How does a Flat plate collector heat water? What benefit does a selective surface give?
The radiant energy from the sun plus the diffuse energy passing through the glass is absorbed by the flat absorber plate. The plate gets hot and heat is conducted through the plate to the water in the copper risers which then flows to the storage tank. This process continues until the tank is sufficiently hot. Heating occurs whenever sunlight is available. Some heat escapes the collector through the glass cover as it radiates from the absorber plates. The use of a selective surface allows us to reduce this re-radiation or ‘emittance’ to much smaller figure. What is the function of the collector glass? Collector glass serves two main purposes. The first is to allow solar radiation to enter the collector, and secondly to prevent the wind from cooling the absorber plate and thus removing heat. What is the function of insulation in the collector? If the outside air is very cold such as in winter times, the hot air that builds up in the collector between the glass and the absorber plate is
