What is Geothermal Energy?
Geothermal energy is produced by harnessing the heat of the Earth. Geothermal resources have been harnessed for centuries, beginning in direct use cases such as heating and bathing. Modern geothermal resources began in Boise, Idaho in the 1890s to heat commercial and residential buildings.1,2 Geothermal energy for electricity generation began in the 1960s in the Geysers region of California, the world’s most active geothermal field in electricity generation capacity.3
Geothermal Heat Pump
Enhanced Geothermal Systems (EGS)
Geothermal energy can be incredibly diverse. Historically, there have been two main ways to harness geothermal resources – through geothermal heat pumps or hydrothermal resources. Geothermal heat pumps are an example of direct-use, which captures the heat from geothermal resources and redirects the energy for beneficial uses such as space heating and cooling, which utilizes the temperature difference between the ambient air and the temperature of the geothermal resource. Hydrothermal resources use existing hot water or steam in naturally occurring regions, where the resource is at the Earth’s surface or comes close to the surface. Hydrothermal steam or hot water can also be captured to drive a turbine, similarly to thermal electric power generation or hydropower, generating clean electricity.4
Geothermal energy is a clean, renewable resource available in most regions. A recent DOE study, GeoVision, highlighted the potential to combine other energy sector technologies with geothermal energy to tap into regions once thought impossible. These are called enhanced or engineered geothermal systems (EGS), where existing and safe oil and gas technology is utilized to access larger geothermal resources or to create artificial reservoirs through the injection of water in hot rocks.
EGS is considered an unconventional resource when compared to hydrothermal geothermal energy. EGS can be found at any temperature above “ambient temperature” where an energy conversion can occur.5
According to GeoVision, improved technology development and reduced costs could increase geothermal electricity generation to an estimated 60 GW of always available, flexible, clean, and dispatchable electricity.6 When comparing geothermal energy to other renewable resources such as wind and solar, geothermal energy’s generation capacity can be 2-4 times greater. To ensure equal participation of clean energy resources, and to unlock the 60GW of geothermal potential, geothermal energy policy must be reformed.
A Geothermal plant will generate 2-4 times as much electricity as a wind or solar plant of the same capacity
How to Reform Geothermal Policy
Reorient and bolster geothermal research, development, and demonstrations to include EGS while improving technology development for heat pumps and conventional hydrothermal resources.
Dots Indicate Existing Hydrothermal Sites
Shaded Regions Are Potentially Suitable for EGS
- Mink, L.L. 2017. “The Nation’s Oldest and Largest Geothermal District Heating System.” Geothermal Resources Council Transactions, Volume 41: 205-212. ⬏