Radio 5 Live Interview

On Thursday 26^th February I was invited to speak on BBC Radio 5 live on the Breakfast Show with Rachel Burden and Rick Edwards about the United Downs Deep Geothermal Energy Project that was going live that day.

Personally, this was huge – this was the first time I spoke on national radio! Clips were also played in the news on Radio 2 and Radio 6 as well, so it was quite the day!

The topic of conversation was very interesting as well. It was all about the UK’s first geothermal power plant that was going live that day. The United Downs Deep Geothermal Power Project, operated by Geothermal Engineering Ltd (GEL), has been decades in the making, and it is now producing electricity for the national grid to supply enough energy to power the equivalent of 10,000 homes.

I was asked to provide a bit of scientific context as to why Cornwall is one of the few places in the UK where deep geothermal energy is economically viable.

Geothermal heat (that is the amount of heat energy in the rocks beneath our feet) is at its greatest near to tectonic plate boundaries. This is because of the tectonic stresses and geological processes around those narrow zones that produce higher energy. So places like Iceland for example, which are world famous for their geothermal energy production. Here it is very cost-effective to produce energy using geothermal power.

Here in the UK though, well away from any tectonic plate boundary, things are a bit cooler as you go deeper underground. Saying that, it does get hotter with depth, around 20°C per kilometres depth. But this does make it more challenging to extract energy from the ground, both in terms of engineering and cost.

In Cornwall, however, it gets hotter quicker, about 40°C per kilometres depth. And this is all because we are underlain by granite.

The granites in Cornwall formed from magma intrusions between 290-270 million years ago. They have long since crystallised, and the heat produced is not magmatic in origin. Instead, it actually comes from the radioactive decay of minerals containing elements like uranium, thorium, and potassium. Whilst this is nothing to worry about for our health at surface, the granites are analogous to naturally occurring nuclear reactors deep beneath our feet.

Not only that, but granite as a rock is a great thermal insulator. That radiogenic heat that is produced stays in the granite for a long time.

All of this makes Cornwall one of the most prospective places in the UK for extracting geothermal power. However, it is still quite the engineering challenge!

How companies like Geothermal Engineering Ltd (GEL) will extract this energy is very impressive. At United Downs they have drilled two boreholes incredibly deep into the rocks below; one that is approximately 3 km deep to act as an injector well that will inject water underground, and a second that is around 5 km deep to act as a production well to pump the super-heated water back to surface again. The deeper borehole is one of the deepest onshore borehole in the UK.

I have included a diagram taken from the BBC news article below, which itself is credited to Geothermal Engineering Ltd (GEL) (https://www.bbc.co.uk/news/articles/cewzg77k721o).

To ensure maximum recovery of the water injected into the ground, these types of projects are targeting known fault and fracture zones that pass deep down through the granite. This is to increase natural permeability in the rock so that the heated waters can be picked up by the deeper production well. The United Downs project has drilled and intersected a major NW-SE structure known as the Porthtowan Fault, named after where it crops out further to the northwest along the coast. This structure passes down through the peninsula and is several km deep.

The waters at 5 km depth were reaching temperatures of just under 200°C. They also contain elevated levels of dissolved lithium within them, making them a potential target for lithium extraction alongside the geothermal energy production.

This project, along with others in the area, have been a great addition to Cornwall’s growing georesources sector at the moment. As with all of these new projects there has been a great deal of risk and uncertainty during the planning and experimental phases, so it is fantastic to see them go live. Hopefully this will bring confidence to invest in other projects like this, which provide a clean, green, long-lived, uninterrupted energy source to the UK.

As always, these projects can offer a bit of uncertainty and concern to members of the public. Thankfully, Geothermal Engineering Ltd (GEL) and other companies have been doing a great job with outreach to explain and educate people about what they are doing, and how this type of energy production has very minimal impact on the landscape and environment.

Aside from all these benefits, we now have samples of granite from 5 km depth! This has opened up a whole world of new academic research that allows us to better understand how these granites formed. That might have to be for a different post though as I have rambled on a lot here!

You can find out more from the GEL website here - https://gel.energy/about/united-downs/

If you wanted to listen to my interview on BBC Radio 5 Live you can do so here (I was about at about 7:42 am, which is about 1 hour 42 minutes in to the programme) – https://www.bbc.co.uk/sounds/play/m002rqnj

I have also posted the clip below.