Geothermal energy often remains overlooked and underutilized in our quest for sustainable and renewable energy sources. Harnessing the earth’s natural heat to generate power has immense potential to meet our energy needs while reducing greenhouse gas emissions.
What is Geothermal Energy
Geothermal energy is heat generated within the Earth. In Greek, Geo means “earth,” and thermal means “heat.” The slow decay of radioactive particles in the Earth’s core produces geothermal energy. Since heat is continuously produced inside the Earth’s core, geothermal energy is considered a clean, renewable resource that can be harnessed for use as heat and electricity.
Geothermal reservoirs are naturally occurring areas of hydrothermal resources. These reservoirs are deep underground and are largely undetectable above ground. Geothermal energy finds its way to the earth’s surface in three ways:
- Hot springs
The most active geothermal resources are usually found along major tectonic plate boundaries where most volcanoes are located.
The History of Geothermal Energy
The use of geothermal energy has a rich history dating back to ancient civilizations. The earliest recorded use can be traced to China, where hot springs were employed for bathing and medicinal purposes. Evidence shows that Native Americans used geothermal energy for cooking as early as 10,000 years ago. The Greeks and Romans also recognized the power of geothermal energy, constructing bathing complexes and heating systems that relied on underground hot water.
The world’s first district heating system was installed at Chaudes-Aigues, France, in the 14th century. The hot springs have provided a source of income and energy for the town since the 1300s. Today, tourists flock to the town for its elite spas. The low-temperature geothermal energy also supplies heat to homes and businesses.
It was not until the late 19th century that other cities, as well as industries, began to realize the economic potential of geothermal resources. Geothermal energy development gained momentum with the first geothermal power plant in Larderello, Italy.
Geothermal Energy in the United States
In the United States, geothermal heat was first delivered to residences in 1892, to Warm Springs Avenue in Boise, Idaho.
Today, the United States generates the most amount of geothermal energy of any other country. Every year, the U.S. generates at least 15 billion kilowatt-hours, or the equivalent of burning about 25 million barrels of oil (source). However, geothermal energy only accounts for .04% of all energy used within the United States. Geothermal energy is still a highly untapped renewable resource.
The largest geothermal development in the world is at The Geysers north of San Francisco, California. Despite the name, there are no geysers there and the energy used is all steam rather than hot water. In the United States most of the geothermal energy is produced in four states:
Top Producing Countries for Geothermal Energy
Here’s a look at a few of the countries leading the way in the implementation of geothermal facilities (source).
- Indonesia: Analysts have estimated that Indonesia will overtake the US regarding geothermal capacity by 2027. The country recorded a geothermal capacity of 1,948MW in 2018, making it the world’s second-biggest producer of geothermal energy. Indonesia is home to four of the world’s top 10 geothermal power projects.
- Mexico: Located in northern Mexico, the Cerro Prieto Geothermal Power Plant is the third largest in the world, with an output of 720 MW. The plant is built on a somewhat unique point of geology, a spreading fault line in a landlocked area. The phenomenon is typically found only on the ocean floor.
- Iceland: Nations such as Iceland are well placed to exploit geothermal resources, which they have done since 1907. With 25 active volcanoes and 600 hot springs, 25% of Iceland’s energy comes from five geothermal power plants.
How Geothermal Energy Works
Geothermal power plants tap into the Earth’s heat through three primary methods: dry steam power stations, flash steam power stations, and binary cycle power stations.
- Dry steam plants: The oldest type uses steam directly from a geothermal reservoir to turn generator turbines.
- Flash steam plants: This is the most common type of plant. These plants pull high-pressure hot water from underground and mix it with cooler low-pressure water. This process creates steam that is used to drive a turbine.
- Binary cycle power plants: Most future geothermal power plants are expected to be binary plants. These plants transfer the heat from geothermal hot water to another liquid. The heat causes the second liquid to turn to steam, which is used to drive a generator turbine.
Applications of Geothermal Energy
Geothermal energy has numerous applications across various sectors. One of the most common uses is for electricity generation, where geothermal power plants produce reliable and baseload power. Additionally, geothermal heat pumps are widely employed for space heating and cooling in residential and commercial buildings. These systems extract heat from the ground during winter for heating purposes. They can reverse the process during summer to provide cooling.
Geothermal energy is also utilized in direct-use applications, such as bathing, spas, and greenhouse heating. District heating systems use geothermal energy to provide heating to multiple buildings in a localized area, reducing the reliance on fossil fuels and decreasing greenhouse gas emissions.
The Pros and Cons of Geothermal Energy
There are several advantages to increasing the adoption of geothermal energy which include:
- Renewable and Clean: Geothermal energy relies on the Earth’s internal heat, which is continuously replenished, making it a renewable resource. It produces minimal greenhouse gas emissions and has a smaller environmental footprint than fossil fuels. Each year, U.S. geothermal electricity offsets the emission of 4.1 million tons of CO2, 80 thousand tons of nitrogen oxides, and 110 thousand tons of particulate matter from coal-powered plants (source)
- Cost-effective: Geothermal energy is a cost-effective energy source, especially for heating and cooling applications. Once the initial infrastructure is in place, operational costs are relatively low.
- Baseload Power: Geothermal power plants can provide a constant supply of electricity, making them suitable for baseload power generation
While geothermal energy holds great promise, it does face certain challenges, including:
- Location Dependency: Geothermal resources are geographically limited, requiring specific geological conditions for efficient operation. Not all regions have accessible geothermal reservoirs. Most of the geothermal technologies in the United States are located in the West.
- High Initial Costs: The exploration and drilling required to tap into geothermal resources can be expensive. This initial investment may hinder wider adoption. It costs approximately $2-$7 million for a plant with a 1 megawatt capacity (source).
- Sustainability: To maintain the sustainability of geothermal energy, fluid needs to be pumped back into the underground reservoirs faster than it is depleted. This means that geothermal energy needs to be properly managed to maintain its sustainability.
- Earthquakes: Geothermal energy also runs the risk of triggering earthquakes. This is due to alterations in the Earth’s structure due to digging. This problem is more prevalent with enhanced geothermal power plants, which force water into the Earth’s crust to open up fissures to greater exploitation of the resource. However, since most geothermal plants are away from population centers, the implications of these earthquakes are relatively minor.
Geothermal energy represents a largely untapped resource with immense potential. Its ability to provide clean, reliable, and sustainable power, with its minimal environmental impact and economic viability, makes it an attractive option for pursuing a greener future.
As technology advances and costs decrease, geothermal energy has the potential to play an even more significant role in the global energy transition. Capitalizing on the Earth’s heat can reduce our dependence on fossil fuels and mitigate climate change while enjoying the benefits of reliable and sustainable power generation, heating, and cooling systems.
With its ancient roots and modern applications, geothermal energy holds great promise as a renewable energy source. Continued research, technological advancements, and increased investment, should push geothermal energy to emerge as a significant player in the global energy landscape, offering an additional pathway toward a sustainable and decarbonized future.
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