A theoretical analysis of basin type solar still with flat plate external bottom reflector

A basin type solar still with a flat plate external bottom reflector extending from the front wall of the still in addition to the internal (two sides and back walls) reflector is presented and analyzed theoretically on three days (the spring equinox and summer and winter solstices) at 30°N latitude. We proposed a geometrical model to calculate the direct solar radiation reflected by the external bottom reflector and then absorbed onto the basin liner. We also performed a numerical analysis of heat and mass transfer in the still. We found that the external reflector can reflect the sunrays to the basin liner and increase distillate productivity. The daily amount of distillate of the still with internal and external bottom reflector is predicted to be 41%, 25% and 62% greater than that of a conventional basin type still on the spring equinox and summer and winter solstices, respectively, by setting the external reflector's inclination to the proper values according to the seasons when the glass cover's inclination angle is fixed at 20° from horizontal and the length of the external reflector is the same as the length of the basin liner.

Research highlights
► Flat plate bottom reflector of basin type solar still is analyzed theoretically.
► The glass cover inclination is fixed at 20°.
► The optimum reflector's inclination was found on three typical days.
► The bottom reflector can increase the distillate productivity of basin type still.