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Ground Sourced Hot Air

Hospitals and schools could be powered by underground heat, says Royal Academy of Engineering - Telegraph

The UK is sitting on a "vast resource of untapped energy", a Royal Academy of Engineering conference on the potential use of geothermal energy was told.
By using ground source heat pumps, the energy can be transferred from hundreds of feet below the ground to the central heating system, while the same pump can also cool the building by taking heat out of the air in the summer.
The technology is widely used in Scandinavia and the US but has failed to take off in the UK because of the cost and the availability of cheap oil and gas...

Um doesn't the US have even cheaper oil and gas? And a quick peek at petrol and Diesel prices in Scandinavia shows they are cheaper than here. So I think the spanner monkeys had better come up with a more convincing explanation, like the systems aren't cost effective and require you have a half acre garden....


I suspect that "widely used" actually means:

Some rich greenies in America have installed the system as have some Swedish and Norwegian municipalities. The rich septics subisdise their system themselves, the Viking taxpayers subsidise the ones in their countries.
By the way, if one drills down hundreds of feet, as the authors claim, you don't need half an acre, you substitute depth for area. You do, however, have to have a shedload of money to pay the drilling company.

Doesn't the Gaia-killer Dubya use geothermal energy on his ranch? Strange that, in comparison to an incredibly wealthy Algor who just burns through gas and leccy like there's no tomorrow.

Are there any "spanner monkeys" left in that organisation? I doubt if any of them know what a spanner is, but they will all have degrees, probably in sociology!

I sometimes wonder if old coalmines could be deployed as massive heat pumps. The digging has already been done. Fill the tunnels with pipes and away you go.

Air source heat pumps could do the job reasonably well without all the expense of digging but they never garner attention.

I wonder if 2 things are being confounded here.
Geothermal hear relies on going deep enough to get "hot rocks". Here you pump water at pressure (to stop it turning to steam) and use a heat exchanger or reduce pressure to get steam and electricity. In Iceland these are close to the surface (!). The closer they are the less drilling you have to do. If you don't think about the chemistry then you could be dissolving silica and other minerals at high temperature and pressure which then deposits and blocks the cooler tubes. This is a (valid) industrial scale process under the right conditions (Iceland / New Zealand). I wonder about the practicality of using air as a heat transfer medium if this is what they are suggesting.

The alternative is to lay a km or so of thin plastic pipe underground in your garden. Below a certain depth I believe the temperature is fairly constant (unaffected by diurnal or annual effects) and some of this can be absracted. Again, this is practical but requires a large area and really is only practical if you are starting from scratch with a large house on an even larger plot.

Quite a number of our neighbours in Canada have both 'ground source' heat pumps and the 'air source' variety. They all report significant fuel bill savings, (One farmer even has a basement swimming pool installed to get rid of the excess heat) although the air exchange models supposedly aren't worth a damn when temperatures duck below zero.

There was project run for many years near Falmouth/Penryn, Cornwall which was to tap geothermal energy called 'Hot Rocks', if I recall correctly. It had some success but but was ultimately found to be uneconomic and full of technical difficulties. There are very few good sites in the UK where this would be even remotely useful.

Ground heat is merely laying lots of pipes under the ground and using heat-pumps to extract the available heat, or indeed to pump it into the ground during hot weather. There is no doubt that they work, but they come with drawbacks. They require large areas and have limits. It you extract too much heat in the winter you will further cool the ground and conversely in summer you will heat it more. What effect will that have on your prize lillies?

The best part about heat pumps (air conditioning units) is that you can move more heat energy than you put in and typically this should be well in excess of 3 times. So in a sense you get something for nothing ... a kind of magic ( cue CD) ... and thus despite using electricity which is more expensive than gas, it works out cheaper.

Don't tell the government or they will tax them more!

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