3 new-tech geothermal plans to be considered for boosting power at The Geysers

Three cutting-edge technologies that could give California a big boost in always-generating emission-free electricity are being eyed for pilot projects in and around massive geothermal field straddling Sonoma, Lake and Mendocino counties.

The Sonoma Clean Power board, made up of public officials from city and county governments the utility serves in Sonoma and Mendocino counties, on March 2 is set to consider cooperation agreements with Canada-based Eavor Technologies, Chevron New Energies and Salt Lake City-based Cyrq Energy. Each agreement calls for building a demonstration power project, each capable of generating up to 20 megawatts If successful, each plan would scale up to production of 200 megawatts.

The agency’s Community Advisory Committee on Feb. 16 recommended board approval of the agreements.

If the three pilot projects are successful, the full-scale projects producing a combined 600 megawatts would move California toward its goal of 1,160 megawatts of new geothermal power generation over the next five years. It would also increase by 85% the current roughly 700 megawatts of power output from existing plants in The Geysers.

The balance of that California Public Utilities Commission goal for new geothermal power statewide is expected to come from projects in Nevada and the Imperial Valley.

But that statewide projection for new geothermal power is based on existing technologies, and Sonoma Clean Power officials think new tech can push that envelope significantly.

“In its most recent internal portfolio planning, (Sonoma Clean Power) sees a future where as much as 40% of its energy supply will be sourced from advanced geothermal resources,” said CEO Geof Syphers.

As of Oct. 1, 2022, half the agency’s power sold to customers came from renewable sources, and geothermal was the biggest of those sources (20%), followed by biomass and biowaste (11%), solar electric (10%) and wind (9%). Most of the remainder (41%) comes from large-scale hydroelectric plants, with 1% from nuclear. Sonoma Clean Power’s 100% renewable-power plan (EverGreen) sources 83% from geothermal and 17% from solar.

In 2021 the California Public Utilities Commission voted to update its plan for grid energy resources with more geothermal as well as solar and battery storage.

Late that year, Sonoma Clean Power unveiled its plan for a geothermal opportunity zone, or GeoZone, to spur increased power production from the Clear Lake Volcanic Field that supplies The Geysers power plants with steam to generate electricity.

“Baseload power is only effective means to shut down fossil fuel completely,” Syphers told the advisory committee. “Even with an unlimited amount of solar and wind and batteries, we can’t shut down (natural) gas plants at all, because they have to be ready when the sun is not shining and the wind is not blowing and the batteries are empty.”

The first plant was built at The Geysers in 1959. More were added during the 1980s, and the last new one was completed in 1989 as steam output and power production started dropping. To recharge the geothermal steam reserve, treated wastewater started being piped in from Clearlake 1997 and Santa Rosa in 2003 and injected deep underground.

The key requirements for the GeoZone proposals were scalability, minimal water coming in or going out, and a small surface footprint.

Eavor and Chevron’s proposals involve closed-loop technologies, which circulate fluid inside tubes going down into the hot rock and coming back up with heated fluid. That limits the amount of new water that has to be added for moisture lost in traditional geothermal plants before reinjection down into the rock.

Cyrq’s idea is to use a renewable energy like solar to “charge” a storage unit with heat next to an existing plant at The Geysers, and when the sun goes down, the unit would superheat incoming steam to produce more power during the evening hours when the grid’s solar electrical output starts to wane.

Based on a model from a retired plant at The Geysers, Cyrq estimates it can increase power output by 110% while reducing water consumption per megawatt-hour by 43% at night.

“I think closed-loop technologies are what we’re really aiming for,” said Woody Hastings, polluting-fuels phaseout manager for The Climate Center, a Santa Rosa-based advocacy group.

He said that key to the GeoZone project will be “environmental and social safeguards,” particularly ample input from residents and other stakeholders around the project sites.

If Sonoma Clean Power’s board approves the cooperative agreements at the March meeting, the agency plans to hold its first post-agreement public stakeholder meeting this spring. The first stakeholder meeting was in June.

The agency also is in the midst of applying for Department of Energy grants to “buy down” the cost of the pilot projects that would have to be paid by customers to a level that would be market-rate power, according to Syphers.

“If we get a larger grant, the larger system could be built and there would be market-rate (power) on more of it,” Syphers said. “It is scalable.”

The grants sought range from $4 million to $50 million, but Syphers said the projects could end up with funding somewhere in the middle of that.

Jeff Quackenbush covers wine, construction and real estate. Before coming to the Business Journal in 1999, he wrote for Bay City News Service in San Francisco. Reach him at jquackenbush@busjrnl.com or 707-521-4256.

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