Quantitative comparisons of selected natural absorbents for solar refrigeration

Abstract

The use of calcium chloride as the absorbent in solar absorption refrigeration systems results in increased costs of such systems. The purpose of this study was to search for a cheaper and more readily available absorbent that can replace calcium chloride in solar refrigeration systems. This was done by measuring the absorbent and swell properties of Sodium Chloride, Kaolinite, Bentonite and Calcium Chloride-Bentonite mixture and comparing them with those of Calcium Chloride.

The results obtained show that the swelling properties of the four materials under study are better than those of Calcium Chloride. The highest percentage swell is that of Bentonite which is only 41 of that Calcium Chloride after six cycles. The absorption properties of these materials are, however, much lower than those of calcium chloride. The highest again is that of Bentonite which is 13 of that of calcium chloride after six cycles.

These materials are therefore, more suited for solar refrigeration with respect to swelling properties than to absorbability properties. The low swelling levels allow for the development of smaller solar collectors. This consequently reduces the manufacturing costs of these types of refrigeration systems.