Geothermal is key to clean energy future

Water boils at the surface of a pool at The Geysers, billed as the world’s largest geothermal resource for generating electricity.
Water boils at the surface of a pool at The Geysers, billed as the world’s largest geothermal resource for generating electricity. The Press Democrat file

Gov. Jerry Brown is pursuing a goal for California to get at least 50 percent of its power from renewable energy sources by the year 2030. While the focus has been on solar and wind, geothermal is our oldest and most proven source of renewable energy, and the only source that can ensure a balanced and stable portfolio.

California’s unique geology has created underground pockets of steam and hot water that can be tapped to generate energy. The Legislature declared Thursday as Geothermal Awareness Day – a reminder that as early as the 1960s, long before attention turned to solar and wind, utilities were harvesting this form of energy to power homes and businesses throughout the state.

Ever the pioneer in alternative energy, California built the second geothermal power facility ever used in the world. Although we now value geothermal as a way to reduce greenhouse gas emissions, in those early years it was valued for its reliability.

With California’s abundance of natural underground steam reservoirs, geothermal power plants supply nearly a quarter of the state’s renewable energy. That’s more than solar and hydropower combined, and ranks behind only wind, according to the California Energy Commission.

The world’s largest geothermal resource developed for generating electricity is 70 miles north of San Francisco, where a complex of power plants called The Geysers generates about 36 percent of all the geothermal electricity in the United States, enough to sustainably meet almost 60 percent of power demand for the entire coast from the Golden Gate Bridge to the Oregon state line. The complex supplies 18 percent of the state’s renewable electricity, preventing 2.7 million tons of carbon dioxide from going into the atmosphere, the equivalent of taking 492,100 cars off the road.

Most importantly, geothermal power is the bedrock upon which other, more intermittent renewable energy sources such as solar and wind can be added. Unlike solar and wind, geothermal keeps working after the sun goes down and the wind stops blowing. It is known as a “baseload” energy source because it supplies a constant flow of energy. That means it can be increased, decreased and combined with other power sources to efficiently match energy supply with energy demand.

The governor’s goal will reduce the state’s reliance on energy sources such as coal and nuclear power, but also requires increased focus on maintaining affordable power rates and reliable service for ratepayers. Total success will depend on a diverse and balanced portfolio of energy sources.

No renewable energy source is better positioned than geothermal to help us meet those goals. It is part of our clean energy past, and it’s the path to our clean energy future.

Steve Ponder is executive director of the Geothermal Resources Council, a nonprofit based in Davis.