Solar distillation
Solar distillation: Solar water distillation is the process of using energy from sunlight to separate fresh water from salts or other contaminants. The untreated water absorbs heat, slowly reaching high temperatures. The heat causes the water to evaporate, cool, and condense into vapour, leaving the contaminants behind. Solar stills can be used for low capacity and self- reliant water supplying systems. A solar still works on two scientific principles- evaporation and condensation.
The salts and minerals do not evaporate with the water. For example, table salt does not turn into vapour until it gets to a temperature over 14000C. However it still does take a certain amount of energy for water to turn into water vapour. While a certain amount of energy is needed to raise the temperature of a kilogram of water from 00C to 1000C, it takes five and one half times that much to change it from water at 1000C to water vapour at 1000C. Practically all this energy, however, is given back when the water vapour condenses. Most stills are simple black bottomed vessels filled with water and topped with clear glass or plastic. Sunlight that is absorbed by the balck material speeds the rate of evaporation. The evaporation is then trapped by the clear topping and funneled away. Most polltants do not evaporate, so they are left behind. Most stills need to be about six m2 in size to produce enough water for a single person for a day. Multiple solar distillation systems are required to produce a large quantity of distilled water.