ground source vs solar vs air to water

Boxerman · 9 May 2008

Can anyone recommend a company to speak to about these types of installations, I'm looking to haet my home with something alternative to oil which has nearly doubled in cost this year. I realise that the initial expense is high but prepared to absorb that for long term annual savings.

Thanks

Agile · 9 May 2008

Solar can heat hot water but not your home.

Ground or air sourced heat pumps can heat your home but the cost may not give any saving in running costs and will have a high capital cost and might fail if there was a really severe winter.

Dont imagine that there is any CO² saving using heat pumps. That only occurs in places like Scandinavia where the electricity is generated by hydro. To a lesser extent in France perhaps where nuclear is 80% of capacity. In the UK its about 17% I think, with the rest being generated from fossil fuel.

Far better to save your money on insulation and controls as they give a return on capital. The cheapest of all is to wear a thick pullover like teachers used to.

Tony

Boxerman · 9 May 2008

I'm not too fussed about the CO2 side of things, just the £250/month average heating bills which are only going to increase!!

I have a solid wall house so not too easy to insulate without destroying some very nice old coving if I insulate the internal walls, loft has 15" insulation so not sure where else to make savings.

Pullovers definitely not an option

Agile · 9 May 2008

Boxerman said:
Pullovers definitely not an option

A real wool pullover at £20 will save you about £50 per month in the heating season. Thats a return of about 1500% !

Solid walls are a problem with insulation but its only needed on the exterior walls and will make a big difference.

Tony

Boxerman · 9 May 2008

I take your point on the pullover however I'm still interested in other forms of heating. There would be an awful lot of work involved with re-plastering to insulate the exterior wall, I already have a coal fire and wood burning stove too but I like the idea of 'free' energy such as solar or ground source.

Nixt · 9 May 2008

Heatpumps are far from free. They are another form electric powered heating system that utilises air or ground temp to greatly improve their efficiency. As said earlier our electric production is mainly coal or gas generated which keeps prices high enough to prevent even 400% efficient heatpumps from being free or very cheap to run.

Solar does give virtually free energy. You could couple one to a thermal store to contibute to the heating of the home. The cheapest short term fix is to use more wood.

Agile · 9 May 2008

Your coal fire and possibly your wood stove may be a big part of your problem!

They can take more centrally heated air out of your house than heat they produce.

If either is not being used its essential that the flue is closed off to stop your expensive heat being lost.

As far as I know know mains gas is about 4p/kw, oil and LPG about 5.5 p/kw and electricity about 13p/kw. A heat pump used 1 kW of electricity to give about 3-4 kW of heat under ideal conditions but during cold weather that falls to 1-2 kW.

The main problem with heat pumps is that they are only efficient when delivering heat at 40-50°C which is only suitable for water heating ( just ) and underfloor heating. You just dont get a flow of 80° to existing rads!

These things may sound fine until you know a lot about them.

I am qualified for solar but still dont see it as worthwhile fitting on my own home yet as the payback on materials only is about 5% which is less than interest on the cost!

Tony

BigBurner · 9 May 2008

Agile said:
Solar can heat hot water but not your home.

It can actually. You would need low temperature UFH and a large array of panels on the roof, probably covering most of the roof. Evacuated tubes are he best with increased cost to suit. A thermal store solar cylinder then provides the heat for the UFH. Using low temperature UFH is the key, as on cloudy days not enough heat will be captured to run radiators. It also needs a quite a lot of solar panel area. This would be fine if you need to re-lay the roof as well. Of course, high insulation and double glazing to help along.

Ground or air sourced heat pumps can heat your home but the cost may not give any saving in running costs and will have a high capital cost and might fail if there was a really severe winter.

Using solar panels and UFH will be no more expensive and cheaper too. Well worth costing and really gives that eco look and good for re-sale.

Far better to save your money on insulation and controls as they give a return on capital. The cheapest of all is to wear a thick pullover like teachers used to.

Tony

Insulation is the number 1 attack on keeping bills down. It is cheap and easy. Cavity wall fill works well too. As regards heat pumps and solar I would consider UFH and a large array of panels on the roof if the roof is pointing the right way.

Nixt · 9 May 2008

Agile said:
Your coal fire and possibly your wood stove may be a big part of your problem!

They can take more centrally heated air out of your house than heat they produce.

Only if they are open fires. If closed stoves connected to factory made flue or through lined chimney with stove pipe and register plate assembly, then heat loss not a problem.

Agile · 9 May 2008

BigBurner said:
It can actually. You would need low temperature UFH and a large array of panels on the roof, probably covering most of the roof. Evacuated tubes are the best with increased cost to suit. A thermal store solar cylinder then provides the heat for the UFH. Using low temperature UFH is the key, as on cloudy days not enough heat will be captured to run radiators. It also needs a quite a lot of solar panel area. This would be fine if you need to re-lay the roof as well. Of course, high insulation and double glazing to help along.

Well, yes of course it can in theory. Little help in practice though!

The first problem is solar in southern UK gives about 0.9 kw/m² during the summer but drops to about 0.1kW/m² during a clear cold day with tubes for about five hours.

Even if you could provide enough collector area the storage volume required becomes impossible. Just try calculating the volume even if you could store it at 80° which you cannot achieve during cold weather.

Thats apart from the fact that much of the UK winter its totally overcast and raining when no useful heat will be gained.

Tony

Nixt · 9 May 2008

It's still worth considering solar even if it will only contribute to rather than provide a solution in itself. The cost of buying and installing can be reasonable and only seems excessive because we have become used to and reliant on gas combi boilers that are increasingly made of coke tin grade metal and tesco carrier bag grade plastic held together with clips that would have struggled to keep Ina Sharples hairnet in place.

BigBurner · 9 May 2008

Agile said:
BigBurner said:

It can actually. You would need low temperature UFH and a large array of panels on the roof, probably covering most of the roof. Evacuated tubes are the best with increased cost to suit. A thermal store solar cylinder then provides the heat for the UFH. Using low temperature UFH is the key, as on cloudy days not enough heat will be captured to run radiators. It also needs a quite a lot of solar panel area. This would be fine if you need to re-lay the roof as well. Of course, high insulation and double glazing to help along.

Click to expand...

Well, yes of course it can in theory. Little help in practice though!

In practice it works even in Britain. The evacuated tubes will produce hot water on even a cloudy day. Having a whole roof full of them makes it work.

Even if you could provide enough collector area the storage volume required becomes impossible. Just try calculating the volume even if you could store it at 80° which you cannot achieve during cold weather.

On cloudy days when only low temperatures are being produced by the panels, there will be enough to keep the UFH working most of the time. This of course has to be calculated.

Thats apart from the fact that much of the UK winter its totally overcast and raining when no useful heat will be gained.

Tony

You will be surprised how much heat can be gained from a cloudy day. The evacuated tubes covering most if not all of a roof may be enough to keep a very well insulated and pretty air sealed house running with UFH without the boiler cutting in. The bigger the solar thermal store the better as any heat gained will assist DHW as well in winter. In summer the solar panels will cope alone for DHW. So much so that it is highly unlikely a boiler or immersion is used.

Cost up UFH and a full roof of panels and it will compare with a ground bore hole and a heat pump to install and cost virtually nothing to run. A downside is that is it a big upheaval as UFH has to be installed and roof work too. I would direct anyone to this route if doing a renovation and a suitable oriented roof is available.

Using air to air heat pumps ideally UFH has to be used as well to get maximum efficiency and economy as they do not generate high temperatures in winter. UFH and electric backup for DHW is common using air to air heat pumps.

Corgigrouch · 9 May 2008

Air to air heat pumps are worth a look.. They are cheaper to install than air to water or ground source... They can either be ducted from a central unit (Ideal for bungalows or upstairs rooms) or run one unit per room.. They can heat or cool a room very quickly indeed so you can turn them on only when you intend to use the room... which saves energy... Inverter units are especially good as they can ramp their output down when their full output is not needed and will boost their output to around 120% of their rated output for quick temperature changes.. Toshiba rate their kit at an outside temperature of minus 10c.. they will still produce heat below that but their efficiency falls off drastically then.... But minus 10 is rare unless you live in the North of Scotland..

Although many guys here question the pay back time of heat pumps and solar.. they also base their statements on the current price of fuel...which as we have all noticed has started to increase considerably.. Sure electricity prices are affected by gas and coal prices at the moment but as new Nuclear plants come on line (Yes I know it will be a good few years yet) this difference will make electrically operated heating come into their own.

JPC · 9 May 2008

dont forget that all these pumps run on electricity and it costs 4 times the price of gas....so 400% cop (if your lucky) simply brings it in line with the cost of gas heating

Agile · 9 May 2008

Corgigrouch said:
They are cheaper to install Sure electricity prices are affected by gas and coal prices at the moment but as new Nuclear plants come on line (Yes I know it will be a good few years yet) this difference will make electrically operated heating come into their own.

I dont know why you think that!

The cost of designing, building and debugging a new generation of nuclear plant will be prohibitive and will be on line in about 12 years time. To give any chance of a payback the resulting output will need to be sold at the then price of 40p+/kW

The current ratio of different fuels is unlikely to change over the next 20 years.

More insulation and wool pullovers are the way forward! Its cheaper to buy the pullovers during the summer!

Tony

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ground source vs solar vs air to water

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