THE BURNED OVER DISTRICT

Is being rejiggered with some modern touches to bring it into the 21st century. Evaporation/condensation has long been used to purify water, but the energy costs have made modern applications too expensive. An adaptation of solar technology is almost ready to bring the cost down to affordable levels.

The giant solar receiver installed on a wheat field here in California’s agricultural heartland slowly rotates to track the sun and capture its energy. The 377-foot array, however, does not generate electricity but instead creates heat used to desalinate water.

It is part of a project developed by a San Francisco area start-up called WaterFX that is tapping an abundant, if contaminated, resource in this parched region: the billions of gallons of water that lie just below the surface.

Financed by the Panoche Water District with state funds, the $1 million solar thermal desalinization plant is removing impurities from drainage water at half the cost of traditional desalinization, according to Aaron Mandell, a founder of WaterFX.

If the technology proves commercially viable — a larger plant is to be built this year — it could offer some relief to the West’s long-running water wars.

WaterFX faces a daunting and urgent task. The water is tainted with toxic levels of salt, selenium and other heavy metals that wash down from the nearby Panoche foothills, and is so polluted that it must be constantly drained to keep it from poisoning crops....

The parabolic-shaped receiver is a standard unit made by a Colorado company called SkyFuel for solar thermal power plants. It uses a reflective film rather than expensive mirrors to focus the sun on tubes containing mineral oil that are suspended over the solar array.

As the oil warms to 248 degrees, the heat is piped into refurbished, 1960s-era evaporators to generate steam. The steam then condenses fresh water and separates the salts and heavy metals. The cycle is repeated to further concentrate the brine.

WaterFX relies on off-the-shelf equipment except for a heat pump of its own design. The pump recycles excess steam for reuse through a chemical process rather relying on an electricity-driven compressor.

“It cuts the number of solar collectors you need roughly in half,” Mr. Mandell said.

That savings means WaterFX can purify water using half as much energy as conventional desalinization.

During the pilot project, WaterFX produced 14,000 gallons of purified water a day. A commercial version of the plant, set to be built this year on 31 acres of land, will produce 2,200 acre-feet a year. That’s the amount of water that would cover an acre of land at a depth of one foot, or 717 million gallons. The company will store excess heat generated by the solar array in molten salt to allow the plant to operate 24 hours a day.

Mr. Mandell said WaterFX currently produces an acre-foot of water for $450. That compares to about $280 an acre-foot charged by the Central Valley Project — when water is available.

The costs may be high now, but a drought is the perfect time to bring this online and work the bugs out and the price down.