A method of comparing flat-plate air and liquid solar collectors for use in space heating applications

An investigation is conducted concerning a suitable approach for comparing the performance of different types of solar heating systems. In the liquid collector system considered, an antifreeze solution passes through the collector and transfers the solar energy which it received to a second fluid loop (usually water). In the typical air system, heated air from the collector is directed either to the space for heating or to a pebble bed storage. In the traditional method, the collector efficiency is plotted against a parameter obtained by dividing the difference between the collector inlet temperature and the ambient temperature by the solar radiation incident on the collector plane per unit area. It is found that this traditional plot is not useful in the considered comparison. A useful comparison technique should include the effects of other system components which contribute to system performance.