Directly or indirectly, the sun has been the source of most of the conventional energy sources on earth. Be it fossil fuels, biomass, or hydroelectricity. In the more direct from sunlight, consisting of the visible spectrum, ultraviolet, and infrared rays, is a rich and inexhaustible source of energy which can be used to a diverse set of applications ranging from direct harnessing into electrical energy to solar cooker to solar water purifier. Now, solar water purifiers can be categorized into two broad categories, namely, sunlight treatment process and photovoltaic cell based water filtration systems.

Conventionally, for ages, people all over the world have been using sunlight for sun-curing food products and eliminating microorganisms. Water can be purified by direct exposure of water to sunlight for certain duration of time. Scientific studies have concluded that keeping water in sunlight for 1 hour and raising the temperature of water to 50 degree Celsius makes it safe to drink as far as microbial contamination is concerned. To remove solid contamination, solar energy can be used for the distillation process. It is an established fact that one does not need to boil water to evaporate it in order to recollect the water from the evaporated vapor. So raising the temperature of water by sunlight can significantly increase the rate of evaporation and thus can enhance the process of distillation. This, in fact, has the advantage over the conventional method boiling water for distillation as in the case of boiling, a number of volatile solid also gets evaporated with water.

The second category of solar water purification systems is based on the process of heating, filtration, and reverse osmosis and it uses electricity derived from solar energy. They actually are more commercially viable and are able to process a large quantity of water. In these units, photovoltaic cells, solar cells in popular parlance, are used to convert the solar energy to electrical energy which in turn is used to run the filtration and RO unit and heating the water. It usually consists of a solar panel to harness the solar energy, a battery to store the electrical energy thus harnessed, a water pump, a sedimentation filter, a carbon filter, an RO membrane and an ultraviolet (UV) treatment chamber. The sedimentation filter filters the macro level impurities contained in the input water whereas the carbon filter removes the finer solid particles. The RO membrane then removes the dissolved solids and maintains the Total Dissolved Solid (TDS) in the prescribed range. The water pump runs on the electrical power stored in the battery and generates the necessary pressure to commence the process of Reverse Osmosis. Finally, the UV chamber kills the germs left in the water.

A solar energy water filtration system is environment-friendly in addition to being economical. It reduces the electricity bill by being an off the grid unit. Moreover, lesser electricity consumption means lesser utilization of fossil fuels in thermal power stations. Solar water filtration systems are baby steps towards a better and greener future!