The Geysers

The Geysers

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The Geysers is a complex of 22 geothermal power
Geothermal power
Geothermal energy is thermal energy generated and stored in the Earth. Thermal energy is the energy that determines the temperature of matter. Earth's geothermal energy originates from the original formation of the planet and from radioactive decay of minerals...

 plants, drawing steam from more than 350 wells, located in the Mayacamas Mountains  north of San Francisco, 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 largest in the world, the Geysers has
of active installed capacity with an average production factor of 63 % (955 MW).
Calpine Corporation operates and owns 19 of the 22 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 Bottle Rock Power plant owned by the US Renewables Group has only recently been reopened.
Another plant is under development by Ram Power Corp, formerly Western Geopower, with operation set to begin in 2010.
Since the activities of one geothermal plant affects those nearby, the consolidation of plant ownership at The Geysers has been beneficial because the plants operate cooperatively instead of in their own short-term interest.

Description


The Geysers geothermal development spans an area of around in Sonoma
Sonoma County, California
Sonoma County, located on the northern coast of the U.S. state of California, is the largest and northernmost of the nine San Francisco Bay Area counties. Its population at the 2010 census was 483,878. Its largest city and county seat is Santa Rosa....

, Lake
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...

 and Mendocino
Mendocino County, California
Mendocino County is a county located on the north coast of the U.S. state of California, north of the greater San Francisco Bay Area and west of the Central Valley. As of the 2010 census, the population was 87,841, up from 86,265 at the 2000 census...

 counties in California, located in the Mayacamas Mountains. Power from The Geysers provides electricity to Sonoma, Lake, Mendocino, Marin, and Napa counties. It is estimated that the development meets of the power demand for the coastal region between the Golden Gate Bridge
Golden Gate Bridge
The Golden Gate Bridge is a suspension bridge spanning the Golden Gate, the opening of the San Francisco Bay into the Pacific Ocean. As part of both U.S. Route 101 and California State Route 1, the structure links the city of San Francisco, on the northern tip of the San Francisco Peninsula, to...

 and the 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...

 state line.

Steam used at The Geysers is produced from a greywacke
Greywacke
Greywacke or Graywacke is a variety of sandstone generally characterized by its hardness, dark color, and poorly sorted angular grains of quartz, feldspar, and small rock fragments or lithic fragments set in a compact, clay-fine matrix. It is a texturally immature sedimentary rock generally found...

 sandstone reservoir, that is capped by a heterogeneous mix of low permeability rocks and underlaid by a Felsite
Felsite
Felsite is a very fine grained volcanic rock that may or may not contain larger crystals. Felsite is a field term for a light colored rock that typically requires petrographic examination or chemical analysis for more precise definition...

 intrusion
Intrusion
An intrusion is liquid rock that forms under Earth's surface. Magma from under the surface is slowly pushed up from deep within the earth into any cracks or spaces it can find, sometimes pushing existing country rock out of the way, a process that can take millions of years. As the rock slowly...

. Gravity and seismic studies suggest that the source of heat for the steam reservoir is a large magma
Magma
Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...

 chamber over beneath the ground, and greater than in diameter.
Unlike most geothermal resources, the Geysers is a dry steam field, which means it mainly produces superheated steam. Because the power plant turbines require a vapor phase input, dry steam resources are generally preferable. Otherwise, a two-phase separator is required between the turbine and the geothermal wells to remove condensation that is produced with the steam.
The Geysers complex 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.

Induced Seismicity



Current studies of The Geysers Geothermal Field seismicity have reached the conclusion that deep-well injection in the field produces mostly microseismic events between magnitude 0.5-3.0 on the Richter Scale (M). As can be seen in the figure, the seismicity between magnitude 3.0 and 4.6 (the largest event recorded in The Geysers field which was in 1973) is on the order of a few M4 events per year and on the order of 20 to 30 M3 events per year. Although the M4 events have been increasing, the number of M3 events have been relatively constant since the mid 1980s.

Worldwide, the largest induced seismic event to date linked to Enhanced Geothermal System (EGS) activity was M3.7 in the Cooper Basin
Cooper Basin
The Cooper Basin is a sedimentary geological basin in Australia. The basin is located mainly in the north-east part of South Australia and extends into south-west Queensland. It is named after the Cooper Creek which is an ephemeral river that runs into Lake Eyre. Part of the Cooper Basin is...

 of Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

. However, research based on maximum fault lengths indicates that a M5.0 is the largest possible (but not probable) event in the Geysers.

A concern to the residents is not only the amount of seismicity but the magnitude of the largest seismic event likely to occur. Although no one can accurately predict earthquakes, the magnitude of an earthquake is dependent on the surface area that can slip — the length times the depth or width of the fault. Therefore, a large earthquake can occur only on a large fault. There are no mapped faults of large length in The Geysers, so it is extremely unlikely that induced seismicity caused by activities in The Geysers will lead to a large earthquake.

History



The first recorded discovery of The Geysers was in 1847 during John Fremont's survey of the Sierra Mountains
Sierra mountains
Sierra is a Spanish word meaning "saw". The corresponding word in Portuguese and Latin is serra. This name is used for various mountain ranges in Spanish-speaking and other countries ....

 and the Great Basin
Great Basin
The Great Basin is the largest area of contiguous endorheic watersheds in North America and is noted for its arid conditions and Basin and Range topography that varies from the North American low point at Badwater Basin to the highest point of the contiguous United States, less than away at the...

 by William Bell Elliot. Elliot called the area "The Geysers," although the geothermal features he discovered were not technically geysers, but fumaroles. Soon after, in 1852, The Geysers was developed into a spa for The Geysers Resort Hotel, which attracted the likes of Ulysses S. Grant
Ulysses S. Grant
Ulysses S. Grant was the 18th President of the United States as well as military commander during the Civil War and post-war Reconstruction periods. Under Grant's command, the Union Army defeated the Confederate military and ended the Confederate States of America...

, Theodore Roosevelt
Theodore Roosevelt
Theodore "Teddy" Roosevelt was the 26th President of the United States . He is noted for his exuberant personality, range of interests and achievements, and his leadership of the Progressive Movement, as well as his "cowboy" persona and robust masculinity...

, and Mark Twain
Mark Twain
Samuel Langhorne Clemens , better known by his pen name Mark Twain, was an American author and humorist...

.

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.

Future


The Geysers electrical plant reached peak production in 1987, at that time serving 1.8 million people. Since then, the steam field has been in gradual decline as its underground water source decreases. Currently, the Geysers produce enough electricity for 1.1 million people.

Techniques developed from 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...

 research will increase the production of the region in the future. By reinjecting greywater
Greywater
Greywater is wastewater generated from domestic activities such as laundry, dishwashing, and bathing, which can be recycled on-site for uses such as landscape irrigation and constructed wetlands...

 from the nearby city of Santa Rosa, existing wells will be recharged. This water will be naturally heated in the geothermal reservoir, and be captured by the existing power plants as steam. The project should increase electrical output by , enough for about 85,000 homes.

See also


  • Geothermal energy in the United States
    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 led the world in geothermal electricity production with 3,086 megawatts of installed capacity from 77 power plants; the largest group of geothermal power plants in the world is...

  • Geothermal power
    Geothermal power
    Geothermal energy is thermal energy generated and stored in the Earth. Thermal energy is the energy that determines the temperature of matter. Earth's geothermal energy originates from the original formation of the planet and from radioactive decay of minerals...

  • AltaRock Energy
    AltaRock Energy
    AltaRock Energy Inc., headquartered in Seattle, Washington and having a technology development office in Sausalito, California, is a privately held corporation that focuses on the development of geothermal energy resources and Enhanced Geothermal Systems...


External links