70% of earth's surface is covered with water but still there is scarcity of water at many places because the sea water contains salt which makes it unsuitable for human consumption. As the fresh water demand is increasing day by day people are spending a lot of money and energy in separating the salt content from the sea water or in desalinating it.
Solar desalination is a process which can be used to desalinate the sea water. The basic principle behind the cleaning process is condensation (the process in which water is collected in an insulated tank and forced to evaporate, the water molecules which cant escape get condensed and are collected in another chamber attached to it.)
This process will be clearer to you after watching this small clip.
In this type of solar desalination set up, an insulated tank is taken in which a big bowl-shaped container is placed.The sea water is allowed to enter the bowl with the help of a hollow pipe. The vertical walls of the insulated tank are cut in an inclined form at the top of the tank and are covered with a glass sheet. The glass sheet is connected to the long tubes cut in the semi circular form and are fixed with the glass sheet which collect the condensed water and take it to the fresh water tank.
When this set up receives the sun's radiations, the glass sheet allows the infrared radiations to enter the tank and as it is insulated it does not allow radiations to leave thus creating the green house effect which super heats the tank and water in the bowl starts evaporating. The water molecules starts rising up, get condensed and are collected by the semi circular tubes and are sent to the fresh water tank.
This process is quite effective as it produces 7.2 litres of fresh water from 8.3 litres of contaminated water.
Video below shows another type of solar desalination plant.
