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The planet we share is full of natural energies. Could the geothermal energy in the ground beneath us be used to help power our homes renewably?
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We all want to take active steps to drive down our energy bills and live our lives more sustainably. Switching to a green energy supplier and / or a renewable tariff can help us to do both. However, as the energy industry rises to the challenge of creating a world where we no longer need fossil fuels to generate electricity, it needs to consider new ways of harnessing the planet’s natural energies. Could geothermal energy be an efficient way to create a more renewable future?
Most of us are familiar with solar power, wind farming, hydroelectricity and biomass energy. These methods of renewable energy production are infinitely scalable. They are employed in large scale energy farms and in domestic settings alike. In many ways, the same can be said for lesser-known geothermal energy. Here we’ll take a close look at geothermal energy, and its potential place in a more renewable future.
What is geothermal energy and how does it work?
Deep within the earth’s core the molten rock and magma can reach extraordinarily high temperatures of over 4000°C. And every now and then, we get a jarring reminder on the surface of just how explosive that heat can be. Every time we see a volcano, or even something as comparatively benign as a geyser erupt, we’re reminded of the enormous reserves of heat energy deep beneath us.
Geothermal energy uses this heat to generate renewable electricity.
Of course, leveraging geothermal energy is nothing new. Civilisations have been using geothermal energy to cook their food, bathe and heat their homes for centuries. The ancient Greeks and Romans as well as the Native Americans have all been documented users of geothermal energy.
What’s more, geothermal power plants have harnessed this energy for over a century, with the first geothermal plant opening in Tuscany, Italy in 1904.
Geothermal energy is at a historical high, with 92 teraWatt hours (tWh) generated all over the world in 2019. An increase of 3% over the previous year. However, it is not currently on track to reach the required Sustainability Development Scenario (SDS) level, which would require 10% annual growth by 2030 to reach its target of 282 tWh per anum.
The International Energy Agency (IEA) has some useful data on geothermal energy, its rise and targets. You can access their website here.
How geothermal energy works?
The principle behind geothermal energy is not dissimilar to the principles behind nuclear energy generation. In both cases extreme heat is used to generate steam which powers a turbine that generates electricity. Although different geothermal power plants operate in slightly different ways.
Wells up to a mile or more in depth are drilled into underground heat reservoirs. The geothermal energy in rocks and water can be exploited naturally. However, enhanced geothermal systems can either enhance existing geothermal resources or create new ones from scratch.
These use a process called hydraulic stimulation which is not dissimilar to the process of hydraulic fracturing (fracking). Whether geothermal resources are natural or enhanced the resultant steam is used to drive turbines which then generate electricity.
What are the advantages of geothermal energy?
Because geothermal energy is a vast and relatively untapped resource, it brings with it a number of inherent benefits for generating electricity:
- It is eco-friendly and low-carbon. Although some pollution is created it pales in comparison to burning fossil fuels. Indeed, carbon emissions are a sixth those of a natural gas power plant.
- It’s infinitely renewable as geothermal energy is constantly available and always being replenished.
- It is not reliant on weather conditions like solar or wind power.
- Geothermal energy has huge potential and is a fast-evolving part of the energy industry.
- It’s highly scalable. The domestic ground source heat pumps that heat water in many homes use the principles of geothermic energy.
What are the disadvantages of geothermal energy?
All methods of energy generation have their inherent disadvantages. Even renewable energy sources like geothermal energy.
Here are some of the disadvantages of generating electricity in this way:
- Geothermal energy generation requires the release of some greenhouse gases that are trapped beneath the earth’s surface. Though nowhere near as damaging as fossil fuel generation, this means that geothermal energy is not as clean as wind or solar energy.
- Extracting geothermal energy has been known to trigger earthquakes. Although thankfully these tend to have little impact on communities as the power plants are far removed from population centres.
- Generating geothermal energy requires huge upfront costs.
- Geothermal energy is location specific, meaning that it cannot be generated all over the world. Just in areas where geothermal energy is naturally accessible.
Different types of geothermal energy generation
There are three distinct methods of geothermal energy generation:
This is the oldest method of generating electricity from geothermal energy. This takes steam directly from fractures within the earth to drive the turbine.
Pressurised hot water is drawn from deep underground and mixed with lower pressure cool water. This then creates steam that drives the turbine.
These plants use hot water passed through a secondary fluid with a lower boiling point. This secondary fluid is then turned into a vapour that drives the turbine.
Because this is the most stable and reliable method, it is expected that most of tomorrow’s geothermal power plants will be binary plants.
The sustainability of geothermal energy
While geothermal energy is renewable, it needs to be carefully managed in order to be sustainable. Geothermal energy fluid needs to be pumped back into the underground reservoirs at a faster rate than it is depleted.
If this practice is maintained, we can hopefully benefit from near-infinitely renewable geothermal energy for generations to come.
Looking for a new renewable energy supplier? We’re here to help!
Although geothermal energy generation has yet to take off in the UK, we do have significant energy from renewable sources in our energy mix. What’s more, there are a wealth of green suppliers offering 100% renewable tariffs.
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Geothermal energy FAQs
Is geothermal energy production possible in the UK?
At present the UK has no geothermal power plants. Nonetheless, the UK does have the potential for geothermal energy production. While we have no active volcanic sites, solar energy can still be harnessed from within the ground. Likewise granite deposits deep beneath the surface can act as energy exchanges, heating water in order to create steam that could drive a turbine.
Are ground source heat pumps geothermal energy?
Technically no. Although they do work on a very similar principle. Ground source heat pumps also take advantage of the natural heat energy deep below the ground. However, these pumps do not penetrate the earth’s surface to nearly the same degree that’s required for geothermal energy generation.
These pumps use a combination of water and antifreeze to transfer heat energy from within the ground to a heat exchanger in your home where it is used to heat up your home’s water supply.
While not technically geothermal energy, ground source heat pumps can be a great way to heat your home more renewably, saving you up to £1,200 a year.
How sustainable is geothermal energy?
Reserves of heat energy beneath the surface are vast and near-infinitely renewable. However, geothermal energy fluid must be pumped back into the underground reservoirs at a faster rate than it is depleted in order for it to remain sustainable.
Where is geothermal energy used?
Geothermal energy is not readily accessible all over the world. However, it is generated in 20 countries across the globe. The USA has numerous geothermal hot spots and Iceland also benefits from significant geothermal resources. Latin America also has a more modest geothermal capacity.
Other countries that harness geothermal energy include:
- Papua New Guinea
- New Zealand
To read more on this topic, check out these guides:
Updated on 24 Nov, 2020