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Energy Guide

What Is Geothermal Energy?

Geothermal energy is heat that is stored in the sub-surface of the earth that can be harnessed to generate electricity. Not only is it a renewable energy source, but it is also constantly available, thanks to radioactive decay and the heat that has been stored below the earth’s crust since its formation.

How Is Geothermal Energy Produced?

Unlike unsustainable energy sources, geothermal power does not require the burning of fossil fuels. Steam from the hot water found in the underground reservoirs is all it takes to power a generator and produce electricity.

Magma, which is found in the earth’s mantle, heats water that is trapped in cracks of porous rock. This heated water becomes a natural heat source, known as geothermal.

The water and steam found in these heated reservoirs can be harvested by constructing a well to connect the reservoirs to the power plants above.

Sometimes, cracks in the earth allow for this steam to naturally escape to the earth’s surface, which appears in the form of geysers and hot springs.

How Does Geothermal Energy Work?

How Else can Geothermal Energy Be Used?

Outside of electrical power generation, geothermal resources can be harnessed through direct use and geothermal heat pumps.

Direct use

Pumps and generators are not required to harness the power of geothermal resources; they can be used directly. This is the oldest form of geothermal usage that dates back to ancient history when hot springs were used for bathing and cooking food.

Direct use of this renewable energy source is still popular today and can be used to heat buildings. With the help of piping and a heat exchanger, geothermal energy can be extracted from the source and used to power a house directly. Direct harnessing is also used in some swimming pools, spas, and greenhouses around the world.

Geothermal heat pumps

Geothermal heat pumps can be installed underneath homes to heat them during the winter and cool them in the summer. Normally positioned around 6 metres below the surface of the earth, geothermal heat pumps take advantage of the consistent heat levels found down there, which normally ranges between 10 and 16 °C, depending on your location.

A geothermal heat pump uses a heat exchanger and a loop of pipes to harness this below-ground energy source. Once harnessed, it can then be used to heat the building above in the winter. In the summer, this geothermal heat pump can work in reverse, by channelling the hot air in your home down to the cool earth below.

The Pro and Cons of Geothermal Energy

Is Geothermal Energy a Good Option for Home Heating?

Geothermal energy is more reliable, sustainable, and cost-effective as a home-heating solution than other energy sources. It is the cheapest form of clean energy available in terms of maintenance. Plus, home heating solutions such as geothermal heat pumps have long warranties, with heat pump pipes said to last between 25 and 50 years.

It is a costly investment to install, with ground source pumps costing sometimes as much as £20,000. However, it could save you over 80% in monthly energy bills, making it a worthwhile investment in the long term.

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Final Thoughts


Can geothermal energy replace fossil fuels?

Geothermal electricity is a viable alternative to fossil fuel energy. It creates far fewer emissions than the likes of coal. In total, a geothermal plant produces 99% less carbon dioxide than a fossil fuel plant of a similar size.

Is geothermal energy cheap?

Although expensive to set up, geothermal renewable energy costs less than gas, electric storage, oil-fired, and LPG heating annually.

Which country is the world’s largest producer of geothermal energy?

The U.S. is the largest producer of geothermal power, with an installed capacity of 3,676MW. The Geysers in California is the largest collection of power plants dedicated to geothermal energy use in the world.

The installed capacity of the leading geothermal renewable energy producers are as follows:

  • U.S. – 3,676MW
  • Indonesia – 2,133MW
  • The Philippines – 1,918MW
  • Turkey – 1,526MW
  • New Zealand – 1,005MW

How much does it cost to drill a geothermal well?

When drilling a geothermal well for home use, each metre of depth costs around £40.