A rational procedure for predicting the long-term average performance of flat-plate solar-energy collectors

T HE flat-plate collector is the simplest and one of the most effective means of collecting solar energy for use in systems that require thermal energy at com-paratively low temperatures. Flat-plate collectors have been used successfully for many years in the southern United States and elsewhere as water heaters, and potentially can be used for space heating, drying, refrigeration, power generation and similar purposes. The majority of these potential applications of solar energy have not been fully evaluated, but experi-ments ~-7 in solar space heating conducted uring the past two decades have shown that space heating with solar energy is entirely feasible. It is now recognized that with the rapid depletion of fossil fuels, solar energy will be increasingly utilized. In comparison with collectors of the concentratin