Ground Source Heating

[Peekaboo]

Having just searched for any exchanges on this subject, I see that this was last discussed back in February 2005.  ( Forgive me if I am wrong and you are all bored to death on the subject.) Does anyone have any updates or recent views? 

We are buying a property in the Alps at an altitude of 700 m with 1600 square metres of land, this has a small swimming pool a three bedroomed chalet and a larger 6 bedroomed house - not a massive amount of land left but bigger than you would imagine with that lot on it.  Recent investigations in the U.K. has led me to believe that you no longer require acres of land for chauffage geothermie and I would love to know if anyone has installed one, successfully using it and what contacts they have made in France (department 74 Haute Savoie would be great news). News on grants etc would be good too !

The entire property is typically electrically heated - ouch !  The small chalet is already underfloor heated and we are intending to radically alter the large house and install underfloor heating there also.  We will also install a wood burning stove in the main living space (can't have a house in the Alps without a log fire). 

Looking forward to some good news !

 

[Will]

If you search on 'geothermal' you will find a lot of newer information. Underfloor heating is ideal for this form of heating, as the water temperature is somewhat lower than with other wet heating types. Geothermal too works using electricity, but I understand uses only about a third of the energy of a conventional heating system. I have seen a system successfully installed in a smallish lawn, using radiators, though larger radiators are needed due to the lower temperature.

[Gluestick]

PKBoo:

I do quite a lot of research into this topic a couple of years ago: and re-visited it, last year.

Sources:

Simply, Boreholes, (self-expanatory); "Slinkies": Lakes.

Slinkies, are long plastic tubes, sunk circa 1.5 - 2.5 Metres, into trenches. Their length is predicated by the heat demand necessary, in terms of required output. (Allowing for the losses in the Heat Pump).

Type of heat Exchange:

Favoured, is underfloor (Wet), since as Will has already stated, operating temperature is lower. Warm air is possible, as are rads., however they are simply not as efficient.

The main objection seems to be the Capital Cost. Even allowing for the gains over (e.g.) gas and oil, it takes a considerable time to amortise the front end costs; by which time it is probable that the heat pump would need replacement.

Grants are apparently only available against mainstream income tax, for which applicants have to be fully registered and based totally within the French system.

I am presently awaiting the final analysis of overall electricity costs and efficiency of a chum's borehole geo-thermal installation, in a newly completed Welsh barn conversion, using underfloor wet system. This will be very interesting, since it was a very cold and long Winter! He also has excellent insulation, as one might expect, being only completed, last year.

A new contender, BTW, is a system which extracts heat from external air.

 

 

[Peekaboo]

Thank you Gluestick. Your findings are very helpful, I would be grateful if you could share your chums borehole geo-thermal installation results, once known - I have just begun reading up on this and it could be the answer. However, I am still looking for firm evidence that these systems work in minus 25 degrees or possibly more. With all these "alternative" energy supplies it seems the initial outlay costs far more than the savings !  Our renovation won't start  before Spring 2007 and I suspect we will install underfloor heating (wet system) anyway and can change the power source at a later date.

Thanks to Will too.

[Gluestick]

I shall chase him up: I would like to see the answers too! Don't hold your breath, as they say, he travels a lot.

Apparently, the claim ([8-)]) is that despite low ambient air temps. the gound can provide significant heat gains, as the deeper one goes, the less the temp is affected by air temp.

Caves are normally quoted as illustrative. What does concern me (and obviously yourself!) is the energy cost to extract heat as the temp drops!

I too am concerned about the real amortisation of the capital costs  against the (alleged) savings.

It does seem to work, provided one is circa 30 and the equipment will last for twenty years!

 

[Gluestick]

My email finally caught up with my chum amd he will shortly revert to me with the electricity costs for the Winter, the actual area of the barn conversion etc.

He did tell me he is absolutely delighted with his geothermal heating: the glycol was leaving at -5C and returning @ +2C in very heavy frosts: and maintaining ambient room temps. of 18C.

So now all we need is the running cost!

 

[friend of stouby]

If the "slinkies" are laid into a hillside, do they follow the contour of the land or must they be laid horizontal?

[Gluestick]

I am guessing, here F of S.

My gut reaction is that what is critical is the depth of the trench, since latent heat is extracted from the strata, as the ground protects the earth from heat loss.

Prevailing winds would be critical, obviously, due to the chill factor.

In any case, suppliers normally carry out a site survey which apparently includes planting sub-terranean thermometers.

Bore holes are more effective. According to some sources.

 

[Albert the InfoGipsy]

There might be some interesting stuff here:

http://www.earthenergy.co.uk/groundswell/

Earthenergy is a commercial operation, but the newsletter might have some useful ideas.

[Gluestick]

Yes, it is interesting Albert, thanks.

One aspect that has to be emphasised, however I feel, is that large projects achieve -obviously - greater benefit due to economies of scale.

Personally, I believe that with new build residential, the future will include central sewerage processing, grey water re-cycling + rainwater capture and, of course, ground source heating fitted as some form of shared facility. (Probably discrete heat pumps taking the energy input/disposal from/to one core and large resource).

In theory, it is even now quite possible to stand-alone process sewerage and be independant for cooking gas, for example.

What does surprise me is that no sizeable speculative developer in the UK (particularly in the South) has identified the attractiveness potential of environmentally friendly and green technology.

As water resources become even scarcer and more expensive and as energy costs rise, exponentially during the next few years, perhaps this will -late - force their hand.

 

[Gyn_Paul]

[quote user="Gluestick"]

..........A new contender, BTW, is a system which extracts heat from external air.

 

 

[/quote]

I was at a presentation from a chap selling these systems and he estimated that the capital cost of the plant for my friend's 3-bed cottage with good insulation would have been something in the order of 12K Euros after subtracting the rebate. This made us all wince a bit but not so much as the bomb-shell he then quietly dropped which was the little fact that the efficiency of the air-to-air (or indeed air-to-anything) systems starts to decline from 10C downwards until at (from memory, so don't hold a gun to my head on this) 3C it is no more efficient than an ordinary electric heater (i.e. 1kw of energy produces 1kw of usable heat) and from zero C it doesn't work at all.

So the end result is that you still need an alternative source of heat for the cold periods of - say - 7C and below, so in the case of the friend above he would still need to keep his oil boiler serviced and the tank filled.

Needless to say he didn't get many orders form the assembled company!

[Gluestick]

I have been quite cynical about this concept, GP, since it was obvious to me that ambient air temp, when it's cold, is one of the core reasons that buildings become cold!

The whole rationale -allegedly - about GSH is that subterranean temps tend to be stable, irrespective of external conditions and higher than ambient air temp.

Thus perhaps we can classify Air Heat Exchange as great for hot water when the sun is shining! In which case, solar would be cheaper and easier.

Yet another example of CCTV to shave with!

 

[Deimos]

Re: Aerothermal Heating

I had some experts round a couple of years ago who did a pretty thorough investigation of my property. the local ADEME approved plumber brought them round after Id been chatting with him about renewable energy and my wishes to install something (he even brought round a translator).

These experts were really careful about recommending anything (due to the 10 year "come back" I would have). As I live in a water mill the property presented them with quite a few challenges. Geothermal rejected because of the height of the water table. They were saying that aerothermal is good and works well at all temperatures - but is very sensitive to humidity. they were saying that an aerothermal system will work well at -7 deg C provided the air is dry. In fact they said it would work better at -7 deg C in dry air than at 0 deg C in mist.

(Just repeating what they said - as I have not yet been able to get any prices from them - but that does not surprise me).

Ian

[Gyn_Paul]

Good luck getting dry air in/near a water mill!

p