Geothermal energy technologies convert the earth's internal heat energy to usable energy products (see http://www1.eere.energy.gov/geothermal/ for information on geothermal electrical generation and heat pumps).
Where geothermal resources (geologic formations with elevated temperatures) lie relatively close to the surface, direct conversion of geothermal heat to electricity is possible. For example, the nation of Iceland produces the majority of its electrical energy from geothermal energy reservoirs, and western US is home to a number of geothermal electrical generating plants. In some cases (including many of locations in Iceland), geologically pressurized and heated water relatively close to the surface is used to generate electric power. The geological conditions of Yellowstone National Park, for example, would be favorable for geothermal energy development if not for the Park's current use and high value as a recreational resource.
Geothermal electricity can also be generated where geothermal heat reservoirs are located deep below the surface. Development of such resources occurs by drilling from the surface into heated rock formations. In some cases, energy drawn from such formations thousands of feet below the surface is used for electricity production. Fluids from the surface are injected into the heated rock formations, creating a pressurized steam that can be used to generate electric power at the surface.
The state of Virginia does not contain any electrical generating plants that use geothermal energy. The state's greatest potential for geothermal development occurs in western Virginia, including Bath County's Warm Springs area.
Geothermal Heat Pumps
Homeowners and commercial establishments throughout the state use a more easily available form of geothermal energy, as "geothermal" heat pumps are used to heat and cool buildings. The heart of such an installation is a standard heat pump, an electrically powered device that heats and cools interior space by exchanging heat energy with the ambient environment. A heat pump is similar to a common refrigerator, which removes heat from a cooled interior space and expels it to the environment through condensing coils. A heat pump can cool a building's interior through an operation that is very similar to a refrigerator or an air conditioner, and it can heat the same interior by reversing the energy flow. While a standard heat pump's condensing coils are commonly placed outside the home, a geothermal heat pump's coils are placed below the earth's surface. Because the earth is generally cooler in summer and warmer in winter than the outside air, the geothermal heat pump is able to operate more efficiently (i.e., using less electricity) than a standard heat pump installation.
In order to install a geothermal heat pump, the condenser coils must be buried in the ground. A common practice is to remove the earth from an area outside the home that is being leveled (such as a front lawn) in order to bury the coils a few feet below the surface. It is also possible to drill holes in the earth's geologic structure, similar to those used for a water well, as a means of placing the heat pump's condenser coils well below the surface.
- 1 Labled in EIA report as GECCB
- 2 Labled in EIA report as GERCB
- 3 Labled in EIA report as GETCB
- Totals may not equal sum of components due to independent rounding.
Virginia Geothermal Production Data
Virginia Case Studies
The following are case studies of Virginia facilities using geothermal heat pumps to reduce consumption of electrical energy for heating and cooling. For a general description of these systems' operation, please reference: http://www.geoexchange.org/public/how_it_works.htm