Enhancement of cascade solar still productivity with sloping absorber plate

A step-type solar still with a sloping absorber plate was developed. The productivity index was investigated experimentally in two types of solar still, namely the modified and the ordinary stills, under identical operating conditions. A mathematical model was developed to calculate the theoretical amount of solar radiation emitted to the absorber plate in the ordinary and modified solar stills. An evaluation of the theoretical model showed that the amount of absorbed solar radiation in the new design of absorber plate was 36% higher than that in the ordinary still on a sunny day. The daily efficiency of 42.3% was calculated for the ordinary still with a total productivity of 4.46 kg/m(2). day, while the total productivity of the modified still reached 5.19 kg/m(2). day, corresponding to an efficiency of 49.2% on a sunny day. The results also demonstrated a 16% productivity increase with the modified cascade solar still on a sunny day, while there was no significant difference in productivity between the two evaluated stills on a cold day.