CHARCOAL-METHANOL ADSORPTION REFRIGERATOR POWERED BY A COMPOUND PARABOLIC CONCENTRATING SOLAR COLLECTOR

A compound parabolic concentrating solar collector (CPC) of concentration ratio 3.9 and aperture area 2.0 m2 was used to power an intermittent solid adsorption refrigerator and ice maker using activated charcoal (carbon) as the adsorbing medium and methanol as the working fluid. The copper tube receiver of the CPC was packed with 2.5 kg of imported adsorbent 207E3, which was only utilised when the performance of activated charcoal (ACJ1, produced from local coconut shells) was found to be inferior to the imported adsorbent. Up to 1 kg of ice at an evaporator temperature of -6-degrees-C was produced, with the net solar coefficient of performance (COP) being of the order of 0.02. Maximum receiver/adsorbent temperature recorded was 154-degrees-C on a day when the insolation was 26.8 Mj/m-2. Temperatures in excess of 150-degrees-C are undesirable since they favour the conversion of methanol to dimethyl ether, a noncondensable gas which inhibits both condensation and adsorption. The major advantage of this system is its ability to produce ice even on overcast days (insolation approximately 10 MJ/m-2).