UK geothermal project passes milestone

Aurora · Post by **Aurora** » 24 Jun 2010, 07:38

Financial Times - 23/06/10

A landmark project to investigate the potential of a new source of renewable energy took a leap forward on Wednesday with the pumping out of hot water from 1,000 metres underground.

Naturally occurring low-level radiation in the “hot rocks” deep underground in Upper Weardale, County Durham, in north-east England heats the water that flows through the granite.

Article continues ...

biffvernon · Post by **biffvernon** » 24 Jun 2010, 08:56

Article continues... behind a pay wall.

Of course hot rock geothermal should be a significant part of the mix and it's good to hear that work continues.

But, strictly speaking, it should not be described as renewable. The rate of radioactive heating and up-welling energy from deep down is so slow that what one is actually doing is 'mining' a resource of heat. Extracting the hot water cools the rocks, eventually to the point where you have to give up. Still, in the right locations, that could take a very worthwhile length of time.

Post by **kenneal - lagger** » 08 Dec 2010, 17:11

The article isn't behind a pay wall, but you might have to register to read it.

It's another from of nuclear in this case, as the radioactive granite decomposes it releases heat. Some geothermal heat comes from fault lines which allow water up from great depths where the heat is of volcanic origin.

Southampton city centre gets some of its heat from geothermal pumping.

biffvernon · Post by **biffvernon** » 27 Jun 2011, 20:35

Newcastle borehole: http://www.bbc.co.uk/news/uk-england-tyne-13914718

Post by **kenneal - lagger** » 28 Jun 2011, 02:18

biffvernon wrote:.....But, strictly speaking, it should not be described as renewable. The rate of radioactive heating and up-welling energy from deep down is so slow that what one is actually doing is 'mining' a resource of heat. Extracting the hot water cools the rocks, eventually to the point where you have to give up. Still, in the right locations, that could take a very worthwhile length of time.

It would be renewable if the rate of extraction of heat matched the rate of production and dissemination.

With this sort of geothermal set up two boreholes are often drilled and the rate of production depends on the porosity of the rock between the two holes. This is because water is pumped down one hole, through the hot rock and up the other. Modern fracking and horizontal drilling methods could increase the efficiency of this system.

biffvernon · Post by **biffvernon** » 28 Jun 2011, 07:36

kenneal wrote: It would be renewable if the rate of extraction of heat matched the rate of production and dissemination.

It doesn't, though it takes a very long time to run down.

Post by **kenneal - lagger** » 28 Jun 2011, 14:30

There's no reason why it couldn't, apart from, possibly, human greed. If the temperature of the water started dropping just reduce the flow rate until it picks up again.

biffvernon · Post by **biffvernon** » 28 Jun 2011, 18:55

I think it's like sucking water out of a swimming pool with a straw - it will run out, but slowly, very slowly because there is a tap dripping into the pool.

With some hot rock geothermal it's actually quick enough to make it not worthwhile. In other places there's no bother. Heat flow rates are critical. I'm just pointing out that, strictly speaking, geothermal is not 'renewable'. One is mining a resource, though in some places the resource is very large.

Post by **kenneal - lagger** » 29 Jun 2011, 02:09

The problem would be if we sucked so much heat out of the core that it solidified causing the earth to lose its magnetic field. That, in turn, would cause the loss of much of our atmosphere. We would have to go at geothermal pretty hard to do that though.

biffvernon · Post by **biffvernon** » 29 Jun 2011, 08:14

The deepest borehole (exploratory not geothermal) has only reached 0.2% of the way to the centre of the Earth so I guess it'll be a while before we achieve the heat death of the planet.

Post by **kenneal - lagger** » 29 Jun 2011, 15:02

Beware the power of exponential growth!!

mindscience · Post by **mindscience** » 02 Aug 2011, 08:56

That would require some prolonged and very dedicated digging, kenneal

I agree about the geothermal is not renewable point. My friend has a website that deals with like geothermal energy and he keeps writing renewable energy sources, yet I am inclined to believe that just because something hasn't been proven as non-renewable, there is also a complete lack of evidence to support the former. If that makes any sense.

Consequently, I'd also be inclined to believe that drawing energy from hot rocks with such slow speed of heat generation could prove rather insignificant, if not useless. Yet it is good they are trying to explore more options.