Where are we with geothermal energy as a viable option in the UK?

[John J]

Idly browsing I came across this. Seems to be a greeny production but there's some core food for thought in it. -

[Chris Hogg]

I am no expert, but I thought that although it was a bit biased towards geothermal, it wasn't too bad.

I'm not sure how much geothermal energy is available in Iceland. Some years ago, it was quite a small amount. A lot of Iceland's electricity is hydro, using the many rivers they have. But geothermal seems to have increased recently, although they still only produce 0.75 GW in total, split between six power stations, the largest producing only

300MW. I think the idea that Iceland has masses of geothermal energy and could power the UK and some of Europe is wildly optimistic, even assuming the subsea interconnects were put in place. The Icelink project seems to have stalled for the moment There have been several attempts to recover geothermal energy down here in Cornwall. Cornwall is underlain by a granite batholith, running from east of Dartmoor in Devon to west of the Isles of Scilly. Granite is associated with higher temperatures and higher heat flows than other types of rock - clays, slates and shales for example, and is likely to provide higher amounts of geothermal energy. Other parts of the country are also suitable, although many would be better suited to district heating rather than power generation. The Rosemanows Quarry project, started in 1977 and was completed in 1980, although some research continued for several years thereafter. Recently, attempts were made to heat the Jubilee Swimming Pool in Penzance by geothermal heat, but it was not wholly successful as a lot of the water being pumped down leaked away and was not recoverable, so it has to be supplemented by heat pumps.

The Eden Project in mid-Cornwall is attempting to heat its biomes (massive greenhouses) by geothermal heat. I don't know how far the project has got, but I see no reason why it shouldn't be successful as far as it goes.

There is another geothermal project at the site of the old United Downs copper mine near Redruth. The lower levels of this mine were always pretty hot, partly due to oxidation of the copper ores as they were exposed to the air but partly from geothermal heat. The current operation aims to produce around 2MW of electricity from a pilot plant operation. There are other projects down here aimed at recovering lithium from the brines circulating through the granite, and I imagine they will take advantage of any energy they can extract from the water that's pumped back up to surface. Some general comments - you can't just drill a couple of wells anywhere in the country and get masses of geothermal energy back up. You have to be selective in the sites you choose. (I suppose you could get hot water up from anywhere if you drill deep enough, but you'd have to go very deep and it would be horrifically expensive and you'd never recover your investment!).

Most if not all of the projects involve FRACKING! AAAAARGH! But I'm sure the Greens will say it's OK if it leads to geothermal power, but not OK if it leads to natural gas, and they've conducted an effective FUD campaign against it in the latter case! That may change in view of the Ukraine situation. I hope so!

So far the projects seem very small scale. OK, so they may be exploratory pilot plants ATM, but even in Iceland the power plants don't exceed a few hundred MW.

[newshound]

I agree with Chris, it was a bit greeny (the reference to "nasty" chemicals in gas fracking) but, unusually, he did point out that drilling was expensive and uncertain, so that the economics was by no means certain. So overall a rather more balanced piece than most.

As the youtube presenter said, most places where it is being developed seriously are on plate boundaries, where energy is more accessible.

The CEGB were putting research money into geothermal in the 70's as well, mainly IIRC in the Southampton area where there are warm spots, but also because it was local to the engineering research laboratories at Marchwood. I don't think I ever saw any published details, but according to one of the senior managers there were two main problems. Firstly, they recovered rather less water than they put in, so this was an economic cost. Secondly, if they recovered energy at a useful rate, the accessible reservoirs would cool down in ~ 50 years to the point where they were no longer productive. Of course both drilling and fracking technology have advanced considerably in the past 50 years, so the limitations at that time might no longer apply.

[Tim Streater]

Better not tell them, either, that geothermal power is, in fact, nuclear. Caused by the largish amounts of uranium and other radioactive elements in the liquid core of the Earth. Shhh!

[The Natural Philosopher]

Better not tell them that wind and solar are, in fact, nuclear power, driven by the Great Reactor In The Sky that kills 3000 people a year in the UK from radiation induced cancer.

[Harry Bloomfield Esq]

The Natural Philosopher wrote on 25/04/2022 :

Best wear a tin foil hat, to prevent the radiation.

[jon]

There is only 370,000 people in Iceland.

[The Natural Philosopher]

sunblock is more effective.

"There are around 2,300 melanoma skin cancer deaths in the UK every year, that's more than 6 every day (2016-2018). Melanoma skin cancer is the 19th most common cause of cancer death in the UK, accounting for 1% of all cancer deaths (2018). In females in the UK, melanoma skin cancer is the 18th most common cause of cancer death, with around 940 deaths in 2018. In males in the UK, melanoma skin cancer is the 17th most common cause of cancer death, with around 1,400 deaths in 2018. "

And that is just the melanomas

[The Natural Philosopher]

you is wrong. There *are* only 370,000 people in Iceland.

[Chris Hogg]

So they don't need to generate much electricity - yes, I get that. But why build several little power stations, when one big one would do all they would need? Presumably because the sources of heat at depth can only supply power at a limited rate.

Here's the list from the Wiki I linked to.

Hellisheiði Power Station (303 MW) Nesjavellir Geothermal Power Station (120 MW) Reykjanes Power Station (100 MW) Svartsengi Power Station (76.5 MW) Krafla Power Station (60 MW) Þeistareykir Power Station (90 MW)

[The Natural Philosopher]

That is correct. there is a limit to rate of thermal replenishment that renders many geothermal sites dead after a decade and in need of furlough to 'recharge'. Obviously nearby red hot magma will help that.

according to El Wiki, Iceland has about 3GW total capacity of which the majority is hydro (2.1GW) and the rest mainly geothermal (755MW, as above).

[newshound]

I expect one reason is that because the hot water coming up is full of dissolved minerals, they spend a significant amount of time being down for maintenance.

[#Paul]

Geothermal has been in use in NZ for a while; there is apparently about a GW of generation in the Taupo region, and "In 2017, electricity generation from geothermal accounted for over 17% of New Zealand's total electricity supply." FWIW, the population of NZ is over 10 times that of Iceland. I'm less sure about the ratio of Area(Taupo region)/Area(Iceland) :-)

See e.g.

(or just search for something like "NZ geothermal generation").

#Paul

[John J]

Delicious - I'm nabbing that quote to annoy greentards with..

[Chris Hogg]

Thanks for the info.

I have no doubt that geothermal will occupy a position in the supply of renewable electricity and heating in areas where there are suitable sources of heat, but because of that restriction it will always be a bit-player in the grand scheme of things.