YIELD OF SOLAR-STILLS WITH POROUS BASINS

Following a brief review on the recent trends for improving the economy of direct solar distillation, a new simple still is described. In the proposed conceptual design the construction cost is greatly reduced by eliminating the concrete structure for the still's basin and the black lining materials. Instead a site is filled with powdered soot (carbon powder 40-50 mu m size) obtained free of charge from oil-fired power plants. The effects of the powder and the basin's insulation layer on the yield from the solar still are examined experimentally. Outdoor testing of a pilot unit in Jeddah, Saudi Arabia (latitude 21 degrees 45'N) shows an average yield of 2.5-4 litres/m(2) day using the soot in the still's basin. Removing the basin's insulation reduces the productivity by 13-17%. Economic analysis of the proposed design for a plant of 50 m(3)/day productivity shows a potable water production cost of US$2.4/m(3), which is 66% less than previous estimates.