Solar vs heatpumps in sunny Ireland ?

Question:

Hi All We’re planning on making a move from sunny Suffolk-by-the-sea to the south-west of Ireland. It’s possible that we may do a ‘self-build’ project over there – but even if we buy an existing property we’ll want to make it as energy-efficient as possible. Here in Suffolk we have a ‘thermomax’-baed system for domestic hot water, assisted by a boiler on the woodburner and mains electric as a last resort ! I know that you don’t need ‘blazing sunshine’ to work the thermomaxes – but does anybody have experience of running a solar dhw system in the sourth of the Republic – where the weather is notoriously ‘soft’ <g Also – I know little or nothing about ground-based heatpump systems – other than they appear to offer very cheap energy for dhw and ch use. I’m happy to Google for more information – but I’m looking for ‘hands-on’ comments from people who have this type of system are have lived with it…. Many thanks in advance Adrian Suffolk UK (for the time being!) take out the papers and the trash to reply

Response:

Also – I know little or nothing about ground-based heatpump systems – other than they appear to offer very cheap energy for dhw and ch use. I’m happy to Google for more information – but I’m looking for ‘hands-on’ comments from people who have this type of system are have lived with it….

I’m looking into the same thing at the moment. Google can find no end of stuff about the principles involved, but precious little hard information about the practicalities – like who sells it, exactly what models are available / required, and how much they cost. I went to a building exhibition where I talked to several suppliers. All took my details and promised to contact me to sort out a surey / quote. None have. I am beginning to think this is just a nice theory with nothing practical available. I wonder how difficult it would be to get service if it is so hard to buy in the first place. — Duncan

Response:

I’ve had hands on with GSHP’s. Look at www.econar.com Yes, they can be powered with PV if you spend enough on panels …. Steve Spence Dir., Green Trust http://www.green-trust.org Contributing Editor http://www.off-grid.net http://www.rebelwolf.com/essn.html – Hide quoted text — Show quoted text – Also – I know little or nothing about ground-based heatpump systems – other than they appear to offer very cheap energy for dhw and ch use. I’m happy to Google for more information – but I’m looking for ‘hands-on’ comments from people who have this type of system are have lived with it…. I’m looking into the same thing at the moment. Google can find no end of stuff about the principles involved, but precious little hard information about the practicalities – like who sells it, exactly what models are available / required, and how much they cost. I went to a building exhibition where I talked to several suppliers. All took my details and promised to contact me to sort out a surey / quote. None have. I am beginning to think this is just a nice theory with nothing practical available. I wonder how difficult it would be to get service if it is so hard to buy in the first place.

Response:

HI Duncan Thanks for the reply – Hide quoted text — Show quoted text – Also – I know little or nothing about ground-based heatpump systems – other than they appear to offer very cheap energy for dhw and ch use. I’m happy to Google for more information – but I’m looking for ‘hands-on’ comments from people who have this type of system are have lived with it…. I’m looking into the same thing at the moment. Google can find no end of stuff about the principles involved, but precious little hard information about the practicalities – like who sells it, exactly what models are available / required, and how much they cost. I went to a building exhibition where I talked to several suppliers. All took my details and promised to contact me to sort out a surey / quote. None have. I am beginning to think this is just a nice theory with nothing practical available. I wonder how difficult it would be to get service if it is so hard to buy in the first place.

Fair comments <g The one bit that sticks in my mind is something about using one unit of electricity to get 3 units of ‘heating effect’ – but I can’t remember where that came from….. The solar installation we have here works very well – but I’m not so sure how well it’d work in a much ‘cloudier’ environment. As I understand it, a heat pump is simply a ‘fridge in reverse – in which case it would use fairly standard ‘aircon’ components – which should be easily serviced / replaced etc. I guess the most difficult / specialist bit would be recharging the system with refrigerant – and the initial burying of the ‘earth-end’ of the system – one site mentioned burying at 10ft – which could get interesting….. We’re hopefully looking at a site of 1 – 2 acres, if the self-build idea goes ahead, so no great lack of space for coil burying… I’d also heard that running water can be used as a heat source – no great shortage of that in Ireland <g…… So – does anybody have experience of heat-pump installations in the UK / Republic of Ireland ?? Thanks in advance Adrian Suffolk UK take out the papers and the trash to reply

Response:

- Hide quoted text — Show quoted text – HI Duncan Thanks for the reply Also – I know little or nothing about ground-based heatpump systems – other than they appear to offer very cheap energy for dhw and ch use. I’m happy to Google for more information – but I’m looking for ‘hands-on’ comments from people who have this type of system are have lived with it…. I’m looking into the same thing at the moment. Google can find no end of stuff about the principles involved, but precious little hard information about the practicalities – like who sells it, exactly what models are available / required, and how much they cost. I went to a building exhibition where I talked to several suppliers. All took my details and promised to contact me to sort out a surey / quote. None have. I am beginning to think this is just a nice theory with nothing practical available. I wonder how difficult it would be to get service if it is so hard to buy in the first place. Fair comments <g The one bit that sticks in my mind is something about using one unit of electricity to get 3 units of ‘heating effect’ – but I can’t remember where that came from….. The solar installation we have here works very well – but I’m not so sure how well it’d work in a much ‘cloudier’ environment. As I understand it, a heat pump is simply a ‘fridge in reverse – in which case it would use fairly standard ‘aircon’ components – which should be easily serviced / replaced etc. I guess the most difficult / specialist bit would be recharging the system with refrigerant – and the initial burying of the ‘earth-end’ of the system – one site mentioned burying at 10ft – which could get interesting….. We’re hopefully looking at a site of 1 – 2 acres, if the self-build idea goes ahead, so no great lack of space for coil burying… I’d also heard that running water can be used as a heat source – no great shortage of that in Ireland <g…… So – does anybody have experience of heat-pump installations in the UK / Republic of Ireland ?? Thanks in advance Adrian Suffolk UK take out the papers and the trash to reply

Hi Adrian. I myself am building a house in the Irish midlands at the moment and am also very anxious that it should be as energy efficient as reasonably possible and that as much energy as reasonably possible is obtained from renewable sources. Heat pumps theoretically return about 4kw for every 1kw input. In Ireland at the moment each kw costs about 0.15EURO, including taxes (about 0.104STG or 0.195USD) and this is expected to rise steeply over the coming years. That could make the running costs of a heat pump prohibitive, but that would depend on lots of other factors. What I intend to do is to make provision for a heat pump installation which can be linked into another central heating system at a later date by creating extra service entrances into the house through which heat pump piping can be routed and also by the use of underfloor heating which should lend itself to future heat pump use as well as an oil fired/other heat source for the moment. Naturally I intend to use as much insulation as is practicable, particularily in those areas that cannot easily have insulation added after the build is complete (floor and cavity wall insulation). You may find the following link to your Solar Trade Association useful. This suggests you could achieve 1150kwhr/m2/year (falling on the solar panel) in SW Ireland. http://www.greenenergy.org.uk/sta/solarenergy/ukresource.htm Best of luck. Mike.

Response:

Hi Mike <big snip ! So – does anybody have experience of heat-pump installations in the UK / Republic of Ireland ?? Thanks in advance Adrian Suffolk UK Hi Adrian. I myself am building a house in the Irish midlands at the moment and am also very anxious that it should be as energy efficient as reasonably possible and that as much energy as reasonably possible is obtained from renewable sources.

OK – a man after my own heart ! Heat pumps theoretically return about 4kw for every 1kw input. In Ireland at the moment each kw costs about 0.15EURO, including taxes (about 0.104STG or 0.195USD) and this is expected to rise steeply over the coming years. That could make the running costs of a heat pump prohibitive, but that would depend on lots of other factors.

I guess you’d expect the costs of other energy sources to also rise – bit of a guessing game, though, – isn’t it ? Any idea on the practical ‘yield’ from heatpumps ..? What I intend to do is to make provision for a heat pump installation which can be linked into another central heating system at a later date by creating extra service entrances into the house through which heat pump piping can be routed and also by the use of underfloor heating which should lend itself to future heat pump use as well as an oil fired/other heat source for the moment.

Yes – underfloor does seem the way to go (I wasn’t aware of it until a couple of weeks ago, but a house in the village was built with oil-fired underfloor heating last year – and we had a look round it. Very nice – no radiators <g – also a ‘warm feel’ to the place… no cold spots. In our current bungalow we heat via a multifuel stove and radiators (mostly wood-fired) – but I can see there will come a time when I don’t want to cut & split 3 woodsheds of timber each year – even assuming that I’ll be able to source the stuff at reasonable cost in Ireland. Naturally I intend to use as much insulation as is practicable, particularily in those areas that cannot easily have insulation added after the build is complete (floor and cavity wall insulation).

Yes – looking at timber-frame construction at the moment – seems to offer advantages in build speed and insulation…. The house in the village has a floor system  which includes 6" of polystyrene….. You may find the following link to your Solar Trade Association useful. This suggests you could achieve 1150kwhr/m2/year (falling on the solar panel) in SW Ireland. http://www.greenenergy.org.uk/sta/solarenergy/ukresource.htm

That’s an interesting map. Suggests that insolation is about similar for SW Ireland to where we are now (Suffolk). Sounds as if solar for DHW is a possibility – I know it works very well over here (disregarding the payback period !) – looks as if we could do the smae over there. Hopefully looking at the area around Skibbereen / Bantry etc – though we’ll probably move over & rent for a little while before settling on a particular property or build location. Wonder where you are in the midlands ? How are you finding the build – are you doing the work yourself or organising subbies. I’m rubbish at brickwork, but reasonably good at everything else – though I expect there are restrictions on ‘enthusiastic amateurs’ doing things like electrical wiring ..? Still – need to sell our current place first – anybody want to buy a nice bungalow near the Suffolk coast on 1.75 acres, paddock, polytunnels, solar dhw,  etc  ?? <g Nice to hear from you, Mike – thanks for the info Adrian Suffolk UK take out the papers and the trash to reply

Response:

- Hide quoted text — Show quoted text – Hi Mike <big snip ! So – does anybody have experience of heat-pump installations in the UK / Republic of Ireland ?? Thanks in advance Adrian Suffolk UK Hi Adrian. I myself am building a house in the Irish midlands at the moment and am also very anxious that it should be as energy efficient as reasonably possible and that as much energy as reasonably possible is obtained from renewable sources. OK – a man after my own heart ! Heat pumps theoretically return about 4kw for every 1kw input. In Ireland at the moment each kw costs about 0.15EURO, including taxes (about 0.104STG or 0.195USD) and this is expected to rise steeply over the coming years. That could make the running costs of a heat pump prohibitive, but that would depend on lots of other factors. I guess you’d expect the costs of other energy sources to also rise – bit of a guessing game, though, – isn’t it ? Any idea on the practical ‘yield’ from heatpumps ..?

Although the costs of electricity generation will vary with the costs of whatever energy sources are being used there is an extra factor here in Ireland. Our ESB (Electricity Supply Board) is being prepared for privitisation. Up to about seven years ago we had pretty much the cheapest electricy in Europe – now it is amongst the most expensive. The cost of electricity will almost certainly rise to maximise the profits of the ESB and make it more attractive to investors. – Hide quoted text — Show quoted text – What I intend to do is to make provision for a heat pump installation which can be linked into another central heating system at a later date by creating extra service entrances into the house through which heat pump piping can be routed and also by the use of underfloor heating which should lend itself to future heat pump use as well as an oil fired/other heat source for the moment. Yes – underfloor does seem the way to go (I wasn’t aware of it until a couple of weeks ago, but a house in the village was built with oil-fired underfloor heating last year – and we had a look round it. Very nice – no radiators <g – also a ‘warm feel’ to the place… no cold spots. In our current bungalow we heat via a multifuel stove and radiators (mostly wood-fired) – but I can see there will come a time when I don’t want to cut & split 3 woodsheds of timber each year – even assuming that I’ll be able to source the stuff at reasonable cost in Ireland. Naturally I intend to use as much insulation as is practicable, particularily in those areas that cannot easily have insulation added after the build is complete (floor and cavity wall insulation). Yes – looking at timber-frame construction at the moment – seems to offer advantages in build speed and insulation…. The house in the village has a floor system  which includes 6" of polystyrene….. You may find the following link to your Solar Trade Association useful. This suggests you could achieve 1150kwhr/m2/year (falling on the solar panel) in SW Ireland. http://www.greenenergy.org.uk/sta/solarenergy/ukresource.htm That’s an interesting map. Suggests that insolation is about similar for SW Ireland to where we are now (Suffolk). Sounds as if solar for DHW is a possibility – I know it works very well over here (disregarding the payback period !) – looks as if we could do the smae over there. Hopefully looking at the area around Skibbereen / Bantry etc – though we’ll probably move over & rent for a little while before settling on a particular property or build location.

Although PV generated electricity driving a heat pump is pretty much a dream of mine, I don’t think it will be practical here for some time to come. Domestic Hot Water from solar does seem much more practical, particularly since heating water consumes so much electricity. I have fabricated a small (0.74sq m) solar panel for experimental purposes – I hope to have results later this year). One possible option… but please do your research carefully. I believe the ESB have a scheme whereby you can purchase off-peak electricity at a reduced rate, e.g. 50%. If this was used to run a heat pump at night then the running costs would be about 7.5 cents (Euro) per kw/hr consumed from the grid or a tad under 2 cents (Euro) for each kw/hr output from the heat pump (assuming a 1:4 input:output ratio for the heat pump). The heat pump could be used to heat the floor slab at night and give back the heat during the day. There would almost certainly have to be some top-up heating (from the heat pump or another source) during the following evening if not during the following day. I understand the ESB prefer to have electric heating elements buried in the floor slab but this would tie you to grid electricity for ever, and ever, and ever… Wonder where you are in the midlands ? How are you finding the build – are you doing the work yourself or organising subbies. I’m rubbish at brickwork, but reasonably good at everything else – though I expect there are restrictions on ‘enthusiastic amateurs’ doing things like electrical wiring ..?

I am building in Daingean, County Offaly, about halfway between Tullamore and Edenderry. I am doing as much of the build as possible myself. I’m no professional builder, but intend to take it as slow as necessary to get the quality I need. There are some things you should know… Unlike the UK, the Irish state does not return VAT (materials and services tax) to the self-builder. Here that amounts to 13.5% on concrete and 21% on pretty much everything else. Also, there are no grants from the state or others for renewable technology in the home. Here is a link to our Sustainable Energy Ireland site, which you may find useful http://www.sei.ie – Hide quoted text — Show quoted text – Still – need to sell our current place first – anybody want to buy a nice bungalow near the Suffolk coast on 1.75 acres, paddock, polytunnels, solar dhw,  etc  ?? <g Nice to hear from you, Mike – thanks for the info Adrian Suffolk UK take out the papers and the trash to reply

Response:

HI Mike Thanks for the reply – comments inline ……. – Hide quoted text — Show quoted text – Hi Mike <big snip ! So – does anybody have experience of heat-pump installations in the UK / Republic of Ireland ?? Thanks in advance Adrian Suffolk UK Hi Adrian. I myself am building a house in the Irish midlands at the moment and am also very anxious that it should be as energy efficient as reasonably possible and that as much energy as reasonably possible is obtained from renewable sources. OK – a man after my own heart ! Heat pumps theoretically return about 4kw for every 1kw input. In Ireland at the moment each kw costs about 0.15EURO, including taxes (about 0.104STG or 0.195USD) and this is expected to rise steeply over the coming years. That could make the running costs of a heat pump prohibitive, but that would depend on lots of other factors. I guess you’d expect the costs of other energy sources to also rise – bit of a guessing game, though, – isn’t it ? Any idea on the practical ‘yield’ from heatpumps ..? Although the costs of electricity generation will vary with the costs of whatever energy sources are being used there is an extra factor here in Ireland. Our ESB (Electricity Supply Board) is being prepared for privitisation. Up to about seven years ago we had pretty much the cheapest electricy in Europe – now it is amongst the most expensive. The cost of electricity will almost certainly rise to maximise the profits of the ESB and make it more attractive to investors.

Ah – I see. I was hoping to escape this sort of lunacy – that’s why we’re doing the move to Ireland from the UK. Ah well – so long as they don’t privatise the Irish sense of humour….<g – Hide quoted text — Show quoted text – What I intend to do is to make provision for a heat pump installation which can be linked into another central heating system at a later date by creating extra service entrances into the house through which heat pump piping can be routed and also by the use of underfloor heating which should lend itself to future heat pump use as well as an oil fired/other heat source for the moment. Yes – underfloor does seem the way to go (I wasn’t aware of it until a couple of weeks ago, but a house in the village was built with oil-fired underfloor heating last year – and we had a look round it. Very nice – no radiators <g – also a ‘warm feel’ to the place… no cold spots. In our current bungalow we heat via a multifuel stove and radiators (mostly wood-fired) – but I can see there will come a time when I don’t want to cut & split 3 woodsheds of timber each year – even assuming that I’ll be able to source the stuff at reasonable cost in Ireland. Naturally I intend to use as much insulation as is practicable, particularily in those areas that cannot easily have insulation added after the build is complete (floor and cavity wall insulation). Yes – looking at timber-frame construction at the moment – seems to offer advantages in build speed and insulation…. The house in the village has a floor system  which includes 6" of polystyrene….. You may find the following link to your Solar Trade Association useful. This suggests you could achieve 1150kwhr/m2/year (falling on the solar panel) in SW Ireland. http://www.greenenergy.org.uk/sta/solarenergy/ukresource.htm That’s an interesting map. Suggests that insolation is about similar for SW Ireland to where we are now (Suffolk). Sounds as if solar for DHW is a possibility – I know it works very well over here (disregarding the payback period !) – looks as if we could do the smae over there. Hopefully looking at the area around Skibbereen / Bantry etc – though we’ll probably move over & rent for a little while before settling on a particular property or build location. Although PV generated electricity driving a heat pump is pretty much a dream of mine, I don’t think it will be practical here for some time to come.

No – PV still seems horrendously expensive – or is it that ‘mains’ electricity is still relatively cheap…? Domestic Hot Water from solar does seem much more practical, particularly since heating water consumes so much electricity. I have fabricated a small (0.74sq m) solar panel for experimental purposes – I hope to have results later this year).

What’s the construction of your panel ? Our installation here uses Thermomax evacuated tubes – seem to work very well – but they aren’t cheap to buy. I did play many years ago with using central heating radiators as collectors – they worked insofar as they heated water – but, at the time, the installation they were connected to wasn’t really suitable to see how well they worked. I’m guessing that your panel is a variation on the ‘pipe on a black surface’ idea …? One possible option… but please do your research carefully. I believe the ESB have a scheme whereby you can purchase off-peak electricity at a reduced rate, e.g. 50%. If this was used to run a heat pump at night then the running costs would be about 7.5 cents (Euro) per kw/hr consumed from the grid or a tad under 2 cents (Euro) for each kw/hr output from the heat pump (assuming a 1:4 input:output ratio for the heat pump). The heat pump could be used to heat the floor slab at night and give back the heat during the day. There would almost certainly have to be some top-up heating (from the heat pump or another source) during the following evening if not during the following day. I understand the ESB prefer to have electric heating elements buried in the floor slab but this would tie you to grid electricity for ever, and ever, and ever…

Hmm – like a giant ‘nightstore’ heater. My late parents had the conventional ‘nightstore’ heaters in their littl bungalow in Cornwall. Only trouble was, you needed to know how hot or cold tomorrow was going to be in order to acquire sufficieint heat overnight to ‘store’ for the next day. We don’t like our house to be too hot, anyway – and certainly not at night (allow the woodburner to go ‘out’ at night in all but the coldest conditions) – so I’m not sure that’s the right solution for us… but thanks for the suggestion. Wonder where you are in the midlands ? How are you finding the build – are you doing the work yourself or organising subbies. I’m rubbish at brickwork, but reasonably good at everything else – though I expect there are restrictions on ‘enthusiastic amateurs’ doing things like electrical wiring ..? I am building in Daingean, County Offaly, about halfway between Tullamore and Edenderry. I am doing as much of the build as possible myself. I’m no professional builder, but intend to take it as slow as necessary to get the quality I need.

That’s a good plan – at least then you’l be happy with the end result – and get a real sense of achievement. We’ll probably move into rented accomodation when we get over there – and either do a ‘self-build’ or buy ‘ready-made’ – if we can find the right property. If we do ‘self-build’ it’ll probably be managed by a builder with us doing the things that we’re good at – so not ‘self-build’ in your sense…..  This plan seems to make sense on the grounds that a good local builder will know who the local tradesmen are, and will be able to organise them… There are some things you should know… Unlike the UK, the Irish state does not return VAT (materials and services tax) to the self-builder. Here that amounts to 13.5% on concrete and 21% on pretty much everything else. Also, there are no grants from the state or others for renewable technology in the home. Here is a link to our Sustainable Energy Ireland site, which you may find useful http://www.sei.ie

Thanks – bookmarked. Odd that there are no grants available – I’d got the impression that Ireland was fairly positive towards ‘green’ issues…. Thanks again for the info Adrian take out the papers and the trash to reply

Response:

Here’s some thoughts for your ground source heat pump questions. I spent much of the last year researching GSHP systems and had one installed in December (I live in Pennsylvania, USA). If I were to do it again, I would do it differently, but I’d still get a GSHP. First, my home is built on a hill which is essentially solid granite so there is very little water movement. The system I had installed is a closed loop system with vertical loops – they drill boreholes and put tubing down the holes. The ground heat "flows" in to supply heat to the fluid in the tubing, which then runs through a refrigerant cycle (either directly or via a heat exchanger depending on the design). Now, just like a normal air source heat pump, the effectiveness of the system decreases with the temperature. So a system you buy that is rated at "4-tons" may only actually produce 2-tons of heat if the ground temperature is below freezing. On the other hand, if the ground temperature is able to stay warm, say 50F all winter, then your 4-ton system may produce the full 4-tons of heat. The problem with the system I had installed was that the installers did not do their estimation right and after a little use, the ground would freeze, so that the system would produce very little heat. Note too that other GSHP installers I talked to do actually design their systems to put out the desired amount of heat capacity with ground temperature at freezing. This will help, but it’s really not the optimal solution. In fact, all closed loop systems will lower the temperature of the ground through the winter to some extent. This is normal. The key is to put in enough loops that the ground temperature never drops below a reasonable temperature, say 40F. As I said, if I were to do it again, I’d do it differently. The best efficiency is gained if you use an open loop system. that is, the ground temperature water is drawn from one well (that must be able to continuously supply about 2 gallons/minute per ton of heating capacity) then injected into another well (or pond etc.). In this way, the temperature of the "heat source" is always the ground temperature water and you’re not lowering the temperature of the water throughout the heating season. So, if you have a good well water supply that can provide maybe 10 gallons/minute all year long, you’re probably in good shape. Using such a system with ground water temperatures of around 50F will give you a system that will typically provide a COP of 3.5 to 4 depending on the system. COP is the number you were referring to – a COP of 4 will give you four watts of heat out for one watt of electricity in. This is all a very simplified description, but it should be enough to get you going. One more thing – from everything I’ve read, a radiant heating system will provide you with the most efficient and comfortable heating for your home. So rather than the ground source heat pump putting out hot air, you would use it to heat up a water tank. Then you use this hot water to heat your floors and your domestic hot water. If you can put solar on there too, you’re even better off. Best of luck.

Response:

One more thing, Since the mean winter temperature in Ireland is 4C, you might be just as well off using a normal air source heat pump. At 4C, you’ll get plenty of heat capacity from a normal air source heat pump and won’t have to go through the complexity and expense of a ground source heat pump.

Response:

TDI Using such a system with ground water temperatures of around 50F TDI will give you a system that will typically provide a COP of 3.5 to TDI 4 depending on the system. COP is the number you were referring to TDI – a COP of 4 will give you four watts of heat out for one watt of TDI electricity in. Here in California, four watts of heat from natural gas costs about the same as one watt of electricity.  What are the relative rates in Ireland? Remember that to make that one watt of electricity, they have to burn fuel to make multiple watts of heat, then extract electricity from that heat.  The process is governed by the same heat-engine equations that govern your GSHP.  Inefficiency in the various stages — thermal to mechanical, mechanical to electrical, transmission, electrical to mechanical, mechanical to thermal again — usually overcome the leverage you have of pumping heat up from 4C to 32C (+10%) versus dropping heat in a turbine from 870 C to 100 C (-67%). My point is just that the physics make it inevitable that electricity will cost a lot more than fuel, and thus make heat pumps a marginal idea.  They work great in places like Florida where the amount of heat needed per year is small, and the heat pump is needed anyway for refrigeration (A/C) for most of the year. I’m using unglazed plastic rooftop panels for heating the pool in my current house, and glazed metal rooftop panels for heating the house in the next one.  The new system does not break even economically. I’m doing it because (a) it decouples the value of the house from the cost of fuel, and (b) I’d rather pay money to American labor to assemble stuff than pay slightly less money to folks in the mideast with a scary religious agenda.

Response:

– Hide quoted text — Show quoted text – TDI Using such a system with ground water temperatures of around 50F TDI will give you a system that will typically provide a COP of 3.5 to TDI 4 depending on the system. COP is the number you were referring to TDI – a COP of 4 will give you four watts of heat out for one watt of TDI electricity in. Here in California, four watts of heat from natural gas costs about the same as one watt of electricity.  What are the relative rates in Ireland? Remember that to make that one watt of electricity, they have to burn fuel to make multiple watts of heat, then extract electricity from that heat.  The process is governed by the same heat-engine equations that govern your GSHP.  Inefficiency in the various stages — thermal to mechanical, mechanical to electrical, transmission, electrical to mechanical, mechanical to thermal again — usually overcome the leverage you have of pumping heat up from 4C to 32C (+10%) versus dropping heat in a turbine from 870 C to 100 C (-67%). My point is just that the physics make it inevitable that electricity will cost a lot more than fuel, and thus make heat pumps a marginal idea.  They work great in places like Florida where the amount of heat needed per year is small, and the heat pump is needed anyway for refrigeration (A/C) for most of the year.

Your physics is quite right.  But another point is the relative cost of heat in different forms of fuel.  While it may take four watt-hours of heat to make one watt-hour of electricity, if the fuel used to generate that it is cheaper than the fuel you might use for direct heating, you can still come out ahead.  If the electric is from coal, nuclear, hydro or wind, the per-watt-hour cost of electric can make heat pumps still attractive. For example, if residential natural gas costs $0.80 per therm (100 000 BTU), and you have a 90% efficient furnace, you pay $0.889 for 100 000 BTU delivered.  If you have a heat pump operating with COP of 3.75, you would need about 7.8 kWhr of electricity to deliver the same 100 000 BTU. (1 therm is about 29.3 kWhr).  If your electric is only $0.08 / kWhr, then the heat pump wins the day. daestrom

Response:

Daestrom Your physics is quite right.  But another point is the relative Daestrom cost of heat in different forms of fuel. Daestrom While it may take four watt-hours of heat to make one watt-hour of Daestrom electricity, if the fuel used to generate that it is cheaper than Daestrom the fuel you might use for direct heating, you can still come out Daestrom ahead. But here’s the thing: the OP is building a house.  These things have a lifetime of about a century (or 30 years here in the Bay Area, after which they get knocked down in a "remodel").  I wouldn’t want to bet on the relative cost of fuels in 30 years, because it’s so far out, and there is so much regulation that can change in that time. That said, though, it’s a lot more likely that the electric utility will figure out a way to use the cheapest fuel around, than your future homeowner.  Score a point for the heat pump. I can’t find it right now, but I’ve seen a report on various solar water heaters which listed, among other things, the effective COP: in this case, the heat delivered divided by electrical energy used to run the pumps. The tests were done in Florida, and as you can imagine, the solar systems creamed heat pumps.  IIRC, some systems had COPs in the mid-60s!  It’s worth noting, though, that most did not. I would imagine that the challenge in Ireland is to collect heat when it’s cold outside.  The efficiency curve for Heliodyne Gobi glazed panels is:          x = (inlet_temp – outside_temp)/(radiation*0.317) efficiency = 0.737 – 0.804*x excuse the units: inlet and outside temp in degrees F, radiation in watts/m^2, efficiency tells how many of those watts end up in the water coming out of the panel.  To make this useful to the OP:                   outside  tank      radiation      eff California, Jan:   50 F    120 F    900 watts/m^2   0.540 Ireland, Jan, est: 35 F    120 F    800 watts/m^2   0.467 The latitude there is 54 N as opposed to 37 N here, so the collectors will have to be at more of an angle.  My simulations indicate that the angle isn’t really that critical, but it’s probably more critical up there.  At that latitude, it’s probably better to think of the panels as being wall mounted rather than being roof mounted. I spoke to the owners of a house nearby which was heated with glazed solar collectors.  The system looked pretty beat up.  In 30 years, it had the controller go once, both sensors failed once, and it froze three times.  So, a failure every five years, half of which were real money to fix, but that half could have been avoided with anitfreeze. I spoke with a local solar contractor who, summarizing what he’s seen for 20 years, suggested that pumps eventually fail too. It seems like a solar system is more maintenance than a furnace, but if the OP is building the house himself I’d imagine the maintenance wouldn’t be too difficult, mostly a matter of getting the parts.

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– Hide quoted text — Show quoted text – Daestrom Your physics is quite right.  But another point is the relative Daestrom cost of heat in different forms of fuel. Daestrom While it may take four watt-hours of heat to make one watt-hour of Daestrom electricity, if the fuel used to generate that it is cheaper than Daestrom the fuel you might use for direct heating, you can still come out Daestrom ahead. But here’s the thing: the OP is building a house.  These things have a lifetime of about a century (or 30 years here in the Bay Area, after which they get knocked down in a "remodel").  I wouldn’t want to bet on the relative cost of fuels in 30 years, because it’s so far out, and there is so much regulation that can change in that time. That said, though, it’s a lot more likely that the electric utility will figure out a way to use the cheapest fuel around, than your future homeowner.  Score a point for the heat pump.

Agreed.  And the utility can invest in energy sources to generate cheap electricity that the typical home owner cannot.  The fuels usable for heating is a much shorter list (oil, gas, coal, wood, biomass, solar) than for electric generation (add on hydro, wind, nuclear, to name a few).  I think the heat pump leaves more options open.  But the lifetime maintenance may be higher. – Hide quoted text — Show quoted text – I can’t find it right now, but I’ve seen a report on various solar water heaters which listed, among other things, the effective COP: in this case, the heat delivered divided by electrical energy used to run the pumps. The tests were done in Florida, and as you can imagine, the solar systems creamed heat pumps.  IIRC, some systems had COPs in the mid-60s!  It’s worth noting, though, that most did not. I would imagine that the challenge in Ireland is to collect heat when it’s cold outside.  The efficiency curve for Heliodyne Gobi glazed panels is:         x = (inlet_temp – outside_temp)/(radiation*0.317) efficiency = 0.737 – 0.804*x excuse the units: inlet and outside temp in degrees F, radiation in watts/m^2, efficiency tells how many of those watts end up in the water coming out of the panel.  To make this useful to the OP:                  outside  tank      radiation      eff California, Jan:   50 F    120 F    900 watts/m^2   0.540 Ireland, Jan, est: 35 F    120 F    800 watts/m^2   0.467 The latitude there is 54 N as opposed to 37 N here, so the collectors will have to be at more of an angle.  My simulations indicate that the angle isn’t really that critical, but it’s probably more critical up there.  At that latitude, it’s probably better to think of the panels as being wall mounted rather than being roof mounted.

Agreed.  Althought they have a ‘mild’ climate thanks to the Gulf-Stream, they are really quite a was north compared to CONUS. I spoke to the owners of a house nearby which was heated with glazed solar collectors.  The system looked pretty beat up.  In 30 years, it had the controller go once, both sensors failed once, and it froze three times.  So, a failure every five years, half of which were real money to fix, but that half could have been avoided with anitfreeze. I spoke with a local solar contractor who, summarizing what he’s seen for 20 years, suggested that pumps eventually fail too. It seems like a solar system is more maintenance than a furnace, but if the OP is building the house himself I’d imagine the maintenance wouldn’t be too difficult, mostly a matter of getting the parts.

Of course, heat pumps have maintenance issues too.  And if the OP is intending to ‘retire’ there, they may get tired of maintenance that they have to do themselves.  If it wasn’t a ’30-year’ home, then I’d bring up resale values as well ;-) daestrom

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The latitude there is 54 N as opposed to 37 N here, so the collectors will have to be at more of an angle. My simulations indicate that the angle isn’t really that critical, but it’s probably more critical up there.  At that latitude, it’s probably better to think of the panels as being wall mounted rather than being roof mounted. Agreed.  Althought they have a ‘mild’ climate thanks to the Gulf-Stream, they are really quite a was north compared to CONUS.

Ireland is the same latitude as England. Panels on roofs are the best option.  Parts of Ireland never get below freezing on many years.  A temperate climate. It seems like a solar system is more maintenance than a furnace, but if the OP is building the house himself I’d imagine the maintenance wouldn’t be too difficult, mostly a matter of getting the parts. Of course, heat pumps have maintenance issues too.  And if the OP is intending to ‘retire’ there, they may get tired of maintenance that they have to do themselves.  If it wasn’t a ’30-year’ home, then I’d bring up resale values as well ;-)

Electrical items in many cases have no annual servicing which shouls be added to any equation. Only service on breakdowns. A heavily to superinulated home that only requires a very small heat input, may be more economical running the small heating system by electricity, even thought it cost 4 times as much to run than gas.  Once the lack of an annual service is costed in it, it may be quite cheap to run.  Also electrical equipment is generally cheaper to install than gas or oil equipment.

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Hi Adrian. I have got some information on an installed Heat Pump with underfloor heating. The building is a dormer bungalow with concrete floors throughout. The floor area is about 2300 square feet. Heat Pump: There is about 300 meters (sorry for mixing measurement standards – just repeating what I have been told) of (sorry again) 2 inch plastic piping buried (!!!) 1 meter down and 1 meter apart. This is connected to a Thermia Diplomat model 10 heat pump. This has a rated input power of 3.6kW and a rated output capacity of 9.54/9.24 kW dependant upon output temperature at which the measurement is made (35 deg C/50 deg C) giving a Coefficient of Performance of 4.4/3.3. (This information from the manufacturer’s data sheet and doesn’t quite ‘add-up’ as far as I am concerned). Underfloor Heating. As both floors are concrete, there is also underfloor heating upstairs. This consists of a clear 1/2 inch PEX piping in the floor slab. Each room has its own temperature control. Living areas are set to 20 deg C, bedrooms to around 15 deg C and the bathroom to around 24 deg C. Having visited the house, I can say that it is very comfortable – neither noticably warm nor cool – and there are no draughts. Installation Costs I understand the total cost to be aound 15,000 Euro, of which 11,000 was for the heat pump and the other 4,000 for the underfloor heating. Seems expensive to me, but what do I know? Running Costs There has been several ‘mixups’ in the ESB bill and to date only one bill for 40 odd Euro has been received, so the exact cost is not known. However the owner was able to give the usage information from the heat pump controller. The system was switched-on at the end of September 2004 (new house build) and had 2509 running hours for home heating with a further 279 hours for domestic hot water in the 31 weeks to the beginning of May 2005. The system makes use of the a ‘night saver’ electricity supply between the hours of 11pm and 7am. This is about 46% of the standard cost. The supplier makes two claims: 1: That 60% of the total running hours will be ‘at night’, specifically during the ‘night saver’ period. 2: That about 30% of the useage during the 1st year will be due to the house drying out and that the true running costs will only be apparent in the second year and thereafter. Presenting the supplier with the usage information, the supplier estimates the actual running costs for the above installation for the 31 week period to be about 900 euro. Other From an earlier query, my self constructed solar panel is a serpentine

copper pipe soldered to copper sheet. This is fitted in a timer frame with a standard window glass on the front (or upper part) and has four inches of fiberglass insulation behind the copper sheet. There was a simple series of tests conducted yesterday at 16:30hrs (ambient around 17 deg C) – the panel conservatively produced 250W. Mike.

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