Ground heat source pump? (geothermal)

don_ky01

Hi
I have been considering installing a heat source pump in an upcoming renovation, in an attempt to reduce heating costs and dependance on oil.
I'd like to be able to use this method to provide underfloor heating in the building on the ground floor only.
Has anyone locally any experience of these? Have you one installed or do you know someone who has? What are your thoughts on this type of system? Is it suitable for our climate here in Northern Ireland or not?
I'm in the Ballymena area and the ground around the renovation area is heavy clay soil.

Thanks

motorguy

Cant answer directly, but we looked at them as part of an overall strategy for our new build

We looked at

• ground source
• air to heat
• solar (by way of generating heat)
• solar (by way of generating electricity)
• wood pellet
• electric
• oil

and combinations thereof.

We also looked at

• return on investment of these devices.
• Insulation of piping from these devices to the house
• How the heat is dissipated through the house (radiators / underfloor)
• Heat loss in the house (uprated U (mu?) rated glass, thermal breaks in frames, use of drymaster system instead of vents in windows)

The issue with ground source / air to heat / solar is that they all require another source of heat for the periods that enough heat cannot be extracted from the air / ground / sunlight, which here in northern ireland is probably a reasonably proportion of the year.

You're also looking at doing this via a thermal store.

This either means you fall back to electric, oil or wood pellet burner for your (possibly main) alternative supply.

Ultimately, we opted for a wood pellet burner instead of an oil burner, and we have a highly insulated pipe running from the boilerhouse to the house to reduce heat loss to something like less than 1 degree over the distance.

We then have installed underfloor heating upstairs and downstairs. The advantage of this is that the water temperature needs to be only something like 45 degrees as opposed to 65 / 70 degrees for conventional radiators. Each room has its own thermostat.

We upgraded the glass to a mu rating of 1.1 over the standard glass. Also, we didnt fit the window vents / letter box, etc but have opted for the drymaster system.

Finally, we run solar panels on the roof feeding a thermal store. These heat the water for hot water, and when there is excess it is passed to the heating system.

We believe the ROI on the pellet burner to be 7 years, but we expect to spend our days in this house so will benefit from much cheaper costs in the long term.

Hope this helps trigger some thoughts.

For info, we used a company called Green Energy based outside banbridge, and so far have found them very knowledgable.

Pretani

I can only state what I think about underfloor heating, not the geothermal stuff. I know people in county down who have put in underfloor heating and tiled over it. They go through alot of oil, they're also burning coal fires to keep the place warm. The heat is similar to economy 7, it's a dry heat because of the floor tiles. It takes around 12 hours to heat up.

If you go for underfloor heating, install an automatic digital thermostat which keeps each room at a constant temperature. A simple timer thermostats doesn't work that well with underfloor heating, you end up with the room either too cold or too warm.

Best advice would be to talk to people directly, don't rely on the word of the sellers.

CL

I have a Ground source heat pump installed, Its in a newly built house (aug 09) so its still drying out and difficult to compare like for like figures for heating power usage but so far it seems to be working well, I'll know better after a full year or two.

The heat from the underfloor heating system is very comfortable although it is not as responsive as oil so you need to plan when you will want the rooms to be warm as it takes a good while for it to heat up from cold.

pgilc1 wrote: »

The issue with ground source / air to heat / solar is that they all require another source of heat for the periods that enough heat cannot be extracted from the air / ground / sunlight, which here in northern ireland is probably a reasonably proportion of the year.

I'm not sure where this information comes from and it is not the case with our system, we have no oil or any other source of heat, there are no electric imersion heaters installed in the system, we do have two wood burning stoves but they do not feed into the heating system and are just mainly to have something in the fireplace for extra heat, not that this is normally required.

We run the heat pump overnight to heat the house and heat our 500l domestic hot water tank, we use economy 7 electricity for this, we also run the heat pump for a few hours in the evening as a top up.

Our DHW tank uses a heat exchanger which means the water does not havet o be heated to above 60 degrees as with some other systems this is a requirement to combat the build up of legionella.

If you have any more questions please ask.

motorguy

Pretani wrote: »

If you go for underfloor heating, install an automatic digital thermostat which keeps each room at a constant temperature. A simple timer thermostats doesn't work that well with underfloor heating, you end up with the room either too cold or too warm.

+1

We went for digital stats in each room

motorguy

CL wrote: »

I have a Ground source heat pump installed, Its in a newly built house (aug 09) so its still drying out and difficult to compare like for like figures for heating power usage but so far it seems to be working well, I'll know better after a full year or two.

The heat from the underfloor heating system is very comfortable although it is not as responsive as oil so you need to plan when you will want the rooms to be warm as it takes a good while for it to heat up from cold.




I'm not sure where this information comes from and it is not the case with our system, we have no oil or any other source of heat, there are no electric imersion heaters installed in the system, we do have two wood burning stoves but they do not feed into the heating system and are just mainly to have something in the fireplace for extra heat, not that this is normally required.

We run the heat pump overnight to heat the house and heat our 500l domestic hot water tank, we use economy 7 electricity for this, we also run the heat pump for a few hours in the evening as a top up.

Our DHW tank uses a heat exchanger which means the water does not havet o be heated to above 60 degrees as with some other systems this is a requirement to combat the build up of legionella.

If you have any more questions please ask.

Sounds like a good system - how did it cope with the very cold spell during jan?

CL

pgilc1 wrote: »

Sounds like a good system - how did it cope with the very cold spell during jan?

It coped very well, I didn't notice any increase in the electricity usage due to the lower outside temperatures, The ground loops are buried fairly deep about 1.2m so the outside temperature doesn't affect it the same way it would an air to water heat pump

Wookey

I've heard nothing but good things about ground source heating, give it 20 years or so and i reckon it will be the standard heating system in most new builds.

harryhound

I very much doubt you will need to wait 20 years. I would give it five.

Last week I was at "ecobuild" that has grown from a "beards and sandals" new age event 4 years ago, to a mainstream exhibition that is now too big to fill all of Earls Court, that probably had 50K visitors over its three days.
Next year it will be at the extended ExCel in Olympic- Docklands; see you there.:D
All the talking heads, many of them wanting to get re-elected, dropped in for the cameras
http://www.ecobuild.co.uk/2010-gallery.html.

Six years ago, when considering my thirty year old gravity fed anthracite, central heating system and thinking: this is well past its probable "mean time to failure", there were less than 700 of these systems installed in the whole country.
Last year in the teeth of the recession, 10,000 heat pumps were installed:- 8,000 quick win air source and 2,000 GSHP, hopefully with a mean time to failure at least as good as the 21.5 years being recorded in Germany. (I've got a 35 year old freezer made in Austia and yes my heating system has died and we are currently "managing" with 100 GBP of second hand night storage heaters).

We now have "the feed in tariff" (FiT) - generate your own electricity and get paid 0.413 GBP per unit (kWh) for using it (but only 0.03 for feeding it backwards into the grid).
The example given was a bungalow with a nice 30 degree south facing roof making its owner more than 1000 GBP better off per year tax free inflation proofed, for an investment of 7K - 12K GBP - this level of return is so good that you should be able to get a mortgage to raise the 7K- 12K that will be tied to the house not you. Hopefully a house buyer would be happy to buy the mortgage with the house. A combination of night time rates of 0.05 GBP and hugely subsidised PV day time electricity, must make a GSHP (ground source heat pump) the heating of choice for anyone off the gas grid.

However the installation MUST be put into a well insulated, draught proof home by an authorised installer to get the subsidised electricity and the (coming next year) RHI (Renewable Heat Initiative) payment.
Yes the ground will start to run out of stored heat and the pump will start to be inefficient at this time of year, when the temperature stubbornly stays below zero, and if your installation is badly designed it will take two years before you find you have a herculean mole under the patio because you are freezing the ground ( a bit like all those people who discovered that condensate draining out of their gas boiler freezes at sub zero temperatures). So be prepared to light the log burner or turn on the night storage heater if you don't fancy a full price electric fire or turning on the immersion heater fitted to the heat pump..

Harry.

the renovation area is heavy clay soil. Clay is good, the wetter the better, as the (say) 12 degree underground temperature flows through the clay easily to get to your just above freezing extraction pipework. There is a company offering a quick no mess service for people with small gardens on clay. It involves a truck with a hydraulic ram. This can shove a hollow stainless steel spear with a disposable point. It is rammed into the clay at various angles if required. The collector tube loops are dropped into the spear, going down as much as 15 meters and then the spear is withdrawn to be used on the next hole.

Finally, we run solar panels on the roof feeding a thermal store; When did you get this done? "Solar thermal" is being squeezed out between heat pumps and subsidised "Solar Electric" (PV) now. You might be able to get retrospective entry to RHI subsidies depending on when your system was commissioned; there was a great deal of muttering about "Solar Thermal" panels being uninstalled and reinstalled by the now competent installer, without the use of ladders or scaffolding.;)
Is you installer going for his "MCS"?

I have a Ground source heat pump installed, Its in a newly built house (aug 09)
Make representations now, possibly via your MP, as to how unfair it would be if you are excluded from the July 09 retrospective invitation to join FiT, saying that the same date should apply to RHI subsidies.
Is you installer going for his "MCS"?

The issue with ground source / air to heat / solar is that they all require another source of heat for the periods that enough heat cannot be extracted from the air / ground / sunlight, which here in northern Ireland is probably a reasonably proportion of the year.
It is vital that the building is so well insulated and draught proofed that it can be serviced by (say) a 3kW pump creating 9kW of heat inside the house. (That is nine bars of electric fire) as against a typical 1980's house load of 13 kW from a gas boiler.

The whole thing has to be DESIGNED after the house insulation has been upgraded. It makes far more sense to spend 300GBP on insulation, rather than 3,000 GBP on a bigger pump. When it is all installed, "the put a bigger pump on it or open up the valve a bit further and turn up the boiler stat", tricks of the gas plumbing trade can't work. (How many condensing boilers were badly sized and ran without actually condensing to get at the latent heat of the steam?).

You also need to check out your electricity supply - the electricity supply companies are very worried they will have a power cut leaving thousands of heat pumps all primed to kick off with a starting current of (say) 25 amps, and blowing the local stations fuses..
Alternatively there is newer technology of "inverters" coming in, it enables the pumps to go faster or slower depending on the demand for heat BUT our clapped out electricity supply has inadequate protection to prevent thousands of these starting up together and blowing up the local transformer. Chatting to you local Electricity Representative will cost you a couple of hundred pounds.

Finally the major problem now will be customers multiplying faster than the industry can train up operatives in the "new" technology.
You have to use a qualified person - beware of your installation being his "apprentice piece" on which he tries to get his "MCS" qualification; unless he/she appears to be truly sympathetic and understanding of the new technology.

BTW "MCS" Stands for Microgeneration Certification Scheme - you won't get the subsidy without the certificate. Over on the ASHP threads you will find some people who might have trouble convincing the certifiers that their rules of thumb are the best approach. (However if you are buying second hand airconditioning units for a few hundred, you can afford to plug in an extra one if needed)

If anyone knows of someone talented, prepared to take on a "retrofit" in Essex - please let me know.

Now where is Mr C when we need him?

Well here is something like I'm sure he would like to say, and I rather agree, but the government is desperate to "decarbon" the grid to meet the undertakings it has given..
(Coincidently the German scaling back from their "misguided" FiT is causing problems for the UK as there is a final scramble in Germany, causing a shortage of the magic technology box that converts solar PV at say 600V DC into 240+V AC (it has to be at slightly raised "pressure" to make it go backwards into the mains if not required on site.)

http://www.guardian.co.uk/commentisfree/2010/mar/01/solar-panel-feed-in-tariff

and here is the opposite view from someone who left Greenpeace to set up a renewable micro generating company:

http://www.guardian.co.uk/environment/cif-green/2010/mar/09/george-monbiot-bet-solar-pv

wdyw

CL wrote: »

It coped very well, I didn't notice any increase in the electricity usage due to the lower outside temperatures, The ground loops are buried fairly deep about 1.2m so the outside temperature doesn't affect it the same way it would an air to water heat pump

1.2m deep isn't that deep for a horizontal system. The closer to the surface the greater the seasonal variation. the only reason you might see a change in the system in very col weather is your house will always be losing some energy to the outside and as everyone knows heat transfer is a function of temperature difference. so simply put, the larger the temp difference between inside your house and outside, the more energy you lose, the more you have to replace. If your house is well insulated then !!!!!! all heat is lost in cold or very cold weather.

Gound source heat punps are the future for new builds (ground cinditions dependent), but for existing houses you really need to be an eco-warrior to consider retro fitting a system unless they start dishing out huge grants. 1 unit of energy in to get out 3-5 units of heat ..... bargain!!! (though comparing to an electrical resistance bar heater is not quite as straightforward as has been suggested).

Even better, reverse the system on the one day of summer we get each year and instead of extracting energy from the ground, you are using the ground as a heat sink and nice cool air.

What you always have to factor in on these systems is what if it goes wrong. you lose your boiler or develop a problem with your current system (pump / pipework) and its realtively easy to track and fix. What if your vertical pipe that might go down 80+m develops a problem?