Geothermal

U.S. Potential for Enhanced Geothermal Systems

I recently read about a report from MIT that says geothermal energy is a tremendous energy source, and it talks about enhanced geothermal systems that could provide power just about anywhere. Is the US doing anything about developing an enhanced geothermal system project? What do you think about this MIT report? — Ron Martin, New York, New York

Hi Ron, You’re right: a report prepared by the Massachusetts Institute of Technology (MIT) considers the immense potential from Enhanced Geothermal Systems (EGS), sometimes referred to as Engineered Geothermal Systems. The MIT report, called “The Future of Geothermal Energy – Impact of Enhanced Geothermal Systems (EGS) on the United States in the 21st Century,” was released in January 2007. The MIT report suggests that 100,000 megawatts (MW) of electrical generation capacity could be met through EGS by 2050 with a modest investment in Research & Development (R&D). The group that performed the study is highly reputable, with scientists contributing from the European Union and Canada. Before I go into more detail about the study, let me tell you about geothermal technology and where EGS stands. Jefferson Tester, an MIT professor of chemical engineering, said in recent Congressional testimony that “expanding our energy supply portfolio to include more indigenous and renewable resources is a sound approach that will increase energy security in a manner that parallels the diversification ideals that have made America strong.” This includes not only EGS, but also other applications of geothermal energy and other renewable energy sources. As you probably know, geothermal power plants have been producing electricity for many years. Conventional geothermal power plants make use of underground steam or hot water and are known as “hydrothermal” systems. In order for hydrothermal systems to work, they must have: (1) high enough temperatures; (2) water or steam saturation of the field; and (3) good permeability. Rocks are permeable due to minute fractures and pore spaces between mineral grains. With EGS technology, heat is extracted by fracturing rocks underground to make the subsurface more permeable. After the fracturing process, water is added to the system through injection wells. Injected water is heated by contact with the rock and returns to the surface through production wells, as in naturally occurring hydrothermal systems. With an EGS system, the three critical factors listed above (temperature, water, and permeability), are not essential. Even if the water isn’t present or the rock structure isn’t sufficiently permeable, the systems can be “engineered” by manually fracturing the rocks and adding water. Although 100 percent EGS technology is currently in the research, rather than deployment stage, there is potential for research to produce significant amounts of energy in the near-term while developing the techniques and technology to tap the great potential of the earth’s natural heat. As the MIT report points out, geothermal resource development is a continuum. By using EGS techniques to expand production from the hydrothermal resource base, we can help meet current energy needs while developing technology for the future. U.S. demonstrations of EGS technology were underway at sites in California and Nevada, near existing geothermal fields. But recent cutbacks in federal research funding have led to the cancellation of these projects. While EGS potential is significant, the U.S. has unfortunately not done enough to develop the technology. According to Tester’s Congressional testimony, “the geothermal option for the United States has been largely ignored.” Tester continues: In the short term, R&D funding levels and government policies and incentives have not favored growth of U.S. geothermal capacity from conventional, high-grade hydrothermal resources. Because of limited R&D support of EGS in the United States, field testing and support for applied geoscience and engineering research have been lacking for more than a decade. Because of this lack of support, EGS technology development and demonstration recently has advanced only outside the United States, with limited technology transfer, leading to the perception that insurmountable technical problems or limitations exist for EGS. However, in our detailed review of international field-testing data so far, the panel did not uncover any major barriers or limitations to the technology. So how can the U.S. become a leader in EGS development? First, the White House should reinstate funding for the Department of Energy’s Geothermal Technologies program, which has been zeroed out for the second year in a row. Second, the program should be funded at the level needed to advance geothermal technology development. According to the MIT study, a modest investment in EGS over fifteen years — $800 million to $1 billion — would be sufficient to develop EGS potential. That’s roughly what the Bush Administration proposes to spend on fusion energy research in just two years, or less than one-half of the expected cost of one next generation nuclear power plant, as estimated by another MIT study. EGS offers the chance to extend our use of geothermal resources to new geographic areas, including most of the U.S. It also has the potential to expand geothermal energy production in places where conventional resources already exist. For example, one study by the University of Utah’s Energy and Geosciences Institute indicated that an area in Southern California roughly the size of one oil field could produce all of the electricity needed for the state using EGS technology! According to the MIT study, more than 100,000 MW of economically viable EGS capacity can be developed in the continental United States by 2050. That’s enough electricity to power the entire country of Canada, but its only part of the potential contribution geothermal resources can make to meet our energy needs. As National Renewable Energy Laboratory (NREL) researchers Bruce Green and Gerry Nix point out in their recent report Geothermal — The Energy Under Our Feet (NREL/TP-840-40665, November 2006) “the United States possesses vast underground stores of heat whose full potential has yet to be realized.” The Geothermal Energy Association and other organizations are working hard to ensure that we realize that potential in the near future.