Today hydrothermal resources are the only kind in wide use. The other three resources are still in the infant stages of development. Hydrothermal resources have the common ingredients of water hydro and heat thermal. These geothermal reservoirs of steam or hot water occur naturally where magma comes close enough to the surface to heat ground water trapped in fractured or porous rocks, or where water circulates at great depth along faults.

Hydrothermal resources are used for different energy purposes depending on their temperature and how deep they are. Low Temperature: "Direct Use" or Heating. When the temperature of a hydrothermal resource is around 50F and up, it can be used directly in spas or to heat buildings, grow crops, warm fish ponds, or for other uses.

Hydrothermal resources suitable for heating occur throughout the United States and in almost every country in the world. Most of the people in Iceland and over , people in France use geothermal heat for their public buildings, schools, and homes. In the United States, geothermal heat pumps are used in 45 states to heat and cool homes and buildings. Idaho, Oregon, Nevada, and some other states use geothermal energy to heat entire districts.

Heat from geothermal resources is also used to dry ceramics, lumber, vegetables, and other products. When the temperature of a hydrothermal resource is around F and up, it can be used to generate electricity. Most electricity-producing geothermal resources have temperatures from to F, but geothermal reservoirs can reach nearly 1,F. Two main types of hydrothermal resources are used to generate electricity:.

Dry steam reservoirs are rare but highly efficient at producing electricity. The Geysers in California is the largest and best known dry steam reservoir. Here, steam is obtained by drilling wells from 7, to 10, feet deep.

In a dry steam reservoir, the natural steam is piped directly from a geothermal well to power a turbine generator. The spent steam condensed water can be used in the plant's cooling system and injected back into the reservoir to maintain water and pressure levels. Hot water geothermal reservoirs are the most common type.

In a liquid-dominated reservoir, the hot water has not vaporized into steam because the reservoir is saturated with water and is under pressure. To generate electricity, the hot water is piped from geothermal wells to one or more separators where the pressure is lowered and the water flashes into steam. The steam then propels a turbine generator to produce electricity.

The steam is cooled and condensed and either used in the plant's cooling system or injected back into the geothermal reservoir. A binary cycle power plant is used when the water in a hot water reservoir is not hot enough to flash into steam.

Instead, the lower-temperature hot water is used to heat a fluid that expands when warmed. The turbine is powered from the expanded, pressurized fluid. Afterwards, the fluid is cooled and recycled to be heated over and over again.

Geothermal Energy Production and Economics. Geothermal energy is put to work in many places around the world. The best known geothermal energy sources in the United States are located in western states and Hawaii. Some moderately hot geothermal resources also exist in the Dakotas, along the Atlantic coast, and in Arkansas and Texas. Someday we may be able to use these resource too. Most geothermal energy is produced in four states--California, Nevada, Utah, and Hawaii.

Today the total installed capacity of geothermal power plants in the United State is 3, megawatts MW That's the energy equivalent of three nuclear power plants. Diesel fuel. Heating oil. Also in Oil and petroleum products explained Oil and petroleum products Refining crude oil Where our oil comes from Imports and exports Offshore oil and gas Use of oil Prices and outlook Oil and the environment. Also in Gasoline explained Gasoline Octane in depth Where our gasoline comes from Use of gasoline Prices and outlook Factors affecting gasoline prices Regional price differences Price fluctuations History of gasoline Gasoline and the environment.

Also in Diesel fuel explained Diesel fuel Where our diesel comes from Use of diesel Prices and outlook Factors affecting diesel prices Diesel fuel surcharges Diesel and the environment. Also in Heating oil explained Heating oil Where our heating oil comes from Use of heating oil Prices and outlook Factors affecting heating oil prices.

Hydrocarbon Gas Liquids. Natural gas. Also in Hydrocarbon gas liquids explained Hydrocarbon gas liquids Where do hydrocarbon gas liquids come from? Transporting and storing Uses of hydrocarbon gas liquids Imports and exports Prices. Also in Natural gas explained Natural gas Delivery and storage Natural gas pipelines Liquefied natural gas Where our natural gas comes from Imports and exports How much gas is left Use of natural gas Prices Factors affecting natural gas prices Natural gas and the environment Customer choice programs.

Also in Coal explained Coal Mining and transportation Where our coal comes from Imports and exports How much coal is left Use of coal Prices and outlook Coal and the environment. Renewable sources. Renewable energy. Biofuels: Ethanol and Biomass-based diesel.

Also in Hydropower explained Hydropower Where hydropower is generated Hydropower and the environment Tidal power Wave power Ocean thermal energy conversion. Also in Biofuels explained Biofuels Ethanol Use and supply of ethanol Ethanol and the environment Biomass-based diesel fuels Use of biomass-based diesel fuel Biomass-based diesel and the environment.

During the cold season, the liquid absorbs underground geothermal heat. It carries the heat upward through the building and gives off warmth through a duct system. These heated pipes can also run through hot water tanks and offset water-heating costs. During the summer, the GHP system works the opposite way: The liquid in the pipes is warmed from the heat in the building or parking lot, and carries the heat to be cooled underground.

The U. Environmental Protection Agency has called geothermal heating the most energy-efficient and environmentally safe heating and cooling system. Harvesting Geothermal Energy: Electricity In order to obtain enough energy to generate electricity, geothermal power plants rely on heat that exists a few kilometers below the surface of the Earth. In some areas, the heat can naturally exist underground as pockets steam or hot water. Dry-Steam Power Plants Dry-steam power plants take advantage of natural underground sources of steam.

The steam is piped directly to a power plant, where it is used to fuel turbines and generate electricity. Dry steam is the oldest type of power plant to generate electricity using geothermal energy. The first dry-steam power plant was constructed in Larderello, Italy, in Today, the dry-steam power plants at Larderello continue to supply electricity to more than a million residents of the area.

Since Yellowstone is a protected area, The Geysers is the only place where a dry-steam power plant is in use. It is one of the largest geothermal energy complexes in the world, and provides about a fifth of all renewable energy in California.

Flash-steam power plants use naturally occurring sources of underground hot water and steam. Any remaining water can be flashed in a separate tank to extract more energy. Flash-steam power plants are the most common type of geothermal power plants. The volcanically active island nation of Iceland supplies nearly all its electrical needs through a series of flash-steam geothermal power plants. The steam and excess warm water produced by the flash-steam process heat icy sidewalks and parking lots in the frigid Arctic winter.

The islands of the Philippines also sit over a tectonically active area, the " Ring of Fire " that rims the Pacific Ocean. Government and industry in the Philippines have invested in flash-steam power plants, and today the nation is second only to the United States in its use of geothermal energy. In fact, the largest single geothermal power plant is a flash-steam facility in Malitbog, Philippines. Binary Cycle Power Plants Binary cycle power plants use a unique process to conserve water and generate heat.

The hot water is contained in a pipe, which cycles above ground. The hot water heats a liquid organic compound that has a lower boiling point than water. The organic liquid creates steam, which flows through a turbine and powers a generator to create electricity. The only emission in this process is steam. The water in the pipe is recycled back to the ground, to be re-heated by the Earth and provide heat for the organic compound again.

The Beowawe Geothermal Facility in the U. The organic compound used at the facility is an industrial refrigerant tetrafluoroethane, a greenhouse gas. This refrigerant has a much lower boiling point than water, meaning it is converted into gas at low temperatures. The gas fuels the turbines, which are connected to electrical generators.

Enhanced Geothermal Systems The Earth has virtually endless amounts of energy and heat beneath its surface. However, it is not possible to use it as energy unless the underground areas are "hydrothermal. Many areas do not have all three of these components.

An enhanced geothermal system EGS uses drilling, fracturing, and injection to provide fluid and permeability in areas that have hot—but dry—underground rock.

Depending on the type of rock, this can be as shallow as 1 kilometer 0. High-pressure cold water is injected into the drilled space, which forces the rock to create new fractures, expand existing fractures, or dissolve. This creates a reservoir of underground fluid. It warms a secondary fluid that has a low boiling point, which evaporates to steam and powers a turbine.

The brine cools off, and cycles back down through the injection well to absorb underground heat again. There are no gaseous emissions besides the water vapor from the evaporated liquid. Pumping water into the ground for EGSs can cause seismic activity, or small earthquakes.

In Basel, Switzerland, the injection process caused hundreds of tiny earthquakes that grew to more significant seismic activity even after the water injection was halted. This led to the geothermal project being canceled in Geothermal Energy and the Environment Geothermal energy is a renewable resource. The Earth has been emitting heat for about 4.

However, most wells that extract the heat will eventually cool, especially if heat is extracted more quickly than it is given time to replenish. Re-injecting water can sometimes help a cooling geothermal site last longer. Geothermal systems do not require enormous amounts of freshwater. In binary systems, water is only used as a heating agent, and is not exposed or evaporated. It can be recycled, used for other purposes, or released into the atmosphere as non- toxic steam.

However, if the geothermal fluid is not contained and recycled in a pipe, it can absorb harmful substances such as arsenic, boron, and fluoride. These toxic substances can be carried to the surface and released when the water evaporates. In addition, if the fluid leaks to other underground water systems, it can contaminate clean sources of drinking water and aquatic habitats.

Advantages There are many advantages to using geothermal energy either directly or indirectly:. They can be used to heat, cool, or power individual homes, whole districts, or industrial processes. Geothermal Energy and People Geothermal energy exists in different forms all over the Earth by steam vents, lava, geysers, or simply dry heat , and there are different possibilities for extracting and using this heat.

In New Zealand, natural geysers and steam vents heat swimming pools, homes, greenhouses, and prawn farms. New Zealanders also use dry geothermal heat to dry timber and feedstock. Other countries, such as Iceland, have taken advantage of molten rock and magma resources from volcanic activity to provide heat for homes and buildings.

Iceland also relies on its natural geysers to melt snow, warm fisheries, and heat greenhouses. The United States generates the most amount of geothermal energy of any other country.

Every year, the U. Industrial geothermal technologies have been concentrated in the western U. In , Nevada had 59 geothermal projects either operational or in development, followed by California with 31 projects, and Oregon with 16 projects.