12. Converting Solar Radiation to Thermal Energy With a Glazed Flat Plate Collector

There are numerous ways to convert solar radiation to thermal energy in a fluid. In this chapter only glazed flat plate solar radiation collectors will be treated. The function of a solar radiation collector is to absorb solar radiation energy by means of a high absorptivity, i.e. greater than 0.95, surface and convert it into thermal energy. The thermal energy is then transferred from the absorber surface to flowing fluid by means of high thermal conductivity tubes. The collector is protected from convective losses to the environment with a thin film coated glass cover that is highly transparent to incoming short wavelength radiation, i.e. greater than 0.85 transmissivity, but prohibits long wavelength radiation leaving the collector due to its very low emissivity, i.e. less than 0.1. Insulating material is placed along sides and back of the collector in order to minimize convective heat losses to the environment.