Can Solar Desalination Slake the World's Thirst?

http://www.scientificamerican.com/article/can-solar-desalination-slake-the-world-s-thirst/?WT.mc_id=SA_WR_20150923

September 21, 2015

Solar desalination is a technique used to remove salt from water via a specially designed still that uses solar energy to boil seawater and capture the resulting steam, which is in turn cooled and condensed into pristine freshwater. Salt and other impurities are left behind in the still.

Less than one percent of the world’s desalination is powered by renewable energy sources today, but that could all change soon if companies like California-based WaterFX have anything to say about it. Its Aqua4 “concentrated solar still” (CSS) uses a concentrated solar thermal collector to compress heat, create steam and distill water at 30 times the efficiency of natural evaporation. It can produce 65,000 gallons of freshwater per day—and it can desalinate a wide range of water sources, not just seawater.

To wit, the company will start employing solar desalination to treat some 1.6 billion gallons of salt-laden irrigation drainage from California’s drought-stricken, agriculturally-rich Central Valley next year. Crops extract nearly pure water from soil, leaving behind salt and other potentially toxic minerals like selenium that naturally occur in the water. These excess minerals must be drained from the soil, or crop productivity plunges.

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“If we don’t start removing the salts now, at least 10 percent of all current farmland in production in California will have to be retired, and in many scenarios this number could be up to 30 to 40 percent, especially on the west side of the Valley where the salinity is very high,” says WaterFX’s Matthew Stuber. “Water in the drainage areas will contaminate groundwater and natural surface waterways at an accelerated pace, eventually polluting sources of drinking water and the natural environment. Once that is released into the environment, you severely damage the natural habitat and wildlife.”