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GMEG - Geology, Minerals, Energy, & Geophysics Science Center

Geothermal Resource Investigations





Issue: Based on current projections, the United States faces the need to increase its electrical power generating capacity by approximately 300,000 Megawatts-electrical (MWe) over the next 20 years. A critical question for future energy planning is the extent to which geothermal resources can contribute to this increasing demand for electricity. Geothermal energy constitutes one of the nation’s largest sources of renewable and environmentally benign electric power, yet the installed capacity of approximately 3000 MWe fall short of the estimated resources. Under the mandate of the Energy Policy Act of 2005, the USGS Geothermal Resource Studies Project in 2008 produced a new assessment of the identified and undiscovered moderate-temperature (90 to 150 °C) and high-temperature (>150 °C) conventional geothermal resources capable of producing electric power. The resulting mean estimate of potential power production capacity from identified geothermal systems (including those currently under production) is approximately 9000 MWe, and the mean estimate of potential capacity from undiscovered resources is approximately 30,000 MWe, all concentrated in the western United States.

Objectives: The ultimate goals are to develop improved techniques for assessing geothermal resources and expand the existing assessment to cover both conventional and unconventional geothermal resources across the entire United States in order to meet the requirements of the Energy Independence and Security Act of 2007. We are addressing these goals through a number of activities that are divided into six science tasks.

  1. Work with the DOE-sponsored National Geothermal Data System to compile and make publicly-available relevant data from geothermal exploration, development and assessment studies.
  2. Conduct targeted, prioritized field investigations of certain hydrothermal systems in order to obtain critical data that will allow us to develop better models for the spatial and temporal occurrence and evolution of natural hydrothermal systems.
  3. Incorporate the results of field studies with numerical and analytical life-cycle models for hydrothermal systems to develop improved, physically-based methods of assessing undiscovered geothermal resources.
  4. Adapting our conventional geothermal resource assessment methods to the evaluation of unconventional Enhanced/Engineered Geothermal Systems.
  5. Starting an expanded effort to assess deep sedimentary basin geothermal resources.
  6. Launching a new study of the impacts of geothermal development, with a focus on monitoring the effects of expanded geothermal production in Long Valley, CA.

Relevance: The results of these assessment and research studies will provide State and Federal government policy makers with the information they need to estimate the potential contribution of geothermal energy to the nation’s energy mix. Many states have either adopted or are considering renewable portfolio standards which require a minimum percentage (typically 5 to 10%) of renewable sources of electric power. A necessary element in both the establishment and fulfillment of these standards is a reliable estimate of the distribution and size of the domestic geothermal resource.


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