Brightsource's 500-megawatt Rio Mesa solar thermal project is being shelved after multiple delays, but the company is forging ahead with two similar projects that are further along in development. A Brightsource spokesperson confirmed the power purchase agreements (PPA) with Southern California Edison (SCE) for both Rio Mesa 1 and Rio Mesa 2 have been cancelled, and the permitting process for both sites have been suspended with the CED, though the company hopes to keep them available for future project consideration.

The proposed Rio Mesa project consists of two 250-megawatt (MW) (nominal) concentrated solar thermal power plants on 4,000 acres on the Palo Verde Mesa in Riverside County, California, 13 miles southwest of Blythe. Anticipated construction was to begin in 2013 and be completed in 2016.

In October the California Public Utilities Commission (CPUC) rejected the PPA plan for Rio Mesa 1, citing poor price and value compared to other recently approved contracts and to other solar thermal projects offered to SCE. The CPUC did, however, approve Rio Mesa 2's PPA because of its importance to Brightsource's technology development plan to incorporate molten salt storage.

Why the decision now to put the Rio Mesa projects to sleep? After more than a year of permitting review, "there remained a number of areas at the Rio Mesa site which required additional analysis," the spokesperson acknowledged. These included uncompleted geoarchaeological and archaeological studies, surveys of birds and bats and late-season botany, and clarification of project acreage and further impact assessment (e.g. on desert tortoise and water delineation). And last year Ice Age fossils were discovered under the project site, necessitating a paleontological resources study.

In December the CEC asked for a six-month extension of the preliminary environmental impact report originally scheduled for this month, adding further delays to the process.

With permit approval from the California Energy Commission (CEC) and Bureau of Land Management (BLM) required before construction could begin on schedule later this year, "the inability to resolve the concerns in a timely manner led us to conclude that we could no longer meet the commercial terms of our PPA," the Brightsource spokesperson said.

Undeterred, Brightsource is turning its attention to a similar project further along in the development process: Palen, a dual 250-MW install in Riverside County, Calif. acquired from bankrupt Solar Millennium in August 2012. Palen already has a CEC final decision for construction and operation of a 500 MW solar thermal plant, completed environmental review (NEPA) and "was very close" to receiving a BLM Right of Way Grant in 2010, the Brightsource spokesperson said. It is located within both the Desert Renewable Energy Conservation Plan (DRECP) area and one of the Solar Energy Zones established pursuant to the Federal BLM's Programmatic Environmental Impact Statement (PEIS).

Moreover, changing Palen's original parabolic trough technology to Brightsource's own "power tower" technology (the company filed a CEC amendment petition in December) will make it more environmentally suitable. As in the Rio Mesa and the under-construction 377-MW (nominal) Ivanpah project, a field of tracking heliostat mirror fields (approximately 85,000 per plant) surrounds a solar power boiler on a 750-ft concrete tower; concentrated sunlight hits the boilers' pipes, heating water to create superheated steam which is pumped into a turbine. Specifically the technology switch will reduce the project's footprint by about 13 percent (to ~3800 acres) vastly reduce land grading (from 4.5 million cubic yards down to 200,000), and reduce water usage by a third (300 acre feet/year to 201 AFY). It also removes the need to relocate an existing SCE 161 kV transmission line.

A revised development plan for Palen is being prepped for the BLM "within the next few weeks," the spokesperson said; decisions on both are expected by year's end, with construction beginning soon after. A formal PPA isn't required for the CEC schedule, but the company expects to make an announcement "in the next couple of months well in advance of the final permit issuances." While citing confidentiality, the spokesperson added the utility partner "will likely be one of our current customers."