Solar Collectors
Solar Collectors
• Solar Collectors : Device for collecting solar
radiation and transfer the energy to a fluid.
• Consist of a plate where solar radiation falls
• The material can be copper, aluminum or steel.
Classification
Solar Collectors
Non –
Concentrating type
concentrating type
(a) Liquid flat‐plate collector
(b) Flat‐plate air‐heating collector
Concentrating
Type
Line Focus Point Focus Non Focus
Type Type Type
a. Cylindrical parabolic a. Parabolic dish a. Modified flat plate
concentrator collector collector
b. Fixed mirror solar b. Hemispherical bowl b. Compound
concentrator mirror concentrator parabolic
c. Linear Fresnel lens c. Circular Fresnel lens concentrating type
collector collector
d. Central tower
receiver
Liquid Flat Plate Collectors
1. Absorber plate
2. Tubes, channels or passages
3. Weather tight insulated container
4. Transparent cover of glass
Flat plate can absorb both beam and diffused radiations
Metallic absorber plate absorbers the solar radiation and its
temp rises
Liquid Flat Plate Collectors
Liquid Flat Plate Collectors
• Heat is transferred to water circulating in the tube,
beneath the absorber plate.
• Tubes are either welded, soldered or pressure
bonded.
• Water is moved either forcefully or naturally by
placing it inclined.
• Absorber plate and tubes is made of copper.
• At bottom and along side walls thermal insulation.
• Gives a temperature about 60 degree above
ambient i.e., < 100 degree with 30-50% efficiency
Different types of Flat Plate Collectors
• Pipe and fin type collectors are
expensive but having good corrosion
resistance
• In pipe and fin type because of liquid
flows only in pipe , having low wetted
area and liquid capacity
• In sandwich type wetted area and
capacity of water are high and they are
cheap
Best choice depends on application:
• Low temperature Application
(Swimming pool): Full water
sandwich
• Domestic and industrial high
temperature application: Pipe and fin
type
Flat‐plate Air‐heating Collector
• Similar to liquid flat plate with a change in configuration of
absorber and tube.
• Application drying for agricultural and industrial purpose
and space heating.
Air flow
Flat plate air heating collector
Flat‐plate Air‐heating Collector
Advantages over liquid flat plate collector
Corrosion is eliminated
Leakage of air from duct is less severe
Freezing is eliminated
Pressure inside collector does not become high
Disadvantages
Large amount of fluid is to be handled
Heat transfer is poor
Less storage of thermal energy due to low heat capacity
Concentric collectors
By using concentrator the intensity of soar radiation received by the receiver increases
and amount of increase in solar intensity can be given by concentration ratio
CONCENTRATION RATIO “C” defined as ratio of aperture area of concentrator to
the absorber area of the receiver
Axis tracking is mandatory in concentric plate collectors
Modified Flat Plate Collector(V-Trough)
(NON-FOCUS TYPE)
• Booster mirrors are provided at the edges , reflects
additional radiation to receiver.
• It is aligned in the east- west direction
• Requires periodic tilt adjustment.
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Compound Parabolic Concentrator(CPC)
Consist of two parabolic mirror attached to flat receiver.
Orientation : focus of one is the bottom end of other in contact
with receiver.
Rays from central region reach
directly
Rays from edges undergo
reflection
Concentration ratio: 3-7
Cylindrical Parabolic Concentrator
Or
Parabolic trough concentrator
LINE FOCUS TYPE
Consist of cylindrical parabolic trough reflector and
a metal tube receiver at focal point.
Receiver tube is blacked at outer surface
Rotated about one axis to track the sun.
Fluid flows through the receiver tube.
Orientation : east-west, north –south or polar.
Single axis sun tracking mechanism needed
Concentration ratio : 5- 30
Cylindrical Parabolic Concentrator
Cylindrical Parabolic Concentrator
Cylindrical Parabolic Concentrator
Fixed Mirror Solar Concentrator
• Consist of fixed mirror strips arranged on a circular
reference cylinder with tracking receiver tube.
• Receiver tube rotated about center of curvature to
track the sun.
• Concentration ratio same as no of mirror strips
Fixed Mirror Solar Concentrator
Fixed Mirror Solar Concentrator
Parabolic Dish Collector (POINT FOCUS)
• Parabolic shape : a parabola is rotated about its optical axis
• Beam radiation is focused at a point in the paraboloidal.
• Requires two axis tracking
• Concentration ratio : 10 to few 1000s
• Temperature : up to 1000ᵒC
Parabolic Dish Collector
TH A N Q
