by John King: Last year, the California Public Utilities Commission (CPUC) approved a historic decision ordering utilities to procure 11.5 GW of clean energy to come online between the years 2023 and 2026…
Meeting this directive is especially daunting as the inherent intermittency of solar and wind have led to increased grid strains. Most storage technologies deployed today are costly and deliver only hours or days of backup power. As extreme weather events in California worsen year after year, lesser-known but proven viable technologies will be critical to meeting the state’s climate and resilience goals. One such solution lies in abundance in the very bedrock of our state—and can supply the energy equivalent of a billion Tesla Powerwalls—offering the Public Utilities Commission a path to increasing the state’s access to clean and resilient power.
Geological Thermal Energy Storage (GeoTES) technology is a hybrid geological solar power plant that uses existing oil drilling infrastructure to store carbon-free thermal energy underground in massive quantities. Clean energy can be stored underground at oil well sites for six months or longer and can be extracted and converted to electricity at any time using traditional geothermal power generation technologies. The National Renewable Energy Laboratory (NREL) estimates that geological thermal energy storage could cost ratepayers ten times less than the best technologies on the market, and it can be deployed across much of the United States where sunlight and sedimentary formations are plentiful.
Will it Work?
Over the last sixty years, the California oil industry has employed enhanced oil recovery (EOR) practices by which steam is injected into the ground to produce oil, and spent billions optimizing thermal efficiency techniques in the process. From this data, we know that 70 percent of thermal energy sent into the ground stays there, and for months at a time. Replacing natural gas with solar power to create steam for EOR operations has already been proven at scale in a number of projects, including Chevron’s Coalinga project in California.
How Much Will it Cost?
Six decades of EOR activities in California offers more than proof of concept. It provides immediate access to billions of dollars worth of existing facilities, including more than 100,000 pre-drilled wells and supporting surface infrastructure. In addition to wells, California has supported the deployment of gigawatts worth of special-purpose power plants that send waste steam to EOR wells since the 1980s. These plants already have transmission infrastructure in place, completed grid impact studies, and have been putting power on the grid for decades.
The state’s EOR oil production has been declining in output for years, leading to a decline in steam demand and causing approximately 2 GW of this special purpose capacity to sit idle – enough to power over a million homes. California can put these plants back to use and reconfigure them to run on zero carbon geosolar steam at a fraction of the cost of a greenfield power plant. Finally, the EOR retrofit approach makes CSP eligible for California’s Low Carbon Fuel Standard Program (LCFS), which offset much of the costs through credits.
Can it Scale (quickly)?
GeoTES offers significant scalability advantages with respect to cost and timelines of transmission line upgrades and expansion. It will take about 20 years to make transmission upgrades plus $11.65 billion in out-of-state wind power to support full decarbonization of California’s grid. In addition to the 2 GW of EOR special purpose capacity and transmission capacity sitting idle in San Joaquin Valley that can be tapped at any time, building in-state transmission lines for GeoTES plants requires far shorter planning and construction timelines than interstate power lines for distant wind farms. Moreover, GeoTES offers 80 percent capacity factor compared to wind’s 33 percent capacity factor, which means it costs less to deliver this energy.
GeoTES is the low hanging fruit for California’s energy transition
Despite global calls for electrification and reducing the economy’s reliance on fossil fuels, our society still depends on oil and the industry isn’t going away anytime soon. The EOR industry in California spends over $1.3 billion on thermal energy annually to extract oil at well sites, which is harmful to the environment since natural gas carries carbon emissions. If just 20 percent of California’s 100,000 oil and gas wells were retrofitted for geothermal energy storage, the state would benefit from an additional 100 TWh of clean energy annually, which exceeds the total combined output of all the natural gas power plants in the state.
California faces a real opportunity, as the value equation is increasingly dominated not by the cost to generate electric power, but the cost to store energy. The energy storage challenge is so significant that the CPUC procurement has called on 1 GW of “nascent or as-yet-undefined technologies” to help solve it. Taking advantage of the enormous solar battery already under our feet is a win-win for the energy transition, offering a tool for oil industry decarbonization while providing clean low-cost electricity and an additional lever in the fight against climate change all in one.
