A solar energy collector is a device for collecting solar radiation from the sun and transfer the energy to a fluid (usually air, water, or oil) flowing through the collector. To utilize solar energy, we need solar energy collectors.
The solar energy collected through solar collector is transferred to the circulating fluid either directly to the hot water or space conditioning equipment, or to a thermal energy storage tank for useful work.
Classification of Solar Energy Collectors
Solar energy collectors are majorly classified into two types. They are,
- Non-concentrating or flat plate type
- Concentrating type
Non-concentrating or flat plate type collectors can be divided into two types. They are,
- Liquid heating collectors
- Air or gas heating collectors
The main types of concentrating type collectors are,
- Parabolic trough collector
- Mirror strip reflector
- Fresnel lens collector
- Flat type collector with adjustable mirrors
- Compound parabolic concentrator
The non-concentrating or flat plate type collector
A typical flat-plate collector consists of an absorber surface which is usually dark and thermally conducting surface and is made in rectangular panels, the area is about 1.7 to 2.9 sq.m. Flat plates can collect direct solar radiation and also can collect diffuse solar radiation. So, they are partially effective even on cloudy days when there is no direct radiation.
An absorber plate which is normally black metallic surface. This is used to absorb the incident solar energy. The main properties required for absorber plate are,
A transparent (glass) cover which is one or more sheets of glass which transmits the radiation to the black absorber plate. Also, it prevents the radiative and convective heat loss from the surface. It should have transmittance for solar radiation and should not deteriorate with time.
Tubes, fins, passages or channels which are integrated or connected with the absorber plate. It carries water, air or other fluids that absorb the heat from the absorber plate.
Insulation covers the sides and bottom of the collector to minimize the heat losses. Standard insulation materials used in the flat plate collectors are fiberglass or styrofoam. It reduces conduction loss and maximizes efficiency. It is usually made of the material such as polyurethane foam or mineral wool. The insulation thickness is about 5 to 10 cm thickness.
Casing or support structure protects the components from the weather and it facilitates proper installation of the collector on roof or frame. The materials are usually galvanized steel or aluminum.
Main components of the flat plate type collector:
- High absorptivity
- High thermal conductivity
- Good corrosion resistance
- Adequate tensile and compressive strength
The absorber plate is a metal plate, usually made of copper, steel or aluminum.
A transparent (glass) cover which is one or more sheets of glass which transmits the radiation to the black absorber plate. Also, it prevents the radiative and convective heat loss from the surface. It should have transmittance for solar radiation and should not deteriorate with time.
Tubes, fins, passages or channels which are integrated or connected with the absorber plate. It carries water, air or other fluids that absorb the heat from the absorber plate.
Insulation covers the sides and bottom of the collector to minimize the heat losses. Standard insulation materials used in the flat plate collectors are fiberglass or styrofoam. It reduces conduction loss and maximizes efficiency. It is usually made of the material such as polyurethane foam or mineral wool. The insulation thickness is about 5 to 10 cm thickness.
Casing or support structure protects the components from the weather and it facilitates proper installation of the collector on roof or frame. The materials are usually galvanized steel or aluminum.
Sunlight passes through the transparent cover, strikes the absorber plate and gets heat up. So, the absorber plate converts solar energy into useful heat energy by transferring that heat to the fluid passes through the tubes that are attached along with the absorber plate. The absorber plate is usually made from a metal sheet of 1 to 2 mm in thickness. The metal tubes connected to the absorber range in diameter from 1 to 1.5 cm. Tubes are brazed, soldered or clamped to the bottom (in few cases, the tubes are attached to the top) of the absorber plate with the pitch range from 5 to 15 cm.
Applications of flat plate type collector:
Commercial applications:
- Laundromats
- Car washes
- Space heating system
- Power generation
- Water pumping
Domestic applications:
- Water heating
- Air conditioning
- Cooking
Advantages of flat plate type collector:
- Collects both direct and diffused radiation
- Requires little maintenance
- Easy to manufacture
- Low cost
Continue reading Solar Energy Collectors - Simple Explanation (Part 2)
Also read about:
Introduction to Solar Cells- Simple Explanation
Introduction to Solar Cells- Simple Explanation
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