PERFORMANCE CHARACTERISTICS OF FOUR SOLAR STILL DESIGNS
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Four solar still designs were evaluated based on their condensed water production and solar radiation absorption efficiency. The designs of the four distillation units were: (1) flat bottom reservoir with single inclined glass (SS1), (2) stair-step reservoir with single inclined glass and continuously fed (SS2), (3) flat bottom reservoir with woven wick material on an absorber plate and double inclined glass (SS3), and (4) flat bottom reservoir with woven wick material on an absorber plate, double inclined glass, and continuously fed (SS4). The water surface areas of solar stills SS1, SS3 and SS4 were 0.5 m 2 and of SS2 was 1 m2. Water input and condensed water output were measured each day, as well as solar radiation absorbed. Solar energy conversion efficiency for water distillation was evaluated for the four designs. Condensed water production per square meter of the solar still was correlated to the solar energy received to determine if there was a statistically significant correlation. Results showed that all solar stills showed a 1 slope regression coefficient that was statistically different than zero, when determining a correlation between condensed water production and solar radiation. SS2 had an average distilled water production rate of 2.9 L/m2/day followed by SS1 and SS3 at 2.2 L/m 2/day. SS4 had a distilled water production rate of 1.2 L/m 2/day. The average energy conversion efficiency was 50% for SS2, 36% for SS3, 31% for SS1, and 21% for SS4. To generate 2 L of distilled water per day (the current daily per capita consumption in the United States), it would take less than 0.7 m2 of solar collector surface area. The yearly condensed water production rate, for a still utilizing the SS2 design and the developed prediction model, in Austin, Texas was estimated to be 1290 L of condensed water per square meter of still surface area (341 gal/m 2/yr). 2011 American Society of Agricultural and Biological Engineers.
