ground source heating

[Stewart]

Jim, he has already been advised that he will need air conditioning in the summer because of the amount and quality of the insulation - solar panels should operate this.

[The Natural Philosopher]

Don't be silly. It gets fed loads of oxygenated rainwater, and that seeps away into the subsoil.constantly renewed and plenty of oxygenating plants

[The Natural Philosopher]

Heat recovery ventilation is mandatory of you want to get by on sunlight. Otherwise the actual ventilation needs render insualtion ineffective.

Also triple glaze and use insulation over windows at might as well - curtains or shutters.

Need plenty of thermal mass inside the insulation to keep warm at night too.

[The Natural Philosopher]

He doesn't. What he does need is shade from midsummer sunlight - overhanging eaves, and mass inside the insulation. Then open windows at night when its cool, and seal up and shutter/curtain down by day.

works a treat here.

[Roger Chapman]

600m seems a lot. Is that the normal sort of length for a ground loop and (without the well) how much land would be needed?

[Adrian Brentnall]

We have the same size of collector - 6 x 100m pipes, in 3 trenches - comes back to a pair of manifolds (one flow & one return so individual loops can be isolated if required...

Adrian

[The Natural Philosopher]

a lot depends on the soil. dry sandy is crap, wet soggy clay is very good. I was quoted 200-400m in clay, no loop within 2 meters of any other, for 12kw peak.

so 400 square meters minimum, for me, 800 squares better.

[Colin Wilson]

Cheers - might also be worth putting in the wiki to give others an idea about real-world installations, rather than a salesmans' "in a perfect world" figures...

[Roger Chapman]

0.1 to 0.2 of an acre seems to give me a better idea of the size. Should fit in some (but by no means all) back gardens but installation would make a complete mess of said garden even if it is practicable to dig the trenches at 2 metre centres. If I ever get round to it I might consider the adjacent field instead but that could bring its own problems.

[Roger Chapman]

TNT's advice was that pipes should be at least 2m apart so did your installer dig 2m wide trenches or work to a lower limit?

[Tim Lamb]

If I ever get round to GSHP using buried pipe I will try to *mole* it in rather than trench. Subsoils here are clays and gravel and I have pulled

50m lengths of blue poly for water supplies without problems. I like the manifold idea as pulling loops with more than two legs would be difficult. Luckily the *moles* will fill with water so there is no lack of contact.

regards

[Adrian Brentnall]

It was a few years back...... but I'm fairly sure that the trenches were about that wide

- big bucket on the digger! Can't really remember the layout of the pipes in each trench - they were laid flat not 'slinky' style

Can't find a photo that shows the tranches - but definitely 6 loops x

100m each

Actual depth of the pipes varies -probably 5 - 8 ft depending on the slope of the land...

[Adrian Brentnall]

Best done at the 'building / earthworks' stage. We had an area that dipped away sharply - and we wanted it to end up level so's we could put a big polytunnel on it.

Wet soil ? - we're in Ireland - not a problem! In fact, for much of the winter months (and last summer!) the adjacent stream makes its way down to the road via our garden & collector loops. Most of the time it's underground - sometimes it just flows on the surface. No shortage of water here

[dennis]

Given that the average air temp in the UK appears similar to the ground temp how much extra does a GSHP save over an ASHP? I was toying with the idea but I would need a bore hole for a GSHP and they are not cheap. Also as the heat for the GSHP is actually solar there must be a problem replacing the heat in the bore hole if the neighbours also decide to drill them, there isn't enough land in the cities to absorbed the solar radiation needed.

I wonder if BT or the cable co would notice if I pulled my collectors along their ducts?

[JimK]

so are you saying the deeper you drill the colder it gets?

JimK

[Roger Chapman]

snip

IIRC moles can't get down to the sort of depth really needed for heat pumping but I would be glad to be proved wrong even though the back lift on my neighbours tractor doesn't work properly so I would have to hire the equipment to do it.

On a connected topic there is a particular form of plough used to make a form of land drain. Can anyone tell me what it is called please. We have a very boggy hollow that really needs draining presumably because the land drain has collapsed. I can't find the actually drain but even if I could I lack the resolve to dig out and rebuild what might be as much as

100 yards of drain having spent a couple of weeks last Autumn on a section less than 15 yards long.

[Roger Chapman]

Ground temperatures are much more even than air temperatures and the deeper you go the more constant the temperature.

The deeper you go the warmer it gets but ISTR TNT saying here quite recently that the major source of near surface heating is solar.

[JimK]

are you trying to actually create a drain with this plough? or break up the so called "pan" between subsoil and topsoil with a "subsoiler" plough?

Cheers Jim

[Calvin Sambrook]

You're in good company with that sort of misconception. Darwin went to his grave struggling to reconcile his calculations for the age of the earth based on his theory of evolution with those of Fahrenheit (IIRC although it could well have been Kelvin, history was never my strong point) who calculated how hot the earth should be given that the only source of heat was the sun. Of course that was before anyone knew about radioactivity.

In the case of GSHPs you're operating at a much smaller scale so you can't really consider the system as closed. Effectively you're sucking heat out of the earth but as there's an awful lot there in the first place you can consider it nearly infinite. That said, I did read recently about some town scale GSHP schemes (Southampton springs to mind) which will need to consider the cooling effect they will have on the ground as it will make their schemes less efficient over the decades.

[The Natural Philosopher]

you hope. here they use moles to drain fields ;-)