Experiences with ground source heat pumps?

[Pete C]

Thinking about it, the best option for the OP if they go for a ground source heat pump might be to use that to preheat DHW and then use normal electricity or even Economy7 to heat it further to DHW temperatures. For showers/baths you might get hot enough water from the heat pump anyway.

The problem with solar is that in mid winter we average 2hrs/day of sun, so you would need a huge collector and huge amounts thermal mass to collect and store enough heat to rely on it alone for general heating. This could be doable for a new build but would be hard to retro fit.

However a vacuum tube solar collector could make a useful contribution to DHW. For a new build it would be worth ensuring the south facing side of the roof could take the extra weight of a solar collector.

In fact it would be nice if developers were required to make roof trusses that bit stronger to make it easy to fit a collector, instead of the usual minimal size.

cheers, Pete.

[IMM]

They struggle in winter.

The whole south facing roof.

true.

[Mike Deblis]

My wife has relations in Sweden, and we have consulted them over the IVT heat pup we are considering - they use these but have a lake they use as the heat source (never less than 4C at the bottom of the lake?).

I've heard this, but in the UK it seems to be partly apocryphal - we are a lot warmer than the Swedes, and laying under a lawn, between 1 and 2M down scarcely effects the surface temperature where the grass is. We have a 2 acre lawn (South facing) that we intend to use for this (3 x 50M trenches with 250M of "slinky" coils, vertically in 2M x

20cm trenches, backfilled with sand to 1M, then soil). The available energy absorbed by the lawn, even on winter days, is many many times what we are proposing taking from it.

In Sweden maybe - here it should not be a problem... its been suggested than in the winter we may see about 0.5C average temperature reduction at the surface. I've been looking at some UK "Energy Efficiency best Practice" reports (amongst others), and for us, the rationale looks good, especially as we will use Economy 7 to boost DHW temps, so we can run the pump at its optimum temperatures.

I'm going to the Homebuilding show at Wembley next w/e to speak to Ice Energy and the other suppliers we are considering. Should be interesting.... ;-)

Rebuilding and extending an old, messed about, house makes for, well... interesting times (in the old Chinese curse sense)...

Thanks

Mike

[Sean]

Anybody have a rough idea of how much more expensive this option is to the standard heating installation in percentage terms for a new build??

Sean

[Pete C]

No, but for a new build it might be worth laying the pipe while doing any garden landscaping, so it can be installed easily in future.

Also consider building in UFH and lots of thermal mass as heat pumps and solar heating are more suitable with these.

If you have mains natural gas it would be cheaper to use that at current prices, though heat pumps should improve a lot in the next 5 to 10 years.

cheers, Pete.

[Alan Campbell]

Hi Mike,

I for one would appreciate if you let us all know what Ice Energy say and what else you find out. I'm also very interested in the economics of it. I always thought that there is no cost benefit to be had as the cost/kWH for the electricity is so much more expensive than the cost of oil or gas/kWH so ground source heat pumps were only of use (on purely economical grounds) if you do not have the option of gas or oil.

I've tried to work it out - I'd appreciate anybody letting me know if this is completely rubbish -

My (oil) boiler is rated at 22kW (I think that is 22kW/h) I read you can get 11.5kW/l of heating oil. so assuming during the winter months, my boiler runs 50% of the day I will use approx 11.5l of oil a day. Factor in efficiency (91% for me according to SEDBUK) that means roughly 12.5l/day At say 20p/l cost this means £2.50 a day. Looking at my oil bill this seems about right to me.

If a heat pump is 350% efficient then for the same 11kWh of heat, I need to put in 3.14 kW of electricity for 12 hours. At say 8p/kWH that means £3 a day. Of course, economy tariffs and a high efficiency house would reduce it but on the face of it, my calculations look about right.

I'm working towards self-sufficiency and am looking at generating my own electricity so a ground source heat pump would make sense for me but only when I start generating my own electricity.

Alan.

[Rick Dipper]

I really want one of these type of systems, my place is remote, oil woud have to be loaded on a tractor to get there.

I have read quite a bit. Some issues.

The further down you get the colleting pipe the better. you can dig deep trenches and put the pipe in loops vertically in the tranch.

You need to get good contact bewteen the pipe and the soil, so backfilling with lumpy clay is not a brilliant idea, sand is better.

You can cool the ground if you pump too much, and then effieciency reduces.

If you can get the pipe into flowing water, much better.

A local has told me that he knows a guy with a well digging machine on the back of a land rover, this might be better for me.

I have a small stream that runs in the winter neer my house so I will run my pipe in that and on the land, I will look at this guy who can dig wells too.

The heat output from these things is arround 40 degrees, you can get hoter but efficeincey drops. 40 degrees is just right for underfloor heating, so the two in combination should good.

I will look at suplementing with solar pannels for hot water, and log fires for cold winter nights.

I reckon that where you put the pipe is critical, and that is worth putting too much in.

And you can run them in reverse in summer, to dump heat back into the ground for collong, not all pumps support this.

Rick

[Pete C]

[Pete C]

Hi,

Sounds good, but if your current heating is OK it might be worth waiting a few years; energy prices will go up but so will heat pump efficiency.

cheers, Pete.

[G&M]

You'd better make sure your electricty supply is up to it. Heat pumps use about 20 to 25% of their output as input electricity. Given that you may still want to use existing heavy electrical usage equipment (cooker, shower, etc) this extra load may cause the line to be overloaded. We had a survey done by one heat pump company with the aim of using our stream as the heat source and they thought we would have to get the cable uprated.

[Alan Campbell]

Hi,

I've just been to the scottishpower site and also a couple of comparison sites and nowhere does it mention 5.01p/unit - are you sure this is right? Is this an average based peak and off peak metering?

For power, I am going to use wind (I've got plenty land and no neighbours). It is almost always windy here. I may then either grid-tie it and pay for electricity when there isn't much wind or perhaps in time invest in a little PV. From a financial perspective it doesn't make a whole lot of expense - a large cost up front which will take 15-20 years to pay back even after you factor in a clearskies grant. I am not doing it for financial reasons - mainly for self-sufficiency reasons and also for environmental ones. When I eventually get going with it, I will post my experience here. Extracting heat from the ground is much futher off but I am looking to spec my wind turbine large enough to cope with this future demand.

Alan.

[Dave Liquorice]

It damn well better be!

Try

then LH "Home Energy" item, bottom of that page "Energy Products" bottom of the list "View Our Prices", select Norweb and "Go". Unfortunately the site then uses some browser/OS specific code that doesn't work for me. How ever that is where I'd expect to find the relevant pricing information. Will check later on a doze/ie machine,

No it (should be) the pence per unit on a normal domestic tariff (not Economy 7 or similar) paid by monthly direct debit, managed online in the Norweb area.

Wind here seems to have dropped off in the last year or two. When we first moved up here it would blow at 20mph+ for days on end but not now. Wind power is certainly something I'd like to look at along with a ground heat source and solar panels but cash flow is a problem and there are more pressing things like rotten, drafty, window frames that need sorting first. Wish we had a stream, plenty of fall (good 50' maybe more) for a small hydro plant and of course a heat pump...

[G&M]

Best I can find from them is 5.48p

[Dave Liquorice]

Thats inc VAT, I always ignore the VAT as it's possible to mislead yourself by using inc VAT prices due to rounding errors. Though in this case it probably won't happen as we are talking 1/100ths of a penny difference.

Anyway are you looking at the "online" prices, the default on the page described above is "standard" tarrifs, I made that mistake as well. B-)

Start at the Scottish Power homepage I've just spotted a "View our Prices" link there (middle of the RH column at the bottom), then "Online Energy" in the "Pricing info for...", then Norweb, Go.

That shows 5.00p/unit (5.25 inc VAT).

[NickIniquity]

I've installed an air-to-water heat pump and I did a similar calculation. In my case I wanted to use the unit to provide heating in winter to a large outbuilding that I had insulated and converted to a workshop. In the summer, I use the unit in reverse to provide chilled water to cool both the workshop and the main house. (except _this 'summer' obviously!) The heat-pump works out at about 330% efficiency as it consumes 2.1Kw and produces 7Kw of heat output (or around 6Kw of cooling). This was about the largest unit I could find that would run from a single phase supply and match my anticipated load...The short term start-up current is around 10Kw(!) which has a minor lamp-dipping effect! In reality the efficiency will be lessened because the unit has to periodically defrost itself to remove frost off the outside air coils. Not needing to defrost is an advantage of using a ground source heat-pump.

My house is heated by a gas-fired non-condensing combi.... on purely economic grounds this is just about cheaper to run than the heat pump. I wasn't too keen on extending the house c/h loop into the workshop (effort factor...lots of digging and the risk of freezing), and I decided that a heat-pump was a better bet than using an electric heater. (and the temptation of adding a/c to the main house might have been a factor here too). My workshop is divided into an electronics 'shop and a general diy/woodwork area. As the heat emitting device in the workshop is a fan-coil (water-to-air fan-coils or UFH are the way to go with the lower water temp produced by heat-pumps) this gave another advantage. I was able to make the electronics end of the 'shop have a higher airflow than the wood 'shop...this results in no sawdust getting in the clean(er) area!

I went for air-to-water rather than ground source because I didn't want to mess about digging up my lawn. Using a water loop for the heat/chilling output side allowed easy diy installation of zoned a/c into the house. Had I not wanted to a/c the house too, I would have just installed a simple air-to-air split-packaged heat-pump to heat the workshop instead.

Nick

[Alan Campbell]

Hi,

At first glance. it appears that Scottishpower are ripping off their Scottish customers -

If you are in the Norweb area then you get your electricity for

5.48p/kWh you are in the Scottish Power area then you get your electricity for 7.54p/kWh 's almost 38% dearer!!!!!

So, does anyone know why this is the case? - is there more competition in the Norweb area forcing them to reduce prices to remain competitive?

Alan

[G&M]

One has to say that if the page makes it difficult to work our what you will pay then what else will they be difficult with. But I'll have another go. Powergen now own the old Norweb and promptly put up units to over 8p so need a new supplier.

[G&M]

> That's almost 38% dearer!!!!!

Scottish generators are more expensive to run and then the supply has longer to travel. And the weather makes more repairs needed.

[Alan Campbell]

Hi Nick,

Nice information. Thanks. It is good to get real world information.

Roughly where are you geographically and can you give us more details about the heat pump you installed?

Thanks,

Alan.

[IMM]

Firstly I can't see why you bought a heat pump. You have gas and using an inefficient cheap boiler you equal the running cost of a heat pump You want some ventilation. That can be done by using just fans and ducting. The UK doesn't need cooling as decent ventilation, with added insulation, will be enough.

To me it sounds as if you spent a lot of money to stand still.