Effect of the gap spacing on the shallow solar pond performance

It is stated by Garg et al. [Energy Convers. Mgmt 22, 117 (1981)] that, for a shallow solar pond where the gap spacing is large (300 mm), the convective heat loss is somewhat lower than for a conventional collector with a shorter gap spacing (20 mm). How much the total heat transfer coefficient is lowered, and what is the effect of the gap spacing on the performance of the shallow solar pond were not mentioned. In this study, the effect of gap spacing on shallow solar pond performance is studied. For this purpose, a computer program is constructed and is experimentally tested using a shallow solar pond of 6.6 m² area. It is concluded from the results that the effect of gap spacing on the top loss coefficient is independent of the temperature difference between the upper film of the water bag and the glazing of the shallow solar pond. The results also show that the change in gap spacing of the shallow solar pond has not an important effect on the pond performance. Hence, the large gap spacing in the conventional design shallow solar pond (300 mm) cannot be considered as a major difference with the flat plate collector design (20 mm), as Garg et al. stated.