History
Methods of solar distillation have been employed by humankind for thousands of years. From early Greek mariners to Persian alchemists, this basic technology has been utilized to produce both freshwater and medicinal distillates. Solar stills were in fact the first method used on a large scale to process contaminated water and convert it to a potable form.
In 1870 the first US patent was granted for a solar distillation device to Norman Wheeler and Walton Evans. Two years later in Las Salinas, Chile, Carlos Wilson, a Swedish engineer, began building a direct method solar powered distillation plant to supply freshwater to workers at a saltpeter and silver mine. It operated continuously for 40 years and produced an average of 22.7 m3 of distilled water a day using the effluent from mining operations as its feed water.
Solar desalination of seawater and brackish groundwater in the modern United States extends back to the early 1950s when Congress passed the Conversion of Saline Water Act, which led to the establishment of the Office of Saline Water (OSW) in 1955. The OSW’s main function was to administer funds for research and development of desalination projects. One of the five demonstration plants constructed was located in Daytona Beach, Florida and devoted to exploring methods of solar distillation. Many of the projects were aimed at solving water scarcity issues in remote desert and coastal communities. In the 1960’s and 70’s several modern solar distillations plants were constructed on the Greek isles with capacities ranging from 2000 to 8500 m3/day. In 1984 a MED plant was constructed in Abu-Dhabi with a capacity of 120 m3/day and is still in operation.
Of the estimated 22 million m3 of freshwater being produced a day through desalination processes worldwide, less than 1% is made using solar energy. The prevailing methods of desalination, MSF and RO, are energy intensive and rely heavily on fossil fuels. Because of inexpensive methods of freshwater delivery and abundant low cost energy resources, solar distillation has, up to this point, been viewed as cost prohibitive and impractical. It is estimated that desalination plants powered by conventional fuels consume the equivalent of 203 million tons of fuel a year. With the approach (or passage) of peak oil production, fossil fuel prices will continue to increase as those resources decline; as a result solar energy will become a more attractive alternative for achieving the world’s desalination needs.
Read more about this topic: Solar Desalination
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