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Push for always-on California North Coast zero-emissions energy advances

California’s quest for more 24/7 renewable power to rapidly replace natural gas and nuclear energy took another step forward in the North Coast’s massive geothermal field.

Boards of supervisors for two of the three counties asked to buy-in on a geothermal opportunity zone, or GeoZone, have now done so, leaving promoters prepping to call for site, technology and project proposals this spring. On Feb. 8, Sonoma County supervisors voted to join the GeoZone, and Mendocino County supervisors did so on Dec. 7.

Lynda Hopkins, whose 5th District covers northwest Sonoma County, at the board meeting called it an “exciting opportunity” to extend power production in The Geysers area, which is the largest producing geothermal energy field in North America. Hopkins represents the county on the board of Sonoma Clean Power, a community choice aggregation utility for Sonoma and Mendocino counties and a key backer of the GeoZone effort.

“One of the biggest challenges with renewable energy is the variability, which requires us to keep traditional fossil fuel plants online to replace the energy when the sun is not shining or when the wind is not blowing,” Hopkins said.

The existing geothermal plants at The Geysers, mostly operated by energy company Calpine Corp., produce a net of 700 megawatts of power around the clock, accounting for 10% of California’s renewable electricity production and one-third of the country’s geothermal power.

The Geysers geothermal resource area covers 45 square miles straddling Lake and Sonoma counties. It produces dry steam, which can directly turn power plant turbines, a resource that only has its equal in the world in Larderello, Italy, according to Calpine. There are currently 13 geothermal power plants operating there with 321 wells into the hot rock.

“It’s a fantastic asset that we have in Sonoma County, but it has struggled with the amount of water that it uses,” Hopkins said.

As power production started to fall off at The Geysers in the 1980s as dry steam in the hot rock decreased, plans were hatched to recharge the hot rock by pumping water down to replace what was lost to stream and not recovered by condensation. A 42-mile pipeline was built in 2003 to carry 39 acre-feet (12.6 million gallons) of treated wastewater daily from a plant west of Santa Rosa to the geothermal field, which includes the northeast edge of the county as well as southeastern Mendocino and southwestern Lake counties.

That’s supplemented by as much as 28 acre-feet (9 million gallons) of treated wastewater pumped 40 miles daily from Lake County communities to The Geysers, a pipeline first built in the late 1990s to shift from pulling water out of Clear Lake.

California craves round-the-clock zero-emissions energy

The state’s energy planners are leaning heavily on the potential for more geothermal power in the state to replace the Diablo Canyon nuclear plant when it is decommissioned three years from now.

To do that, the California Energy Commission decided to increase production of power from 80% capacity-factor renewable energy — sources that can be depended on to supply electricity much of the time, such as hydro and geothermal — by over 1,000 megawatts in the next few years.

Lake County supervisors have been less enthusiastic about the GeoZone venture, voicing concerns about more water usage, seismic activity, volcanic gas emissions and local use of power generated. After tabling a vote in November, the supervisors on Jan. 25 rejected the proposal to join the GeoZone on a 3-2 vote but expressed interest in revisiting the concept once projects are identified.

Supervisor Bruno Sabatier said he that in addition to concerns about geothermal quakes, emissions of hydrogen sulfide gas from more wells he was worried about any added use of water beyond treated waste.

“The more we continue to experience droughts, the more that's definitely something of concern, as that would be added pressure on the resources that we have,” Sabatier said.

Geof Syphers, CEO of Sonoma Clean Power, responded at the meeting that among the technologies being courted for the GeoZone is closed-loop geothermal technology. It would use far less water than traditional dry-steam systems in use at The Geysers for the past six decades and could dramatically reduce gas emissions. He noted that existing geothermal plants at The Geysers have worked with the Northern Sonoma County Air Quality District to limit such emissions.

With Sonoma and Mendocino counties on board with the GeoZone, requests for proposals on locations for small-scale pilot projects could be issued as soon as this spring.

But already in motion is pilot project by a San Francisco company with its own test of closed-loop geothermal technology at The Geysers. GreenFire Energy on Feb. 17 announced it received a $2.7 million-plus grant from the California Energy Commission to install its Steam Dominated GreenLoop technology in a demonstration project at an existing Calpine well at The Geysers.

“It has plenty of heat and a lot of steam,” GreenFire CEO Joseph Scherer told the Business Journal, referring to The Geysers field. The company’s system uses heat exchangers in the well to transfer heat to a special liquid, which transfers heat to conventional geothermal plant systems on the surface. “It allows us to be able to harvest that heat without removing the steam to the surface.”

The idea is to use far less water in geothermal energy. GreenFire received a similar grant in 2017 for a demonstration project in the Coso geothermal field in the state. Sonoma Clean Power wrote a letter of support to the commission for GreenFire’s latest grant.

An undercurrent to the GeoZone discussion in Lake County is an ongoing conversation over the past few years between local officials and Sonoma Clean Power about the county’s joining the utility. Syphers noted to the supervisors on Jan. 25 that the cost structure for Pacific Gas & Electric power transmission is expected to change after that utility’s Diablo Canyon plant is decommissioned, potentially making Lake County’s use of local geothermal energy more economically feasible.

Lake County in late 2021 inked an exploratory agreement with Trane Technologies to build a form of closed-loop pumped storage hydropower system, shown at right, north of Lakeport. The Trane system would also include connections for firefighters to connect to the water tanks to fight nearby blazes. (U.S. Department of Energy graphic)
Lake County in late 2021 inked an exploratory agreement with Trane Technologies to build a form of closed-loop pumped storage hydropower system, shown at right, north of Lakeport. The Trane system would also include connections for firefighters to connect to the water tanks to fight nearby blazes. (U.S. Department of Energy graphic)

But Lake County is pursuing other technologies for 24/7 renewable power. Last fall, it entered an agreement with Trane Technologies to install a novel form of energy storage that uses solar power to pump water uphill when the sun is up then lets the water flow downhill in the evening to produce power in the evening, when solar production falls off.

Trane is undertaking a feasibility study on what it calls a firemain linked auxiliary supply hydraulic energy storage, or FLASHES, system north of Lakeport. The company also has inked similar agreements elsewhere in the state, with Tuolomne County and the Hidden Valley Lake Community Services District.

Closed-loop pumped hydroelectric power uses large tanks or reservoirs at top and bottom. The firemain aspect is intended to allow rural firefighting crews to fill up trucks or helicopters to battle nearby blazes. While the details on the envisioned Lake County system are thin at this point, Trane officials told Tuolomne County supervisors last fall that a system there would involve a 35 million-gallon upper tank.

The California Department of Forestry and Fire Protection, or CalFire, is neutral on such water storage technologies, but the service likes to have private resources available, like water tanks at remote homes, according to Tom Knecht, with the pre-fire division for the Sonoma-Lake Fire Protection Unit.

“We firefighters are pretty good in state responsibility areas to suss out water sources from air or ground,” Knecht said.

Jeff Quackenbush covers wine, construction and real estate. Before the Business Journal, he wrote for Bay City News Service in San Francisco. He has a degree from Walla Walla University. Reach him at jquackenbush@busjrnl.com or 707-521-4256.

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