Strip footings or insulated raft?

[scottishjohn]

10 hours ago, saveasteading said:

I don't begin to agree on this broad statement. In clay and rock, gsh is not efficient because thd heat is not replaced. In fact, boreholes freeze.

In porous ground it can work, but with great capital expense and too many disappoinments.

 

I have been going to gshp industry  presentations for decades and noted how the wild promises were gradually altered to suit reality.

Without grants the true value became apparent.

 

It is now acknowledged that most boreholes need to be reheated in summer (pump running) So it is really air source or solar, with the ground evening out the seasons. 

Slinky coils take solar energy from higher ground and can be OK in large sunny spots, but they also chill out in cold weather.

 

I know this from observing failed projects in SE clay  and the industry recently acknowledging it.

 

You have inspired me to look at the EST website. They show better savings from gs than as, but at much higher capital cost. But they are very quiet on ground conditions.

 

Air source works well, and reliably, except in very, very cold conditions.

 

Convince me otherwise  please.

 

you only need to look at ground temps for uk at 1.5m and you will see that it will work

bore holes are used mainly in areas where you have ground water leaking from the sea as wet ground transmission is at least  twice as good as dry ground condtions , or no space for slinkies 

 but most do not fit a large enough area of slinies due to space and cost 

maybe the SE has a problem due to the amount of wtaer that is extracted and lowering the water table?-so ground is dry

I looked at that before I fitted ASHP to current house and the costs were prohibitive ,especially as they could not warranty how much heat they could get  till they drilled the hole  ,and then said we might need to drill another one -- 

solid rock is not good as the specicfic heat or any sort of rock is way below normal damp soil-

unles your going dowmn to voer 100m .

 

 my brother in law was involved in a proposed project in cornwall to use a bore hole for geothermal heat to run a power station  using old mining shafts as a a starting point

It never happedned as they needed to get down 1km+ and then they would get superheated steam at over 300c+ back up the hole 

EST website --you got a link .

If you had very boggy marshy ground around you or a lake or a river  you can dump the GSP slinky into they work very very well in this country  and willl outperform ASHP  ,but cost is always going to  alot more than ASHP

and for the few days that the COP goes to 1-1 the ASHP will always be cheaper overall in uk

[markc]

Boreholes are common in Netherlands, many industrial units now have them pretty central on the building plan with an access cover in the concrete floor. 

[scottishjohn]

1 minute ago, markc said:

Boreholes are common in Netherlands, many industrial units now have them pretty central on the building plan with an access cover in the concrete floor. 

netherlands is very low and most reclaimed land --so lots of wet ground at not to deep a depth  and use brine loops for the bore holes

[SteamyTea]

1 hour ago, scottishjohn said:

my brother in law was involved in a proposed project in cornwall to use a bore hole for geothermal heat to run a power station  using old mining shafts as a a starting point

It never happedned as they needed to get down 1km+ and then they would get superheated steam at over 300c+ back up the hole 

Jubilee Pool wanted to try something similar, but ended up with, in effect, a small well supplying a heat pump.

 

There was a geothermal hot dry rocks project here. Achieved its goals of getting water back out at 100⁰C. Well when I say achieved, they pumped in 100 litres of liquid and got 1 kg of steam out.

Then the project moved to France as it was EU funded.

Can't happen down here are the whole of Cornwall has a moratorium on fracking.

Worth noting that at Rosenanowes Quarry, Cornwall has the best resources, there is a resource of 120 mW/m².

 

So that is about 1 kWh/m².year.

 

Makes you wonder why they bothered.

[scottishjohn]

1 hour ago, SteamyTea said:

Jubilee Pool wanted to try something similar, but ended up with, in effect, a small well supplying a heat pump.

 

There was a geothermal hot dry rocks project here. Achieved its goals of getting water back out at 100⁰C. Well when I say achieved, they pumped in 100 litres of liquid and got 1 kg of steam out.

Then the project moved to France as it was EU funded.

Can't happen down here are the whole of Cornwall has a moratorium on fracking.

Worth noting that at Rosenanowes Quarry, Cornwall has the best resources, there is a resource of 120 mW/m².

 

So that is about 1 kWh/m².year.

 

Makes you wonder why they bothered.

it was 20+ years ago my BL was involved  and it failed for funding-no other reason--

[SteamyTea]

1 hour ago, scottishjohn said:

it was 20+ years ago my BL was involved  and it failed for funding-no other reason--

Next time you chat to him, ask him which project he was dealing with.

The  Rosenanowes Quarry project started in 1977 and achieved its aims sometime in the late 1980s, think the site was eventually closed down in the early 1990s because it was only a proof of concept, never intended to be a production site.

 

This one is still going, but seems to have lead times similar to a new nuclear power plant.

https://geothermalengineering.co.uk/united-downs/

 

I am not against geothermal (HDR), just think that a bit  of sanity has to be brought into the mix.  It is really, really, hard to do and so far not been achieved, in 45 years (so can't really be claimed to be new technology).

Hot Wet Rock and other Enhanced Geothermal Systems is a different matter, this has been going on for decades.