Sonoma Clean Power’s initiative to secure affordable, reliable clean energy for our region.
Subscribe to email updatesSonoma Clean Power, in partnership with the counties of Sonoma and Mendocino, is leading an effort to build 600 megawatts (MW) of new, next-generation geothermal energy in our service area.
This initiative is called the Geothermal Opportunity Zone, or “GeoZone”.
Our goal is to secure a long-term supply of affordable, reliable clean energy for our region, while helping to fight the global climate crisis.
Map of the GeoZone early interest area.
The GeoZone aims to deliver important benefits to Sonoma and Mendocino counties.
Next-generation geothermal technologies have the potential to provide around-the-clock renewable resources for California’s electric grid and end our dependency on fossil fuels once and for all. These new technologies use less water and can be developed in far more locations than conventional geothermal.
Sonoma Clean Power encourages early and frequent public engagement with our GeoZone effort. Through community presentations, town halls, public meetings, and more, we hope to provide a variety of opportunities for the community to ask questions and establish preferences that can steer the design of new, local geothermal development.
Sonoma Clean Power’s GeoZone partners are required to develop projects that are responsive to our community values. While our partners are taking the lead on the project-specific details, we at Sonoma Clean Power will continue to facilitate public engagement as project locations and technologies are identified.
Please contact us with questions or comments, and sign up for our GeoZone email updates.
Sonoma Clean Power includes a GeoZone update at every monthly Community Advisory Committee meeting and invites the public to join and provide input.
Because geothermal power can generate clean energy 24/7, it has significant potential to replace natural gas as a reliability resource on a large scale.
If the GeoZone is a success, Sonoma Clean Power can provide 100% clean energy to our customers around-the-clock and stop sending millions of dollars to natural gas power plants.
Limits of Conventional Geothermal
Over the last decade, there has been minimal growth in geothermal capacity in the state. Our region is already home to the Geysers - a world-class geothermal resource - but its existing output is not enough to support the clean energy transition.
In addition, all existing geothermal resources at the Geysers are contracted for, meaning Sonoma Clean Power cannot purchase more energy from their facilities at this time.
A natural gas power plant in the Los Angeles area.
The Geysers is special because it sits in a volcanic zone with underground water flowing through permeable rock. Next-gen geothermal has found ways to expand renewable power production in areas without these conditions.
Near-term increases in California’s geothermal capacity will primarily come from Nevada or the Imperial Valley in Southern California. Long-term, the GeoZone is well-positioned to provide a significant amount of geothermal power locally and statewide.
Because geothermal power can generate clean energy 24/7, it has significant potential to replace natural gas as a reliability resource on a large scale. If the GeoZone is a success, Sonoma Clean Power can provide 100% clean energy to our customers around-the-clock and stop sending millions of dollars to natural gas power plants.
Conventional geothermal power production works by using underground heat to produce electricity. There are places where magma comes close to the Earth’s surface and warms the solid rock directly above it to very high temperatures.
Conventional geothermal requires three things: 1) the presence of hot solid rock near the Earth’s surface, 2) naturally permeable rock, and 3) a steady supply of water.
Energy is generated by sending water down a pipe into the field of hot rock and passing it through the rock’s fractures. As the water heats up it creates steam, which comes back up another pipe and powers a turbine to generate electricity.
Conventional versus next-generation geothermal energy production.
In 2022, the GeoZone effort kicked off with Sonoma Clean Power issuing a Request for Information to identify companies with capabilities to deliver next-gen geothermal resources through a public-private partnership in Sonoma and Mendocino counties.
This process was modeled after the partnership established by Redwood Coast Energy Authority (the Sonoma Clean Power equivalent serving Humboldt County) to pursue offshore wind development.
After a comprehensive evaluation process, which included review by industry experts, a local permitting agency, and public stakeholders, the SCP Board of Directors selected three finalists with successful development experience and technologies that met Sonoma Clean Power’s selection criteria, including:
Since then, further advancements in next-generation geothermal have continued to validate Sonoma Clean Power’s interest in these technologies.
In March 2024, the U.S. Department of Energy published a report highlighting research findings that widespread deployment of next-generation geothermal technologies could cut the cost of achieving 100% clean energy in the Western grid by as much as 25%, compared to the status quo.
SCP’s three development partners are Eavor Inc., Chevron New Energies, and Cyrq Energy. Every partner has proposed different next-generation geothermal technologies to test and explore within the GeoZone, each with their own advantages. To increase the chances for success, Sonoma Clean Power is pursuing multiple emerging technologies and private partners.
Eavor, Inc. plans to pilot an advanced closed-loop geothermal system. This technology involves drilling a closed loop of pipes through a field of solid hot rock under the Earth’s surface to allow water to move through.
Once heated, the water is drawn up to the surface and the heat is extracted to produce electricity. The cooled water is then sent back down to be used again in a closed loop. Because the water stays within the pipe system, this closed loop technology has the potential to use significantly less water than many other energy resources.
Chevron New Energies is aiming to pilot an Enhanced Geothermal Systems (EGS) project. EGS creates pathways for water to move underground, similar to the natural pathways found in conventional geothermal fields, by creating cracks to connect two wells in deep hard rock far below the earth’s surface. Water is pumped through the fractures, heated by the rock, and used to drive an electric turbine at the surface.
Although EGS is a new technology, it is rapidly maturing. This is largely due to improvements in horizontal drilling and hydraulic fracturing technologies from the oil and gas industry. For more information on how EGS is superficially similar to, but significantly different from fracking for oil and gas, please see our EGS attachment.
In early 2024, Chevron New Energies’ GeoZone project was selected to negotiate a grant award from the Department of Energy’s Geothermal Technology Office to help fund early GeoZone demonstration activities.
Cyrq Energy plans to deploy thermal energy storage technology at existing geothermal power plants at the Geysers to improve their flexibility and reliability. In short, this storage would enable conventional geothermal systems to produce more power when we need it, and less when we have other renewable sources in abundance.
During the day when there is ample solar power on the grid, instead of producing electricity, the geothermal system charges up Cyrq’s thermal energy storage composed of concrete blocks. In the evening, when solar generation drops but energy consumption increases (as people come home and turn on their lights and appliances), the stored heat is used to superheat steam entering the geothermal plant, increasing the system’s output by about 45%.
Important documents and records from the GeoZone initiative, including the resolutions formalizing the creation and membership of the GeoZone, the solicitation for private partners, and agreements with other agencies.
