An enhanced geothermal system (EGS) produces carbon-free power by harnessing the earth’s heat from far below the ground. An EGS accesses the heat by injecting water at high pressure from wells on the surface. The water creates fractures in deep rock formations, and the rocks, in turn, heat up the water. The water is then pumped back up, carrying enough heat to produce steam for power generation. EGS promises to harness the inexhaustible heat of the earth’s crust to help power the world for generations to come.
Figure 1: An enhanced geothermal system
EGS would provide firm power around the clock while emitting little to no greenhouse gases, complementing intermittent renewables like wind and solar. The International Energy Agency’s Net Zero by 2050 report estimates that 126 gigawatts (GW) of additional geothermal capacity will be needed by 2050 to avert the worst impacts of climate change. That’s about 8 times as much capacity as the world has today. Most geothermal projects draw on conventional hydrothermal reservoirs—natural pockets of heat and water not far below the surface. However, only 2 percent of the earth’s geothermal resources are available through such reservoirs. Future capacity additions must come from EGS, which has the potential to provide 40 times the energy needed to achieve net-zero greenhouse gas emissions globally. 
But tapping into geothermal resources deep in the ground can be quite tricky. Current drilling technologies and techniques are not suitable for penetrating ultra-hot and dry rock formations, making the drilling process time-consuming and expensive. Elevated temperatures and corrosive environmental conditions deep beneath the surface can cause well-construction materials like steel to wear, and drilling electronics to melt. Next-generation high-temperature, high-pressure sensors, drilling tools, and well-casing materials are vital for EGS to become cost-competitive with other power-generation sources.
Figure 2: Diversity of geothermal resources and applications