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How geothermal energy works

Did you know that hot water from the earth is a source of renewable energy? Here’s the lowdown on geothermal energy – what it is, how it works, and how it can help you.

Did you know that hot water from the earth is a source of renewable energy? Here’s the lowdown on geothermal energy – what it is, how it works, and how it can help you.

Written by
Dan Tremain
Energy and business energy expert
19 JANUARY 2021
4 min read
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What is geothermal energy?

Power plants create electricity using heat. Most of them use gas, coal, or nuclear power to generate that heat, but some use geothermal energy – heat from deep down inside the earth.

Geo means earth, and thermal means heat, so geothermal energy is just another way of saying heat from the earth. When you see geysers and volcanoes erupt, what you’re actually watching is geothermal energy at work. 

How does geothermal energy work?

The further beneath the earth’s surface we go, the hotter it gets – geologists calculate by as much as 15ºF for every mile. Geothermal power plants work by capturing that heat energy and using it to generate electricity. You can also get geothermal heat pumps, commonly referred to as ground source heat pumps, which access heat closer to the earth’s surface and use it to warm our homes.

Where does geothermal energy come from?

We can access hot water and steam from deep inside the earth by drilling down. It’s a bit like drilling for oil. Obviously, the wells need to go down pretty far – some go as far as a mile or two. Not everywhere in the world has the right geological conditions to create geothermal energy.

Ground source heat pumps work by extracting heat from soil just metres from the earth’s surface. A device positioned at a customer’s property then converts this heat into energy for the home.

How is geothermal energy generated?

Geothermal energy is generated in power stations. These look a lot like other types of power station, with huge generators and turbines.

We can also use volcanic rocks to make electricity. Some rocks contain uranium, a radioactive substance that releases hot energy. The rocks heat up water in the ground, which creates steam. This then rises to the surface and powers electricity generators and turbines.

Some countries also have volcanoes where underground water reservoirs reach temperatures of some 200 degrees – double the boiling point. Drilling wells down to these reservoirs means we can access the steam and use it to power turbines, generating electricity.

What are the advantages of geothermal energy?

Geothermal energy has lots of benefits. Here are a few of them:

  • Geothermal energy is renewable – that’s to say, the earth is producing heat all the time, so there’s no danger we’ll run out of it.
  • Unlike solar or wind energy, geothermal energy is available in all weathers.
  • Geothermal energy is an area with lots of room for growth.
  • Geothermal energy is arguably safer than nuclear power.

What are the disadvantages of geothermal energy?

Geothermal energy comes with its downsides, too. These include:

  • There aren’t that many places in the world with the right geological conditions to create geothermal energy.
  • If not carefully managed, a well – or borehole – may not be reusable for decades.
  • Extracting water from the earth can potentially release harmful gases, like CO2, into the atmosphere.
  • Building geothermal power plants costs a lot of money.
  • Geothermal power plants take up huge amounts of space that could be put to other uses.

How long have we been using geothermal energy?

Geothermal energy isn’t a new technology. The first industrial power plant to harness it opened in Italy back in 1904, but geothermal resources have actually been used by humans for thousands of years. It’s something we’ve found ourselves returning to as we look for more sustainable energy sources.

Where can you find geothermal power stations?

There are geothermal power stations in Italy, New Zealand, Ecuador and Hawaii, among other places. And you’ll find the world’s biggest group of geothermal power stations at a place called the Geysers in California. It’s a massive area, home to some 22 power plants.

You’ll also find geothermal power plants in Iceland – which perhaps isn’t surprising in a country that’s famous for its volcanoes and hot springs. Iceland has five geothermal power plants that produce a quarter of the country’s energy.

Are there geothermal power stations in the UK?

There aren’t any geothermal power plants in the UK right now, although we could potentially build one. Obviously, geysers and volcanoes aren’t something we have an abundance of here, but we do have thermal springs in places like Bath.

What we also have is granite, particularly in Cornwall. Granite has unique mineral properties that make it hotter than the earth around it. Think of it like a little heater. To create electricity, you can drill into the granite and run water through the hole. The water will heat up, and you can use the steam to power a turbine.

Is geothermal energy renewable?

Geothermal energy is considered to be both renewable and sustainable because it uses natural heat from the earth.

Will geothermal energy ever run out?

One of the great things about geothermal energy is that it will never run out. We’ll have heat from the earth for as long as we have the earth. And because it’s not weather-dependent, geothermal energy can produce electricity around the clock.

How do I find a renewable energy provider?

When looking for an energy provider, it’s always a good idea to shop around. That way you can not only compare price, you can also see how environmentally friendly your supplier is, too.

Switching energy suppliers is easy. The transition is seamless, so you won’t find yourself without a power supply.

Start comparing cheaper energy tariffs with Compare the Market today.

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