It’s a hot topic: Geothermal energy, and how USGS science could help harness it
Beneath the Western U.S. lies a vast, largely untapped reservoir of energy: geothermal heat.
A hot planet, a nearly limitless supply of energy
Humans have taken advantage of the natural heat of our planet for thousands of years, for instance by using hot springs to heat ancient homes. But as technology has advanced, the possibilities for accessing using geothermal energy have become expansive, including heating and cooling, electricity production, and even energy storage.
Since the 1970s, scientists at the U.S. Geological Survey have worked to quantify the potential of this enormous resource. Last month, USGS published a new assessment, showing how harnessing geothermal heat in the Great Basin that could be accessed using emerging technologies.
They found that if current technologies work as projected, the Great Basin alone could provide energy to meet 10% of all electricity needs in the U.S. If geothermal technology continues to advance in coming years, the Great Basin could meet far more of the nation’s electricity needs, perhaps even most.
The Geysers Geothermal Field near Clear Lake, California - the largest geothermal power producing system in the world.
The (quantifiable) promise of geothermal energy
During the energy crisis in the 1970s, the U.S. began eyeing geothermal heat as a potentially important source of baseload energy – the base level of demand on electrical grids. Geothermal heat remains appealing as a renewable and reliable resource that could be added to the U.S.’s energy portfolio.
But where are accessible geothermal resources? And how much energy could they provide?
Enter USGS science.
In 1975, the USGS published the first ever assessment of conventional geothermal resources in the U.S., mapping the locations of hydrothermal systems in the western U.S., Alaska and Hawaii. These systems occur in geologically active locations often marked by hot springs and geysers, where naturally circulating groundwater brings the Earth’s heat to the surface. This heated water can then be used to create steam that turns a turbine, generating electricity.
Today, the U.S. produces more power from geothermal power plants than any other country – but power from geothermal still makes up less than 1% of the Nation’s total power generation.
“Our science here at USGS has shown that there is enormous untapped potential for geothermal energy in the U.S. using a range of conventional and emerging technologies,” said Erick Burns, a USGS research hydrologist who leads the Geothermal Resources Investigations Project.
In 2008, the USGS estimated that, using modern technology, the U.S. could generate 9,000 Megawatts of electricity (MWe) from identified conventional geothermal systems alone – or roughly enough to power 5 to 9 million homes.
The USGS also estimated that the U.S. likely contains significant undiscovered conventional geothermal resources, including mostly “hidden” hydrothermal systems that aren’t obvious at the surface (unlike hot springs). Undiscovered resources have an estimated untapped potential of an additional 30,000 MWe – enough to power an additional 18 to 30 million homes, or enough to power every home in California - and, at the high end, Texas as well.
The development of geothermal resources has traditionally been centered on these natural hydrothermal systems, where circulating groundwater brings heat closer to the Earth’s surface.
New technologies, however, are opening up the possibility to access geothermal resources in hot rock without natural circulation, vastly expanding the potential to harness the geothermal potential of the Earth.
New technologies, expanded frontiers
The USGS has estimated that with advances in technology nearly 520,000 MWe could be generated in high-temperature but low-permeability rock formations. This is more than enough energy to power every home in the U.S.
One way of accessing these resources is through Enhanced Geothermal Systems, in which permeability is created, often by injecting high-pressure water into the Earth to create fractures that allow circulation of water to circulate through hot rocks and be extracted for the generation of electricity.
“We anticipate that technology transfer from the oil and gas industry will help advance EGS technology. EGS technology is also benefitting from focused research supported by the Department of Energy.” said Burns, “These technological improvements have opened a new frontier for geothermal potential.”
Burns said there is significant potential for EGS systems throughout the Western U.S., particularly in the Great Basin, which includes most of Nevada and parts of Utah, Idaho, Wyoming, Oregon and California. Here, tectonic activities have stretched the crust of the continent thin, and the geologic conditions are regularly favorable for allowing the creation of open fractures.
The team hopes to expand future detailed assessments of EGS and other unconventional resources to other parts of the U.S., including by using machine learning and a range of other computational tools.
The USGS is also looking at ways of assessing the potential for other next generation geothermal technologies. For instance, USGS is developing methods to assess geothermal resources that exist in rock formations that are not hot enough to generate electricity but could be used to heat and cool buildings directly. Currently, around one-third of all energy in the U.S. is for heating and cooling.
The USGS is studying the potential for using geologic formations and the Earth’s insulating qualities to store hot or cold liquids below the Earth’s surface, essentially turning the Earth into a battery where excess thermal energy can be stored until ready for use.
Science for the future
Geothermal energy could be a powerful part of the U.S. energy portfolio: it’s renewable, it’s domestic, and the U.S. contains unique resources that could increase energy independence.
“USGS science is paving the way forward to better understand and utilize the Nation’s potential for geothermal energy now and in the future,” said Alicia Lindauer, program coordinator for the USGS Energy Resources Program.
