What is historical significance of solar still use?

Ancient Origins of Solar Stills

The ancient Indus Valley Civilization, located in present-day Pakistan and northwestern India, is believed to have first employed solar stills around 2,500 BCE. These early stills consisted of shallow depressions in the ground, where seawater was poured and allowed to evaporate under the hot desert sun. The resulting condensation was collected as clean drinking water. This basic technique was likely shared with sailors, who used it to extract water from seawater during long ocean voyages.

Modern Improvements and Applications

The original design of the solar still was improved upon by 19th-century sailors, who developed a more efficient still using a clear plastic sheet or a tin plate to concentrate the sun’s rays. In the 20th century, engineers designed more complex solar stills using glass or plastic domes to maximize water collection. These modern stills were employed in various emergency and military situations, including the 1970s Apollo missions to the moon, where astronauts used a solar still to extract water from lunar regolith.

Practical Techniques for Solar Still Use

To build a simple solar still, dig a shallow depression in the ground and line it with a plastic sheet or a clear stone. Pour the contaminated water into the center of the still, and weigh down the edges with rocks. Cover the top with a clear plastic sheet or a tin plate, and weigh it down to ensure no air leaks. As the sun heats the water, the resulting condensation will collect on the underside of the plastic sheet or tin plate, and can be collected as clean drinking water.