Energy Saving Trust Q&A Centre

Energy_Saving_Trust_company_representative

Cardew wrote: »

Hi,

Notwithstanding the above, my biggest gripe is that potential customers are bombarded with adverts promising 3 or 4 units of heat for each unit used.

Unless they are 'switched on' -

1. They have no way of knowing if their house is suitable for an ASHP.

2. They have no way of knowing if the installer is competent.

3. They have no way of knowing what results their system is achieving.

4. They have no guarantee of performance.

5 They have no redress if the performance is poor.

I agree entirely that this is the main issue surrounding ASHPs. We see it as our remit to make sure that as many consumers as possible are 'switched on'.

We would advise all consumers to obtain several quotes, to only use a Microgeneration Certification Scheme installer, and to ask for references.

The new MCS standard for heat pump installers will be out soon, and will address a number of issues including communicating likely performance to the customer before they sign up to anything. Apart from improving installation standards generally, this will also create new routes for redress against any installer that does not comply with the standard.

For existing customers who believe their system is underperforming, they could try complaining to the installer and/or the manufacturer. Believe it or not, this does sometimes work. All consumers have statutory rights if they have been sold a product that is not fit for purpose.

Energy_Saving_Trust_company_representative

zeupater wrote: »

Hi

So a heating season of October to March would benefit from 3600kWh of passive/semi-passive heat, with an additional 2000kWh available if heating was required in September & April .... Agreed, the energy isn't available on demand, but dumping this level of heat into the internal thermal mass of a building would provide a considerable positive benefit in terms of energy saving ..... I suppose that it's just not 'sexy' enough and potentially far to 'cheap' a solution when developed for anyone to consider looking into properly .....

As mentioned, simplistic and obviously wrong, but probably not that wrong to be considered as not being 'effective' ..... any architects out there to run the same figures through their 'dynamic modelling software' to see how close the above estimate is likely to be ??

HTH
Z

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.

Rodders57

@EST. I would like to know why heat pumps are so popular on the continent if deemed to be inefficient by your field trials. Having looked into this myself could it be a mix of, better insulation of the building envelope, better trained installers, low temp UFH for space heating. Also there must be case studies in the UK where off grid buildings have benefited from having heat pumps installed, would it not be wise to run tests on those properties as well for comparison. I`m not sure about the new MCS standards for heat pumps but I do know that on the continent the qualifications for HP installers are more robust as in the EU.CERT.HP . Your report highlights poor designs, installation issues and commissioning. I hope that MCS takes on board your results from the field trials and ask questions of the industry to be more robust in quality training because at the moment this useful technology is not being used to its potential because of its poor image. BPEC and Logic qualifcations are not the answer.

Cardew

Energy_Saving_Trust_company_representative wrote: »

I agree entirely that this is the main issue surrounding ASHPs. We see it as our remit to make sure that as many consumers as possible are 'switched on'.

We would advise all consumers to obtain several quotes, to only use a Microgeneration Certification Scheme installer, and to ask for references.

The new MCS standard for heat pump installers will be out soon, and will address a number of issues including communicating likely performance to the customer before they sign up to anything. Apart from improving installation standards generally, this will also create new routes for redress against any installer that does not comply with the standard.

For existing customers who believe their system is underperforming, they could try complaining to the installer and/or the manufacturer. Believe it or not, this does sometimes work. All consumers have statutory rights if they have been sold a product that is not fit for purpose.

Thank you.

I wish that our concerns were addressed by a Regulator with some teeth.

The cynic in me is concerned that the 'new MCS Standard for Heat pump installers' will be circumvented in the same way as some solar PV installers have used.

On Solar PV we were promised that MCS involvement would mean the end of Double Glazing sales techniques of yesteryear.

However some MCS installers have given up any pretence of sticking to the standards as the recent WHICH report shows:

Some solar panel companies are using dodgy sales tactics and giving poor advice to people looking to buy solar PV (photovoltaic) panels, shows a Which? undercover investigation.
Three quarters of companies investigated overestimated how much energy the solar PV panels would produce and most of them underestimated how long it would take for the system to pay for itself.
Poor solar panel advice

We investigated the selling tactics and advice given by 12 solar PV panel companies for the installation of solar panels on the roof of a house in southern England. We found:

• seven companies did not take into account the fact that part of the roof was in the shade, so putting solar panels there was questionable
• only two companies mentioned that the inverter, which transforms the current produced by the solar panels into usable electricity, almost always needs to be replaced within 25 years at a cost of at least £1,000
• using the government methodology, we calculated that eight companies underestimated the time it would take for the system to pay for itself.

Can we really expect MCS registered heat pump installers to abide by the new Standards?

Can we really expect firms to advise potential customers that their house is just not suited to an ASHP?

What redress will a customer have if his expectations are not met? MCS have no 'teeth'. Even in the unlikely event they withdrew accreditation after a string of complaints, the firm would start up again with a new name.

Cardew

Energy_Saving_Trust_company_representative wrote: »

Firstly, I think I should apologise for the wording of our field trial report. It does describe 6 of the results as "estimated" but this doesn't adequately describe the nature of these results.

Six of the sites were monitored using a different methodology to the one specified for the trial. We looked at the data produced for these six, assessed its validity and comparability with the rest of the results, and concluded that these results were reliable and comparable and should be included.

Once these figures are included, the median for the quoted results comes out at exactly between 2.0 and 2.2. The median of the origninal non-rounded results comes out at near to 2.2 and so we used that as our typical system efficiency.

If the "estimated" figures are accepted, the figure of 3.0 for a system that performs well is also reasonable.

I fully understand that people will have been suspicious of the higher figures given the way the report was worded. However, I can assure you that all the data was assessed independently by us and our contractors and was not simply based on manufacturers' estimates or other unreliable sources.

I should also apologise for the inconsistent figures that were found on our web site. This is an old assumptions page, describing the numbers that we used to use in one of our online tools. We do not use these figures (modelled performance figures as used in SAP) now that we have actual measured performance figures, but we failed to update the assumptions page. I will look into getting this page corrected as soon as possible.

Thank You.

Without repeating the points made earlier, on your trial we had eight houses out of 28 with a system COP of 1.6 or worse.

I suggest it is a racing certainty they were told that they would get 3.0 or higher. To pay £12,000 or so for that level of performance is a disgrace.

rogerblack

Cardew wrote: »

Thank You.

Without repeating the points made earlier, on your trial we had eight houses out of 28 with a system COP of 1.6 or worse.

I suggest it is a racing certainty they were told that they would get 3.0 or higher. To pay £12,000 or so for that level of performance is a disgrace.

I note earlier in the thread that it says solid walls have not been insulated in the trial.

This is _vastly_ more expensive than cavity or roof, but once you start looking at an up-front outlay of 12K (with a life of a decade or two), versus actually insulating the building properly, which will trivially reduce heating bills by a factor of 2.2...

Even solid wall insulation, and underfloor is not unreasonable in some cases at a comparable outlay.

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

At 6% efficient you're effectively proposing that a thermal collection system as proposed is less than half as efficient as solar pv ...... I have an 8' leaky, draughty and single glazed greenhouse which becomes remarkably warm on a sunny winter day so that's about 7sqm of glass facing the sun .... it would probably take the entire output of my 27sqm of pv to run a fan heater in the greenhouse to achieve anywhere approaching the same heat ... funnily enough 27/7 is almost the same 4:1 ratio as the efficiency assumed before .....

To be objective .... if the collector was a 25sqm S/W decent double glazed window, what would the solar gain be for the heating months as a direct comparison ... ?

Z

jomknight

I have just installed 1.65kw pv solar panels south facing. Will it be cheaper to use the inmmersion heater for water or gas (condensing boiler) assuming the immersion is on when little other electricity is being used elsewhere e.g. just the frig and light use. and i restict the time the immersion is on for.

Energy_Saving_Trust_company_representative

jomknight wrote: »

I have just installed 1.65kw pv solar panels south facing. Will it be cheaper to use the inmmersion heater for water or gas (condensing boiler) assuming the immersion is on when little other electricity is being used elsewhere e.g. just the frig and light use. and i restict the time the immersion is on for.

In theory, there could be times when a home with a PV system could find it cheaper to use an immersion heater than a condensing gas boiler to heat their water. However, this would only happen if the solar installation was bigger than yours AND there was full bright sunshine in the early afternoon in June AND you were using very little other electricity in the house.

In practice, the vast majority of the electricity you would use to heat your water with an immersion heater would still be bought in at maybe 14 pence per unit or more. Heating the water with gas will cost you less than 6 pence per unit allowing for boiler water heating efficiency.

So stick with the gas - it's cheaper.

Energy_Saving_Trust_company_representative

rogerblack wrote: »

I note earlier in the thread that it says solid walls have not been insulated in the trial.

This is _vastly_ more expensive than cavity or roof, but once you start looking at an up-front outlay of 12K (with a life of a decade or two), versus actually insulating the building properly, which will trivially reduce heating bills by a factor of 2.2...

Even solid wall insulation, and underfloor is not unreasonable in some cases at a comparable outlay.

Yes, I agree. We would ALWAYS recommend that people consider upgrading their insulation levels before looking at installing a heat pump. Even the more expensive options like solid wall insulation may be more cost effective, and they have the added advantage of improving the potential efficiency of a heat pump system.