George Osborne demands massive cuts to windfarm subsidies

[ahinton]

Which is where PVs come into their own. A near neighbour (an astro-physicist by trade) made a very exhaustive study of costs and benefits of all renewable sources and populated a very creditable and as far as I can see faultless spreadsheet. Groundsource heat pump/ PV array (a large one) won hands-down. Since he installed it, he has continually monitored it and the figures have exceeded his worst case scenario. So, no, in this case you are wrong.

Heat pumps are a great idea and are considerably more efficient than once they were; recent improvements in efficiency of air source ones has been greater than those of ground source ones. Where I'm going, a ground source heat pump would be incredibly expensive because it would have to be wholly immersed in an inert second chamber because the limestone (calcaire) around there can destroy these things if in direct contact with them, as I know from someone who installed on without such sheathing less than five years ago and it's now almost a write-off. OK, that's a very localised situation, I agree. However, with all of these assessments about cost benefits and the rest it is important to remember at all times that all these figures are subject to constant change and, when one particular method reduces in price disproportionately to its alternatives and when fossil fuels and electricity generated from their use shoots up in price (as it can do especially when subsidies such as those that the French have long enjoyed begin to be cut or removed altogether).

Also ground and air source heat pumps require more maintenance than does solar equipment, although it's not the bigest issue with them.

[Resurrection Man]

Actually my misdirection...he doesn't use a groundsource as you or I would know it..ie loads of pipes laid out over a large area. He uses a borehole and pumps the water up from there.

[ahinton]

Ahinton/Dave2002
If you're about to embark on the schemes you've outlined (Ahinton into French solar PV, Dave2002 into solar thermal) then do make sure you do a proper financial assessment, Don't fall into the trap (like many have done over the solar PV scam) of taking the annual income, dividing it by the capital expenditure and then declaring that 'I'm making an 8 % return on my PV system'. You're not: you've forgotten that you've no longer got your capital in the bank.

I'm not looking at it like that. To begin with, I wouldn't buy the stuff in France because it's considerably dearer there than in UK; furthermore, not only are subsidies on its acquisition available in France only to those who are already taxed in France and apply only to the materials and not to the labour costs, the subsidy benefit available even to the French taxpayer is often less than the difference between purchasing it in France and doing so in UK. I'm not thinking of a PV system as an income source per se but as a means to reduce outgoings. Whilst it's true that one no longer has the purchase and installation cost of PV in the bank once its bought and installed (no, I have not "forgotten" this!), the same applies to any alternative that still needs to be put in, such as a conventional oil boiler and tank and all the trappings that go with it. It's easier to work out the comparative figures (subject, of course, to their constant fluctuations) for a completely new build than for an existing one where one might be changing from one existing power system to another and the benefits are usually greater in these circumstances than when chaging an existing installation for a new one.

Ahinton: I used the 'foolish' example of heating domestic water from on-peak electricity as a 'highest cost alternative' to solar thermal heating to paint solar thermal in the best financial light. It looks as if, even on that basis the straight payback period is over 20 years, not the 10-15 years Dave2002 claims. If you factor in discounted cash flow (if you will, an alternative to accounting for your lost investment interest on your sunk capital) the payback periods are much longer; indeed, perhaps never. Now consider that any fool (sorry Alpine) in that situation would see that their on-peak electricity bill was too high, and as an alternative, switch to off peak electricity - halving their domestic hot water costs, and pulling the domestic solar payback to nearly 40 years!

The problem with having solar thermal for heating water and solar PV for everything else is that materials and installation costs are far greater than is the case if one opts solely for solar PV to produce electricity for everything including heating water. I am wholly distristful of all payback period assessments because, realistically, they can be based only on current prices for alternative fuel supplies and on current prices for purchase and installation, all of which are open to constant change. In France, where there has long been wise dependency on nuclear power to supply most grid electricity, they're running out of capacity from this source and are clearly unable to build and commission new nuclear reactor installations in a mere metter of weeks or months so, without viable immediate alternatives, electricity prices for customers are like to escalate rapidly (and indeed are already beginning to do so), especially as they've been more heavily subsidised than in UK for quite some time now.

Your French PV example is worrying. You're proposing to invest on the basis that the French government pays solar PV operators handsomely for the electricity they export. Do you expect that to continue forever?

No, I don't and, the more that the prices for materials and installation reduce, the more I would expeect any subsidies to be cut (and indeed quite rightly so). The contract as it currently stands in France is for 20 years so, if it were to be changed or abolished, the French government would be obliged by law adequately to compensate those who had already entgered into such contracts. The benefits of such contracts have already reduced, however, in that EDF used to purchase electricity for almost 8 times the rate at which they charge for supplying it, but this is now areound 5 times (or was when last I looked). It may also be argued that the likelihood that production costs of solar equipment can reduce substantially is considerably greater than appears currently to be the case for heat pumps.

The only domestic renewable energy production system that ticks all the economic boxes seems to me to be water or air source heat pumps - widely used in Japan, Scandinavia and New Zealand.

As I've already stated, these are very useful devices but they're quite expensive to purchase and do require considerable amounts of electricity; someone I know in France has installed an air source heat pump and has slahed his electricity bills by around 70%, which is hardly to be sneezed at - but 70% is still 30% less than 100% and, whilst initially I'd given serious consideration to having an air source heat pump and a PV installation so that at least the electricity that the pump uses will cost nothing, this would be much more expensive at the outset than PV alone.

[ahinton]

Actually my misdirection...he doesn't use a groundsource as you or I would know it..ie loads of pipes laid out over a large area. He uses a borehole and pumps the water up from there.

I see. Do you mean sinking a borehole into somewhere where a water supply souce already exists? If so, that would be no good in France now unless there was already such a source to be tapped and where there is an existing operating well with a history, for it has become illegal (certainly in some if not all areas of rural France) to drill new wells for this or any other water source use because the water table has become so low in some areas that this restriction has been placed in order to try to curtail the future impact of this.

[Resurrection Man]

I see. Do you mean sinking a borehole into somewhere where a water supply souce already exists? If so, that would be no good in France now unless there was already such a source to be tapped and where there is an existing operating well with a history, for it has become illegal (certainly in some if not all areas of rural France) to frill new wells for this or any other water source use because the water table has become so low in some areas that this restriction has been placed in order to try to curtail the future impact of this.

Correct. The borehole goes down about 50m to the water table. But the water goes back into the ground after the heat has been extracted.

[Serial_Apologist]

Perhaps one should factor into all this the added value to a property converted for greater energy efficiency.

[ahinton]

Correct. The borehole goes down about 50m to the water table. But the water goes back into the ground after the heat has been extracted.

Mon Dieu, that's quite a distance and must represent considerable expense! I'm not sure whether you'd be allowed to do that in France now as a completely new installation (i.e. in a situation where no well has previously been sunk), even though the water is recycled; perhaps it would be possible, but I'm not sure.

[An_Inspector_Calls]

There's no reason at all why a ground source heat pump should be affected (whether ground loop or borehole) by the soil acidity. The heat extraction system in all cases uses a brine loaded, closed-loop circulation system usually using plastic pipe.

There's nothing wrong with using payback analysis against a background of inflating costs. It may be the case that one fuel cost shifts against others, but commonly they all move together at much the same rate.

I'm not aware of the French being short of capacity - rather the opposite is the case. If they were, Germany would be in real trouble. As for their nukes, they are refurbishing each and every one of them for a 25 year life extension.

As for energy producon capacity of the systems you're thinking of, your domestic energy consumption is likely to be about 4.75 MWhpa electricity, and 20 MWhpa space heating (for a small house, perhaps less in France). PV is not going to come close to meeting those numbers. A 4 kW PV array in the UK might produce 3.5 MWhpa mainly in the summer, during the day, of which you'll be able to use perhaps 25 %. At that size, it's little more than a toy. A heat pump could produce all your space heating for an energy input of 6 MWhpa, a saving of 14 MWhpa. And as for maintenance - what maintenance? - when did you last service a fridge?

[ahinton]

Perhaps one should factor into all this the added value to a property converted for greater energy efficiency.

Indeed so, although this would apply to greater or lesser degree to properties where advantage has been taken of any of the alternative power sources, be they heat pumps, solar thermal, solar PV, wind turbines or wheatever else. One particularly inexpensive installation (at least in terms of its potential returns provided that the property is very well insulated and especially if it has underfloor heating) is an HRV - i.e. a heat recovery ventilation system - that effectively works something like a fridge in reverse and, in recycling, can contribute heavily to reduction in power use for heating whatever the power source; they're also good at minimising the risk of condensation because the inernal air is contanlty moving, so they also have quite useful potential health benefits, too. Again, a couple that I know of in the Limousin (where it can on occasion get extremely cold in January - daytime temperatures that don't rise above -5C and night-time ones that can descend to -18C are far from unknown) have built a timber frame house from SIPs (prefabricated structurally insulated panels) and have an underfloor heating system throughout as well as an HRV, excellent roof and underfloor insulation and xenon-filled triple glazed exterior windows and doors (and, OK, those last really aren't cheap!) and they've since rather bemoaned the cost of their heating system because it's only ever actually come on at all in fairly extreme cold conditions; they don't have solar PV or even a heat pump (perhaps surprisingly), but their actualy energy consumption is minuscule.

[ahinton]

There's no reason at all why a ground source heat pump should be affected (whether ground loop or borehole) by the soil acidity. The heat extraction system in all cases uses a brine loaded, closed-loop circulation system usually using plastic pipe.

The soil conditions dpo not, of course, directly affect the interior workings of such a pump but can corrode the exterior as has happened to the one put in for that unfortunate person I mentioned earlier; a proper borehold installation can allow for this problem to be overcome but the cost is far from small.

There's nothing wrong with using payback analysis against a background of inflating costs. It may be the case that one fuel cost shifts against others, but commonly they all move together at much the same rate.

They don't, actually; oil costs (for both domestic heating oil [usually kerosene] and petrol /diesel) fluctuate more and more frequently than do either the electricity or mains gas prices paid by the customer and, in any case, I was not referring to energy cost fluctuations in isolation - I also mentioned reductions in the reital prices of alternative energy source materials, either by means of government subsidies or actual manufacturers' price reductions that can come about as a consequence of increasing sales volumes.

I'm not aware of the French being short of capacity - rather the opposite is the case. If they were, Germany would be in real trouble. As for their nukes, they are refurbishing each and every one of them for a 25 year life extension.

But how long will this take? Too long compared to the increases in demand.

As for energy producon capacity of the systems you're thinking of, your domestic energy consumption is likely to be about 4.75 MWhpa electricity, and 20 MWhpa space heating (for a small house, perhaps less in France). PV is not going to come close to meeting those numbers. A 4 kW PV array in the UK might produce 3.5 MWhpa mainly in the summer, during the day, of which you'll be able to use perhaps 25 %. At that size, it's little more than a toy. A heat pump could produce all your space heating for an energy input of 6 MWhpa, a saving of 14 MWhpa. And as for maintenance - what maintenance? - when did you last service a fridge?

Last things first; when did you last keep a fridge in a fixed position outside, as one would with an air source heat pump?! I did say that this was not a big isse with such appliances in any case, merely that maintenance (and, for that matter, wear and tear) is a little greater than is the case with solar panels that have no motors and almost no visibly moving and/or corrodable parts. What can be gotten from solar, be it PV or thermal (especially in the south west) is admittedly considerably greater than can be gotten anywhere in UK, even on the south cost of Cornwall, but the overall ultimate results will inevitably be very much dependent also upon efficiency of those other factors including wall, window/door, roof and underfloor insulation, the use of an HRV and an efficient underfloor heating system such as the one that I mentioned earlier whose running requires very little electricity - and the additional use of low energy lighting where possible and economical white goods can also help in terms of reducing the amount of electricity needed in the first place which, to me, as at least as important a consideraton as what energy sources to use in order to produce the electricity used.

Changing the subject partially, it occurs to me that this thread has now reached 40 posts yet, despite being about George Osborne, has hardly mention him at all - so not all news is bad news, evidently!...

[An_Inspector_Calls]

Well we'll disagree on payback analysis. The French nuclear refurbishment is a rolling programme. It will take years for it to complete, but I doubt there'll be much impact on the total French nuclear capability. They're making too much money from the Germans!

An air source heat pump does not have working parts outside the house.

And I'm keeping my fingers crossed for George - go get 'em!

[Dave2002]

An air source heat pump does not have working parts outside the house.

And I'm keeping my fingers crossed for George - go get 'em!

Depends. Some air source HPs do have an external fan unit. The fan unit can go inside the house, for example, in the loft, but that may cause vibrations.

IMO almost anything proposed by Osborne is inevitably a bad idea!

Re my own thoughts on water/solar, I'm cerainly not doing that in the near future, as we had a new boiler and tank a few years ago. If I'd known then what I know now things might have been different. I might have gone for solar/water and/or a heat pump system.

Heat pumps do use energy, but a 1 kW input could give over 4 kWs heat output. Coupling with PVs makes sense. There may be problems with ground source HPs in the winter though, as it's quite possible that the ground will crack up as it freezes. I even know of one enthusiast who has fitted regular radiators to a heat pump system, which is not generally recommended. It works fine, but the garden did crack up a bit last year.

[An_Inspector_Calls]

Heat pumps do use energy, but a 1 kW input could give over 4 kWs heat output. Coupling with PVs makes sense. There may be problems with ground source HPs in the winter though, as it's quite possible that the ground will crack up as it freezes. I even know of one enthusiast who has fitted regular radiators to a heat pump system, which is not generally recommended. It works fine, but the garden did crack up a bit last year.

Not many heat pumps (at present) will manage 1 unit in, 4 out; more like 3.

If the ground loop is buried .75-1.25 m below the surface and is properly sized I doubt there'll be any freezing problems at the surface. In my installation the incoming brine temperature drops to 0 C for only about 6 weeks of the year but that's the temperature 1 metre down; the cow still has grass to graze at the surface. A fall of rain is like a coal delivery! I run my heat pump into regular radiators - you don't need under-floor heating. Under-floor heating would improve performance, perhaps, but only if you don't cover the floors with carpeting. Another way of improving performance would be to improve insulation so that the demand temperature falls. My (energy) averaged CoP is 2.9. The heat pump also heats all our domestic hot water (included in that CoP figure).
PS: You're right about the fan units on larger ASHPs (such as the Danfoss units), they are outside; I'm not aware of the fridge unit ever being outdoors.

[Dave2002]

Some of the air source HPs also function as air conditioning units. Indeed we are planning to use one such in a replacement conservatory which incidentally we also intend to have fitted with electric underfloor heating (!!).
Somewhat to my surprise, the calculations for electricity consumption seem to be bearable - indeed modest, but that is assuming that the new building work is as well insulated as it is claimed to be.

Do ground source HPs also have the ability to function as air conditioning units? Presumably it depends on the design/implementation. You won't get that with fixed radiators.

We were keener on heating using water pipes until we had a leak a few years ago. The damage and upheaval as a result was considerable, though we were reimbursed by insurance. Sometimes one has also to consider practical matters.

[Resurrection Man]

If one had the luxury of building ones own house from scratch then best-practice would appear to be massively thick external walls with insulation on the outside, triple glazed windows, airlock external doors (in other words, two doors so that the minimum of heat is lost when going in/out of the house) and a heat-exchanger/cleaner for recirculating hot air from the top of the house to the lower floor(s). If anyone is interested, I can put them in touch with an architect who has focussed on these type of houses for most of his working life. He lives in one and his heating bill was IIRC £12 last year.