Sunday Brunch: Geothermal as a solution - but not just yet
Sustainability, Strategy & Finance

Sunday Brunch: Geothermal as a solution - but not just yet

One of the challenges around renewables based electricity grids is coping with the periods when the variable generation sources, such as wind and solar, are insufficient to meet demand. Which is where geothermal has a role.

Geothermal power technology has shown compelling advances that can enable it to become a key contributor to secure, domestic, decarbonized power generation for the US as a source of clean firm power - US Department of Energy 2024

One of the challenges around renewables based electricity grids is coping with the periods when the variable generation sources, such as wind and solar, are insufficient to meet demand. Part of the answer is moving the demand, which is easier and more effective than you might think. The other part is having low carbon sources of generation, that we can dial up & down when we need them. This is where geothermal could play a part.

It's clear that Next Generation Geothermal offers the potential to materially assist in decarbonising our electricity supply system. How? By offering both clean firm power (always producing - what used to be called baseload power) and clean flexible/dispatchable generation.

That is the good news, especially the dispatchable generation element. As the percentage of wind & solar on our electricity grid rises, we are going to need flexible supply to fill the gaps when renewables are insufficient to meet demand. And the most 'valuable' form will be long duration storage - which is where geothermal supply can sit, making it especially valuable.

But, we also need a note of caution. In much the same way that some commentators leap on every problem as being terminal for the net zero transitions, it's also possible to be overly optimistic. Even at full potential, geothermal will only be able to meet part of the demand for long duration storage. And it's going to remain expensive. Plus, it's more of a 2030's onward part of the solution. So we need to think about it as part of the tool kit of solutions, not the total answer.

It's one of the tougher aspects of how we need to think about the electricity grid of the future. It's complicated. There will be lots of elements, from more renewables, to geothermal, pumped storage hydro, batteries and interconnectors. Plus demand management will become really important. And sadly, the human race likes simple solutions. We don't cope well with complexity.

That doesn't mean we shouldn't get excited about the potential of geothermal. It should have a place in most investors portfolio of longer term electricity decarbonisation solutions. But don't over promise.

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Geothermal as a solution - but not just yet

I grew up in New Zealand. Because of our location on the Pacific Ring of Fire we have a lot of earthquakes. And the same geological conditions that led to us being earthquake prone also enabled us to have 'always on' geothermal electricity. But New Zealand is the exception. In most of the world traditional geothermal electricity is not possible.

What is geothermal electricity generation? It's using the naturally occurring supply of heat within the earth's subsurface to heat fluids, which in turn are used to spin turbines to create electricity. In theory, there is enough geothermal energy to power the entire world thousands of times over. But in practice, it's hard to deliver this energy in a cost effective way.

Looking just at the US, there is around 40 GW of estimated conventional geothermal resource, of which only 25% is currently identified. This generates circa 3.7GW of electricity, which is about 0.4% of total US electricity production. So a lot smaller than say hydro. And remember the US has more installed geothermal than anywhere else.

The good news is that what is known as Next Generation Geothermal (also called Enhanced Geothermal Systems or EGS) is starting to change this. Next Generation Geothermal is very different from the traditional hydrothermal generation we are used to. As the US Department of Energy puts it in a recent report, "next-generation geothermal technologies make their own reservoirs from ubiquitous hot rock, rather than hunting for naturally occurring reservoirs in unique locations".

Next-Generation Geothermal Power - Pathways to Commercial Liftoff
Learn more about the U.S. Department of Energy’s Pathways to Commercial Liftoff Report on Next-Generation Geothermal Power

This doesn't mean we could have geothermal electricity generation anywhere, but it massively expands the potential.

And perhaps more importantly, Next Generation Geothermal not only offers the potential for geothermal to be sited in a much wider range of locations. It also allows it to be used for flexible, dispatchable electricity. This is because it can utilise a loop system (either open using fracking or a closed loop).

Putting this in layman's terms, this new geothermal can ramp supply up and down depending on system demand. Which means it can supply electricity when renewable resources such as wind and solar are insufficient. This would enable geothermal to replace the existing use of fossil fuel 'peaker plants', enabling further decarbonisation of our electricity systems.

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