What is geothermal energy?

Have you ever been in a natural hot spring or mud bath? Did you know that that heat comes from under the Earth's surface, and that that same energy source can be used to both heat and cool your home!

There is even evidence that geothermal heating has been used as an energy source for well over 10,000 years, with Ancient Greek, Roman, Chinese and Native American cultures records showing they also used it for various cooking, bathing and warming purposes.

Even though our purposes and uses for collecting this energy are not so different, how we harness this energy has definitely progressed since the prehistoric ages.

How does geothermal heating work?

Now, for water heat pumps we use a system of pipes that travel deep down into the ground that pump fluid through them which warms naturally as it absorbs the heat from underground. These pipes then bring the heated water back up to a ‘heat exchanger’ that then pulls the heat from the liquid to turn it into hot air to warm us or even heat water to use in our homes.

Not only that, but they can cool during the summer by essentially working in reverse - absorbing the heat from inside your home and moving it back down into the Earth where it will stay until it’s extracted again, acting as almost a thermal battery. It’s beautifully simple!

These systems aren’t just for homes, but can also be adapted for larger scale energy harvesting at geothermal power plants. They do this through essentially the same system as for our homes: by tapping into hot water and steam sources deep in the ground, which is then used to drive an electrical generator to create energy that our homes and cities can use.

In some parts of Iceland, geothermal hot water pipes run under roads and footpaths to melt the ice and snow in winter to keep the streets safer for both pedestrians and drivers. Such a clever idea!

Geothermal heating pump illustration in home

Geothermal pumps use a system of pipes that travel deep down into the ground that pump fluid through them which warms naturally as it absorbs the heat from underground.

Image: Studio Harmony
Shutterstock Standard License

Why should we use geothermal energy?

Geothermal energy is a great resource to have as it doesn’t produce any carbon dioxide or require fossil fuels such as coal or oil.

Considering geothermal energy essentially comes from heat from the sun absorbed into the ground, the supply is basically limitless, constantly accessible, and essentially free. A typical geothermal power plant is able to provide electricity for around 8,600 hours per year and is not affected by whether it is day or night and it is not affected by seasonal weather conditions (factors that with wind and solar power need to be managed with batteries).

Currently it is estimated that the global energy consumption level is roughly 15 terawatts - well within the realms of possibility for the entire potential energy that geothermal sources could provide. We have the resources, now we just need to create the systems!

Action: Look up some diagrams of how a geothermal heating and cooling pump works. Learn about the system installed in a housing development in Blacktown, Sydney. If you have the opportunity, visit a natural hot spring to feel the Earth's heat for yourself!