Geothermal energy in the United States

Geothermal energy in the United States continues to be an area of considerable activity. In 2010, the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

led the world in geothermal electricity production with 3,086 megawatts (MW) of installed capacity from 77 power plants; the largest group of geothermal power plants in the world is located at The Geysers

The Geysers

The Geysers is a complex of 22 geothermal power plants, drawing steam from more than 350 wells, located in the Mayacamas Mountains north of San Francisco, California.The largest in the world, the Geysers has...

, a geothermal field in California

California

California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

. The United States generates an average of 15 billion kilowatt hours of geothermal power per year, comparable to burning some 25 Moilbbl of oil or 6 million short tons of coal per year.

Geothermal power plants are largely concentrated in the western states. They are the fourth largest source of renewable electricity, after hydroelectricity

Hydroelectricity

Hydroelectricity is the term referring to electricity generated by hydropower; the production of electrical power through the use of the gravitational force of falling or flowing water. It is the most widely used form of renewable energy...

, biomass

Biomass

Biomass, as a renewable energy source, is biological material from living, or recently living organisms. As an energy source, biomass can either be used directly, or converted into other energy products such as biofuel....

, and wind power

Wind power

Wind power is the conversion of wind energy into a useful form of energy, such as using wind turbines to make electricity, windmills for mechanical power, windpumps for water pumping or drainage, or sails to propel ships....

. A geothermal resource assessment shows that nine western states together have the potential to provide over 20 percent of national electricity needs.

History

According to archaeological evidence, geothermal resources have been in use on the current territory of the United States for more than 10,000 years. The Paleo-Indians first used geothermal hot springs for warmth, cleansing, and minerals.

The first commercial geothermal power plant producing power to the U.S. utility grid opened at The Geysers in California in 1960, producing eleven megawatts of net power. The Geysers system continues to operate successfully today, and the complex has grown into the largest geothermal development in the world, with an output of 750 MW.

Plants

The largest dry steam field in the world is the Geysers

The Geysers

, 116 km (72.1 mi) north of San Francisco. It was here that Pacific Gas and Electric began operation of the first successful geothermal electric power plant in the United States in 1960. The original turbine lasted for more than 30 years and produced 11 MW net power. The Geysers has 1517 megawatt (MW) of active installed capacity with an average capacity factor of 63%. Calpine Corporation owns 15 of the 18 active plants in the Geysers and is currently the United States' largest producer of geothermal energy. Two other plants are owned jointly by the Northern California Power Agency and the City of Santa Clara

Santa Clara, California

Santa Clara , founded in 1777 and incorporated in 1852, is a city in Santa Clara County, in the U.S. state of California. The city is the site of the eighth of 21 California missions, Mission Santa Clara de Asís, and was named after the mission. The Mission and Mission Gardens are located on the...

's municipal Electric Utility (now called Silicon Valley Power

Silicon Valley Power

Silicon Valley Power is a not-for-profit municipal electric utility owned and operated by the city of Santa Clara, California, USA.-History:...

). The remaining Bottle Rock Power plant owned by the US Renewables Group has only recently been reopened. A nineteenth plant is now under development by Ram Power, formerly Western Geopower. Since the activities of one geothermal plant affects those nearby, the consolidation plant ownership at The Geysers has been beneficial because the plants operate cooperatively instead of in their own short-term interest. The Geysers is now recharged by injecting treated sewage effluent from the City of Santa Rosa

Santa Rosa, California

Santa Rosa is the county seat of Sonoma County, California, United States. The 2010 census reported a population of 167,815. Santa Rosa is the largest city in California's Wine Country and fifth largest city in the San Francisco Bay Area, after San Jose, San Francisco, Oakland, and Fremont and 26th...

and the Lake County

Lake County, California

Lake County is a county located in the north central portion of the U.S. state of California, north of the San Francisco Bay Area. It takes its name from Clear Lake, the dominant geographic feature in the county and the largest natural lake wholly within California...

sewage treatment plant. This sewage effluent used to be dumped into rivers and streams and is now piped to the geothermal field where it replenishes the steam produced for power generation.

Another major geothermal area is located in south central California

California

California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

, on the southeast side of the Salton Sea

Salton Sea

The Salton Sea is a shallow, saline, endorheic rift lake located directly on the San Andreas Fault, predominantly in California's Imperial Valley. The lake occupies the lowest elevations of the Salton Sink in the Colorado Desert of Imperial and Riverside counties in Southern California. Like Death...

, near the cities of Niland

Niland, California

Niland is a census-designated place in Imperial County, California. The town is located north of Calipatria, southeast of Salton Sea. The population was 1,006 at the 2010 census, down from 1,143 at the 2000 census...

and Calipatria

Calipatria, California

Calipatria is a city in Imperial County, California. Calipatria is located north of El Centro, It is part of the El Centro Metropolitan Area. The population was 7,705 at the 2010 census, up from 7,289 at the 2000 census, including 4000 inmates at Calipatria State Prison...

, California. As of 2001, there were 15 geothermal plants producing electricity in the area. CalEnergy owns about half of them and the rest are owned by various companies. Combined the plants have a capacity of about 570 MW.

The Basin and Range geologic province in Nevada

Nevada

Nevada is a state in the western, mountain west, and southwestern regions of the United States. With an area of and a population of about 2.7 million, it is the 7th-largest and 35th-most populous state. Over two-thirds of Nevada's people live in the Las Vegas metropolitan area, which contains its...

, southeastern Oregon

Oregon

Oregon is a state in the Pacific Northwest region of the United States. It is located on the Pacific coast, with Washington to the north, California to the south, Nevada on the southeast and Idaho to the east. The Columbia and Snake rivers delineate much of Oregon's northern and eastern...

, southwestern Idaho

Idaho

Idaho is a state in the Rocky Mountain area of the United States. The state's largest city and capital is Boise. Residents are called "Idahoans". Idaho was admitted to the Union on July 3, 1890, as the 43rd state....

, Arizona

Arizona

Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...

and western Utah

Utah

Utah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the...

is now an area of rapid geothermal development. Several small power plants were built during the late 1980s during times of high power prices. Rising energy costs have spurred new development. Plants in Nevada at Steamboat Springs

Steamboat Springs, Nevada

Steamboat Springs is a small volcanic field of rhyolitic lava domes and flows in western Nevada, USA, located south of Reno. There is extensive geothermal activity in the area, including numerous hot springs, steam vents, and fumaroles...

, Brady/Desert Peak, Dixie Valley, Soda Lake, Stillwater and Beowawe

Beowawe, Nevada

Beowawe is a ghost town in Eureka County in northeastern Nevada in the western United States. Beowawe is a Paiute Native American word meaning "gate", so named for the peculiar shape of the hills close to town which gives the effect of a gateway opening to the valley beyond. The town is located at...

now produce about 235 MW.

Production and development

With 3,040.27 MW of installed geothermal capacity, the United States remains the world leader with 30% of the online capacity total. The future outlook for expanded production from conventional and enhanced geothermal systems is positive as new technologies promise increased growth in locations previously not considered.

As of August 2008, 103 new projects are underway in 13 U.S. states. When developed, these projects could potentially supply up to 3,979 MW of power, meeting the needs of about 4 million homes. At this rate of development, geothermal production in the United States could exceed 15,000 MW by 2025.

The most significant catalyst behind new industry activity is the Energy Policy Act of 2005

Energy Policy Act of 2005

The Energy Policy Act of 2005 is a bill passed by the United States Congress on July 29, 2005, and signed into law by President George W. Bush on August 8, 2005, at Sandia National Laboratories in Albuquerque, New Mexico...

. This Act made new geothermal plants eligible for the full federal production tax credit, previously available only to wind power projects and certain kinds of biomass. It also authorized and directed increased funding for research by the Department of Energy

United States Department of Energy

The United States Department of Energy is a Cabinet-level department of the United States government concerned with the United States' policies regarding energy and safety in handling nuclear material...

, and enabled the Bureau of Land Management to address its backlog of geothermal leases and permits.
In April 2008, exploratory

Geothermal exploration

Geothermal Exploration is a multidisciplinary process used to explore the subsurface in search of viable active geothermal regions with the ultimate goal of building a geothermal power plant, where hot fluids drive turbines to create electricity...

drilling began at Newberry Volcano

Newberry Volcano

Newberry Volcano is a large potentially active shield volcano located east of the Cascade Range and about southeast of Bend, Oregon. It is not a typical shield volcano. In addition to erupting basaltic lavas, it also has erupted andesitic and even rhyolitic lava.The volcano is in diameter and...

in Oregon

Oregon

.

In 2009, investment bank Credit Suisse

Credit Suisse

The Credit Suisse Group AG is a Swiss multinational financial services company headquartered in Zurich, with more than 250 branches in Switzerland and operations in more than 50 countries.-History:...

calculated that geothermal power costs 3.6 cents per kilowatt-hour, versus 5.5 cents per kilowatt-hour for coal."

In 2009 Raser Technologies (nyse:RZ) put a 8.5 MW called Thermo 1 in Utah the facility uses a process called bottom cycling to produce power from a lower heat level. This plant was 2009's power plant of the year. It was built in only 6 months. They have just begun drilling for their next 15MW project called Lighting Dock.

Reliability

Geothermal has a higher capacity factor

Capacity factor

The net capacity factor or load factor of a power plant is the ratio of the actual output of a power plant over a period of time and its potential output if it had operated at full nameplate capacity the entire time...

(a measure of the amount of real time during which a facility is used) than many other power sources. Unlike wind and solar resources, which are dependent upon weather, geothermal resources are available 24 hours a day, 7 days a week. While the carrier medium for geothermal electricity (water) must be properly managed, the source of geothermal energy, the Earth's heat, will be available, for most intents and purposes, indefinitely.

In 2008 the USDOE funded research in Enhanced Geothermal Systems

Enhanced geothermal systems

Enhanced Geothermal System is a new type of geothermal power technology that does not require natural convective hydrothermal resources. Until recently, geothermal power systems have exploited only resources where naturally occurring heat, water, and rock permeability are sufficient to allow...

(EGS) to learn more about the fracture systems in geothermal reservoirs and better predict the results of reservoir stimulation.

Environmental effects

Acquiring steam from geysers, volcanoes, and hot springs is a process that isn't harmful to the environment. However, the actual steam that is being collected and transferred into energy contains chemicals that may contribute to air pollution depending on the methods used, and water mixed with the steam consists of dissolved salts that can damage pipes and harm aquatic ecosystems.

Newer methods of generating geothermal power that separate the hot steam collected underground from the steam used to power turbines substantially reduce the risk of the transfer of air polluting contaminants.

In addition to hazardous salts in our environment, some waters that are collected with the process of geothermal energy have contained high concentrations of toxic elements such as boron

Boron

Boron is the chemical element with atomic number 5 and the chemical symbol B. Boron is a metalloid. Because boron is not produced by stellar nucleosynthesis, it is a low-abundance element in both the solar system and the Earth's crust. However, boron is concentrated on Earth by the...

, lead

Lead

Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...

, and arsenic

Arsenic

Arsenic is a chemical element with the symbol As, atomic number 33 and relative atomic mass 74.92. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. It was first documented by Albertus Magnus in 1250.Arsenic is a metalloid...

. A gas that has been found in geothermal water and steam is hydrogen sulfide

Hydrogen sulfide

Hydrogen sulfide is the chemical compound with the formula . It is a colorless, very poisonous, flammable gas with the characteristic foul odor of expired eggs perceptible at concentrations as low as 0.00047 parts per million...

, which has a bad odor of rotten eggs, and is toxic in high concentrations.

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