How Is Geothermal Energy Harnessed? – Geothermal Energy Extraction

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Geothermal energy is harnessed using 3 types of conversion plants

How  Geothermal energy is harnessed

As the world attempts to shift to non-fossil-based energy sources, more and more companies look at geothermal energy and how to harness it. The earth’s molten interior generates heat continuously, which is responsible for producing geothermal energy.

Interestingly, our ancestors used geothermal heat for daily activities such as cooking, bathing, and treating skin conditions. Some countries have also been harnessing this energy to generate electricity and directly heat and cool properties for years. Nowadays, it’s used for industrial, agricultural, road maintenance, community safety, and more.

Originally harnessed by big power plants, experts have successfully developed smaller systems for property owners. Thus, this shift to geothermal energy use is now accessible to residents and business owners. Allow me to help you better understand how geothermal energy is harnessed, converted to electricity, and generated, how it’s used, and what its advantages are.

Video – Harnessing the Earth’s power; Geothermal Energy

 

How Is Geothermal Energy Generated?

Approximately 1,800 miles or 2,900 kilometers below the earth’s surface is its hottest part, called the core. Its temperatures reach upwards of 9,000°F or 5,000°C. Most of the heat comes from the continuous process of radioactive isotope decay. This core heat constantly radiates outward and warms any present water, rocks, gas, and other geothermal materials.

The heated rock formations underground that reach 1,300 to 2,400°F or 700 to 1,300°F turn into magma or molten rocks. It stays in the earth’s lower crust or mantle but may bubble to the surface as lava or gas. As you can imagine, it heats the surrounding and nearby aquifers and rocks.

The produced hot water is released through hot springs, geysers, mud pots, underwater hydrothermal vents, and steam vents. These are the primary geothermal energy sources we can harness or capture.

On the other hand, some geothermal energy remains in the earth’s mantle and won’t bubble out as steam, water, or magma. This energy slowly emits outward and collects as pockets of dry heat with high temperatures, which we need to access, turn into steam, and convert to electricity.

How Geothermal Energy Is Harnessed From the Internal Heat of Earth

The majority of geothermal energy is obtained through geothermal power plants installed near geysers, hot springs, and/or through volcanic activities.

Wells are drilled about one to two miles deep underground to access heat or heated gas, which is harnessed with the help of spinning turbines. They then pump out heat or steam to the surface.

What Are Other Methods of Harnessing Geothermal Energy?

As of writing, there are two other different ways on how geothermal energy is harnessed, namely:

  • Using ground source or geothermal heat pumps

  • Using enhanced geothermal systems

Using Geothermal Heat Pumps (GHP)

Horizontal pipe loops for heat pump heat extraction

Heat pumps extract geothermal energy using horizontal pipe loops

GHPs are available in different types, but they all work similarly. They take advantage of the differences between subsurface soil and above-ground air temperatures. As such, these multi-pipe pumps are also buried underground.

The fluid or water carrying underground heat moves from one point to another. If the ambient air temperature is lower than the ground temperature, the pump moves the heat from the ground up.

These systems will operate reversely when the ambient air temperature is higher than the ground temperature. That means they will move the ambient air heat into the ground, cooling the building down.

Using Enhanced Geothermal Systems

Aptly named, these systems are drilled deeper into the ground than the ground source or GHPs to provide heat with higher temperatures. Some models inject water into the ground through one of their wells, bringing steam or water to the surface via another well. It is then used as a direct heat source or converted to electricity.

Other EGS varieties will directly capture the underground steam, which we can then convert to electricity.

Advantages of Geothermal Energy

Geothermal energy has many advantages. Here are the most common:

That said, it’s also worth noting that they operate quietly because they are drilled inside the ground. Also, geothermal energy reduces imported energy dependence, promoting a healthier economy due to trade deficit decrease.

Is Geothermal Energy Renewable?

One of the questions concerning the benefits of using geothermal energy is if it’s a renewable energy source. Based on what renewable resource means, we can consider geothermal energy renewable as long as its source, the earth, exists.

How Is the Heat of the Planet Used as a Source of Energy?

The planet’s heat can produce two types of geothermal energy sources. One of these is low-temperature geothermal energy. This energy is obtained from heat pockets with temperatures around 302°F or 150°C. They are found a few meters below the ground. Although efficient as a heat source, it’s also used for generating electricity.

Another is co-produced geothermal energy. Relying on other energy sources, this geothermal energy utilizes gas and oil well steam or hot water byproducts discarded in the past.

Recently, binary cycle plants use the steam produced to generate electricity, helping extend gas and oil field lifespans and lowering greenhouse gas emissions.

How Is Geothermal Energy Used?

Below is a table detailing how geothermal energy is used worldwide based on the Direct Utilization of Geothermal Energy 2020 Worldwide Review and the Geothermal Power Generation in the World 2015-2020 Update Report.

Categories

Examples

Top Users

Space (Individual and District) Heating

  • Building and whole community heating systems

  • District: China, Iceland, Turkey, France, and Germany

  • Individual: Turkey, Japan, Russia, the USA, and Switzerland

Ground Source Heating and Cooling

  • GHP-based heating and cooling systems of buildings

  • China, Finland, Germany, Sweden, and the USA

Space Cooling

  • Air conditioners

  • Bulgaria, Brazil, Australia, Slovenia, Algeria, Albania, and India

Covered Ground and Greenhouse Heating

  • Crop (fruit, vegetable, and/or tree seedling) growing

  • Greenhouse: Turkey, China, Netherlands, Russia, and Hungary

  • Covered Ground: Iceland and Greece

Aquaculture

  • Fish, prawn, shrimp and/or alligator farming or cultivation

  • China, USA, Iceland, Italy, and Israel

Agriculture

  • Crop (fruit, vegetable, and/or grain) drying

  • China, France, Hungary, USA, and Japan

Industrial

  • Boric acid and borate production

  • Chemical extraction

  • Concrete curing

  • CO2 extraction

  • Leather production

  • Milk pasteurization

  • Paper and pulp processing

  • Salt and iodine extraction

  • Water and carbonated drink bottling

  • China, New Zealand, Iceland, Russia, and Hungary

Bathing, Swimming, and Therapy (Balneology)

  • Geothermal energy heated pools and hot springs

  • China, Japan, Turkey, Brazil, and Mexico

Snow Melting

  • Use of geothermal flash-steam heat to melt street, sidewalk, and pavement snow

  • Geothermal energy heated pavements

  • Iceland, Japan, Argentina, USA, and Slovenia

  • Iceland

Others

  • Frost protection, irrigation, and a geothermal tourist park

  • New Zealand

  • Cooking

  • Japan

  • Water boiling

  • Kenya

Power Generation

  • Geothermal energy as a source of electricity

  • The USA, Indonesia, the Philippines, Turkey, New Zealand, Mexico, Italy, Kenya, Japan, and Costa Rica

How Is Geothermal Energy Converted Into Electricity?

To convert and generate electricity, we need to capture or obtain a good amount of geothermal energy deep underground. Based on the information on how to harness geothermal energy, we can do so with the help of geothermal power plants.

How energy is harnessed from geothermal

As noted, geothermal plants can use heat or steam to convert energy to electricity. Thus, you will find several types of geothermal power plants that use specific processes to generate electricity, namely:

  • Dry steam

  • Flash steam

  • Binary cycle

Dry Steam

Dry steam is the oldest geothermal electricity generating plant in the world. These power plants collect naturally occurring underground steam stored in their underground wells. The steam then gets directed to a generator or turbines, where it is converted to electricity.

Flash Steam

Flash steam plants for harnessing geothermal power

Flash steam plants harness the heat from existing high-temperature water reservoirs underground.

Flash steam is the most common way to generate electricity using geothermal energy. As such, these power plants use naturally occurring hot water reservoirs.

Hot water with temperatures higher than 360°F or 182°C flows to the underground wells. As it moves upward, the pressure decreases. The water also begins to boil and rapidly evaporates or “flashes” into steam.

The steam produced separates from the water and gets directed to the generator or turbine, converting energy into electricity. The remaining water and condensation get injected back into a tank or reservoir to extract more energy.

Binary Cycle

This unique process involves steps that help conserve water while generating electricity. The underground water gets heated between 225°F and 260°F or 107°C and 182°C.

This heated water is responsible for boiling a working fluid with a lower boiling point, which is usually an organic compound. The steam it produces flows through a turbine to power the generator and produce electricity. Like in flash team powers plants, the remaining water is injected back into the ground for re-heating.

Harnessing and Using Geothermal Energy

From being harnessed through power plants to creating heat pumps and enhanced geothermal systems even homeowners and small businesses can have installed, geothermal energy has come a long way.

In fact, many can now enjoy the long list of geothermal energy benefits and use. Opting for this clean and 24/7 energy source will help save the environment, conserve natural resources, and help your country’s economy. Of course, geothermal energy isn’t perfect, but the advantages outweigh the disadvantages.

References:

Hyperlinks plus:

http://needtoknow.nas.edu/energy/energy-sources/renewable-sources/geothermal/#:~:text=Geothermal%20energy%20is%20produced%20by,on%20an%20electric%20power%20generator.

https://kids.frontiersin.org/articles/10.3389/frym.2019.00105

https://archive.epa.gov/climatechange/kids/solutions/technologies/geothermal.html

http://plaza.ufl.edu/sarahcon/geothermal.html

https://www.nrel.gov/research/re-geo-elec-production.html

https://www.go-gba.org/resources/green-building-methods/geothermal-energy/

https://www.nationalgeographic.org/encyclopedia/geothermal-energy/

https://www.epa.gov/rhc/geothermal-heating-and-cooling-technologies

https://www.eia.gov/energyexplained/geothermal/use-of-geothermal-energy.php

https://taraenergy.com/blog/geothermal-energy-learning/

Related resources:

Harnessing the Heat Beneath Our Feet: Geothermal Energy

Harnessing Geothermal Energy – Ufl


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