| Solar desalination is the desalination of water using solar energy. Renewable energy overcomes the usually high energy operating costs as well as greenhouse emissions of conventional reverse osmosis. Reverse Osmosis is currently the favoured technology for desalination, being the most cost-effective. Recently, there is evidence of growing research interest in the field. This is prompted by growing energy costs, demand growth in the face of depleted water stores, and the growing human pollution of many communities' water supplies. The severity of fresh water shortage can easily be gauged by the fights that have erupted over water in the recent past in India and outside. Statistics emphasize the same—at least 40% of the world’s population lives without drinking water and roughly 80 000 habitations across the planet have no source of safe water. Of the 575 000 Indian villages, about 162 000 face problems of brackish or contaminated water and scarcity of fresh water. Solar water distillation is a solar technology with a very long history and installations were built over 2000 years ago, although to produce salt rather than drinking water. Documented use of solar stills began in the sixteenth century. An early large-scale solar still was built in 1872 to supply a mining community in Chile with drinking water. Mass production occurred for the first time during the Second World War when 200,000 inflatable plastic stills were made to be kept in life-crafts for the US Navy. Most people see strong potential for solar thermal (or wind) energy to be used in large scale desalination. This is particularly so for solar in arid regions due to the usual coincidence of water shortage, good solar radiation and seawater (or brackish) availability. While there are many theoretical models the process is not yet developed at large commercial level. A number of small solar desalination devices exist, and whilst larger plants are technically feasible, they fall down on energy cost comparisons. A company called Acquasol plans to build a solar-powered desalination plant in the Upper Spencer Gulf to supply the small town of Port Augusta in Australia. The project is a little short on detail, but is worth keeping an eye on.
India gets a solar desalination system Source : The Hindu The Bhabha Atomic Research Cenre in Mumbai has developed a solar energy based desalination system. It is a community level Reverse Osmosis unit which will cater to the drinking and cooking requirements of 3-4 families and addressing issues related to the adverse impacts of climate change. The Bhabha Atomic Research Centre (BARC) here has developed a desalination system based on solar heat and light. A view of the Research Reactor CIRUS at Bhabha Atomic Research Centre, Trombay/ Photo credit: The Hindu Solar energy-based small and community level Reverse Osmosis (RO) unit has been developed for producing safe drinking water, Saly T. Panicker of the Desalination Division of BARC said. In the RO unit, the feed water is passed through the membrane with the help of a DC (Direct Current) pump connected to the Photovoltaic (PV) panels without any batteries. The unit can be operated for 9 to 10 hours on a sunny day, which can cater to the drinking and cooking requirements of three to four families at an average rate of five litres per person per day, Panicker said. “It contains a filter cartridge and a spirally wound RO membrane element,” he said, adding there was no significant variation in the rate of power production from the PV panels. “Thus, the pump is able to maintain its pace, keeping the rate of drinking water production constant,” Panicker, who has developed the technology along with scientists K. L. Thalor and P. K. Tiwari, said. Explaining the system, he said the RO is a pressure driven process, where pure water is continuously drawn from salty water through a semi-permeable membrane. Highlighting the importance of solar-powered system which will be useful especially in remote areas, Panicker said integrating desalination with renewable energy sources is also important for addressing the issues related to adverse impacts of climate change. The source of solar energy is inexhaustible and is free. Also, no harmful gases like nitrogen oxide, mercury, carbon dioxide or sulphur dioxide are emitted, he said. As for cost, he said, “with the improvement in PV efficiencies and the subsidies available, the solar-based desalination system would become very cost effective.”
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