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Electrolysis processes require very clean water. For typical electrolyzers, deionized water is used. This process typically requires several times more water than is used, with the remainder being rejected with the initial water impurities. In the desert Southwest, water is a precious commodity, so we are examining ways of reducing water use in energy production.

A solar still is a way of making more usable water available from each unit of feed. The solar still can replace the deionizer that is used to provide pure water for the electrolyzer, which should reduce the maintenance and operational costs of the system.

A regenerative weir type solar still is being evaluated for this application at our facility. This is a simple inclined still with an inclined absorber plate that is stepped. In this still, feed water flows from the top to the bottom of the absorber plate and circulated back by a small pump. Pure water evaporates from the flow, and it is condensed on the cover plate where it can be collected and used in the electrolyzer.