太陽エネルギー利用の高効率塩水淡水化システムに関する研究

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There are many ways of solar energy application in producing fresh water from brackish or seawater. The simplest and most common method is direct use of the solar energy in basin-type solar still which acts simultaneously as converters of solar energy to heat and as distillers. Objectives of this study is to analyze the basic performance of double slope basin-type stills and to develop the new concept for basin solar still equipped with evaporation stimulator. Results from experimental and theoretical works are as follows :1) The effectiveness of gathering distilled water was varied with the kinds of covering materials for still. Rigid polyester film with anti-droplet treatment was most efficient to gather the water, and inner convection fan in solar still increased the amount of distilled water about 10% more. When the salt water of 3.5% concentration was used as source water, output of pure-water was decreased about 10% by comparing with use of tap water.2) Productivities increased by about 10 to 20% when ultrasonic oscillation was loaded for every three types of radiation absorber in the basin. In comparison with no absorber condition, productivity of pure water using black plastic perforated sheet on water surface increased by about 20% without ultrasonic oscillation, and increased by about 50% with the ultrasonic oscillation.3) Numerical calculation estimating performance of solar stills was done by using heat balance equation, and compared the results of calculation with those of experiments. Calculated values fairly fit the result of measurement. This calculation method seems to be useful for estimating the temperature of basin water and output of water.4) Multi-effect type solar still was introduced and their performance was examined. Output of pure water in this still was about 7 times of the usual basin type solar still.