Geothermal power harnesses the heat of the Earth

If the Earth were reduced to the size of an apple, the crusty shell we call solid ground would be no thicker than the skin of that apple.

Beneath our feet is a world unlike any we could possibly imagine. Scratch below the surface of the Earth, and you reach the Mantle, a 2,900km-thick layer which makes up 84 per cent of our planet’s volume. While it is technically a solid layer, the Mantle can actually have a semi-liquid property, with some scientists describing the melted parts of this layer having the consistency of caramel.

The crust is arranged in such a way that some of this semi-liquid mantle is able to spill out onto the Earth’s surface, often at the bottom of oceanic trenches or through volcanic eruptions.

Despite having a caramel-like viscosity in parts, the bowels of the Earth are anything but sticky and sweet. At 1,000 degrees celsius, any organic material would instantly ignite. As you approach the core, super-heated liquid metal begins to become dominant and grows increasingly dense.

By the time you reach the inner core, temperatures have reached 7,000-8,000 degrees celsius. Life below the surface is impossible, and yet the tumultuous forces at the depths of the Earth are what keep us alive up top. Not only that, but the churning of the Earth is a phenomenal source of clean energy.

Origins of geothermal power

Not all countries have access to this incredible power, admittedly. The Earth’s crust is fractured at distinct points, consisting of a series of floating plates which collide or sink beneath one another, depending on their thickness and density. The Himalayas are a result of two dense plates colliding millions of years ago, which continue to do so to this day.

The junctures between plates are fault lines which can often slip or jerk suddenly and violently, prompting earthquakes and even tsunamis, if the tectonic activity occurs underwater. The UK’s geology paints a picture of a volcanic past, with scientists believing the last UK-based volcanic activity dates back as far as 50 million years ago, during the Palaeogene era.

[Geothermal energy] can provide reliable around-the-clock electricity, which most other renewables cannot do on a standalone basis

– Salem Esber, Energy Market Expert, PA Consulting

You can see examples of ancient volcanoes in places such as Scotland – Castle Rock in Edinburgh is the eroded remnant of a volcanic plug which was piping hot and full of lava 350 million years ago. However, the UK’s volcanic past is very firmly consigned to the history books. The UK is located close to a vast supply of oil and natural gas in the North Sea, but is firmly positioned away from active fault lines.

Countries such as Iceland and Japan, while having to face obvious drawbacks, are more conveniently located to harness the power of the Earth’s molten depths. Iceland sits between the Eurasian and North Atlantic plates, while Japan is placed across no fewer than three tectonic plates: the Eurasian, Philippine and North American plates.

Italy is considered one of the pioneers of geothermal power, sitting at a crossroads between the African and Eurasian plates. In 1904, an Italian scientist, Piero Ginori Conti, was credited with using geothermal energy to power a generator capable of lighting a series of light bulbs. Italy is another candidate for such a source of power, and tectonic activity is prevalent there. There are a number of volcanoes dotted across Italy, such as dormant Mount Vesuvius and the active volcano Mount Etna on Sicily.

How geothermal power works

Geothermal power works very simply. The amount of heat generated just 10,000 metres below the Earth’s surface is estimated to provide 50,000 times more energy than all known reserves of oil and gas on the planet. Not only that, but geothermal energy is constant – unless the Earth’s inner core were to unexpectedly cool off or disappear overnight, the interior of our planet is expected to remain superheated for millions of years to come.

This intense heat is provided by nature itself, meaning no hydrocarbons have to be consumed. Water can be used and superheated to produce steam, powering turbines which generate enough electricity to power generators. The International Renewable Energy Agency (IRENA) is full of praise for this form of power.

In a report on geothermal power, IRENA writes, “Geothermal power has considerable potential for growth…The costs for electricity generation from geothermal technologies are becoming increasingly competitive…it also contributes to reduced global warming effects.”

The report adds that increased usage of geothermal power can result in lower greenhouse gas generation, as well as cheaper electricity and higher capacity factors. The obvious snag is that not all countries are based on fault-lines, allowing them to tap into this source of energy.

Salem Esber, an energy market expert at PA Consulting, told us of the issues surrounding geothermal power. “Utility-scale geothermal is a very site-specific energy source, meaning it only really works when there are good geological conditions for it.”

Out of the 195 countries in the world, at least 26 of them are already using geothermal power, but this special source of power might remain restricted to a select list of nations for a considerable amount of time to come – geological forces are slow acting, meaning changes to the surface of our planet take millions of years to take shape.

The cutting edge of geothermal power

Iceland remains one of the prime candidates for geothermal power, but it is certainly not the largest country to benefit from this form of clean energy. The western regions of the United States are considered well-suited for geothermal energy generation, and there’s a growing argument to shift away from unreliable carbon-based sources in power, especially after a winter which put US energy infrastructure in the spotlight.

Salem explains: “[Geothermal] can provide reliable around-the-clock electricity, which most other renewables cannot do on a standalone basis. The importance of this is underscored by blackouts in California, Texas and the US Midwest in the past year, areas which have become increasingly reliant on intermittent renewables.”
The blackouts experienced in early 2021 serve as a compelling catalyst for action, especially as Texas has the means to start producing a special form of geothermal energy which can be achieved by upgrading existing oil and gas infrastructure.

The Southern Methodist University (SMU) based in Dallas County, Texas, is a private research university which claims that oil and gas extractors can help in tapping into the power of heated shale to generate a form of geothermal energy. The SMU claims: “Many of the same technologies that oil and gas companies pioneered for retrieving natural gas from shale can be used to create steam from the hot ‘dry’ rocks found underneath that shale.”

Diversifying the Texan energy grid away from oil and gas towards something as consistently reliable as geothermal power could help limit the number of future blackouts. That’s because the latest blackout seen in Texas is likely to have primarily resulted from frozen gas-powered equipment. Texas is in an awkward position when it comes to electricity supplies, given that the state has an isolated energy grid and a deregulated energy sector. This means it lacks oversight by the Federal Government, and it can be tricky to import electricity from outside the state.
Perhaps with the addition of geothermal power from super-heated Texan shale, the state can start to literally run on its own steam.

The future of geothermal

Countries including Iceland are able to afford the luxury of using clean, low-carbon energy sources such as geothermal to power 81 per cent of their energy requirements. Unfortunately, geothermal power can’t be exported in the same way that we can move oil and gas around. While those sources of energy can be easily transported by barrels or pipelines, geothermal power is very much limited to the confines of the countries which have access to the vents in the Earth’s surface.

That hasn’t stopped Iceland from looking into ways to become more efficient at generating electricity through geothermal power, and attempting to share it with countries such as the UK. In 2017, reports emerged that Iceland was considering an ambitious $100 million project to tap directly into a magma well at the base of Krafla, an active volcano.

The project is dubbed Krafla Magma Testbed, and will see scientists digging 2.1km down into one of Krafla’s magma chambers. The effort is being coordinated by Iceland’s own Geothermal Research Group, with help from the British Geological Survey, plus 38 institutes and companies from 11 other countries such as the US and Russia.

In an interview with Reuters, Sigordur Markusson, a local project manager for Icelandic utility company Landsvirkjun, claimed “A magma geothermal well can produce 5 to 10 times more energy compared to a conventional well.”

The project was expected to begin in early 2020, with the first phase costing $30 million. However, as of April 2021, it is unclear how much progress has been made. Crucially, part of the project involved the development of the world’s largest interconnector between Iceland the UK. If successful, a 1,000km-long IceLink cable could be created, helping wire up the UK with a steady source of geothermal electricity capable of powering 1.6 million homes.

While geothermal energy remains the reserve of a lucky few worldwide, the means to spread the benefits of this clean source of energy could help us in the fight to tackle climate change during the next century. Who knew so much power could reside right beneath our very noses?

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