Geo Thermal

[Sprotyrover]

Interesting Documentary on France 24 we have 23,000 old Coal mines in Britain contain 2 billion cubic litres of water which can be pumped to the surface passed through treatment facilities and produce 20 degrees  of heat which is then used to provide heating to homes. Potentially a major part of our future energy needs. There is a facility opening in Gates head and another in Seagram. Thorne and a revitalised Moorends immediately springs to mind also Hatfield which has access to 19 Coal seams.

[Bristol Red Rover]

It's hardly Iceland efficient is it. Worth the cost or som friend of Boris scamming?

[Dutch Uncle]

Any non-hydrocarbon energy is definitely interesting, but one point comes to mind. Don't know any figures, but it strikes me it would take a lot of energy to pump that water to the surface, is the energy net result significantly positive? Could it be like the holy grail of nuclear fusion (which I worked on once) where until now more energy has to be put in than can be produced?

The sheer amount of energy that could be produced via nuclear fusion, without the same quantity of radioactive waste makes research still extremely valuable. Although results are improving they still have the running joke that it is always 'just a decade away'.

[wilts rover]

I have heard Ed Milliband talk about this a number of times over the past decade. Abandonded North Sea oil and gas wells was another (and more relevant) source of geothermal energy.

[BillyStubbsTears]

Dutch.

I don't know about practical efficiencies, but the basic thermodynamics is easy to appraise.

Say the mineshaft is 200m deep (h), the energy required to lift 1kg of water (m) is E=MGH, where g is acceleration due to gravity (10m/s^2). That's E=1x10x200=2000J.

The energy held in heated water is E=mCT where m is the mass, C is the specific heat capacity of water (4184J/kg/degree) and T is the temperature of the water above ambient level (20 Celsius according to Sproty). That's E=1x4184x20 = 84,000J.

So, at 100% efficiency, pumping would take less than 2.5% of the a soluble energy.

[BillyStubbsTears]

Something else I'd heard that could be done with mineshafts. Use them as a gravity battery to store renewable energy when it's not being used.

Idea is to have a huge mass on a cable in the shaft. Use off peak electric to lift it up the shaft, then let it fall and turn a dynamo at peak times.

If you had a 5m cube block of steel as the weight, that has a mass of 1,000,000kg. If the mineshaft is 200m deep, the off peak energy to lift the mass is E=1,000,000x10x200=200MJ. That's about 550kWh - enough to power maybe 100 terraced houses. 

Feels like it would need a big capital cost, but would then, maintenance apart, be essentially free electricity.

[Dutch Uncle]

Dutch.

I don't know about practical efficiencies, but the basic thermodynamics is easy to appraise.

Say the mineshaft is 200m deep (h), the energy required to lift 1kg of water (m) is E=MGH, where g is acceleration due to gravity (10m/s^2). That's E=1x10x200=2000J.

The energy held in heated water is E=mCT where m is the mass, C is the specific heat capacity of water (4184J/kg/degree) and T is the temperature of the water above ambient level (20 Celsius according to Sproty). That's E=1x4184x20 = 84,000J.

So, at 100% efficiency, pumping would take less than 2.5% of the a soluble energy.

Thanks BST, sounds theoretically very viable then, even at only say 25% efficiency

I guess one advantage might be that the temperature difference is greater in winter when you need it most? Or are the treatment facilities at a constant temperature and does this then require more energy to be offset as well. I am stupidly guessing in the dark because I didn't see the program and know anything about the process. But I guess it must be promising to be talked about seriously.

Another thing that comes to mind is that if the water can be let back down (generating more energy from its kinetic energy on the way) can it then naturally reheat and be used again, so this could then become an enduring renewable source of energy?   

[BillyStubbsTears]

Dutch.

I guess if you can, then yes, you pump up the water at night then heat-exchange it and drop it back down through turbines at peak demand times.

[SydneyRover]

''New maps reveal heat stored in Britain’s abandoned coal mines
The British Geological Survey (BGS) and Coal Authority have released maps which for the first time, reveal the extent to which heat is stored in Britain’s abandoned coal mines''

01/12/2020


https://www.bgs.ac.uk/news/new-maps-reveal-heat-stored-in-britains-abandoned-coal-mines/

[Dutch Uncle]

''New maps reveal heat stored in Britain’s abandoned coal mines
The British Geological Survey (BGS) and Coal Authority have released maps which for the first time, reveal the extent to which heat is stored in Britain’s abandoned coal mines''

01/12/2020


https://www.bgs.ac.uk/news/new-maps-reveal-heat-stored-in-britains-abandoned-coal-mines/

Thanks Sydney, and Sproty for raising this 

[albie]

This is the vid that Sproty mentions;
https://youtu.be/FxnKjz3cdq8

The cost of retrofitting district heating systems could be an issue, but for estate new build projects this should be under consideration.

[danumdon]

Is this a slight variation on a smaller scale that occures at  Dinorwig power station in Wales every night?

[BillyStubbsTears]

Is this a slight variation on a smaller scale that occures at  Dinorwig power station in Wales every night?

The lifting and dropping is. But the bonus with the mine water is that it's hot (or warm at least) so there's energy to be extracted from that.

Hot water contains phenomenal amounts of energy. A 1 metre cube of water heated up just 10 degrees C has the same energy as you get from burning a litre of diesel.

[big fat yorkshire pudding]

Always found this fascinating. They were all over the place in New Zealand when I was there, understandably.  I think they make up a significant part of energy creation over there. We also visited an amazing hydro power station there that was quite different to what we do in this country. I forget the name of it but the power of the water was I incredible.

[Sprotyrover]

From the Coal authority Website:
The water in these mines is a low carbon, sustainable heat source, which under the right conditions can compete with public supply gas prices and deliver carbon savings up to 75% compared to gas heating.

In the case of a district heating network, this energy can be transferred to a pipe network using a heat exchanger, and then distributed to nearby homes.

This kind of renewable energy technology could help to present coalfield areas as more attractive to investors, which could breathe life back into some areas of the UK where it is most needed.

It could also provide a significant low carbon contribution to Britain’s future renewable energy needs. Many local authorities have already declared a ‘climate emergency’, with pledges to become carbon neutral in the coming years.

[albie]

It will sink or swim on the basis of costs.
If it comes in cheaper than alternatives, it will have legs.

The UK needs to ban new gas installations, so the problem doesn't get worse.
2025 is the date for this, but it needs to be sooner, like in Scotland.