Molly Ayala
Geothermal electricity is a renewable energy source that uses the Earth's natural heat to generate power. The word geothermal comes from the Greek words geo, meaning Earth, and therme, meaning heat. Geothermal energy has been used for thousands of years, with ancient civilisations using hot mineral springs for bathing, cooking, and eating. Today, geothermal electricity generation is used in 26 countries, with countries like El Salvador, Kenya, and Iceland generating more than 15% of their electricity from geothermal sources. With its constant rate of power production and low environmental impact, geothermal energy is an attractive option for meeting the world's growing demand for electricity.
| Characteristics | Values |
|---|---|
| Definition | Geothermal energy is heat energy from the Earth |
| Source | Geothermal energy comes from the slow decay of radioactive particles in the Earth's core |
| Use Cases | Geothermal energy is used for bathing, heating buildings, and generating electricity |
| Sustainability | Geothermal energy is considered sustainable because the heat extracted is small compared to the Earth's heat content |
| Efficiency | The thermal efficiency of geothermal electric stations is low, around 7-10%, due to the low temperature of geothermal fluids |
| Capacity Factor | Geothermal power can have a capacity factor of up to 96% |
| Global Potential | Geothermal energy has the potential to meet 3-5% of global demand by 2050 and 10% by 2100 with economic incentives |
| Current Usage | Geothermal electricity generation is used in 26 countries, while geothermal heating is used in 70 countries |
| Leading Countries | Countries generating more than 15% of their electricity from geothermal sources include El Salvador, Kenya, the Philippines, Iceland, New Zealand, and Costa Rica |
| Technology | Technologies for direct use, such as geothermal heat pumps, are widely used and considered mature |
| Enhanced Geothermal Systems | Enhanced Geothermal Systems (EGS) involve human-made geothermal energy and have the potential to increase capacity |
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What You'll Learn
Geothermal energy is a renewable energy source
The word geothermal comes from the Greek words "geo" (earth) and "therme" (heat). Geothermal energy has been exploited as a source of heat and power for millennia. Ancient Romans, Chinese, and Native Americans used hot mineral springs for bathing, and geothermal heating has been used since Roman times. The first geothermal power generator was tested in 1904 in Italy, and the world's first commercial geothermal power plant was built there in 1911.
Geothermal electricity generation is currently used in 26 countries, with worldwide geothermal power capacity amounting to 15.4 gigawatts (GW) as of 2019. The geothermal gradient of temperatures through the crust is 25-30°C per km of depth in most of the world, but this is much higher near tectonic plate boundaries where the crust is thinner. Wells can be drilled into underground reservoirs to tap steam and very hot water, which can be used for heating or to generate electricity. The heat extracted is minimal compared to the Earth's heat content, making geothermal energy a sustainable source of renewable energy.
Geothermal energy has the potential to meet a significant share of electricity demand in countries such as Iceland, El Salvador, New Zealand, Kenya, and the Philippines. It is also estimated that geothermal power could meet 3 to 5% of global demand by 2050, and with economic incentives, this could increase to 10% by 2100. The development of enhanced geothermal systems and emerging technologies could further increase the generating capacity of geothermal energy.
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Geothermal electricity generation methods
Geothermal electricity is generated using geothermal energy, which is heat energy from the earth. Geothermal resources are reservoirs of hot water that exist or are human-made at varying temperatures and depths below the earth's surface. Wells can be drilled into these underground reservoirs to tap steam and very hot water that can be used for a variety of applications, including electricity generation.
There are three main types of geothermal power plant technologies: dry steam, flash steam, and binary cycle. The type of conversion is part of the power plant design and generally depends on the state of the subsurface fluid (steam or water) and its temperature.
Dry Steam Plants
Dry steam plants use hydrothermal fluids that are already mostly steam, which is a relatively rare natural occurrence. The steam is drawn directly to a turbine, which drives a generator that produces electricity. After the steam condenses, it is frequently reinjected into the reservoir. The Larderello geothermal power plant in Tuscany is the oldest dry steam power plant in the world, first used in 1904.
Flash Steam Plants
Flash steam power plants use hydrothermal resources that are found at lower temperatures than dry steam plants. These resources are brought to the surface through pipes and then separated into steam and water in a tank. The steam is then used to drive the turbines that generate electricity.
Binary Cycle Plants
Binary cycle power plants use hydrothermal resources that are too cool to be used in either dry steam or flash steam plants. In this type of plant, the hydrothermal fluid heats a second fluid with a lower boiling point, which is then converted to steam and used to drive the turbines.
Enhanced Geothermal Systems (EGS)
Sometimes, natural conditions for geothermal electricity generation do not exist—for instance, the rocks are hot, but they lack permeability or sufficient fluid flow. EGS uses human-made reservoirs to create the proper conditions for electricity generation by injecting fluid into the hot rocks. This creates new fractures and opens existing ones to enhance the size and connectivity of fluid pathways. Once this engineered reservoir is created, fluid can be injected into the subsurface and then drawn up through a production well to generate electricity using the same processes as a conventional hydrothermal system.
Geothermal Potential
Estimates of the electricity-generating potential of geothermal energy vary from 35 to 2000 GW depending on the scale of investments. The US has the highest geothermal electricity-generating capacity at just over 4 gigawatts, followed by Indonesia at 1.8 GW. Geothermal electricity generation is currently used in 26 countries, while geothermal heating is in use in 70 countries.
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The history of geothermal power
Geothermal electricity refers to electrical power generated from geothermal energy. Geothermal energy, in turn, is heat energy from the Earth, derived from reservoirs of hot water at varying depths below the Earth's surface.
The use of geothermal energy can be traced back thousands of years. Ancient civilisations such as the Romans, Chinese, and Native Americans harnessed hot mineral springs for various purposes, including bathing, cooking, and eating. However, the modern history of geothermal power, in terms of electricity generation, began in the 20th century.
In 1904, Prince Piero Ginori Conti created the first geothermal power generator at the Larderello dry steam field in Italy. This early generator successfully lit four light bulbs, marking a significant milestone in the development of geothermal electricity. Following this success, the world's first commercial geothermal power station was established in Larderello in 1911, with Italy becoming the sole industrial producer of geothermal electricity until 1958.
In the 1920s, experimental generators were built in Beppu, Japan, and The Geysers, California, showcasing the growing global interest in geothermal power. In 1958, New Zealand joined the fray, becoming the second major industrial producer of geothermal electricity with its Wairakei station, the first to utilise flash steam technology.
The oil crisis of the 1970s and high fuel costs renewed interest in geothermal energy, particularly for district heating. The US government played a pivotal role in promoting the exploitation of geothermal energy during this decade, establishing various programs and enacting legislation to support its development. The 1970s also witnessed the emergence of the first Hot Dry Rock facility, an Enhanced Geothermal System (EGS) for electricity production, in Fenton Hill, New Mexico.
The subsequent decades saw advancements in technology for geothermal power plants, with successful demonstrations of flash steam and binary cycle systems. The 1980s saw a rapid increase in the number of district heating systems in the United States, with 19 systems entering operation, most of them during that decade.
Today, geothermal electricity generation is utilised in 26 countries, while geothermal heating is employed in 70 countries. As of 2019, the worldwide geothermal power capacity reached 15.4 gigawatts (GW), and it continues to grow, with untapped potential estimated to be as high as 2000 GW.
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Geothermal power's viability and potential
Geothermal power is a viable and sustainable source of energy with a long history of use. The ancient Romans, Chinese, and Native Americans all used geothermal energy for bathing, cooking, and eating. Today, most people in Iceland use geothermal energy for heating water and buildings.
The viability of geothermal power lies in its ability to provide a consistent and renewable source of energy. Geothermal power plants can run 24 hours a day, 7 days a week, regardless of weather conditions, and have a capacity factor of up to 96%. Additionally, geothermal power requires no fuel, making it immune to fuel cost fluctuations. However, capital costs for geothermal power can be high, with drilling accounting for over half of the expenses.
The potential of geothermal power is significant. As of 2019, worldwide geothermal power capacity amounted to 15.4 gigawatts (GW), with 3.68 GW installed in the United States. However, the Geothermal Energy Association (GEA) estimates that only 6.9% of the total global potential has been tapped so far, with the potential ranging from 35 GW to 2 TW. The Next-Generation Geothermal Power report identified the potential for up to 300 GW of next-generation geothermal electricity generation with the development of storage capabilities and emerging technologies.
Geothermal power also has a small environmental footprint compared to other power sources. Geothermal power plants use less land per gigawatt-hour than coal, wind, or solar photovoltaic power stations. Additionally, modern geothermal power plants release no greenhouse gases and have a lower life cycle impact than solar or natural gas.
The key to unlocking the full potential of geothermal power may lie in utilizing existing oil and gas wells. There are two methods for producing geothermal energy from oil and gas wells: the abandoned well process and co-production. By using these existing wells, geothermal energy can be generated without the high capital costs associated with drilling new wells.
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Geothermal electricity's environmental impact
Geothermal electricity is generated from geothermal energy, which is heat energy from the earth. Geothermal resources are reservoirs of hot water that exist at varying temperatures and depths below the earth's surface. Wells are drilled into these underground reservoirs to tap steam and very hot water that can be used for heating or electricity production.
Geothermal energy is a clean, renewable energy source that has been used for thousands of years. It is considered environmentally friendly as it produces far fewer carbon dioxide emissions than natural gas or coal-fired power plants. Binary-cycle geothermal plants, which operate in a closed cycle, release zero emissions. The greenhouse gas emissions of geothermal electric stations average 45 grams of carbon dioxide per kilowatt-hour of electricity, or less than 5% of those of conventional coal-fired plants.
However, geothermal power plants can impact water quality and consumption. The hot water pumped from underground reservoirs often contains high levels of sulfur, salt, and other minerals. Most geothermal facilities have closed-loop water systems, where the extracted water is pumped directly back into the geothermal reservoir after use. This prevents contamination and land subsidence. Nonetheless, not all water removed from the reservoir is re-injected, as some is lost as steam, and outside water must be added to maintain the reservoir's water volume. The amount of water needed depends on the plant's size and technology, and geothermal plants can require between 1,700 and 4,000 gallons of water per megawatt-hour.
The movement of fluids into or out of wells can also induce seismic or microseismic activity. The United States has developed a mitigation protocol to address this issue, and all GTO-funded projects are required to follow this protocol.
Geothermal power plants also have low thermal efficiency, typically between 7-10%, as geothermal fluids are at a lower temperature than steam from boilers. This low temperature limits the efficiency of heat engines in extracting useful energy during electricity generation, and exhaust heat is wasted unless used locally, such as in district heating.
Despite these environmental impacts, geothermal energy has the potential to meet 3-5% of global demand by 2050, and with economic incentives, this could increase to 10% by 2100.
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Frequently asked questions
Geothermal electricity is electricity generated from geothermal energy.
Geothermal energy is heat energy from the Earth's crust. It is a renewable energy source because heat is continuously produced inside the Earth.
Technologies used to generate electricity from geothermal energy include dry steam power stations, flash steam power stations, and binary cycle power stations.
Geothermal electricity is considered to be a sustainable and renewable source of energy. It has a large capacity factor, low greenhouse gas emissions, and is not dependent on weather conditions.
Geothermal electricity generation is currently used in 26 countries, including El Salvador, Kenya, the Philippines, Iceland, New Zealand, and Costa Rica.
