After piloting its solar desalination process for two years, California-based WaterFX is about to build its first commercial plant to serve farmers in the Central Valley.
Its subsidiary, HydroRevolution, will use concentrating solar to turn salt water at farms into a sustainable fresh water supply. Rather than taking water from the ocean, the process recycles unusable irrigation drainage water for use by local water districts.
Amazingly, this can turn farmers into water producers rather than consumers! It could make all the difference for California farmers, where an estimated 1 million acre-feet of irrigation drainage water could be reused, according to Think Progress.
"The result could mirror what has happened in energy; rather than relying on large-scale, centralized generation, smaller "distributed" projects across the state could free up hundreds of thousands of acre-feet of water through reuse, reducing overall demand on the water grid," says the company.
HydroRevolution will expand the pilot plant, which has been operating since 2013, on 35 acres farmed with salt-tolerant crops.
How It Works
Its Aqua4TM technology produces heat from huge, parabolic solar reflectors. That heats mineral oil, which flows through a distillation system, evaporating fresh water and condensing brackish water into usable liquid, separating out the minerals.
"Water that dribbles down from nearby hills, and through the soil after being used for irrigation, collects so much salt, selenium, boron and other minerals that it’s not fit for human consumption. The solar plant captures the runoff using a French drain-style system 6-8 feet under the crops, and sends the tainted water through pipes and tanks that heat it," explains the San Francisco Chronicle.
The water can be used again for irrigation, and the minerals are so efficiently distilled that they can be processed and sold – selenium and boron for vitamin supplements and gypsum for drywall, for example.
Aqua4 can treat any kind of wastewater, drainage water, runoff, saline groundwater and industrial process water … all right on site through movable, module units. The resulting fresh water costs $450 per acre-foot – not much more than farmers typically pay – and about 75% less than conventional desalinated water.
In a unique move, HydroRevolution says it will use crowdsourcing to finance the plant’s construction, allowing all California residents to participate as owners.
Another novel, environmentally superior desalination technology is being developed by Voltea, using electric fields to remove salts and dissolved solids from water. The modular devices have been miniaturized to the size of a coffee cup!, the company says. Another technologies uses wind, Wind4Water.
Read about the problems with conventional desalination, Drought Spurs Surge in California Desalination, Can Solar Help?