Solar desalination plant shows promise

Solar desalination plant shows promise

The WaterFX solar thermal desalination plant, and it has been turning salty, contaminated water into ultra-pure liquid for nearly a year. It’s the only solar-driven desalination plant of its kind in the country.

The solar desalination plant produces water that costs about a quarter of what more conventionally desalinated water costs. ($450 an acre-foot versus $2,000 an acre-foot.) An acre-foot is equivalent to an acre covered by water 1 foot deep, enough to supply two families of four for a year. This is about $18.75 per month for a family of four. That makes it a more economically attractive option than any of the 17 conventional desalination plants planned throughout California.

Simple process

The way the solar plant works is simple, which is why the water it produces is cheap. The solar plant uses tainted water through a series of pipes and tanks that heat it. The heat comes from the plant’s huge, parabolic-shaped solar reflector, which focuses the sun on a long tube containing mineral oil. That heated tube in turn creates steam, which condenses the brackish water into usable liquid, separating out the minerals.

More conventional desalination plants – such as a $1 billion operation being built near San Diego – use a reverse osmosis process, in which brackish water is forced through screens to filter out the contaminants. That requires a lot of energy, which is why it is more expensive.

Raising money

WaterFX’s pilot plant cost $1 million in state grants to build last summer. The expansion of the 36-plant complex would cost as much as $30 million, which Mandell is working on raising.

John A. Peters


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