Updating the Classification of Geothermal Resources

Abstract

Resource classification is a key element in the characterization, assessment and development of energy resources, including geothermal energy. Stakeholders at all levels of government, within the geothermal industry, and among the general public need to be able to use and understand consistent terminology when addressing geothermal resource issues such as location, quality, feasibility of development, and potential impacts. This terminology must encompass both the fundamentally geological nature of geothermal resources and the practical technological and economic aspects of resource exploitation while remaining understandable to the broad community of non-specialists. In the United States, the classifications applied to geothermal resources are primarily the legacy of resource assessment and characterization studies conducted in the 1970s during a time of rapid development and new interest in geothermal energy. That many of the standards developed during that time are still in use today is a testament to the quality of the original work. However, developments over the past 30 years, especially advances in geothermal technology, have expanded the scope of exploitable geothermal resources beyond the earlier classifications. As part of its ongoing work to assess geothermal energy resources in the United States, the U.S. Geological Survey (USGS) is working with the Department of Energy (DOE), the geothermal industry, and academic partners to develop a new geothermal resource classification system that will reflect the current state of knowledge regarding geothermal technology and serve as a effective means of characterizing, quantifying, assessing and communicating important aspects of geothermal energy potential. This paper describes the scope of the effort as well as initial progress in establishing the new classification terms.