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.