The application of using a ground source heat pump to heat an indoor swimming pool is the perfect partnership (low temps and all that) but can anyone offer me advice on how to size the heat pump. Certain heat pump manufacturers steer away from this responsibility saying that that it is too detailed and complicated and yet those that do end up specifying a heat pump that is in my opinion, way too big. Any advice would be much appreciated.

Would it be possible to have a swimming pool - under cover - heated by solar in the summer, then use it as a heat source (taking the heat out of it via a heat pump) during the winter? How big would the pool have to be? Would there ever be a time when the pool was warm enough - but not too hot to swim in? What about legionella, or would the chlorine treatment take care of that?

If you were to heat the pool once using portable equipment of some sort and then allow it to cool down you could measure the heat losses and work out the size pump you needed to maintain the required temperature. You then need to work out how fast you need it to warm up.

Regarding use as a heat store.. It's quite easy to work out how much energy is stored in 1L of water...

Energy (Joules) = 4186 x delta T x Volume in Liters

Lets say the pool was small a 5 meters x 3 meters x 1 meter. That would have a volume of 15 cubic meters or 15,000L

If you heated it from 20C to 40C and then it would contain..

4186 x 20 x 15000 = 1256 MJoules

So how long would that heat your house?...Well 1J = 1 Watt Second so...

Lets say your house needed 4KW continuously..

1256 x 10^6 / 4000 = 314000 seconds or 3.5 days.

Perhaps you can check my sums.

i think even though air temp is kept above pool temp (to prevent condensation) the water is also heated separately.

I'd go mega on the solar, and big bucks on a super-duper thermal cover.

Assuming this is a new build, design the poolhouse to the shape required to best harness the sun, rather than designing a retro-fit 'add-on'

Posted By: General advice to site visitors: Don't install a heat pump unless you have enough on-site renewables capacity to power it.
Heat pumps are not a renewables technology.

I'm sorry you didn't get the chance to reply to my email about your claims that heat pumps are not renewable technology.

I believe you are doing your readers a huge dis-service in giving your "general advice" based on one biased report.

I have just received this letter from the Energy Saving Trust an independent NGO who has tested a range of different heat pumps. They confirm significant savings on running costs and reduction of CO2.

The reality is not all heat pump are equal, some are better than others and we (Ice Energy) has demonstratable evidence of seasonally adjusted COPs of greater than 4:1 for ground source and 3.2:1 for air source.

Your uninformed statements as fact and advice does nothing to enlighten your readership about real options in real situations.

Extract from EST letter:

Percentages of Energy and Carbon Dioxide Saved by Heat Pumps
Supplied by Energy Saving Trust

Air Source Heat Pumps
The savings below are based on a detached property, and relate to space heating only.
They assume a typical system, with a seasonal performance factor of 2.5
Figures have been rounded

Gas Oil LPG Electricity Coal Air Source Heat Pump
Running Cost £750 £1,020 £1,100 £1,320 £720 £440
% financial saving 40% 55% 60% 65% 40%
Tonnes CO2 3.8 4.3 4.2 8.9 8.1 3
% CO2 saving 20% 30% 30% 65% 60%

Sample saving statements:
Replacing an oil heating system with an air source heat pump for space heating in a detached home can reduce running costs by 55%, and carbon dioxide emissions by 30%.


Ground Source Heat Pumps
The savings below are based on a detached property. They assume that the heat pump provides 100% of space heating and 50% of water heating, with the remaining 50% of water heating provided by electric immersion heater.
They assume a typical system, with a seasonal performance factor of 3.2.
Figures have been rounded

Gas Oil LPG Electricity Coal Ground Source Heat Pump
Running Cost £970 £1,310 £1,420 £1,560 £900 £550
% financial saving 45% 60% 60% 65% 40%
Tonnes CO2 5 5.5 5.4 10.6 10.2 3.8
% CO2 saving 25% 30% 30% 65% 65%

Sample saving statements:
Replacing an oil heating system with a ground source heat pump for 100% space heating and 50% water heating in a detached home can reduce running costs by 60%, and carbon dioxide emissions by 30%.

Fuel prices and carbon factors
Gas Oil LPG Electricity (heat tariff) Coal
p/kWh 4.03 6.09 5.93 8.27 2.77
Kg CO2/kwh 0.206 0.258 .0.225 0.562 0.313

that said, the point was a little unfair
He is right that it is not renewable, as such, but

"Don't install a heat pump unless you have enough on-site renewables capacity to power it."

this only applies if you are building an off-grid home, and is off no help to anyone trying to reduce their bills rather than eliminate them.

we'd all love to eliminate electricity, but the reality is it is going to happen in stages.
A heat pump, when designed and installed correctly, seems an eminently sensible choice.

Posted By: timevans2000The figues above are mis leading as they do not take into account the 35% efficiency of the central electricity generation.

Looks like they do in the quoted CO2/kWh figures.

Posted By: DantenzHeat pumps for the most part extract renewable energy do they not.

Exactly.

Paul in Montreal.

Heat pumps are not renewable energy

"A heat pump is a device which takes heat energy from a low temperature source and upgrades it to a higher
temperature at which it can be usefully employed for heating" - SAP document (BRE/DEFRA ,2008)

You will note that the EST calculations are theoretical and base on performance assumptions and so should not be regarded as evidence.

It is interesting to note that the EST statement does not make any comparison with more widely accepted renewable solutions, such a Solar and biomass.

It is also interesting that the EST Air Source Heat Pump example does not include hot water - a bit of a selective comparison and indicitive of low standards I have come to expect from the EST

I have a real problem with heat pump salespeople and find Clients are often mis-sold to, based on unrealistic performance claims which can not be substantiated; This diverts money away from sustainable building and true low carbon heating systems. I have only ever ONCE come across a HP sales guy who was prepared to talk about frost cycles and reduced efficiency! (they got the contract)!

Regarding building regulations (ie THE LAW):

In SAP COP's of 2.5 and 3.2 may only be used (for Air source and ground source respectively)

Unless Underfloor heating is used then the efficiency should be multiplied by 0.7 (The EST statement is not clear on the type of heat delivery - but it would be safe to say no GSHP salesperson is going to suggest ripping up your ground floor so their system works better, unless they get to do the work)

Also if the underfloor heating is in a screed the responsiveness of the heating should be adjusted to 0.75, also detrimental to the final rating.... and so on

Another hijack.

Was watching one of those american 'disaster documentaries' the other day - about a solar storm. Electricity gets cut off. . . . .

Hubby started to worry. We have a woodburner that heats rads and water, but it can't do it without electric pumps.

Does the water in our taps get there by gravity alone? I think electricity comes into it somewhere.

Made me start to revise my dream house plans, so that the rainwater harvested can still come out of the taps - or get flushed away - without the need for electricity. . . . . .. does that ramble make sense?