Jefferson Tester: Geothermal energy is alive and well
Geothermal energy is a way to generate electricity from heat stored deep in the Earth. If you’ve ever visited a hot spring, you’ve felt Earth’s inner heat firsthand. We don’t hear much about geothermal energy, but it’s already being used around the world.
Jefferson Tester: It’s not going to take enormous, new discoveries, new science or technologies to make it work.
Jefferson Tester of Cornell University has led scientific assessments on geothermal for the U.S. Department of Energy, National Academy of Sciences, and Intergovernmental Panel on Climate Change.
Jefferson Tester: Geothermal energy is certainly alive and well and being used around the world in three different ways – to generate electricity, to provide heating for buildings, and using natural sources of steam and hot water, for geothermal heat pumps.
Tester said there are a limited number of natural geothermal systems in relatively isolated spots across the globe.
Jefferson Tester: The United States is actually the leading producer of geothermal-based electricity around the world, with about 3,500 megawatts of capacity. And there are many new power plants and geothermal heat pump systems under construction right now.
As of 2010, less than one percent of electricity in the U.S. is from geothermal sources. But Tester said the U.S. has large geothermal reserves, mainly in the west, that could supply 10 percent of its total electricity by 2050. He spoke of enhanced geothermal technology – drilling deep into Earth – to make this possible. Dr. Tester explained more about the basics of geothermal energy.
Jefferson Tester: There are basically three things that are needed to make a geothermal system work. You need sufficiently hot rock close enough to the surface for whatever your intended end use is. You need to have reasonable permeability or porosity of the rock itself and a sufficient quantity of water or steam, either naturally contained or water that you would put underground to provide a means for what I would refer to ‘mining the heat’ from the subsurface.
He added that in the so-called ‘high-grade hydrothermal systems,’ such as in the geyser fields in Northern California, Iceland or New Zealand, nature has really done all the work. It’s provided all three of these ingredients in a high-grade form. In other areas, around the United States or other parts of the world, one or more of these ingredients is missing. That’s where enhanced geothermal systems, or EGS, would have to come into play.
Jefferson Tester: They’re engineered to emulate the characteristics of these natural systems. Usually this means that we invoke some sort of hydraulic stimulation, we pressurize the rock system to cause it to have a higher permeability and to create connections between a set of injection wells, which are drilled into this hot rock formation, and production wells, at depths where the temperatures would be in the range from about a hundred to three hundred degrees Centigrade, depending on the proposed application.
The American west has some of the easiest to reach reserves of geothermal energy, he said