Sonoma County, Windsor to use holding ponds for solar power

In a creative approach to producing clean, cheaper electricity, plans are moving ahead to install floating solar panels on holding ponds operated by the Sonoma County Water Agency and the Town of Windsor.

One of the more appealing aspects of the floating panels is they don't take up agricultural land, open space or scenic corridors, in addition to helping achieve climate protection goals by reducing greenhouse gas emissions.

County Supervisor Shirlee Zane called it “innovative technology, thinking outside the box,” when supervisors, acting as Water Agency directors, approved an agreement earlier this month with Pristine Sun Corp. to pursue a floating array at the Airport-Larkfield-Wikiup Sanitation district's Oceanview Reservoir, off Mark West Station Road.

The action followed previous approvals by the board for San Francisco-based Pristine Sun to develop floating solar photovoltaic systems at six other ponds operated by the water agency, including two north of the Charles M. Schulz-Sonoma County Airport and four in Sonoma Valley.

The solar panels on the half-dozen ponds are part of a lease agreement the county struck with Pristine Sun in 2015 to provide electricity to Sonoma Clean Power, generating 12.5 megawatts, or enough to power 3,000 homes.

“By the end of 2017, we should have a few up and running,” said Water Agency Principal Engineer Dale Roberts, adding the design phase has taken longer than anticipated.

Sonoma Clean Power overtook PG&E two years ago as the default electricity provider for all of Sonoma County, except Healdsburg, which has its own municipal power company.

Sonoma Clean Power provides electricity to more than 195,000 commercial and residential accounts.

The solar power project will help fulfill one of Sonoma Clean Power's central goals of developing local sources of renewable power.

California law requires public utility companies regulated by the state to source at least 50 percent of their electricity from renewable sources, such as wind, geothermal or solar by 2030.

Floating solar panels have become more commonplace in countries such as Japan, Israel and the United Kingdom. In Sonoma County, a handful of wineries have them.

The Windsor Town Council earlier this month directed the town manager to begin contract negotiations with another renewable energy developer, Ciel et Terre, to install floating solar panels on Windsor's largest water reclamation pond, located at the sewer treatment plant off Windsor Road.

The 3 megawatt array will consist of 10,700 floating panels spread over 9 acres of the pond, which holds the highly treated water for irrigation and other uses.

The town would not bear any of the upfront equipment costs of approximately $7 million to $8 million.

Under the proposed 25-year agreement, Ciel et Terre, an international company with an office in Petaluma, will build, own and maintain the equipment and the town will buy the electricity produced.

The electricity, purchased at a fixed rate, is projected to be sufficient to fulfill almost all the demands of the corporation yard and treatment plant and at the same time be less expensive, with the town anticipated to save $8.8 million over 25 years.

Windsor Town Councilman Mark Millan, who works as a wastewater consultant, called the project “pretty interesting and unique.”

Windsor Public Works Director Toni Bertolero said if “anything breaks, they are required to come in and fix it.”

The county struck a similar deal with Pristine Sun.

Although most of the electricity generated by the floating panels on the county's ponds will be sold to Sonoma Clean Power, electricity generated at the Oceanview pond will be sold to the Water Agency to offset its power consumption, with an estimated savings to the agency of $33,000 annually.

Outgoing Board Chairman Efren Carrillo said the potential risk to the county is not significant because Pristine Sun will own, finance and obtain approvals for the project.

You can reach Staff Writer Clark Mason at 707-521-5214 or clark.mason@pressdemocrat.com.