FLAT PLATE COLLECTORS
These solar collectors are flat in shape and consist of a big box with different layers of plate surfaces. At the top there is one or more layer of glass on which the sunlight falls. The light is then absorbed by the absorber plate, which is usually the metal plate like copper or aluminum and it kept below the top cover. Around the absorber plate there are piping of water which absorb the heat from the absorber plate. The whole box of the flat plate collector is insulated and weather shielded. Flat-plate collectors are most commonly used in solar water heaters.
Casing: Casing contains all the components of the collector and protects them from environmental impact. Casing also makes the collector sturdy and stable. Material used for casing must be resistant to corrosion.
- Seal : Seal is made out of elastic material to prevent leakage and ingress of rain water into the collector. Sealing material must withstand high temperature variations and ultra violet (UV) radiations (to ensure a long life of 15 years, or more.)
- Transparent cover : This protects the components inside the collector from environmental impact. It should be made of toughened glass with high transmission co-efficient (close to 1). This also protects the components inside the collector from environmental impact.
- Thermal insulation : Thermal insulation reduces undesirable heat loss from the back and sides of the collector area. The insulation must also be able to withstand the maximum temperature of the absorber plate.
- Absorber plate : Absorber plate absorbs the solar energy and converts it to heat energy. The absorber is made out of high conductivity material like copper with selective coating on it for maximum absorption of solar radiation and minimum emission of infrared radiation.
- Tube : The fluid that flows through the collector collects the heat from absorber plate for useful application. The transfer of heat shall take place mainly through conduction and convection process. Therefore, the tubes should be made out of high conductivity material like copper.
Main characteristics of this collector are:
- Resistance to environmental conditions (marine environment, rain, dust, hail etc.)
- Resistance to large variations in temperature
- Resistance to leakage from any part of the system
- Stable and durable
- Easy to install
- Efficient in energy conversion