Solar Desalination Could be a Game Changer for California Farms

By Sandra Postel (Director, Global Water Policy Project; National Geographic’s Freshwater Initiative Fellow), National Geographic

Let’s be clear from the outset: I’m no fan of conventional desalination. The idea of using climate-altering fossil fuels to drive an energy-intensive de-salting process that threatens coastal environments in order to produce drinking water that, in most cases, could be secured more cheaply through conservation and efficiency improvements, simply fails to pass the bar of economically sensible, environmentally sound solutions to our water problems.

But now desalination of a very different stripe is under way – not by the sea, but in California’s drought-stricken Central Valley farming region. The project is turning salty, contaminated agricultural drainage into fresh water that can be re-used to irrigate crops. Powered not by fossil fuels, but by the sun, the technology has the potential to shift the way water is used and managed in parts of the west, where agriculture accounts for 70-80 percent of water use.

Developed by a San Francisco-based company called WaterFX, the solar desalination unit has been piloted in the Panoche Water District in Fresno County. Farmers in the area grow a wide variety of crops, including almonds, asparagus, tomatoes, pistachios, cotton, alfalfa and wheat. The district is located on the valley’s west side, where farm drainage contains not only high levels of salt, but also selenium, a naturally occurring element that is essential in trace amounts but poisonous at high concentrations.

WaterFX’s “Aqua4” system offers a way of addressing both mounting water shortages and critical contamination problems. The technology uses parabolic mirrors to concentrate the sun’s energy, heating a tube that then distills fresh water out of the salty drainage. It’s an age-old process made far more efficient with modern technology. The system can produce 200 acre-feet (65 million gallons) of water per acre of solar collection area, making it, according to WaterFX, the most efficient solar desalination system available.

Read full article at National Geographic

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