Geothermal Power Today
Modern use of geothermal energy includes not only direct heating uses such as process and space heating, but also indirect uses like heating water into steam to drive turbines for electrical production.
There are four main kinds of geothermal resources: hydrothermal, geopressured, hot dry rock, and magma. Currently, only hydrothermal resources are in wide use. The remaining three resources are still in the initial stages of development. Hydrothermal electricity generation can be further subdivided into three types of power plants, dry steam, flash steam, and binary cycle.
In dry steam power plants, the steam shoots up the wells and is passed through a rock catcher and then directly into the turbine. Dry steam fields are rare. They require the heat source to be hot enough to produce a high enough grade steam to operate a turbine. Steam has little or no water droplets remaining in the mixture.
Flash steam power plants use hot water reservoirs. In flash plants, as hot water is released from the pressure of the deep reservoir in a flash tank, some of it flashes to steam. Flash technology was invented in the geothermal reservoirs of the Wairakei region in New Zealand in the 1950s. These types of plants are the most common, since most geothermal reservoirs are hot water reservoirs.
In a binary cycle power plant, the heat from geothermal water is used to vaporize a working fluid in separate adjacent pipes. The vapor acts like steam and powers the turbine generator. In the heat exchanger, heat is transferred from the geothermal water to a second liquid. The geothermal water is never exposed to the air and is injected back into the reservoir. Binary technology allows the use of lower temperature reservoirs, thus increasing the number of reservoirs that can be used.
Current geothermal fields produce only about one-sixth of the carbon dioxide that a natural gas fueled electrical generating power plant produces and none of the nitrous oxide (NOx) or sulfur bearing (SOx) gases. New state-of-the-art geothermal binary and combined cycle plants produce virtually no airborne emissions.
In 1970, geothermal power was about 9-12 cents per Kilowatt-hour. Today new geothermal power costs are typically in the range of 4.5 - 6.5 per kilowatt-hour. Geothermal power currently supplies 2,800 megawatts (MW) in the United States, sufficient for 2.8 million customers. Current worldwide generation capacity is estimated at 8,500 MW and increasing. The US Department of Energy has estimated that geothermal power production will increase to eventually supply 10% of all power in the West, adding 4,300 MW to new renewable energy production. A USDOE 1999 study estimated that geothermal power could provide all electricity for 865 million people, 17% of the planet's population, increasing to 138,000 MW.
For more information about the current use of geothermal energy, visit the following web sites.
Includes general history about geothermal energy, economics and environmental impact, future of the industry, and an overview of current technology.
Overview of the geothermal power industry, current United States and International usage with projections for future use and industry growth.
Answers to a dozen questions about geothermal energy, from large-scale applications, introductory regulations and policies, access to scientific case studies, a glossary of relevant terms, and more.
An industry overview of modern day geothermal electrical production.
General information, including history, thermodynamics, current technology, regional importance, big industry players.
Information about the current research underway by the Idaho National Engineering and Environmental Laboratory (INEEL) including publications about their studies and general information about geothermal energy.
