Energy Saving Trust Q&A Centre

zeupater

1cat2fish wrote: »

Hello, could tell me whether buildings that are run by a registered charity can have solar panels fitted for free, like people are having fitted on their roof. Thankyou.

Hi

A number of registered charities are using solar to increase their revenue stream .... It would probably be worth looking into this as an alternative to taking on a 'rent-a-roof' system .... if you're good at fundraising, or simply a little cheeky, perhaps you could convince a local or national pv installer to subsidise or even supply a system FOC as a marketing exercise ....

For example see .... http://construction-manager.co.uk/news/mcphillips-builds-worlds-greenest-dog-rescue-centr/ ... note the huge arrays . I know it's an expensive development, but you'll get the idea.


HTH
Z

Energy_Saving_Trust_company_representative

1cat2fish wrote: »

Hello, could tell me whether buildings that are run by a registered charity can have solar panels fitted for free, like people are having fitted on their roof. Thankyou.

There is nothing to stop a "free PV" company putting a system on a building belonging to a charity if they decide it is worthwhile. They will make that choice based on the technical suitability of the site (orientation, shading etc).

However, as Zeupater rightly points out, this may not be your best option. The money you save from a free PV scheme is limited to the savings on electricity bills you will get from using some of the generated electricity directly in the building at the time it is generated. If you use a lot of electricity during the day in June you could save plenty on your bills, but if you use it mostly at night in December you will save next to nothing.

Conversely, if you finance your own system you get paid for every unit generated, as well as any direct savings, and you get paid a bit extra for selling the surplus back to the grid. If you can afford to finance the system yourself, even if you have to borrow some or all of the money, then you are likely to be better off doing it this way.

If you can get a discount because of your charitable status, that will obviously help. However, if you get grant then you won't be eligible for Feed-in Tariff payments, which is likely to make the whole thing uneconomic.

If you are unable or unwilling to borrow money or otherwise finance the scheme, then a Free PV system could be worth considering. You will save a little on your electricity bills for no capital investment and very little hassle, and the climate will benefit either way.

Energy_Saving_Trust_company_representative

zeupater wrote: »

Hi

Why do you suppose and publish that Air/Water ASHPs cost £6k to £10k (excl heat distribution system costs) in the referenced article ... could it possibly be a self defeating issue, you say £x so they charge £x ?

Z

Our figures for typical installation costs for Air Source Heat Pumps are based on analysis of actual sums paid by housholders for 382 systems over the last couple of years. More than 85% of these households paid more than £5,000 for their system, so to quote a typical range of £3,000 to £5,000 would be misleading.

zeupater

Energy_Saving_Trust_company_representative wrote: »

Our figures for typical installation costs for Air Source Heat Pumps are based on analysis of actual sums paid by housholders for 382 systems over the last couple of years. More than 85% of these households paid more than £5,000 for their system, so to quote a typical range of £3,000 to £5,000 would be misleading.

Hi

I understand your point, however the wording could be changed accordingly in order to place a little pressure on the installers to reduce their margins .... perhaps a good start would be to analyse the average installation prices across europe, not just the UK, and really frighten the market into reacting ... It seems that the rule-of-thumb approach used for costing gas boiler installations (charge ~2x unit list price) has simply been carried over to the HP installers (after all, they are mostly the same people), which provides a healthy return for the gas installations at a boiler price of £1000 (~£600 trade), but gives them a massive return for the same(/similar/smaller) installation work effort on a HP unit price which is around 4x more expensive in it's most basic form.

Through not taking a proactive approach to this issue it's my belief that the EST are not actively working towards a basic remit of encouraging the expansion of renewable technologies and could easily be criticised as being 'in league' with the industry, not energy saving, and definately not the consumer.

HTH
Z

Energy_Saving_Trust_company_representative

zeupater wrote: »

Hi
It seems that the rule-of-thumb approach used for costing gas boiler installations (charge ~2x unit list price) has simply been carried over to the HP installers (after all, they are mostly the same people), which provides a healthy return for the gas installations at a boiler price of £1000 (~£600 trade), but gives them a massive return for the same(/similar/smaller) installation work effort on a HP unit price which is around 4x more expensive in it's most basic form.

Heat pump installation costs in some European countries are certainly lower than in the UK, but there are good reasons for that. There is often a well established supply and installation infrastructure with steady sales, allowing companies to spread their overheads between large numbers of installations. Units are also purchased in large quantities keeping the capital costs down. And large numbers of companies selling to a moderately well informed market have to be competitive, so cost savings are passed on to the consumer.

The only way that will happen in the UK is if heat pumps become a much more commonplace technology, and whether that will happen will depend on future levels of support.

zeupater

Energy_Saving_Trust_company_representative wrote: »

Heat pump installation costs in some European countries are certainly lower than in the UK, but there are good reasons for that. There is often a well established supply and installation infrastructure with steady sales, allowing companies to spread their overheads between large numbers of installations. Units are also purchased in large quantities keeping the capital costs down. And large numbers of companies selling to a moderately well informed market have to be competitive, so cost savings are passed on to the consumer.

The only way that will happen in the UK is if heat pumps become a much more commonplace technology, and whether that will happen will depend on future levels of support.

Hi

Looks like a typical chicken & egg scenario then ... so what are the EST going to do to help remove the roadblocks ?. It's quite strange that most consumer goods establish themselves in the marketplace without subsidy, but isn't that the issue at hand, historical grant schemes have just maintained artificially high price levels ....

Anyway, what's the typical installed price for a HP in the UK v other European markets ? ... is it as you mention 'certainly lower', or is it 'certainly substantially lower', and better still, what is the difference in price through the distribution chain pre-installation ? ... I think that a little research into this area and publishing the results would pay great dividends in assisting the country meet it's carbon & energy obligations .... isn't this something which the EST should be doing as a matter of course, or would yet another body need to be funded with public money to do this ?

HTH
Z

zeupater

Energy_Saving_Trust_company_representative wrote: »

Our assessment of the viability of retrofitting passive solar elements to a house is based on the experience of the early pioneers of solar architecture, who did their initial sums, built their Trombe walls and other features, found that they did very little in practice, and moved on to other solutions. It is always possible that you could come up with a better solution that fits your circumstances and provides with a useful amount of heat. I don't want to dissuade you from pursuing such a scheme, but I do want to warn you against making any decisions based on simple static calculations where passive solar is concerned.

To illustrate my point, I will pick a couple of holes in your figures. I know they were very "back of the envelope" indeed, and I'm not trying to criticise - it's just another exercise to illustrate a point.

Firstly, you assume 60% efficiency for your collector. Even an evacuated tube collector in mid summer feeding a cold water cylinder will not reach this efficiency. A flat plate collector in mid winter will not reach 10% even when feeding a cold cylinder. So I would assume the winter efficiency for your large but low tech collector, feeding a room temperature heat sink, to be less than 10%, let's say 6%.

Secondly, you assume losses of 14% i.e. 86% efficiency of heat transfer to useful space heating either directly or via internal thermal mass storage. This is an area where retrofit passive solar systems notoriously underperform, with heat migration and storage being totally uncontrolled. Let's say actual useful contribution is half what you estimate, i.e. 43%.

On this basis your savings come down to between 180 and 280 kWh per year, or round about £10 to £15 per year in gas (allowing for boiler efficiency and new gas price increases).

Clearly this calculation isn't correct either. But on the basis of the success of earlier attempts at this technology, it's probably closer to the truth than your first stab.

I'm happy to be proved wrong on this, either by experienced solar architects with dynamic software chipping in, or by you building the thing and telling us it works. But I have to warn you that I'm not optimistic.

Hi

I suppose that the issue here is the understanding of how differential temperatures effect the efficiency of generating useful heat. :wall:

Take this example with the following assumptions for the flat panel mentioned above ....

Glass (single glazed) heatloss.... around 5W/C/Sqm/Hr
Flat panel size .... 2x1 m
Collector average temperature for useful heat (>tank temp) ... 70C
Outside temperature during collection (Winter) ... 10C

So the heatloss from just the glass in a flat panel using the above assumptions would be 600W/Hr (5x(70-10)x(2x1)). Measuring this against irradiation at say 650W/sqm on a sunny winter day we get an efficiency reduction of 46% (600/(650x2)) due to the glazing alone .... that's why the efficiency is so low

Now let's look at double glazing to reduce the heatloss in a passive collection system to 2W/C/Sqm/Hr and having a working useful heat of 20C (The internal temperature of the house) ..... The heatloss under the same conditions for a 2sqm system would be 40W/Hr (2x(20-10)x(2x1)) which seems to suggest that more useful heat would be available to use. Looking at the efficiency reduction on the same basis we get a 3% loss (40/(650x2)) .... an efficiency difference of 43%, or alternatively 15x less heatloss through the glass when heating in full sun ....

Irradiation at 300W/sqm would reach equilibrium of 70C on a water flat panel so no heat would be available to transfer without cooling the panel quickly, whilst the passive system would still be making a contribution of 560W ..... Yes, again it's simplistic .... but a little (being kind here ) more logical that the post referenced above which doesn't take the lower operating temperatures of passive systems into account :doh: ....

HTH
Z

Energy_Saving_Trust_company_representative

zeupater wrote: »

Hi

I suppose that the issue here is the understanding of how differential temperatures effect the efficiency of generating useful heat. :wall:

Take this example with the following assumptions for the flat panel mentioned above ....

Glass (single glazed) heatloss.... around 5W/C/Sqm/Hr
Flat panel size .... 2x1 m
Collector average temperature for useful heat (>tank temp) ... 70C
Outside temperature during collection (Winter) ... 10C

We are well aware of the impact of differential temperature on efficiency - that is why I specifically quoted efficiency figures for solar panels feeding a cold cylinder. These are measured efficiencies for panels installed in homes, with measured cylinder temperatures and all the calculations in the world are not going to change them.

But to come back to the main point - retrofitting semi-passive solar features, such as Trombe walls, to existing houses has been calculated to be effective many times in the past. It has then been tried by several and has proved far less effective in practice, and generally pretty much useless, especially in the UK. If you believe you have a better solution that might work in your situation, then by all means try it out and tell us all how it goes. But in the meantime the Energy Saving Trust will not be advising the world to adopt this approach because it has been shown to be far from cost-effective.

If you want to discuss the theory and practice of this technology further, then I would genuinely suggest you go to the other sites I suggested earlier in the thread, where I think you will find more contributors who can comment constructively. This is, after all, a money saving site and I imagine that most people who visit it are looking for advice on measures that have been shown to be cost effective ways to save money.

I do mean this as a positive suggestion, not a negative dismissal. I just don't think this is the right forum for this type of theoretical discussion.

zeupater

Energy_Saving_Trust_company_representative wrote: »

We are well aware of the impact of differential temperature on efficiency - that is why I specifically quoted efficiency figures for solar panels feeding a cold cylinder. These are measured efficiencies for panels installed in homes, with measured cylinder temperatures and all the calculations in the world are not going to change them.

But to come back to the main point - retrofitting semi-passive solar features, such as Trombe walls, to existing houses has been calculated to be effective many times in the past. It has then been tried by several and has proved far less effective in practice, and generally pretty much useless, especially in the UK. If you believe you have a better solution that might work in your situation, then by all means try it out and tell us all how it goes. But in the meantime the Energy Saving Trust will not be advising the world to adopt this approach because it has been shown to be far from cost-effective.

If you want to discuss the theory and practice of this technology further, then I would genuinely suggest you go to the other sites I suggested earlier in the thread, where I think you will find more contributors who can comment constructively. This is, after all, a money saving site and I imagine that most people who visit it are looking for advice on measures that have been shown to be cost effective ways to save money.

I do mean this as a positive suggestion, not a negative dismissal. I just don't think this is the right forum for this type of theoretical discussion.

Hi

Dismissive and missing the point again ..... how could the following be posted " I specifically quoted efficiency figures for solar panels feeding a cold cylinder" and immediately justified with " These are measured efficiencies for panels installed in homes, with measured cylinder temperatures " ..... surely as the temperature rises in the 'cold' cylinder it is no longer 'cold' and the rise in temperature reduces the system efficiency accordingly .....

I'm pretty sure that you have a point about Trombe walls, however, as has been explained earlier and as you have correctly recognised what is being considered is not a Trombe wall, it's a passive collector which transfers the collected directly heat into the building's interior thermal mass in almost exactly the same way as a window in a south facing wall ..... I consider your reasoning as being flawed and your dismissal as being contrary to the reasoning of any building which utilises solar gain as a form of heating or supplimentary heating ....

Due to the disparity between the relative operating temperatures of solar water heating to what has been described I am really dissappointed in the level of apparent technical ability within the EST .... if a direct comparison was to be made it would be with a window, which would have been far more realistic ....

I really do appreciate that the EST "will not be advising the world to adopt this approach" ... that's not why this was raised in the first place, the initial reasoning was that the EST were effectively dismissive and simply tried to offload to the BRE, who were not entirely surprised at the approach but had absolutely no interest in talking to a consumer without a product to test or market, and that's exactly the same approach as is being employed in the referenced post ..... seemingly, a lack of understanding of anything 'Energy Saving' which is not within the current EST approved brief is seen as not being 'Energy Saving' at all and not worth consideration or discussion .... might as well be run by a marketing agency then ... roll up, roll up ...

Me, well I consider myself as being pretty energy saving savvy anyway, total heating input this season so far is somewhere around 600W/sqm with already meeting one of the main tests of passivhaus requirements, that being on a retrofit basis too, perhaps I should now really question the need to even talk to the EST and just continue talking to other who actually have successfully used passive heating to their advantage ...... is the EST fit for purpose ?, :think: I really am starting to think seriously on this one ....

Z

gogreen99

What do people think about the change of incandescent bulbs to LED bulbs? The most common, most energy efficient bulbs on the market at the moment are LEDs and I, personally think it is an excellent money saver. After a lot of research I have finally come to the conclusion that I will be saving £200 a year, not mentioning the money I would save for buying bulbs (LEDs last up to 25 years in comparison to the 2 years of incandescent).
All in all, the traditional light bulbs were excellent while they lasted but there is definitely a change on the horizon. I've found that evereadylightbulbs.co.uk have an excellent range of cheap energy efficient bulbs and they wholeheartedly support the change too.