Triple effect evacuated solar still system for getting fresh water from seawater

A practical-scale solar-distillation-system (still) was developed which can yield fresh water from seawater without any consumption of fossil resources in the operation. The nominal performance is 100 kg day^-1 unit^-1 in summer at Yokohama, Japan. The still is a self-sustainable system which has 7.8 m² solar collector and 3.7 m² solar cells. It was constructed at the end of November 1996. The distillation performance showed it to be one of the best solar stills, although we tested it for only two months during the winter season, December 1996 and January 1997. A highest distillation performance of 73.6 kg day^-1 was obtained, which corresponds to 9.44 kg m^-2 day^-1 fresh water distilled at a solar radiation of 13.85 MJ m^-2 day^-1(108.3 MJ day^-1). The total latent heat of the distillation (178.8 MJ day^-1) was 1.7 times the solar radiation. The power consumption by a vacuum pump was only 326 Wh day^-1 (1.17 MJ day^-1) while the solar cells generated 952.5 Wh day^-1 (3.43 MJ day^-1) at 12.25 MJ m^-2 day^-1(45.33 MJ day^-1) solar radiation.