Two More Large-Scale California Solar Projects Nearing Final Decisions

If the two separate projects are approved by the full Energy Commission, their combined peak nominal production capacity of 650 megawatts would mean that in a scant few months the state had licensed about 4,140 megawatts of solar energy generation, an amount that a year ago would have been considered staggering.

That power-generating capacity is nearly equal at peak times to that of the state’s two nuclear power plant complexes combined. The nuclear plants can generate electricity night and day – as could one of the solar power plants recommended for approval this week, according to its developer.

If both projects are built, the construction workforces would top out at a combined total of nearly 1,600, according to plans filed with the Energy Commission.

In what is called a Presiding Member’s Proposed Decision, approval was recommended for the 500-megawatt Palen Solar Power Project, a concentrating solar thermal power installation planned off Interstate 10 in the Colorado Desert, about halfway between the cities of Indio and Blythe and 10 miles east of a hamlet known as Desert Center.

The proposed decision opens a 30-day public comment period, which could result in revisions to the plan.

A second proposed decision announced Friday recommended approval of the Rice Solar Energy Project, a 150-megawatt plant to be built northwest of Blythe that would store heat as molten salt and permit solar-sourced electricity to be produced after dark. It would include a 653-foot-tall “power tower.”

The Palen project is a concentrating solar thermal complex that calls for two separate but adjacent 250-megawatt generating systems. It is to be built mostly on public land overseen by the federal Bureau of Land Management, which, like the full state Energy Commission, has not yet signed off on the plans. The initial plans were reconfigured twice to reduce biological impacts at the site.

The Palen complex would use curved trough-like mirrors to focus radiant heat onto tubes containing a fluid that would be heated to about 750 degrees Fahrenheit. The fluid is to be piped through heat exchangers, generating steam to be fed under high pressure through conventional turbine-generators to produce electricity.

Technology of this type, which is unrelated to the solar photovoltaic panels used to generate electricity directly, has been in use on a smaller scale in the California deserts for about 27 years.

The Palen project calls for propane gas to be used with an auxiliary boiler for half an hour to speed up each plant’s startup each morning. The propane-powered boiler also would be used when needed to prevent freezing of the heat-transfer liquid on cold winter nights. The estimated total annual nighttime use would be 100 hours.

Although solar thermal plants can require significant water consumption to cool and condense the hot steam as part of the energy-generating cycle, this project and others planned in the California deserts would be dry-cooled. Dry cooling cuts water consumption by as much as 90 percent, experts say, but reduces generating efficiency, resulting in somewhat higher-cost electricity.

The project is expected to take slightly more than three years to complete, with an average monthly workforce of nearly 600 and a peak construction staff of 1,140 workers. The start of construction must await final approvals from the state and federal governments.

The developer of the Palen project, working through U.S. affiliates, is a company based in Germany called Solar Millennium. The company also is developing the nearly 1,000-megawatt Blythe Solar Power Project, about 30 miles east of the Palen site. That project has received final state and federal approvals.

“The four Blythe power plants and the two Palen power plants together are expected to supply roughly 3,300 gigawatt-hours of electricity annually,” the company said in a recent news posting on its website. “The overall capacity of the planned solar power plants thus exceeds that of a nuclear power plant or a modern large-scale coal-fired power plant.”

The developers are seeking a right of way from the Bureau of Land Management for about 5,200 acres. The area to be disturbed would be less, with the amount depending on which configuration is ultimately approved.

Another proposed decision recommends approval of the Rice Solar Energy Project, a 150-megawatt installation planned at the site of the remains of an abandoned desert military camp called Rice, off Route 62 about 40 miles northwest of Blythe.

The project would occupy about 1,410 acres of a larger private property. The planned installation is a concentrating solar thermal complex at which fields of mirrors called heliostats would focus heat onto a collector near the top of a central tower rising 65 stories above the desert floor.

Molten salt would be used as both a heat transfer and storage medium. The hot liquid salt, at up to about 1,050 degrees Fahrenheit, is to be piped to heat exchangers to heat water and produce steam, which would be used to generate electricity in a conventional steam turbine-generator.

According to the Energy Commission, the salt is a mixture of sodium nitrate, which is a common ingredient in fertilizer, and potassium nitrate, a fertilizer and food additive. The mineral products are to be mixed at the site as received directly from mines in solid crystallized form and would be used without additives or further processing other than mixing and heating. The molten salt has a viscosity and appearance similar to water, the commission said, and is circulated through tubes in the receiver, collecting the energy gathered from the sun.

Stored in a special tank, the molten salt retains heat well, allowing electricity to be generated after sunset. The heat can be stored for several days, according to the developers. The technology was demonstrated at a 10-megawatt test plant called Solar Two that operated from 1996 to 1999 in the Mojave Desert near Barstow, Calif.

The Rice project is proposed by a subsidiary of a company called Solar Reserve. Construction is expected to take about 30 months, with a peak workforce of about 440, according to the proposed decision. The project requires approval from the federal Bureau of Land Management for a proposed electrical tie-in line and a planned substation, which would occupy public land.

The abandoned community known as Rice, where the project is to be built, was the site of a military encampment during World War II that was overseen by Gen. George S. Patton. The site included an Army Air Field and Camp Rice, which was part of the Desert Training Center, California-Arizona Maneuver Area. The area was used to train soldiers for the North African campaign, according to the Energy Commission’s documentation, and Camp Rice housed the 5th Armored Division.

In 1964, the area was used for a military training exercise called Joint Exercise Desert Strike, which, according to the website of the 506th Airborne Infantry Regiment Association, was better known as “The Long, Hot Walk.”

The Camp Rice buildings and Air Field structures are now mostly gone except for crumbling foundations, and the scrub-covered site from the ground is almost indistinguishable from the surrounding desert.