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Geothermal heat pumps

 
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andyh



Joined: 24 Nov 2005
Posts: 323
Location: New Zealand

PostPosted: Mon Sep 04, 2006 10:05 pm    Post subject: Geothermal heat pumps Reply with quote

This technology is all new to me - anyone have any experienc of it - it almost seems to good to be true? We are toying with having a house built here and these systems seem amazing..........
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clv101
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Joined: 24 Nov 2005
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Location: Bristol

PostPosted: Mon Sep 04, 2006 10:48 pm    Post subject: Reply with quote

Yeah - they are good. They produce something like 2.5-3.5 more low-grade heat energy than the input electricity. Think of them as multiplying electrical energy but converting it to heat.

The problem in the UK at least is that historically electricity has been more than 3.5 time the price of gas so it was cheaper to heat with gas. Heat pumps make a lot of sense in countries where there is lots of relatively cheap electricity (typically hydro) and not much oil or gas - hmm, sounds like New Zealand!
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Adam1



Joined: 01 Sep 2006
Posts: 2707

PostPosted: Thu Sep 07, 2006 10:35 pm    Post subject: Reply with quote

clv101 wrote:
Yeah - they are good. They produce something like 2.5-3.5 more low-grade heat energy than the input electricity. Think of them as multiplying electrical energy but converting it to heat.

The problem in the UK at least is that historically electricity has been more than 3.5 time the price of gas so it was cheaper to heat with gas. Heat pumps make a lot of sense in countries where there is lots of relatively cheap electricity (typically hydro) and not much oil or gas - hmm, sounds like New Zealand!


My understanding is that there are two types: ground and air source heat pumps. Apparently getting the set up right is crucial to the 'cop'(?) up to 3.5 or more. Badly installed systems only delivery cops of 2 (double the energy out as you put in).

My cousin's husband has replaced their oil-fed central heating system with an air source heat pump. They live in a pretty well insulated house (about 10 years old) near Dublin in Ireland. They have also installed solar hot water and a 750 litre hot water tank. The air source heat pump heats the house via the existing wall mounted radiators and tops up the water temperature, which has been pre-heated by the solar panels. The oil based system heated the central heating water to about 70C. The new set up is expected to heat the water to 45C. This coming winter will be their first with the new system, so it'll be interesting to see how well it works.

If I was building from new, I'd get the insulation as good as possible. That way it makes ground or air source heating (and cooling) cheaper to install and run.
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biffvernon



Joined: 24 Nov 2005
Posts: 16257
Location: Lincolnshire

PostPosted: Fri Sep 08, 2006 11:31 am    Post subject: Reply with quote

There's quite a capital cost, especially when retrofitting an existing building, of the order of ?5000. Because the input temperature is fairly low they are best suited to underfloor heating systems rather than conventional radiators. There is a good case for gshp in new builds as the pipework could be installed at the same time as other groundworks along with the drains and foundations. A typical system has a hundred yards of pipe layed a few feet down. Perhaps it ought to be a condition of Planning or in the Building Regulations, that the necessary infrastructure should be included in new builds. It wouldn't add much to the build cost. Ground is generally better than air since ground temperatures in winter are higher than air temperatures. If you live by a stream or lake then significant gains can be had by putting the heat exchange pipe in the water. I know of someone whose gshp system works from a borehole that was sunk to an underground stream in limestone. This was in an urban area where there was no room for pipes to be layed round a garden.

Gshp makes efficient use of electricity but it's cost is ultimately linked to the price of the electricity that is used.
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brasso



Joined: 20 Jun 2006
Posts: 60
Location: Nottingham, UK

PostPosted: Fri Sep 08, 2006 12:53 pm    Post subject: Reply with quote

I tend to agree with biffvernon - they are dependent on electric. It depends on your view of what will happen past peak. If you're hedging your bets that the economy and infrastructure will still hold, then geothermal may be the way to go, especially with a wind turbine!

However, if you're looking at a 'shotguns and canned food' scenario then a wood stove may suit you better, as an interruption in electric will mean in interruption in your heating system - not good! Remember that heat pumps are not just dependent on electric, but in the case of a breakdown you may need spare parts, etc.

You pays your money, you takes your choice! Smile
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heinbloed



Joined: 24 Nov 2005
Posts: 56

PostPosted: Fri Sep 15, 2006 1:23 am    Post subject: Climate demage by heatpump refrigerants Reply with quote

Think about the climate demaging effect-the so called greenhouse effect- which heatpumps can have. All of them work with refrigerants, some are pretty nasty. HCFCs are banned
since 1995 in new heatpumps, but their replacement in older heatpumps designed to run with HCFC still isn't.
Here are the numbers , comparing the climate demaging effect of 1kg of the refrigerants with the equivalent of carbondioxide:
R12 HCFC ---------6,640 kg CO2 (banned since 1995)
R13 HFC ----------1,300 kg CO2
R404A HFC---------3,260 kg CO2
R407C HFC---------1,530 kg CO2
R410A HFC---------1,730 kg CO2
R744 (CO2)--------1kg CO2
R717 (Ammonia)---0 kg CO2
R290 (Propane)----3 kg CO2
R600 (Butane)-----3 kg CO2
R1270 (Propene)--3kg CO2

Every heatpump for a single family home contains about 1-3 kg of refrigerant, depending on the size of the heated house, the demand.

Let's take for example R404A HFC: If 2 kg of this material is released into the atmosphere it'll have the same influence on our climate as the release of 6,500kg of CO2 ( 6.5 tonnes ). And 6.5 tonnes of CO2 would be released for example when burning 32,500 kWh of gas. Which would heat a standard home for for 3 years, or a well insulated home with an energy demand of 30kwh/m2/a for 9 years.The emissions caused by the generation of the electricity to run the pump is not included in these numbers.......

The refrigerants are released during manufacturing, when refilling the heatpump reservoir at regular intervalls, when scrapping them or when unintentionally demaging them. And -of course- during their operating time. Compare a heatpump with an airconditioner in your car. After so and so many running hours it needs a back-up of refrigerant because the refrigerant is leaching out.

A heat pump is not necessary a wise decision for the environment, so think twice and choose the right one.
Capito, Dimplex, Hautec, Nibe and Tecalor (and other manufacturers maybe as well) have some heatpumps working with R290, but they also sell the bad ones. Ask for the low climate demaging types. R290 (propane) is used in most modern fridges and freezers nowadays, but the heatpump market seemed to be untouched by the climate change discussion.
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Pippa
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Joined: 27 Apr 2006
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Location: Cambridgeshire

PostPosted: Fri Sep 15, 2006 8:28 am    Post subject: Reply with quote

So are gas and oil boilers dependant on electric as they have electronic timers and ignition systems.
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Adam1



Joined: 01 Sep 2006
Posts: 2707

PostPosted: Fri Sep 15, 2006 4:33 pm    Post subject: Re: Climate demage by heatpump refrigerants Reply with quote

heinbloed wrote:
Think about the climate demaging effect-the so called greenhouse effect- which heatpumps can have. All of them work with refrigerants, some are pretty nasty. HCFCs are banned
since 1995 in new heatpumps, but their replacement in older heatpumps designed to run with HCFC still isn't.
Here are the numbers , comparing the climate demaging effect of 1kg of the refrigerants with the equivalent of carbondioxide:
R12 HCFC ---------6,640 kg CO2 (banned since 1995)
R13 HFC ----------1,300 kg CO2
R404A HFC---------3,260 kg CO2
R407C HFC---------1,530 kg CO2
R410A HFC---------1,730 kg CO2
R744 (CO2)--------1kg CO2
R717 (Ammonia)---0 kg CO2
R290 (Propane)----3 kg CO2
R600 (Butane)-----3 kg CO2
R1270 (Propene)--3kg CO2

Every heatpump for a single family home contains about 1-3 kg of refrigerant, depending on the size of the heated house, the demand.

Let's take for example R404A HFC: If 2 kg of this material is released into the atmosphere it'll have the same influence on our climate as the release of 6,500kg of CO2 ( 6.5 tonnes ). And 6.5 tonnes of CO2 would be released for example when burning 32,500 kWh of gas. Which would heat a standard home for for 3 years, or a well insulated home with an energy demand of 30kwh/m2/a for 9 years.The emissions caused by the generation of the electricity to run the pump is not included in these numbers.......

The refrigerants are released during manufacturing, when refilling the heatpump reservoir at regular intervalls, when scrapping them or when unintentionally demaging them. And -of course- during their operating time. Compare a heatpump with an airconditioner in your car. After so and so many running hours it needs a back-up of refrigerant because the refrigerant is leaching out.

A heat pump is not necessary a wise decision for the environment, so think twice and choose the right one.
Capito, Dimplex, Hautec, Nibe and Tecalor (and other manufacturers maybe as well) have some heatpumps working with R290, but they also sell the bad ones. Ask for the low climate demaging types. R290 (propane) is used in most modern fridges and freezers nowadays, but the heatpump market seemed to be untouched by the climate change discussion.


I hadn't considered the refrigerants. It sounds like heat pump technology isn't intrinsically inappropriate, it just has to be chosen carefully.
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XENG



Joined: 28 Feb 2006
Posts: 192

PostPosted: Fri Sep 15, 2006 5:12 pm    Post subject: Reply with quote

I do not disagree that these substances are a threat to the environment, specifically their ozone depletion potential which you fail to mention, and is the reason that the nastier ones are being phased out under the Montreal Protocol, but lets not over react here.
Efficiency is one of the best tools in our box when trying to overcome our energy problems and heat pumps are very efficient for the ammount of energy they consume.
In terms of the global warming potential of these substances, it doesnt seem like a major problem compared to the ammount of CO2 produced by needlessly burning fossil fuels and of course the huge ammount of methane that comes out of various animals bottoms (including ours) and that which is realeased by vegetation of which there is no exact figure, just that it might be quite large.

The solution to this, as has already been said, is to select you refrigerant carefully and make sure that it is recycled or disposed of correctly.
Its not as if we are limited when chosing a refrigerant (obviously there will be some limitations dependant on the application), there is a whole shmorgusboard of refrigerants to choose from, some of which functionally equivalent but are not nearly as bad the old CFCs, R134a being an example.
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heinbloed



Joined: 24 Nov 2005
Posts: 56

PostPosted: Fri Sep 15, 2006 11:45 pm    Post subject: Reply with quote

The only refrigerants that are ozone depleting are banned already -under the Montreal protocol as mentioned by XENG- in new appliances. The standard refrigerants - the HFCs that are used in most standard heatpumps- are not banned. And that is the crux. (As far as I remember it was the German company "Hoechst" that sold the last and "biggest ever build HFC plant" to China-and then Hoechst closed down.)
They-these HFCs- cause more damage than good in heatpumps when the energy demand to run these pumps and to maintain/recycling them is included in the calculation sheet.
And again: only a fraction of what is produced of these substances is actually recycled. Or "safely disposed"-which means in laymen terms more combustion, more climate damage. Get the calculation sheets right and decide then......
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TheNatural



Joined: 25 Jun 2006
Posts: 10

PostPosted: Sat Sep 16, 2006 12:48 am    Post subject: Reply with quote

There's pros and cons on every heating system, so I think we will count on several manners. In our new old house we have two oil ovens. Now, to start with we will add to this with one or two air heat pumps and probably a wood oven in time.
If one have the space, I reckon it's a good thing to have different options as how to keep warm. Prices of oil and electricity is up and down and when that is not an option, there's always wood to be found.
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andyh



Joined: 24 Nov 2005
Posts: 323
Location: New Zealand

PostPosted: Sat Sep 16, 2006 2:52 am    Post subject: Reply with quote

Thanks for all the input folks very interesting. Here in NZ we are lucky in that something like 65% of electricity comes from renewables, and so the source is relatively secure (cp to say Europe and its dependence on Russian gas). We will in due course be buying/building a house and it seems to me the best option for here will therefor be a woodburner which also heats water (what they call a wetback here), which is linked in to a Solar water heater on the roof (its getting to be a frequent combination here). Typically wetbacks are in the wearedodgy and you can boil the kettle/stews on top too - you can also have a fan system to dump the heat from the wearedodgy elsewhere in the house. Then either an above ground heat pump for supplementary heating (if its an existing house we buy - again these are getting more and more common in NZ), or a geothermal based heat pump if we build from fresh.
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kenneal - lagger
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Joined: 20 Sep 2006
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Location: Newbury, Berkshire

PostPosted: Thu Sep 21, 2006 3:48 am    Post subject: Reply with quote

When you're looking at heat pumps you need to look at the energy efficiency not the cost efficiency. Electricity is generated in this country at about 30 - 35% efficiency. The COP of heat pumps with radiators is about 3 so you might as well burn the fuel at home and save yourself ?5000 or more. If used with underfloor heating GSHP's have a COP of 4 so they are just energy efiicient but cost a fortune. If you're on renewable electricity it is a bloody expensive way to use a lot of electricity.

High grade, difficult to produce, energy like electricity should be used frugally for lighting, powering machines and fridges and other things that only electricity can do. There are loads of ways to heat water.

If you're building from scatch, spend ?5000 on insulation, a solar hot water panel and a wood stove and you won't have put any more heat into the house. Not using energy is the best way to save it so insulate first, second and third and then think about heating, hopefully only your DHW.

In NZ if you live in the right area you don't need a heat pump, you can source hot water directly from the ground anyway. If you live in parts of Southampton, UK, you can get geothermal heat now through a district heating scheme. Google "Southampton geothermal".
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heinbloed



Joined: 24 Nov 2005
Posts: 56

PostPosted: Thu Sep 21, 2006 11:17 pm    Post subject: Reply with quote

Thanks Kenneal!
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