Some aspects of the transient response of a flat-plate solar energy collector

The transient response of a flat-plate solar energy collector is analyzed. A two-dimensional transient heat transfer model is developed for this purpose. The parameters varied in the study are the absorber plate and working fluid heat capacities and the absorber plate to working fluid heat transfer coefficient. Both step input and diurnal cycle variations in insolation are considered.

The results of the study indicate that flat-plate solar collector efficiency is not affected by increased heat capacity of the absorber plate or working fluid even though the collector response is slower and the peak working fluid outlet temperature over a diurnal cycle is lower. Energy required to heat a collector in the morning is regained in the afternoon. However, decreases in the absorber to working fluid heat transfer coefficient do cause a decrease in collector efficiency in addition to a slower collector response.