A study on a new maritime lifesaving multiple-effect solar still

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The proposed maritime lifesaving solar still has almost same structure with a downward-heating multiple-effect diffusion-type solar still, and consists of a transparent cover film and a number of horizontal parallel partitions in contact with saline-soaked wicks with narrow air gaps between partitions. The first partition, or uppermost partition, absorbs solar energy to cause evaporation from seawater in the wick on underside of the first partition. The water vapor diffuses through a humid air layer between partitions and condenses on the second partition where latent heat of condensation is recovered to be used further evaporation from the wick of the second partition. Such evaporation and condensation process repeats on all partitions to greatly increase overall production of distillate.We theoretically investigated the performance of the proposed still, and found that the proposed still is estimated to produce about 15 kg/m^2d of fresh water on a sunny day of 22 MJ/m^2d of solar radiation, and such amount of fresh water production is large enough, exceeding the minimum standard set by SOLAS.We also performed indoor-and outdoor-experiments using a single effect still without cover film, which may be easily applied for practical use, and the results of the experiments are summarized as follows: (1) Productivity is 28 % larger with using the partition, on which saline-soaked wick is attached, as natural gum than urethane film. (2) Productivity is 83 % larger for the still of diffusion gap between evaporation and condensation surfaces is 5 mm than that of 7 mm. (3) Salt deposition area is about 4 % of total evaporation area. (4) Single effect still without cover film produced about 2.8 kg/m^2d at a sunny day, and this amount of fresh water meets the minimum requirements set by SOLAS.