Performance of a solar still: Predicted effect of enhanced evaporation area on yield and evaporation temperature

A solar still with enlarged evaporation area was simulated on the computer in order to explore the quantitative relationship between evaporation area and the distillation yield. The results showed a gain of 19.6% in the yield when the evaporation area was quadrupled, and an asymptotic (infinite area) gain of around 30.2%. A thermodynamic analysis of the two separate energy conversion processes occurring within the still led to ''availability'' based definitions of efficiencies for the collector and the evaporator-condenser. This analysis showed that all of the asymptotic improvement in yield is attributable to the more efficient evaporation-condensation process in the still with enlarged evaporation area. The analysis also suggested that stills with enlarged evaporation area could be operated on cheap low temperature thermal energy such as from solar ponds. Finally, the exergy based efficiency defined for the evaporator-condenser was shown to be useful in describing the performance of multiple-effect solar stills as well.