Enhanced geothermal systems (EGS), or human-made geothermal energy, holds the potential to power over 40 million American homes and businesses, and is the next frontier for renewable energy deployment. The Geothermal Technologies Office (GTO) EGS program supports research, development, and demonstration projects that guide enhanced geothermal technologies towards commercial viability.
What is an Enhanced Geothermal System (EGS)?
A naturally occurring geothermal system, known as a hydrothermal system, requires three key elements to generate electricity: heat, fluid, and permeability (when water can move freely through the underground rock).
In many areas, however, the underground rock is hot but there is not enough natural permeability or fluids present. In those cases, an enhanced geothermal system can be used to create a human-made reservoir to tap that heat for energy.
In an EGS, fluid is injected deep underground under carefully controlled conditions, which cause pre-existing fractures to re-open, creating permeability. Increased permeability allows fluid to circulate throughout the now-fractured hot rock, and the fluid becomes hot as it circulates. Operators pump the hot water up to the surface, where it generates electricity for the grid.
EGS could facilitate geothermal development beyond traditional hydrothermal regions, thereby extending geothermal energy production nationwide. EGS advances are being demonstrated worldwide today, in both the public and private sectors.
In the United States, the U.S. Department of Energy (DOE) currently funds a major EGS demonstration in Milford, Utah: The Frontier Observatory for Research in Geothermal Energy (FORGE). At the site, researchers have already demonstrated significant improvements in drilling rates and successful rock stimulation.
DOE also previously funded two successful EGS demonstration projects:
- Desert Peak, Nevada: Ormat Technologies stimulated a non-commercial well on the periphery of its operating conventional geothermal system at Desert Peak, Nevada. The stimulation successfully created an EGS reservoir and added 1.7 megawatts (MW) of electricity production at the existing geothermal power plant.
- The Geysers in Northern California: Calpine, the operators of The Geysers geothermal field, deepened and stimulated two previously abandoned geothermal wells. The refurbished wells added 5.8 MW of power to existing generation.
Though not a DOE project, France’s deep EGS project at Soultz-sous-Forêts in Alsace has provided geothermal electricity to the grid since 2011. In 2016, France also opened the Rittershoffen deep geothermal power plant, which provides heat to local industrial plants using EGS technologies.
The Enhanced Geothermal Shot is an initiative to help usher in a clean energy future by bringing EGS to Americans nationwide. It is part of the DOE's Energy Earthshots Initiative to tackle key remaining technical challenges to reaching U.S. climate goals while creating jobs and economic opportunities for U.S. communities.
The Enhanced Geothermal Shot is a department-wide effort to dramatically reduce the cost of EGS by 90%, to $45 per megawatt hour by 2035. Investments in EGS can unlock affordable clean energy for over 40 million American homes and exponentially increase opportunities for geothermal heating and cooling solutions.
For more information, contact DOE.Geothermal@ee.doe.gov.
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