Enhanced geothermal systems (EGS), or human-made geothermal energy, holds the potential to power American homes and businesses nationwide and is the next frontier for geothermal energy deployment. The Office of Geothermal (OG) EGS program supports research, development, and demonstration projects that guide enhanced geothermal technologies towards commercial viability.
A naturally occurring geothermal system, known as a hydrothermal system, requires three key elements to generate electricity: heat, fluid, and permeability, which is when fluid 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 (EGS) 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 to create new fractures and cause pre-existing fractures to re-open, creating permeability. Increased permeability allows fluid to circulate throughout the more 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. Watch a video to learn more about the steps and benefits in EGS development.
Other next-generation geothermal power generation technologies include closed loop geothermal systems and superhot geothermal systems. Closed loop geothermal systems do not rely on a fracture network. Instead, these systems are somewhat akin to a “radiator”—a series of closed pipes underground that circulate water and working fluids to absorb heat from the subsurface and bring it to the surface to produce power. Superhot geothermal systems tap resources at >375°C. Water injected into these extremely hot environments becomes so hot that it has the properties of both liquids and gases, allowing the superheated water to gather very large volumes of heat energy. At the surface, it can be used to produce power at several times the power density (amount of power per unit volume) than lower-temperature rock.
EGS and other next-generation geothermal technologies 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.
