What is Geothermal power
Unlimited Heat Beneath Our Feet


Geothermal power is electrical power generated from geothermal energy, the term 'geothermal energy' refers to any heat derived from the ground, from depths of a few metres to multiple kilometres beneath the Earth's surface, this energy is widely described as 'ground-source energy' or 'shallow geothermal energy', temperatures at the core–mantle boundary can reach over 4000 °C (7200 °F). Geothermal power technologies in use include dry steam power stations, flash steam power stations and binary cycle power stations. Geothermal electricity generation is currently used in 26 countries, while geothermal heating is in use in 70 countries. Geothermal power is considered to be a sustainable, renewable source of energy because the heat extraction is small compared with the Earth's heat content. As a source of renewable energy for both power and heating, geothermal has the potential to meet 3-5% of global demand by 2050. With economic incentives, it is estimated that by 2100 it will be possible to meet 10% of global demand

Geothermal Electricity Production Basics

Geothermal power plants use steam to produce electricity. The thermal energy contained in the rocks and fluids can be found from shallow depths right down to several miles below the Earth’s surface. Wells drilled into underground reservoirs tap into the geothermal resources, Hot water is pumped from deep underground through the well under high pressure. When the water reaches the surface, the pressure is dropped, which causes the water to turn into steam, the steam spins a turbine, which is connected to a generator that produces electricity.

Dry Steam

Dry steam power plants draw from underground resources of steam. The steam is piped directly from underground wells to the power plant where it is directed into a turbine/generator unit. There are only two known underground resources of steam in the United States, 1) The Geysers in northern California - 2) Yellowstone National Park in Wyoming, where there's a well-known geyser called Old Faithful. Since Yellowstone is protected from development, the only dry steam plants in the country are at The Geysers.

Flash Steam

Flash steam power plants are the most common and use geothermal reservoirs of water with temperatures greater than 360°F (182°C). This very hot water flows up through wells in the ground under its own pressure. As it flows upward, the pressure decreases and some of the hot water boils into steam. The steam is then separated from the water and used to power a turbine/generator. Any leftover water and condensed steam are injected back into the reservoir, making this a sustainable resource.

Binary Steam

Binary cycle power plants operate on water at lower temperatures of about 225-360°F (107-182°C). Binary cycle plants use the heat from the hot water to boil a working fluid, usually an organic compound with a low boiling point. The working fluid is vaporized in a heat exchanger and used to turn a turbine. The water is then injected back into the ground to be reheated. The water and the working fluid are kept separated during the whole process, so there are little or no air emissions. Currently, two types of geothermal resources can be used in binary cycle power plants to generate electricity: enhanced geothermal systems (EGS) and low-temperature or co-produced resources.

Enhanced Geothermal Systems

EGS provide geothermal power by tapping into the Earth's deep geothermal resources that are otherwise not economical due to lack of water, location, or rock type. The U.S. Geological Survey estimates that potentially 500,000 megawatts of EGS resource is available in the western U.S. or about half of the current installed electric power generating capacity in the United States.

Low-Temperature and Co-Produced Resources

Low-temperature and co-produced geothermal resources are typically found at temperatures of 300F (150C) or less. Some low-temperature resources can be harnessed to generate electricity using binary cycle technology. Co-produced hot water is a byproduct of oil and gas wells in the United States. This hot water is being examined for its potential to produce electricity, helping to lower greenhouse gas emissions and extend the life of oil and gas fields.

Geothermal Power History

In the 20th century, demand for electricity led to the consideration of geothermal power as a generating source. Prince Piero Ginori Conti tested the first geothermal power generator on 4 July 1904 in Larderello, Italy, it successfully lit four light bulbs, later, in 1911, the world's first commercial geothermal power station was built there. Experimental generators were built in Beppu, Japan and the Geysers, California in the 1920s, but Italy was the world's only industrial producer of geothermal electricity until 1958. In 1958, New Zealand became the second major industrial producer of geothermal electricity when its Wairakei station was commissioned. Wairakei was the first station to use flash steam technology. In 1960, Pacific Gas and Electric began operation of the first successful geothermal electric power station in the United States at The Geysers in California. The original turbine lasted for more than 30 years and produced 11 MW net power.

Geothermal electric stations have until recently been built exclusively where high-temperature geothermal resources are available near the surface. The development of binary cycle power plants and improvements in drilling and extraction technology may enable enhanced geothermal systems over a much greater geographical range. Demonstration projects are operational in Landau-Pfalz, Germany, and Soultz-sous-Foręts, France, while an earlier effort in Basel, Switzerland was shut down after it triggered earthquakes. Other demonstration projects are under construction in Australia, the United Kingdom, and the United States of America.

Geothermal Heat Pumps

Geothermal heat pumps (GHPs), sometimes referred to as GeoExchange, earth-coupled, ground-source, or water-source heat pumps, have been in use since the late 1940s. They use the relatively constant temperature of the earth as the exchange medium instead of the outside air temperature, they work in the same way as a refrigerator, the compressed fluid heats up heating the radiator, and the decompressed fluid cools down, absorbimg the grounds heat

Although many parts of the country experience seasonal temperature extremes, from scorching heat in the summer to sub-zero cold in the winter, a few feet below the earth's surface the ground remains at a relatively constant temperature. Depending on latitude, ground temperatures range from 45°F (7°C) to 75°F (21°C). Like a cave, this ground temperature is warmer than the air above it during the winter and cooler than the air in the summer. The GHP takes advantage of these more favorable temperatures to become high efficient by exchanging heat with the earth through a ground heat exchanger.

 

 

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