Study On Water Production Performance Of Solar Still Based On Interfacial Solar-steam Conversion Material

Solar desalination is a sustainable technology to produce fresh water from seawater.Commercial solar-powered desalination projects require large infrastructure,high investment costs and long payback periods,and are generally available only in economically developed areas with high population density.In order to solve the problem of daily drinking water shortage of residents in some areas with less developed economy and shortage of fresh water resources,a simple solar desalination device-solar distillation unit was studied in this paper.Based on the theory of interfacial evaporation(reducing the scale between the seawater heating surface and the evaporative surface),this paper mainly studies a kind of interfacial evaporative solar distillation by means of experimental research and theoretical analysis.There are two main processes in the solar distillation,one is the evaporation of seawater,the second is the condensation of water vapor.Therefore,the evaporation rate of seawater and the condensation rate of water vapor should be improved by different means.In this paper,a theoretical model of water production in an interfacial evaporative solar distillation unit is established.The effects of daily mean meteorological parameters on the yield and efficiency of distillers were studied quantitatively in the range of typical daily solar radiation intensity,ambient temperature and outdoor wind speed in Tianjin.Then the hydrophilicity,solar radiation absorption and salt evaporation resistance of the three materials(black cotton,carbon foam and black sponge)were compared through experiments.It is determined that the black cotton material can be used as a kind of light-steam conversion material for a long time in distilling apparatus because of its best hydrophilicity and salt evaporation resistance.Secondly,the form of condensation water on the surface of the cover plate and the yield of the distiller were studied by using different materials of glass cover plate(soft glass,polymethyl methacrylate and ordinary glass).It is determined that soft glass has poor wettability to condensate and can be used as transparent cover plate of distillation apparatus.By changing the tilt Angle of the soft glass cover(35°,40°,45°),the water yield of the distiller using black cotton as solar-steam conversion material was studied.It is determined that the yield of distiller can be increased by increasing the dip Angle of the transparent cover plate.Finally,the water production performance of an interfacial evaporative solar still using plexiglass as shell,black cotton as light-steam conversion material,and soft glass cover with an inclination of 45° was tested.Under the test conditions of 4-day sunny days,the water production efficiency of the distillation unit was stable at over 25%,and the fresh water production capacity per unit evaporation area was over 2 kg/day.The cost of the distillation unit is analyzed.Compared with the mature commercial desalination unit,the distillation unit has the advantage of being used in less developed areas.