Desalination of groundwater by solar stills : field trials in Afghanistan
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Lack of clean drinking water is amongst the leading problems in Afghanistan, especially in form of salinity, being amongst the main concerns. As an attempt to find sustainable solutions, low cost solar stills were designed and built in Kabul city. Four different designs and outlines were proposed for this project, with the aim to use solar energy and the principle of evaporation and condensation in the production of distilled water. Of the proposed designs, three were built, in a total of 6 units, ranging from the size 0.1 to 1m2. The solar stills had different inclination on the glass cover and were built out of a variety of local materials, like plywood, galvanized iron, stainless steel, silicone, paint, insulation and more on. The experiment was conducted from the 17th to 27th of May, 2014. Hourly measurements of radiation, output and temperatures were registered from 07:00 am to 18:00 pm, and wind- and weather conditions were registered. Individual experiments such as cooling of glass, application of coal and increased salt concentration, were conducted within the research period. The solar still with the highest efficiency (57 %) was found to be the Plywood single sloped solar still. This and the Wick solar still had an efficiency of 43 % and 31 % respectively. The two solar stills of the smallest size obtained the lowest efficiency, with 12 % and 8 % for Sink double sloped and Plastic single sloped solar still, respectively. The cost estimates ranged from 7 to 70 USD, where the most pricy still was the one with the highest output and the largest size.