Oil and gas are not the only things in the ground that can power our lives. Heat in the form of geothermal energy is rapidly taking its place alongside other sources of renewable energy, buoyed by the lessons learned from decades of drilling for oil.
“Geothermal is this fantastic resource,” said Susan Hamm, director at the Geothermal Technologies Office in the US Department of Energy. “It’s an always-on renewable energy resource that harnesses the Earth’s natural heat. It improves domestic energy security and flexibility.” These benefits and challenges are the basis of the Geo Vision report (https://www.energy.gov/eere/ geothermal/geovision) created by the Energy Department.
Hamm, along with Tim Latimer, the cofounder and chief executive officer of Fervo Energy, a company working on geothermal energy, and Aparna Raman, president of reservoir performance at Schlumberger, spoke during the Unconventional Resources Technology Conference.
Hamm and Latimer laid out the benefits of geothermal sources of energy beyond its renewability. “It provides dispatchable baseload power,” Hamm said. “And this dispatchable nature is really key. You can turn it on, you can turn it off. You can turn it up, you can turn it down.”
“It not only produces clean power,” Latimer added, “it does it around the clock, 24/7. It’s a fantastic complement to wind and solar resources to decarbonize the hardest parts of the electric grid.”
Hamm mentioned that geothermal complements wind and solar by being widely available, pointing out that geothermal sources are available across the United States (Fig. 1). She also touted geothermal’s reliability, saying that, while solar can provide energy 20% of the time and wind 45% of the time, geothermal sources can provide energy more than 90% of the time.
“In order to have a geothermal resource, you need to have three things,” Hamm said. “You need to have heat at depth, which we’ve already shown is everywhere, just in differing amounts. You need to have a fluid in the subsurface, and you need to have pathways for that fluid to move around to get the heat so you can get it back out.” An enhanced geothermal system (EGS) is a system wherein one or more of those aspects is created where it did not previously exist. “You either fracture the subsurface or you add water, or you do both in order to be able to recover that stranded heat.”
Latimer, who began his career as a drilling engineer, turned toward geothermal sources after working in the Eagle Ford shale, where high temperatures were a problem to be solved. In solving the high-temperature problem, he said cues were taken often from the geothermal industry.