
as Biogas. This process is called anaerobic
digestion.
266. 58
Principles of Bio-Conversion
Bio conversion also known as Bio
transformation.
It is defined as the process of
conversion of organic materials such
as plant or animal waste into usable
products or energy sources by
biological processes.
270. 62
PHOTOSYNTHESIS
In the process of photosynthesis, plants
convert radiant energy from the sun into
chemical energy in the form of glucose
(or sugar).
275. 67
Anaerobic Digestion
(Absence of oxygen)
Anaerobic digestion is a collection of
processes by which micro organisms break
down biodegradable material in the absence
of oxygen.
The process is used for industrial
waste or domestic waste to produce the
fuels.
C6H12O6 → 3CO2 + 3CH4
276. 68
Process of Anaerobic Digestion
Hydrolysis
Acidogenesis or Fermentation
Acetogenesis
Methanognesis
277. 69
1) Hydrolysis
The process of breaking and dissolving
the smaller molecules into solution is called
hydrolysis.
Through hydrolysis the complex organic
molecules are broken down into simple
sugars, amino acids, and fatty acids.
278. 70
2) Acidogenesis or Fermentation
The biological process of acidogenesis
is breakdown the components by acidogenic
bacteria.
The process of acidogenesis is similar
to the milk sours.
279. 71
3) Acetogenesis
In Acetogenesis, simple molecules created
through the acidogenesis phase are further digested
by acetogens to produce acetic acid, as well as
carbon dioxide and hydrogen.
4) Methanognesis
Methanogens are use the intermediate
products and convert into methane, carbon
dioxide, and water.
281. 73
Aerobic Digestion
(Presence of oxygen)
Aerobic digestion process involves the
decomposition of organic wastes in the
presence of oxygen (air).
This process involves the oxidation of
biodegradable matter by aerobic
microorganisms resulting on overall reduction
in the mass of sledge and generation of cells,
CO2, NH3 etc..
282. 74
BIO-GAS DIGESTERS
(also known as biogas plant)
Biogas digester is a large tank where inside
biogas is produced through the decomposition of
organic matter. This process done by anaerobic
digestion.
289. 81
TYPES OF BIO-GAS DIGESTERS
Single Stage Process Digester
Double Stage Process Digester
Fixed Dome Type Digester
Floating Drum Digester
Flexible Bag Type Digester
292. 84
Single Stage Process Digester
In a single-stage digestion system (one-stage),
all of the biological reactions occur within a
single, sealed reactor or holding tank.
Using a single stage reduces construction costs,
but results in less control of the reactions
occurring within the system
298. 90
A fixed-dome plant comprises of a closed,
dome-shaped digester with an immovable, rigid
gas-holder and a displacement pit, also named
'compensation tank'.
The gas is stored in the upper part of the
digester. When gas production commences, the
slurry is displaced into the compensating tank.
Gas pressure increases with the volume of gas
stored, i.e. with the height difference between the
two slurry levels. If there is little gas in the gas-
holder, the gas pressure is low.
Fixed Dome Type Digester
302. 94
Floating Drum Digester
Floating-drum plants consist of an
underground digester and a moving gas-
holder.
The gas-holder floats either directly on the
fermentation slurry or in a water jacket of its
own.
The gas is collected in the gas drum, which
rises or moves down, according to the amount
of gas stored.
305. 97
Flexible Bag Type Digester
A balloon plant consists of a heat-
sealed plastic or rubber bag (balloon),
combining digester and gas-holder.
The gas is stored in the upper part of
the balloon.
The inlet and outlet are attached
directly to the skin of the balloon.
306. GEOTHERMAL POWER PLANT:
Geothermal electricity is electricity generated from geothermal energy. Technologies
in use include dry steam power plants, flash steam power plants and binary cycle power
307. plants. Geothermal electricity generation is currently used in 24 countries while
geothermal heating is in use in 70 countries.
Estimates of the electricity generating potential of geothermal energy vary from 35 to
2000 GW. Current worldwide installed capacity is 10,715 megawatts (MW), with the
largest capacity in the United States (3,086 MW), Philippines, and Indonesia.
Geothermal power is considered to be sustainable because the heat extraction is small
compared with the Earth's heat content. The emission intensity of existing geothermal
electric plants is on average 122 kg of CO2 per megawatt-hour (MW·h) of electricity,
about one-eighth of a conventional coal-fired plant.
OTEC:
Ocean thermal energy conversion (OTEC )uses the difference between cooler deep
and warmer shallow or surface ocean waters to run a heat engine and produce useful
work, usually in the form of electricity.
A heat engine gives greater efficiency and power when run with a large temperature
difference. In the oceans the temperature difference between surface and deep water is
greatest in the tropics, although still a modest 20o
C to 25o
C. It is therefore in the tropics
that OTEC offers the greatest possibilities. OTEC has the potential to offer global
amounts of energy that are 10 to 100 times greater than other ocean energy options such
as wave power. OTEC plants can operate continuously providing a base load supply for
an electrical power generation system.
The main technical challenge of OTEC is to generate significant amounts of power
efficiently from small temperature differences. It is still considered an emerging
technology. Early OTEC systems were of 1 to 3% thermal efficiency, well below the
theoretical maximum for this temperature difference of between 6 and 7%.[2]
Current
designs are expected to be closer to the maximum. The first operational system was
built in Cuba in 1930 and generated 22 kW. Modern designs allow performance
approaching the theoretical maximum Carnot efficiency and the largest built in 1999 by
the USA generated 250 kW .
The most commonly used heat cycle for OTEC is the Rankine cycle using a low-
pressure turbine. Systems may be either closed-cycle or open-cycle. Closed-cycle
308. engines use working fluids that are typically thought of as refrigerants such as ammonia
or R-134a. Open-cycle engines use vapour from the seawater itself as the working fluid.
OTEC can also supply quantities of cold water as a by-product . This can be used for air
conditioning and refrigeration and the fertile deep ocean water can feed biological
technologies. Another by-product is fresh water distilled from the sea.
Cycle types
Cold seawater is an integral part of each of the three types of OTEC systems: closed-
cycle, open-cycle, and hybrid. To operate, the cold seawater must be brought to the
surface. The primary approaches are active pumping and desalination. Desalinating
seawater near the sea floor lowers its density, which causes it to rise to the surface.
The alternative to costly pipes to bring condensing cold water to the surface is to pump
vaporized low boiling point fluid into the depths to be condensed, thus reducing
pumping volumes and reducing technical and environmental problems and lowering
costs.
Closed
Diagram of a closed cycle OTEC plant
309. Closed-cycle systems use fluid with a low boiling point, such as ammonia, to power a
turbine to generate electricity. Warm surface seawater is pumped through a heat
exchanger to vaporize the fluid. The expanding vapor turns the turbo-generator. Cold
water, pumped through a second heat exchanger, condenses the vapor into a liquid,
which is then recycled through the system.
In 1979, the Natural Energy Laboratory and several private-sector partners developed
the "mini OTEC" experiment, which achieved the first successful at-sea production of
net electrical power from closed-cycle OTEC.[12]
The mini OTEC vessel was moored
1.5 miles (2 km) off the Hawaiian coast and produced enough net electricity to
illuminate the ship's light bulbs and run its computers and television.
Open
Diagram of an open cycle OTEC plant
Open-cycle OTEC uses warm surface water directly to make electricity. Placing warm
seawater in a low-pressure container causes it to boil. The expanding steam drives a low-
pressure turbine attached to an electrical generator. The steam, which has left its
310. salt and other contaminants in the low-pressure container, is pure fresh water. It is
condensed into a liquid by exposure to cold temperatures from deep-ocean water. This
method produces desalinized fresh water, suitable for drinking water or irrigation.
In 1984, the Solar Energy Research Institute (now the National Renewable Energy
Laboratory) developed a vertical-spout evaporator to convert warm seawater into low-
pressure steam for open-cycle plants. Conversion efficiencies were as high as 97% for
seawater-to-steam conversion (overall efficiency using a vertical-spout evaporator
would still only be a few per cent). In May 1993, an open-cycle OTEC plant at Keahole
Point, Hawaii, produced 50,000 watts of electricity during a net power-producing
experiment. This broke the record of 40 kW set by a Japanese system in 1982.
Hybrid
A hybrid cycle combines the features of the closed- and open-cycle systems. In a
hybrid, warm seawater enters a vacuum chamber and is flash-evaporated, similar to the
open-cycle evaporation process. The steam vaporizes the ammonia working fluid of a
closed-cycle loop on the other side of an ammonia vaporizer. The vaporized fluid then
drives a turbine to produce electricity. The steam condenses within the heat exchanger
and provides desalinated water.
Working fluids
A popular choice of working fluid is ammonia, which has superior transport properties,
easy availability, and low cost. Ammonia, however, is toxic and flammable. Fluorinated
carbons such asCFCs and HCFCs are not toxic or flammable, but they contribute to
ozone layer depletion. Hydrocarbons too are good candidates, but they are highly
flammable; in addition, this would create competition for use of them directly as fuels.
The power plant size is dependent upon the vapor pressure of the working fluid. With
increasing vapor pressure, the size of the turbine and heat exchangers decreases while
the wall thickness of the pipe and heat exchangers increase to endure high pressure
especially on the evaporator side.
UNIT VII
TIDEL POWER PLANT:
311. Tidal power, also called tidal energy, is a form of hydropower that converts the energy
of tides into electricity or other useful forms of power. The first large-scale tidal power
plant (the Rance Tidal Power Station) started operation in 1966.
Although not yet widely used, tidal power has potential for future electricity generation.
Tides are more predictable than wind energy and solar power. Among sources of
renewable energy, tidal power has traditionally suffered from relatively high cost and
limited availability of sites with sufficiently high tidal ranges or flow velocities, thus
constricting its total availability. However, many recent technological developments
and improvements, both in design (e.g. dynamic tidal power, tidal lagoons) and turbine
technology (e.g. new axial turbines, crossflow turbines), indicate that the total
availability of tidal power may be much higher than previously assumed, and that
economic and environmental costs may be brought down to competitive levels.
Historically, tide mills have been used, both in Europe and on the Atlantic coast of
North America. The earliest occurrences date from the Middle Ages, or even from
Roman times.
Tidal power is extracted from the Earth's oceanic tides; tidal forces are periodic
variations in gravitational attraction exerted by celestial bodies. These forces create
corresponding motions or currents in the world's oceans. The magnitude and character
of this motion reflects the changing positions of the Moon and Sun relative to the Earth,
the effects of Earth's rotation, and local geography of the sea floor and coastlines.
Tidal power is the only technology that draws on energy inherent in the orbital
characteristics of the Earth–Moon system, and to a lesser extent in the Earth–Sun
system. Other natural energies exploited by human technology originate directly or
indirectly with the Sun, including fossil fuel, conventional hydroelectric, wind, biofuel,
wave and solar energy. Nuclear energy makes use of Earth's mineral deposits of
fissionable elements, while geothermal power taps the Earth's internal heat, which
comes from a combination of residual heat from planetary accretion (about 20%) and
heat produced through radioactive decay (80%).
A tidal generator converts the energy of tidal flows into electricity. Greater tidal
variation and higher tidal current velocities can dramatically increase the potential of a
site for tidal electricity generation.
312. Because the Earth's tides are ultimately due to gravitational interaction with the Moon
and Sun and the Earth's rotation, tidal power is practically inexhaustible and classified
as a renewable energy resource. Movement of tides causes a loss of mechanical energy
in the Earth–Moon system: this is a result of pumping of water through natural
restrictions around coastlines and consequent viscous dissipation at the seabed and in
turbulence. This loss of energy has caused the rotation of the Earth to slow in the
4.5 billion years since its formation. During the last 620 million years the period of
rotation of the earth (length of a day) has increased from 21.9 hours to 24 hours;[4]
in
this period the Earth has lost 17% of its rotational energy. While tidal power may take
additional energy from the system, the effect is negligible and would only be noticed
over millions of years.
Generating methods
The world's first commercial-scale and grid-connected tidal stream generator – SeaGen
– in Strangford Lough. The strong wake shows the power in the tidal current.
Top-down view of a DTP dam. Blue and dark red colors indicate low and high tides,
respectively.
Tidal power can be classified into three generating methods:
Tidal stream generator
Tidal stream generators (or TSGs) make use of the kinetic energy of moving water to
power turbines, in a similar way to wind turbines that use moving air.
Tidal barrage
Tidal barrages make use of the potential energy in the difference in height (or head)
between high and low tides. Barrages are essentially dams across the full width of a
tidal estuary.
313. Dynamic tidal power
Dynamic tidal power (or DTP) is a theoretical generation technology that would exploit
an interaction between potential and kinetic energies in tidal flows. It proposes that very
long dams (for example: 30–50 km length) be built from coasts straight out into the sea
or ocean, without enclosing an area. Tidal phase differences are introduced across the
dam, leading to a significant water-level differential in shallow coastal seas – featuring
strong coast-parallel oscillating tidal currents such as found in the UK, China and
Korea.
PUMPED STORAGE:
Pumped-storage hydroelectricity is a type of hydroelectric power generation used by
some power plants for load balancing. The method stores energy in the form of water,
pumped from a lower elevation reservoir to a higher elevation. Low-cost off-peak
electric power is used to run the pumps. During periods of high electrical demand, the
stored water is released through turbines. Although the losses of the pumping process
makes the plant a net consumer of energy overall, the system increases revenue by
selling more electricity during periods of peak demand, when electricity prices are
highest. Pumped storage is the largest-capacity form of grid energy storage now
available.
SOLAR CENTRAL RECIVER SYSTEM:
The solar power tower (also known as 'central tower' power plants or 'heliostat' power
plants or power towers) is a type of solar furnace using a tower to receive the focused
sunlight. It uses an array of flat, movable mirrors (called heliostats) to focus the sun's
rays upon a collector tower (the target). Concentrated solar thermal is seen as one viable
solution for renewable, pollution free energy production with currently available
technology.
Early designs used these focused rays to heat water, and used the resulting steam to
power a turbine. Newer designs using liquid sodium has been demonstrated, and
systems using molten salts (40% potassium nitrate, 60% sodium nitrate) as the working
fluids are now in operation. These working fluids have high heat capacity, which can be
314. used to store the energy before using it to boil water to drive turbines. These designs
allow power to be generated when the sun is not shining.
COST OF ELECTRICAL ENERGY:
Electric power transmission or "high voltage electric transmission" is the bulk transfer
of electrical energy, from generating power plants to substations located near to
population centers. This is distinct from the local wiring between high voltage
substations and customers, which is typically referred to as electricity distribution.
Transmission lines, when interconnected with each other, become high voltage
transmission networks. In the US, these are typically referred to as "power grids" or just
"the grid", while in the UK the network is known as the "national grid." North America
has three major grids: The Western Interconnection; The Eastern Interconnection and
the Electric Reliability Council of Texas (or ERCOT) grid.
Historically, transmission and distribution lines were owned by the same company, but
over the last decade or so many countries have liberalized the electricity market in ways
that have led to the separation of the electricity transmission business from the
distribution business.
Transmission lines mostly use three-phase alternating current (AC), although single
phase AC is sometimes used in railway electrification systems. High-voltage direct-
current (HVDC) technology is used only for very long distances (typically greater than
400 miles, or 600 km); submarine power cables (typically longer than 30 miles, or
50 km); or for connecting two AC networks that are not synchronized.
Electricity is transmitted at high voltages (110 kV or above) to reduce the energy lost in
long distance transmission. Power is usually transmitted through overhead power lines.
Underground power transmission has a significantly higher cost and greater operational
limitations but is sometimes used in urban areas or sensitive locations.
A key limitation in the distribution of electricity is that, with minor exceptions,
electrical energy cannot be stored, and therefore must be generated as needed. A
sophisticated system of control is therefore required to ensure electric generation very
closely matches the demand. If supply and demand are not in balance, generation plants
and transmission equipment can shut down which, in the worst cases, can lead to a
315. major regional blackout, such as occurred in California and the US Northwest in 1996
and in the US Northeast in 1965, 1977 and 2003. To reduce the risk of such failures,
electric transmission networks are interconnected into regional, national or continental
wide networks thereby providing multiple redundant alternate routes for power to flow
should (weather or equipment) failures occur. Much analysis is done by transmission
companies to determine the maximum reliable capacity of each line which is mostly
less than its physical or thermal limit, to ensure spare capacity is available should there
be any such failure in another part of the network.
ENERGY RATES:
Electricity pricing (sometimes referred to as electricity tariff or the price of
electricity) varies widely from country to country, and may vary signicantly from
locality to locality within a particular country. There are many reasons that account for
these differences in price. The price of power generation depends largely on the type
and market price of the fuel used, government subsidies, government and industry
regulation, and even local weather patterns.
Basis of electricity rates
Electricity prices vary all over the world, even within a single region or power-district
of a single country. In standard regulated monopoly markets, they typically vary for
residential, business, and industrial customers, and for any single customer class, might
vary by time-of-day or by the capacity or nature of the supply circuit (e.g., 5 kW,
12 kW, 18 kW, 24 kW are typical in some of the large developed countries); for
industrial customers, single-phase vs. 3-phase, etc. If a specific market allows real-time
dynamic pricing, a more recent option in only a few markets to date, prices can vary by
a factor of ten or so between times of low and high system-wide demand.
TYPES OF TARIFFS:
In economic terms, electricity (both power and energy) is a commodity capable of being
bought, sold and traded. An electricity market is a system for effecting purchases,
through bids to buy; sales, through offers to sell; and short-term trades, generally in the
form of financial or obligation swaps. Bids and offers use supply and demand principles
316. to set the price. Long-term trades are contracts similar to power purchase agreements
and generally considered private bi-lateral transactions between counterparties.
Wholesale transactions (bids and offers) in electricity are typically cleared and settled
by the market operator or a special-purpose independent entity charged exclusively with
that function. Market operators do not clear trades but often require knowledge of the
trade in order to maintain generation and load balance. The commodities within an
electric market generally consist of two types: Power and Energy. Power is the metered
net electrical transfer rate at any given moment and is measured in Megawatts (MW).
Energy is electricity that flows through a metered point for a given period and is
measured in Megawatt Hours (MWh).
Markets for power related commodities are net generation output for a number of intervals usually in increments of 5,
15 and 60 minutes. Markets for energy related commodities required by, managed by (and paid for by) market
operators to ensure reliability, are considered Ancillary Services and include such names as spinning reserve, non-
spinning reserve, operating reserves, responsive reserve, regulation up, regulation down, and installed capacity.
In addition, for most major operators, there are markets for transmission congestion and electricity
derivatives, such as electricity futures and options, which are actively traded. These markets developed
as a result of the restructuring
UNIT VII
Oceanic Energy
Offshore Wave Energy. An inventor approaches you with the design for a wave energy
device that he claims will generate 50 GWh of energy annually. The device has a wave inlet
25 meters wide and converts wave energy to electricity by some secret process he won’t
reveal.
a. Might you be interested in investing in the development of this project? Discuss.
b. How high would waves need to be to generate this amount of power? Assume the
average time between waves is T = 10s and that the wave energy generator works with
100% efficiency (all available wave energy is converted to electricity)
Hint:
a. Calculate the average power of the device per meter of wave inlet assuming
continuous operation (24x365). Compare this value with the Global Wave Energy
317. Averages shown in the lecture slides and available online at
http://www.wavedragon.net/pics/world-map.jpg.
b. Use the wave energy formula P= (H 2
)(T)/2 shown in class to calculate wave height H
Shoreline Wave Energy. The LIMPET OWC (oscillating water column) shoreline wave
generator described in class has a nameplate rating of 500 kW with wave intensities of
about 20 kW/m (http://www.wavegen.co.uk/what_we_offer_limpet_islay.htm)
a. How many household could one LIMPET OWC support assuming that an average
household requires an average of 1 kW power? Assume a capacity factor of 40%.
b. How many LIMPET units would be required to support a community of 25,000
households (about the size of Boulder)?
c. Discuss the pros and cons of incorporating a series of LIMPET units in a new
breakwater that is to be built to protect a large marina in a resort community.
Barrage Tidal System. You have a summer cabin on a remote island in the San Juan
Islands of Peugeot Sound near Seattle. Currently, the only power you have at the cabin is
a noisy and smelly gasoline generator that you would like to replace. On the shore of your
island near your cabin is a natural cleft in the steep shoreline. If build a low dam across
the cleft at the proper height, the dam would be flooded at high tide, but would create a
pool or lagoon behind it at low tide. If you install a pipe through the bottom of the dam
with a simple turbine and generator, you could generate electricity on the ebb flow of the
tide. You do some quick measurements and find that the area of the lagoon behind the
dam would be about 5m wide by 20m long, and the lagoon would be about 3m deep at
high tide, and 1m deep at low tide.
a. As you think about going forward with this project, what environmental factors should
you consider?
b. Assuming a capacity factor of 25%, how much energy could you generate from this
setup with each tidal cycle? Recall that E=1397ηR 2
A for each tidal cycle, where η□is
the capacity factor, R is the range of the tide in meters, and A is the area of the tidal
pool in square kilometers.
c. How long could you light a 100W bulb with this energy if it all could be captured and
used without loss?
318. d. Should you proceed with the project?
Wave Power. A container ship having a displacement of 70,000 metric tons (70 million kg)
is raised 1 meter in 5 seconds by an ocean wave. Compare the lift power of the wave to the
ship’s shaft horsepower of 50,000 hp (37,280 kW). Discuss.
Hints:
Calculate the increase in potential energy when the ship is raised by 1 meter using the
formula E=mgh, where E is energy expressed in Joules (J), m is mass (kg), g=9.8m/s2
is the gravitational constant, and h (meters) is the height to which the mass is raised.
Convert Joules (J) to kWh using 1kWh = 3.6 MJ (million Joules)
Calculate the power (energy per unit time) of the wave – note that the ship is raised in
5 seconds, not 1 hour.
2 Renewable Energy Technologies and Applications
The study focuses on concentrating solar thermal power generation because this is by far the greatest
renewable energy resource in the EU-MENA region, but other renewable energy sources are
represented as well, in order to obtain a well balanced mix of energies that can not only cope with the
growing energy demand, but also with the needs of power security and grid stability. The renewable
energy technology portfolio that was considered within the study is described in the following. An
overview and comparison of all technologies is given in Error! Reference source not found. and in
the literature /BMU 2004-2/, /ECOSTAR 2004/, /NREL 2003/.
1. Concentrating Solar Thermal Power Technologies
Concentrating solar thermal power technologies (CSP) are based on the concept of concentrating solar
radiation to be used for electricity generation within conventional power cycles using steam turbines,
gas turbines or Stirling engines. For concentration, most systems use glass mirrors that continuously
track the position of the sun. The concentrated sunlight is absorbed on a receiver that is specially
designed to reduce heat losses. A fluid flowing through the receiver takes the heat away towards the
power cycle, where e.g. high pressure, high temperature steam is generated to drive a turbine. Air,
water, oil and molten salt are used as heat transfer fluids.
319. Figure 2-1: Principle of concentrating solar beam radiation and the four CSP collector technology main streams realised up to date
(Sources: DLR, SNL, Solarmundo, SBP)
Parabolic troughs, linear Fresnel systems and power towers can be coupled to steam cycles of 5 to 200
MW of electric capacity, with thermal cycle efficiencies of 30 – 40 %. Dish-Stirling engines are used
for decentralised generation in the 10 kW range. The values for parabolic troughs have been
demonstrated in the field. Today, these systems achieve annual solar-to-electricity-efficiencies of
about 10 – 15 %, with the perspective to reach about 18 % in the medium term (Table 2-1). The values
for the other systems are based on component and prototype system test data and the assumption of
mature development of current technology. The overall solar-electric efficiencies include the
conversion of solar energy to heat within the collector and the conversion of the heat to electricity in
the power block. The conversion efficiency of the power block remains basically the same as in fuel
fired power plants.
Power towers can achieve very high operating temperatures of over 1000 °C, enabling them to
produce hot air for gas turbine operation. Gas turbines can be used in combined cycles, yielding very
high conversion efficiencies of the thermal cycle of more than 50 %.
Each of these technologies can be operated with fossil fuel as well as solar energy. This hybrid
operation has the potential to increase the value of CSP technology by increasing its power availability
and decreasing its cost by making more effective use of the power block. Solar heat collected during
the daytime can be stored in concrete, molten salt, ceramics or phase-change media. At night, it can be
extracted from the storage to run the power block. Fossil and renewable fuels like oil, gas, coal and
biomass can be used for co-firing the plant, thus providing power capacity whenever required (Figure
2-2).
reflector
receiver
Capacity
Unit MW
Concen-
tration
Peak Solar
Efficiency
Annual Solar
Efficiency
Thermal Cycle
Efficiency
Capacity
Factor (solar)
Land Use
m²/MWh/y
Trough 10 – 200 70 - 80 21% (d) 10 – 15% (d) 30 – 40 % ST 24% (d) 6 - 8
17 – 18% (p) 25 – 90% (p)
Fresnel 10 - 200 25 - 100 20% (p) 9 - 11% (p) 30 - 40 % ST 25 - 90% (p) 4 - 6
Power Tower 10 – 150 300 – 1000 20% (d) 8 – 10 % (d) 30 – 40 % ST 25 – 90% (p) 8 - 12
35 % (p) 15 – 25% (p) 45 – 55 % CC
Dish-Stirling 0.01 – 0.4 1000 – 3000 29% (d) 16 – 18 % (d) 30 – 40 % Stirl. 25% (p) 8 - 12
18 – 23% (p) 20 – 30 % GT
320. Table 2-1: Performance data of various concentrating solar power (CSP) technologies
(d) = demonstrated, (p) = projected, ST steam turbine, GT Gas Turbine,
CC Combined Cycle. Solar efficiency = net power generation / incident beam radiation
Capacityfactor = solar operating hours per year / 8760 hours per year
Moreover, solar energy can be used for co-generation of electricity and process heat. In this case, the
primary energy input is used with efficiencies of up to 85 %. Possible applications cover the combined
production of industrial heat, district cooling and sea water desalination.
All concepts have the perspective to expand their time of solar operation to base load using thermal
energy storage and larger collector fields. To generate one Megawatt-hour of solar electricity per year,
a land area of only 4 to 12 m² is required. This means, that one km2
of arid land can continuously and
indefinitely generate as much electricity as any conventional 50 MW coal - or gas fired power station.
Thus, two main characteristics make concentrating solar power a key technology in a future renewable
energysupply mix in MENA:
it can deliver secured power as requested by demand
its natural resource is very abundant and practically unlimited
Their thermal storage capability and hybrid operation with fuels allows CSP plants to provide power
on demand. Their availability and capacity credit is considered to be 90 %. CSP plants can be build
from several kW to several 100 MW capacity.
Figure 2-2: Principle of solar thermal co-generation of heat and power
Prospects of CSP Research and Development and Projects Ahead
While present parabolic trough plants use synthetic oil as heat transfer fluid within the collectors, and
a heat exchanger for steam generation, efforts to achieve direct steam generation within the absorber
tubes are underway in the DISS and INDITEP projects sponsored by the European Commission, with
the aim to reduce costs and to enhance efficiency by 15-20% (Table 2-2). Direct solar steam
generation has recently been demonstrated by CIEMAT and DLR on the Plataforma Solar in Almeria/
Spain, in a 500 m long test loop, providing superheated steam at 400 °C and 100 bar. All those R&D
efforts aim at increasing efficiency and reducing costs.
A European industrial consortium has developed the new parabolic trough collector SKAL-ET, which
aims to achieve better performance and cost by improving the mechanical structure and the optical and
Cogen Cycle
Concentrating
Solar Collector
Field
Thermal
Energy
Storage
Cogen Cycle
Concentrating
Solar Collector
Field
Solar
Heat Fuel
Thermal
Energy
Storage
Process Heat
• solar electricity
• integrated backup capacity,
power on demand
• increased solar operating
hours, reduced fuel input
• additional process heat for
cooling, drying, seawater
desalination, etc.
Electricity
321. thermal properties of the parabolic troughs. Another European consortium has developed a simplified
trough collector prototype with segmented flat mirrors following the principle of Fresnel.
The high temperatures available in solar towers can not only be used to drive steam cycles, but also for
gas turbines and combined cycle systems. Such system promises up to 35 % peak and 25 % annual
solar-electric efficiency when coupled to a combined cycle power plant. A solar receiver was
developed within the European SOLGATE project for heating pressurised air by placing the
volumetric absorber into a pressure vessel with a parabolic quartz window for solar radiation
incidence. Multi-tower solar arrays may be arranged in the future so that the heliostat reflectors can
alternatively point to various tower receivers. Like in other Fresnel systems, the horizontally arranged
heliostats almost completely cover the land area and create a bright, semi-shaded space below for
agricultural or other purposes.
A review of presently existing or developed CSP projects is given in Annex 9.
