Content

• Introduction• Types of solar collector• Application • Advantage• Disadvantage

Solar Collectors

•Solar collector is a device for collecting solar radiation and transfer the energy to a fluid passing in contact with it.

•The solar collectors, with its associated absorber, is the essential component of any system for the conversion of solar radiation energy into usable form. E.g. heat and electricity .

• The fundamental process now in general use for HEAT conversion is the Green House Effect

Solar Collectors

Non-concentration concentration

Non-concentration [flat-plate collector]

• Heat produce at temperature below 90*C.

• Flat plate can be collect and absorb both DIRECT and DIFFUSE solar radiation.

• They are effected by cloud and other particles which are present in the atmosphere

Flat-plate collectors

Liquid collector Air collector

Liquid collector

• Liquid heating collectors are used for heating water and non-freezing aqueous solution and occasionally for non-aqueous heat transfer fluids

• Transparent cover (glazing)• Cushion support• Absorber (selective surface)• Insulation• Tubes/water pipe

• Typically a metal plate, usually of copper, steel or aluminium material with tubing of copper in thermal contact with the plates, are most commonly used material.

• The absorber plate is usually made from metal sheet 1 to2mm in thickness.

• Tubes which are also made from metals.

Tubes :

• Diameter :- 1.0 to 1.5• They are soldered or clamped or bind to

bottom of absorber plate from 5 to 15cm.• In some other type of design of liquid

collector we can found, the arrangement of tubes are attached to the absorber plate.

• Various type of arrangement are found

• The glass cover act as a convection shield to reduce the losses from the absorber plate beneath.

• Glass generally use for transparency.

• Reflection may be reduced by coating with thin films of certain substances. e.g. magnesium fluoride

• We can use coating for increase HEAT resistance.

HEAT TRANSFER SYSTEM:-The heat generated in the absorber is removed by

continuous flow of a heat-transport medium, either water or air.

diagram:

Problems:

1. A problem with this design is that in cold weather, moisture may condense on the inside of the transparent cover plate and thus decrease the transmission of the solar radiation.

2. A second problem is the corrosion of the metal tube by the water.

Typical Air Collector[solar air heater]

• Transparent cover• Insulation • Fluid tubes• Absorbing surface• Air has been used so far to a lesser extent as the heat transport

medium in solar collector.• Zig-Zag flow path in Air collecter

Air collector

Non- porous porous

Application

• heating building • Drying agricultural produce and lumber• Heating green house • Air condition• Air heater is useful for energy source for

heat engine

Adwantage

1. They have the advantage of using both beam and diffuse solar radiation.

2. They do not require orientation toward the sun.

3. They required little maintenance.4. They are mechanically simpler than the

concentration reflector, absorbing surfaces and orientation devices of focusing collectors.

Concentrating collectors[focusing type]

• Focusing collector is a device to collect solar energy with intensity of solar radiation on the energy absorbing surface.

Type of focusing collectors

1. Line focusing collectors2. Mirror-strip reflectors3. Fresnel lens collector4. Flat-plate collector5. Compound parabolic concentrator

Line focusing collectors

• The dimension of parabolic cylindrical collector can be very over a wide range the length of a reflecting unit may be roughly 3-5m and the width about 1.5-2.4m,ten or more. Such unit are often connected end to end in a row , such rows are connected in parallel.

• Sun must in a particular direction.• Generally oriented in the east –west or north-

south directions.• East-west:-the collectors are laid flat on the

ground.• North-south:-the can rays north to south

arranged like flat-plate collectors they are less efficient.

2.Mirror-strip reflectors

• We use concave mirror strips• The angle of mirror strips are different as

individuals• Diagram:

3.Fresnel lens collector

• In it use focusing effect of a Fresnel lens.• Lens is rectangle, about 4.7-.95m in width.• Solar radiation collect by this is 30%

greater than east-west collector.• Diagram:

4.Flat-plate collectors

5.compound parabolic concentrator (CPC)

Advantage

• Surface required less material or provide high collection of radiation.

• Heat loss rate is less than flat-plate collection low maintenance .

• Can be used for power generation.• We can get high concentration or radiation.

Difference

Disadvantage

• Only beam radiation collected.• If sun direction is not correct then only

some mirrors are used others are not in use.

• Additional optical losses such as reflectance loss.

• High initial cost.