U.S. Department of Energy - Energy Efficiency and Renewable Energy
Tribal Energy Program
Direct Use of Hydrothermal Resources
Hot water from geothermal resources can be used directly to provide water and space heating. Direct use applications include crop drying, industrial processes, resorts and spas; and heating buildings, greenhouses, and fish farms.
Direct use projects can make use of hydrothermal resources with temperatures between about 70°F and 300°F. In a typical direct use application, a well brings heated water to the surface; a mechanical system—piping, heat exchanger, and controls—delivers the heat to the space or process; and a disposal system either injects the cooled geothermal fluid underground or disposes of it on the surface.
The direct use of geothermal resources for heating can significantly reduce overall energy bills. For example, greenhouse growers in geothermal areas estimate that using geothermal resources instead of traditional energy sources reduces heating costs by up to 80%, which can save about 5%–8% of their total operating cost.
Direct use systems do require a larger capital investment than traditional heating technologies, but have lower operating costs and no need for ongoing fuel purchases.
To learn more about direct use applications, visit the following links:
Direct use of geothermal resources — An introduction to direct use applications provided by DOE's Geothermal Technologies Program.
Geothermal Technologies Program: Direct Use (PDF 2.4 MB) — This 16-page publication describes geothermal direct-use systems, and how these systems have been effectively applied throughout the country. It also describes the DOE program research and development efforts in this area, and summarizes several projects using direct use technology. Download Adobe Reader.
The Geo-Heat Center — This DOE-funded institution, located at the Oregon Institute of Technology, provides software, case studies, a quarterly bulletin, and other publications related to direct use of geothermal energy.
"Direct-Use Temperature Requirements: A Few Rules of Thumb" (PDF 190 KB) — Article by Kevin Rafferty from the June 2004 edition of the Geo-Heat Center Quarterly Bulletin. Download Adobe Reader.
Direct use database — A searchable database provided by the Geo-Heat Center.
Photo of a geothermally heated greenhouse in Hooper, Colorado.