Geothermal Energy

Geothermal energy technologies use heat within the Earth as a source of energy. This heat comes in the form of hot water and steam, which can be used to generate electricity for the grid. Geothermal heat can also be used on a smaller scale to heat and cool homes and businesses. This type of energy is sustainable, reliable and clean domestic resource.

Where is geothermal energy available?

Parts of the western U.S., Hawaii, and Alaska contain some of the best sites for geothermal power plants. These areas possess the most accessible geothermal reservoirs, and geothermal power plants have already been built in some of these states. Many other states have some areas with the ability to provide power from the earth’s heat.

How do the plants convert hot water and steam into energy?

There are several kinds of geothermal power plants: dry steam plants, flash steam plants and binary cycle plants. Each uses a different method. Dry steam plants use reservoirs of steam, and flash steam plants and binary cycle plants use hot water reservoirs to produce steam. Generators in all of these power plants are activated by steam turning a turbine to produce geothermal electricity.

Sounds great, why aren’t we all using geothermal power?

The number of locations suitable for a geothermal energy plant is small. When a site is determined to be ideal and a plant is constructed, there is no guarantee of a constant source. Transporting geothermal energy is difficult and expensive. Also, tapping for steam and hot water may also release hazardous gases and minerals, such as hydrogen sulfide.

How does geothermal energy work in an individual home?

The area below the ground’s surface is generally warmer than winter air, and cooler than summer air. Although not true “renewable energy” because it relies on electricity for operation, a geothermal heat pump (more correctly referred to as a ground-source heat pump) creates a system that draws upon the earth’s stable temperature and uses a heat exchange technology to enable home heating and cooling.

Geothermal systems are expensive to install because they require drilling or excavation. Cost/benefit ratios vary depending on climate and the type of energy source you’re replacing. If you plan to remain in your home for a few years and your energy usage is consistently high, this option may be worth considering. You may also be eligible for a rebate or other incentive.

Geothermal technology resources

How Geothermal Energy Works (UCS)
Geothermal Technologies Program (U.S. DOE)
Types of Geothermal Heat Pump Systems

Sources
Energy Information Administration
National Renewable Energy Laboratory
U.S. Department of Energy: Energy Efficiency and Renewable Energy