A PRESENTATION ON APPLICATIONS OF SOLAR ENERGY TECHNOLOGY, DESCRIBING VARIOUS SOLAR DEVICES ....

1. 1
SOLAR ENERGY
TECHNOLOGY
VANITA THAKKAR
ASSOCIATE PROFESSOR,
MECHANICAL ENGINEERING DEPARTMENT,
BABARIA INSTITUTE OF TECHNOLOGY,
VARNAMA, VADODARA
VANITA THAKKAR

2. 2
LIMTATIONS OF CONVENTIONAL
ENERGY SOURCES
Growing scarcity due to limited
Resources.
Ever increasing cost.
Fear of possible environmental
risks.
VANITA THAKKAR

3. 3
Type of facility Lead time (Years from decision
to start up )
Nuclear plants 8-10
Coal or Oil fired power plants 5-7
Hydroelectric plant 20
Geothermal power plant 5
Gas turbine power plant 2
New coal mine 3-6
New off-shore oil field 2-4
Shale oil plant 5
Liquefaction plant 5
WHY SOLAR ENERGY TECHNOLOGY ? –
CONTEXT – LEAD TIME
VANITA THAKKAR

4. SOLAR ENERGY UTILIZATION
SOLAR DEVICES
DIRECT
CONVERSION
SOLAR THERMAL
CONVERSION SYSTEMS
SOLAR PHOTOVOLTAICS
FLAT PLATE
COLLECTORS
CONCENTRATING
COLLECTORS
4VANITA THAKKAR

5. 5
Transfer of solar radiant energy on to the
electrons of a solid in :
 Photovoltaic cells
 Photogalvanic cells : applied to photolysis
of water.
 Phototubes : Electrons are emitted from
the cathode under illumination may also
serve to generate power.
DIRECT CONVERSION OF
SOLAR ENERGY
VANITA THAKKAR

6. 6
Conversion of radiation energy into heat and
secondarily into electricity in a thermodynamic
process.
 Flat plate solar collectors
 Concentrating solar collectors
 Solar Tower
 Solar Chimney etc.
INDIRECT CONVERSION OF
SOLAR ENERGY
VANITA THAKKAR

7. 7
TECHNOLOGY SELECTION
VANITA THAKKAR

8. 8
SOLAR RESOURCES WORLDWIDE
VANITA THAKKAR

9. 9
THE WORLD’S SUN BELT
VANITA THAKKAR

10. 10
ENERGY FROM SUN
 The Sun generates energy at the rate of 3.8x1023
kW.
 Earth receives only a small part of it, but that is
also considerable.
 Earth receives 1.7x1014 kW or 5.3×1024 J / year
of solar energy
 8.4 × 1023 J / year reaches the surface of Earth.
 Current world consumption of energy is 4.0 ×
1020 J / year from all sources.VANITA THAKKAR

11. 11
ENERGY FROM SUN (contd.)
• All chemical and radioactive polluting
byproducts of the thermonuclear reactions
remain behind on the sun, while only pure
radiant energy reaches the Earth.
• Energy reaching the earth is incredible. By
one calculation, 30 days of sunshine striking
the Earth have the energy equivalent of the
total of all the planet’s fossil fuels, both used
and unused ! VANITA THAKKAR

12. 12
KEY FEATURES OF SOLAR
ENERGY
• It is the most promising renewable
source of energy.
• It is an essentially inexhaustible source of
energy.
• It has potential to meet a significant
portion of the nation’s future energy need
because of its quantitative abundances.
• It is clean and environment friendly
source of energy. VANITA THAKKAR

13. 13
LIMITATIONS OF SOLAR
ENERGY
• It is diluted source of
energy.
• Its availability varies widely
with time.
• It needs storage system.VANITA THAKKAR

14. 14
Solar
Radiation
Load
Contact grid
14
SOLAR PHOTOVOLTAICS
VANITA THAKKAR

15. 15
Photovoltaic effect :
 The direct conversion of sunlight into electric power
is achieved by semi-conductor effect – valence
electrons get freed by the energy gained from
incident sunlight – in solar cells.
 A Photovoltaic conversion effect can be achieved in
all semiconductors.
 Most of the cells are manufactured from
monocrystalline material.
SOLAR PHOTOVOLTAICS (contd.)
VANITA THAKKAR

16. 16
New technological approaches : The thin cell
• A decrease in the consumption of material per
unit of power generation.
• The avoidance of sophisticated metallurgy,
namely mono-crystalline material and ultra-high
purity (often called electronic grade material).
• These technologies are suitable for a
continuous production process.
SOLAR PHOTOVOLTAICS (contd.)
VANITA THAKKAR

17. SOLAR PHOTOVOLTAICS
(CONTD.)
 The fundamental power unit of a PV system is a solar
cell.
 It is a semi conductor generally made of silicon.
 A solar cell is a thin wafer , which is chemically
treated and processed at high temperature .
 Many such wafers are joined together to create a p-n
junction, across which voltage develops when sunlight
falls on these cells .
 There are four common types of silicon photovoltaic
cell :-
 Single crystalline silicon
 Poly crystalline silicon
 Ribbon silicon
 Amorphous silicon
e-
N-TYPE JUNCTION
JUNCTION ZONE
P-TYPE SILICON
e-
V17VANITA THAKKAR

18. Solar photovoltaic panel :- when many cells are connected in
series to increase the voltage.
Several series of cells can be interconnected in parallel to
increase the power output.
Solar cells are extremely fragile , so to protect them from
damage, they are sealed on the top by a layer of glass and
bottom with a layer of plastic or a metal or a combination
of the two .
The SPV panels are rated in terms of peak watt units –
which means minimum no. of hours of sunlight required
to produce a desirable amount of electricity daily.
SOLAR PHOTOVOLTAICS (SPV)
(contd.)
18VANITA THAKKAR

19. SOLAR LANTERN
 Solar lantern is a single light point portable system.
 Apart from the PV panel , it consists of
Lamp
Battery
Electronic components
All placed in a casing , either made of metal plastic or fibre
glass .
 Due to portability, it is found in both indoors and outdoors
applications .
CFL
LANTERN
19VANITA THAKKAR

20. Battery
 A sealed maintenance free, lead–acid battery or a tubular
plate lead acid battery with spill proof feature is used .
PV panel
 A PV panel typically has a power rating of 12 volts .
Electronic component
 Invertors with at least 80 percent efficiency is provided
with system .
 Solar lantern are also provided with two led indicators to
indicate charging and deep discharge state.
SOLAR LANTERN (contd.)
20VANITA THAKKAR

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22. 22VANITA THAKKAR

23. 23
SOLAR PHOTOVOLTAICS (contd.)
VANITA THAKKAR

24. 24VANITA THAKKAR

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27. 27VANITA THAKKAR

28. 28
SOLAR COLLECTORS OR
SOLAR THERMAL SYSTEMS
Solar
Radiation
Load
Thermal
Storage
Auxiliary
Air blower
Solar
Collector
VANITA THAKKAR

29. 29
SOLAR THERMAL HEAT
 Solar cookers – Domestic and Community
type.
 Solar Architecture – Active and Passive
 Medium temperature for water heating
 Solar heated swimming pool
 Crop drying and Industrial process heat –
Pharmaceuticals, Dairies, Textile industries,
Food Processing Units, etc.
 Solar Thermal Power Plants VANITA THAKKAR

30. VANITA THAKKAR
30
Energy conversion chain of solar thermal power
generation
SOLAR THERMAL POWER PLANTS

31. 31
SOLAR THERMAL POWER PLANTS
VANITA THAKKAR

32. VANITA THAKKAR
32
SOLAR THERMAL POWER PLANTS
Vertical tube receivers using salt as heat transfer
medium

33. 33VANITA THAKKAR
SOLAR THERMAL POWER PLANTS (contd.)

34. 34
SOLAR TOWER
VANITA THAKKAR

35. VANITA THAKKAR
35
DISH TECHNOLOGY WITH STERLING CYCLE POWER
GENERATION

36. 36
DISH TECHNOLOGY WITH STERLING CYCLE POWER
GENERATION
VANITA THAKKAR

37. 37
VANITA THAKKAR

38. 38VANITA THAKKAR

39. 39
SOLAR THERMAL CHIMNEY
The solar updraft tower or Solar Chimney
is a proposed type of renewable-energy power
plant in which air is heated in a very large
circular greenhouse-like structure, and the
resulting convection causes the air to rise and
escape through a tall tower. The moving air
drives turbines, which produce electricity.
VANITA THAKKAR

40. 40
VANITA THAKKAR
SOLAR THERMAL CHIMNEY (CONTD.)

41. 41
Key features:
 The generating ability of a solar updraft
power plant depends primarily on two factors:
1. Size of the collector area : With a larger
collector area, more volume of air is
warmed up to flow up the chimney;
collector areas as large as 7 km in diameter
have been considered.
VANITA THAKKAR
SOLAR THERMAL CHIMNEY (CONTD.)

42. 42
Key features (contd.):
2. Chimney height : With a larger chimney
height, the pressure difference increases the
stack effect; chimneys as tall as 1000 m have
been considered.
 Further, a combined increase of the collector
area and the chimney height leads to massively
larger productivity of the power plant.
VANITA THAKKAR
SOLAR THERMAL CHIMNEY (CONTD.)

43. 43
Key features (contd.):
 Heated air, being less dense, raises in tall tower /
chimney.
 Thermal source from ground based thermal
collector around : Heat can be stored inside
collector area greenhouse, to be used to warm
air later on. Water, with its relatively high
specific heat capacity, can be filled in tubes
placed under collector increasing energy
storage as needed. VANITA THAKKAR
SOLAR THERMAL CHIMNEY (CONTD.)

44. 44
Key features (contd.):
 A small-scale solar updraft tower may be an
attractive option for remote regions in
developing countries. The relatively low-tech
approach could allow local resources and
labour to be used for its construction and
maintenance.
VANITA THAKKAR
SOLAR THERMAL CHIMNEY (CONTD.)

45. 45
The chimney had a
height of 195
metres and a
diameter of 10
metres, with a
collection area
(greenhouse) of
46,000 m² (about 11
acres, or 244 m
diameter) obtaining
a maximum power
output of about
50 kW.
VANITA THAKKAR
SOLAR THERMAL CHIMNEY (CONTD.)

46. 46
Based on the test results, it was estimated that
a 100 MW plant would require a 1000 m tower
and a greenhouse of 20 Sq. km.
As the costs lie mainly in construction and not
in operation (free 'fuel', little maintenance and
only 7 personnel), the cost per energy unit is
largely determined by interest rates and years
of operation. VANITA THAKKAR
SOLAR THERMAL CHIMNEY (CONTD.)

47. SPACE REQUIREMENT FOR
VARIOUS SOLAR THERMAL
POWER PLANTS
VANITA THAKKAR 47

48. SOLAR COLLECTORS
 Solar collector - the most important component – form
heart of the Solar Energy Collection Systems : 70-90
% of the system cost.
 Solar collector- intercepts, absorbs and transforms
solar radiations into a usable form.
Solar collector can be :-
WATER HEATING COLLECTOR OR AIR HEATING
COLLECTOR
and each of these collectors can be :-
FLAT PLATE COLLECTOR OR FOCUSSING COLLECTOR.
48VANITA THAKKAR
48

49. SOLAR FLAT PLATE COLLECTORS
The flat plate collector forms the heart of
many solar energy collection systems.
It is designed for operation in low temperature
range from, ambient to 600 C, or medium
temperature range, from ambient to 1000 C.
49VANITA THAKKAR

50. SOLAR FLAT PLATE COLLECTORS
(contd.)
PRINCIPLE:
 If a metal sheet is exposed to solar radiation, its
temperature will rise, until the rate at which energy is
received is equal to the rate at which heat is lost from the
plate (this temperature is termed as the ‘equilibrium
temperature’.)
 If the back of the plate is protected by a heat insulating
material, and the exposed surface is painted black and is
covered by one or two glass sheets, then the equilibrium
temperature will be much higher than that for the simple
exposed sheet and heat can be stored and transferred to the
working medium.
50VANITA THAKKAR

51. 51
SOLAR WATER HEATING COLLECTOR
Tube
Insulation
Water in
Blackened Absorber plate
Glass cover
Solar Radiation
51
VANITA THAKKAR

52. 52
VANITA THAKKAR
SOLAR WATER HEATING COLLECTOR

53. Pictures
Flat plate solar heater Flat plate over roof
53VANITA THAKKAR

54. ADVANTAGES OF FLAT PLATE
COLLECTORS :
Absorb direct, diffused and reflected
components of solar radiation
Are fixed in tilt and orientation and, thus,
there is no need of tracking the sun.
Are easy to make and are low in cost.
Have comparatively low maintenance cost
and long life.
Operate at comparatively higher efficiency.
54VANITA THAKKAR

55. MATERIALS FOR FLAT PLATE
COLLECTORS:
Absorber plate:
It should have:
high thermal conductivity.
adequate tensile and compressive strength.
good corrosion resistance.
Copper is generally preferred. Other materials
are Aluminium, steel and various
thermoplastics.
55VANITA THAKKAR

56. Insulation :
 Several insulating materials which can be used to reduce
the heat loses are available – such as, glass wool, etc.
 Desired characteristics of these insulating material are :
 Low thermal conductivity.
 Stability at high temperature (upto 200oC).
 No degassing upto around 200oC.
 Self supporting feature without any tendency to settle.
 Ease of application.
 No contribution to corrosion.
MATERIALS FOR FLAT PLATE
COLLECTORS (contd.) :
56
VANITA THAKKAR

57. Cover plate :
 Characteristics of cover plates through which solar energy is
transmitted are extremely important in the functioning of a
collector.
 Functions of the cover plate are :-
 To transmit maximum solar energy to absorber plate .
 Minimize upward heat loss from the absorber plate to the
environment .
 To shield absorber plate from direct exposure to weather.
 Other factors such as strength, durability, non-
degradability are important .
MATERIALS FOR FLAT PLATE
COLLECTORS (contd.) :
57
VANITA THAKKAR

58. THE LIQUID FLAT PLATE COLLECTOR:
BASIC COMPONENTS :
 Flat absorbing plate, normally
Metallic upon which the short wave
Solar radiation falls and is absorbed.
 Tubes, channels or passages
attached to the absorber plate to FLAT PLATE COLLECTOR
circulate the liquid required to remove the thermal energy from the
plate
 Thermal insulation provided at the back and sides of the absorber
plate to minimize the heat losses
 A transparent cover of glass or transparent plastic to reduce the
upward heat loss from the absorber plate
 A weather-tight container to enclose the above components.
58
VANITA THAKKAR

59. CLASSIFICATION OF FLAT PLATE COLLECTORS
(According to applications) :
 Simple and low cost collectors with no cover and
insulation.
e.g. for heating swimming pools where less heat is
required.
 Collectors with low cost insulation and one
transparent cover
e.g. in areas requiring domestic water heating.
 Well engineered and sophisticated flat plate
collectors for process heating or small-power
production. 59
VANITA THAKKAR

60. CLASSIFICATION OF ABSORBER PLATES
Pipe and fin type, in which the liquid flows
only in the pipe, and hence has comparatively
low wetted area and liquid capacity.
Rectangular or cylindrical full sandwich
type in which both the wetted area and the
water capacity are high.
Roll bond type or semi-sandwich type,
intermediate between type I and II. 60
VANITA THAKKAR

61. Pictures
Basic collector absorber plate types Flat plate solar heater for swimming pools
61
VANITA THAKKAR

62. Can be of two types :
A FLAT PLATE COLLECTOR
OR
A FOCUSSING COLLECTOR
AIR HEATING COLLECTORS
 Solar energy air collectors are special kind
of heat exchangers that transform solar
radiation energy into internal energy of air.
62
VANITA THAKKAR
62

63. 63
FLAT PLATE SOLAR AIR COLLECTOR
63VANITA THAKKAR

64. DESIGN VARIATIONS OF SOLAR AIR COLLECTOR
Collector with side reflector
Reflector
Absorber
Insolation
64
VANITA THAKKAR 64

65. Collector with multiple glass cover
Collector with selective absorber plate
Double exposure air collector
Top glass cover
Top absorber plate
Stagnant air gap
Bottom absorber
plate
Bottom glass cover
Air Air Air
65
VANITA THAKKAR 65

66. Collector with corrugated absorber
Corrugated
absorber plate
Bottom plate
Air flow channel
66
VANITA THAKKAR 66

67. Jet Plate air collector
Clear glass
Absober
plate
Jet plate
Bottom
plate
Insulation
Air in Air out
67
VANITA THAKKAR 67

68. Overlapped glass plate air collector
Flow
Straightener
Clear glass
Glass
cover
Blackened
glass
Insulation
Air in Air out
68
VANITA THAKKAR 68

69. Evacuated glass tube collector
Structural foam body
Fiber mat absorber
Evacuated tube
69
VANITA THAKKAR 69

70. Absorber plate made of recyclable aluminium cans
Honeycomb solar air collector
Air out
Honeycomb
structure
Glass cover
Insulation
Air in
70
VANITA THAKKAR 70

71. 71
Collector with box type absorber
Artificially roughened solar air collector
Glass cover Roughened surface
Air in Air out
Air flow channel VANITA THAKKAR

72. Collector with fins on absorber plate
Glass cover
Multiple
transmission &
absorption
Air flow
Insulation
Air in
Air out
72
VANITA THAKKAR 72

73. 73
Two pass solar air collector
First glass cover
First air pass
Second glass cover
Second air pass
Absorber plate
Insulation
73
VANITA THAKKAR

74. 74
Collector with metal matrix absorber (packed duct collector)
Air in
Air out
Air out
Air in
Air in
Air outSolar
radiation
Solar
radiation
Solar
radiation
Matrix Matrix Matrix
74
VANITA THAKKAR

75. 75
EFFECT OF PARAMETERS ON PERFORMANCE
System parameters
Number of glass cover
Glass cover emissivity
Selectivity of absorber plate
Plate spacing
Collector tilt
Operation Parameters
Inlet fluid temperature
Mass flow rate
Meteorological Parameters
Incident Solar radiation
Ambient temperature
Wind velocity
Dust on the top glass cover 75
VANITA THAKKAR

76. 76
PERFORMANCE ENHANCEMENT METHODS
76VANITA THAKKAR

77. SOLAR COOKERS
 As the supply of fossil fuels like coal, kerosene or
cooking gas is deteriorating, more and more solar
energy is harnessed for cooking purposes.
THREE BASIC DESIGNS OF SOLAR COOKER:-
 FLAT PLATE BOX TYPE SOLAR COOKER
 MULTI REFLECTOR TYPE SOLAR OVEN
 PARABOLIC DISC CONCENTRATOR TYPE
SOLAR COOKER
77VANITA THAKKAR

78. FLAT PLATE BOX TYPE SOLAR
COOKER
It consists of a solar box of size usually 60 cm
x 60 cm x 20 cm.
 It is made up of inner and outer metal or
wooden box with double glass sheet on it.
 Absorber tray is painted black with dull color
so that it can withstand maximum temperature
attained inside the cooker as well as water
vapour coming out of cooking utensils.
78VANITA THAKKAR

79. FLAT PLATE BOX TYPE SOLAR
COOKER (contd.)
Top cover contains 2 plain glasses 3mm each,
fixed in wooden frame with 20 mm distance
between them.
 Neoprene rubber sealing is provided around
contact surface of glass cover and cooker box. A
small vent is provided in sealing for vapour
escape.
 On one side of glass frame, plane reflecting
mirror is hinged, which remains perpendicular to
the box while cooking and is equal in size to the
box, to form its cover during closed condition.
79VANITA THAKKAR

80. MULTI REFLECTOR TYPE SOLAR
OVEN
The solar oven consists of a well insulated semi-
cylindrical box made of aluminum sheet and
wood.
 Two shells are made and the space between them,
about 7.5 cm, is filled with fibre glass insulation.
The interior sheet is painted black.
 A door of the same insulating material is also
made for keeping and taking out food. 80VANITA THAKKAR

81. MULTI REFLECTOR TYPE SOLAR
OVEN (contd.)
The window (40 X 40 cm) of the oven consists of
two transparent glass sheet (3 mm thk.) with a
spacing of 2 cm.
 Eight reflectors made of silvered glass mirrors,
four of square shape and four of triangular shape
are typically used.
 The oven can be manually tilted and oriented
towards the sun.
With single reflector, temperature attained reaches
upto 160o and in multi- reflector it reaches around
200o to 250o. 81VANITA THAKKAR

82. PARABOLIC DISC CONCENTRATOR
TYPE SOLAR COOKER
 Parabolic disc is used in this type of solar cooker.
 Solar radiations are concentrated at a point, focus.
 Cooking pot is placed at this point where a very high temperature
is maintained, about 450 deg Celsius.
Wall Reflector
Solar Cooker
82VANITA THAKKAR

83. Pictures
Reflective Cooker Inclined box type cooker
Box type solar cooker Inclined Solar Cooker
83VANITA THAKKAR

84. ADVANTAGES OF SOLAR COOKERS :
 No attention is needed in cooking as in other devices.
 No fuel is required.
 Negligible maintenance cost.
 No pollution.
 Vitamins of food are not destroyed and food cooked is
nutritive and delicious with natural taste.
 No problem of charring of food and no over flowing.
84VANITA THAKKAR

85. DISADVANTAGES OF SOLAR
COOKER
 One has to cook according to the sun shine.
 One can not cook at short notice and food can not be
cooked in the night or during cloudy days.
 It takes comparatively more time.
 Chapattis are not cooked because high temperature for
baking is required and also needs manipulation at the
time of baking.
85VANITA THAKKAR

86. SOLAR STILL
A solar still is a low-tech way of
distilling water, powered by the heat
of the sun (more precisely, the heat &
humidity of the soil, and relative cool
of the plastic – in case of pit stills).
Two basic types of solar stills are :
 box stills : more sophisticated.
 pit stills. VANITA THAKKAR 86

87. SOLAR STILL – PIT STILL
• Impure water is contained outside the collector,
where it is evaporated by sunlight shining through
clear plastic.
• The pure water vapour (and any other included
volatile solvent) condenses on the cool inside
plastic surface and drips down off of the weighted
low point, where it is collected and removed.
VANITA THAKKAR
87

88. SOLAR STILL – BOX STILL
• The basic principle : It replicates the way nature
makes rain.
• The sun's energy heats water to the point of
evaporation.
VANITA THAKKAR
88

89. SOLAR STILL – BOX STILL
• As the water evaporates, water vapor rises,
condensing on the glass surface for collection.
• This process removes impurities such as salts
and heavy metals as well as eliminates
microbiological organisms. The end result is
distilled water. VANITA THAKKAR
89

90. SOLAR STILL – BOX STILL
(contd.)
• Solar stills use natural evaporation and
condensation, which is the rainwater
process.
• This allows for natural pH buffering that
produces excellent taste as compared to
steam distillation.
• They can be used to effectively remove
many impurities ranging from salts to
microorganisms and can even be used to
make drinking water from seawater.
VANITA THAKKAR
90

91. SOLAR STILL – BOX STILL
(contd.)
• Simple construction
• No moving parts.
• Material : which can withstand conditions
produced by water and sunlight.
• Operation : Simple –
– water is added (either manually or automatically)
through the still's supply fill port.
– Excess water drains out of the overflow port,
which keeps salts from building up in the basin.
– Distilled water is collected from output
collection port. VANITA THAKKAR
91

92. • Solar still has a top cover made of glass, with
an interior surface made of a waterproof
membrane.
• This interior surface uses a blackened material
to improve absorption of the sun's rays.
• Water to be cleaned is poured into the still to
partially fill the basin.
• The glass cover allows the solar radiation
(short-wave) to pass into the still, which is
mostly absorbed by the blackened base.
VANITA THAKKAR
92
SOLAR STILL – BOX STILL
(contd.)

93. • Water begins to heat up and the moisture content of
the air trapped between the water surface and the glass
cover increases.
• The base also radiates energy in the infra-red region
(long-wave) which is reflected back into the still by the
glass cover, trapping the solar energy inside the still
("greenhouse" effect).
• Heated water vapor evaporates from basin and
condenses on the inside of the glass cover. In this
process, salts and microbes that were in original water
are left behind. Condensed water trickles down
inclined glass cover to an interior collection trough
and out to a storage bottle.
VANITA THAKKAR
93
SOLAR STILL – BOX STILL
(contd.)

94. SOLAR POND
VANITA THAKKAR
94
• A solar pond is a pool of saltwater which
acts as a large-scale solar thermal
energy collector with integral heat storage
for supplying thermal energy.
• A solar pond can be used for various
applications, such as process heating,
desalination, refrigeration, drying and
solar power generation.

95. Intermediate insulating layer : has a salt gradient, which
establishes a density gradient that prevents heat
exchange by natural convection.
Bottom layer : has a high salt content.
If water is relatively translucent and pond's bottom has high
optical absorption, nearly all of incident solar radiation goes
into heating bottom layer. VANITA THAKKAR
95
SOLAR POND (contd.)
There are 3 distinct
layers of water in solar
pond:
Top layer : has a low salt
content.

96. SOLAR POND (contd.)
• When solar energy is absorbed in water, its
temperature increases, causing thermal
expansion and reduced density.
• If water is fresh, the low-density warm water
floats to the surface, causing a convection current.
• The temperature gradient alone causes a
density gradient that decreases with depth.
• However, salinity gradient forms a density
gradient that increases with depth, and this
counteracts temperature gradient, thus
preventing heat in lower layers from moving
upwards by convection and leaving the pond.
VANITA THAKKAR
96

97. SOLAR POND (contd.)
• This means that the temperature at the bottom of
the pond will rise to over 90 °C while the
temperature at the top of the pond is usually
around 30 °C.
• A natural example : Solar Lake in the Sinai
Peninsula of Egypt.
• The heat trapped in the salty bottom layer can
be used for many different purposes, such as the
heating of buildings or industrial hot water or to
drive an organic Rankine cycle turbine or
Stirling engine for generating electricity.
VANITA THAKKAR
97

98. SOLAR POND (contd.)
Advantages and Disadvantages :
• Particularly attractive option for rural areas in
developing countries. Very large area collectors
can be set up for just cost of clay or plastic pond
liner.
• Evaporated surface water needs to be constantly
replenished.
• The accumulating salt crystals have to be
removed and can be both a valuable by-product
and a maintenance expense.
• No need of a separate collector for this thermal
storage system. VANITA THAKKAR
98

99. SOLAR POND (contd.)
VANITA THAKKAR 99
Plant diagram of a solar pond power plant

100. 100VANITA THAKKAR

101. 101VANITA THAKKAR

102. 102VANITA THAKKAR

103. 103VANITA THAKKAR

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105. 105
Range of conversion technologies, Energy devices and
other technological interventions
Sr.
No
Applications Technologies/Devices
1 Cooking  Use of Biogas plants
 Use of improved and efficient chulhas
 Use of Pressure cookers
 Use of high efficient burners with LPG
 Use of solar cookers
 Use of solar water heaters
2 Lighting  Use of photovoltaic conversion
 Use of switch from conventional to
renewable
3 Power generation  PV power packs
 Solar thermal power plants
 Biomass gasifiers options
 Biogas engine gensetsVANITA THAKKAR

106. 106
Sr.
No
Applications Technologies/Devices
3 Agriculture and
Allied activities
 Switch from incandescent lamps to CFL
 Electronic ballast in place of Electro-magnetic ballast
 Switch from diesel to electric motor pump
 Rectification of existing pump and other devices
 Biomass gasifiers based pumping system
Solar PV pump sets
Solar dryers
4 Rural Industry Improved biomass conversion system for thermal needs
Increase availability of electricity
Small cogeneration systems
Use of more renewable sources
5 Transport and
Basic amenities/
Facilities
Improved bullock cart design
PV street light
PV power TV sets/tape recorder/transistors etc.
PV refrigeration
Solar water heating system
Solar and passive architecture in residential,
educational and community buildings.
Community solar cookers for mid-day meal schemes etcVANITA THAKKAR

107. 107
THANK YOU
VANITA THAKKAR

108. 108VANITA THAKKAR