Debate on Electric Heat Pumps

[Andy Simmonds]

Evidence prepared by AECB – the sustainable building association

Re: Heat Call for Evidence Coordinator, Energy Group, The Department for Business,
Enterprise and Regulatory Reform (BERR)

As a result of press coverage on electric heat pumps in Green Building magazine (Spring 2008) I would like to flag up the AECB consultation response that was quoted in the piece. It can be downloaded from the AECB members section, however given the interest that the magazine coverage has created already, I am posting it here to allow access to the document for non-members.

[john cantor]

Thanks for pointing this out, it makes interesting reading.

I have missed the heat pump debate, would you mind telling me where it exists (existed).   I looked at  greenbuildingforum but could not find it.

[Andy Simmonds]

John,
re: greenbuildingforum debate....

I am not a regular user of greenbuildingforum, mark siddall is...

Is there not a reference in the Green Building Magazine to the appropriate link?

[Steve Macken]

Interesting stuff.  I looked through all the options for heating my AECB silver std 'off gas grid' house and concluded a heat pump to be the best choice from a running cost and CO2 emissions point of view, even assuming 'lowish' COP's (3 for heat, 2 for hot water).

Having installed this and run it for a month or so I have no regrets so far.   The flow temp for the UFH is just around 27deg when it's freezing outside to maintain 20 deg inside, such that the COP for heating is likely to be greater than 3 (the manufacturer quotes 4.3 for a flow of 35 deg).  And this is prior to fitting the external edge insulation to the slab!

The flexibility of control is immense, including the opportunity to optimise running costs further by synchronising set back periods with dual rate tariff schemes (at risk of starting another debate....!) thus reducing payback period even further against the less capital cost / highr running cost oil and LPG alternates.

So let's not be hasty in dismissing heat pumps as a low carbon, cost effective option for energy efficient houses.  Sure there is much hype from some sellers just now which is open to challenge, but for those out there weighing up the options heat pumps are a serious contender when pitched against oil and LPG for well insulated 'off gas grid' houses.

[Nick Grant]

Mentioned elsewhere but worth repeating that John has a nice spreadsheet on his excellent website http://www.heatpumps.co.uk/

Heat pump efficiency estimator.

It uses algorithms rather than first principles physics but is intended to make the point you make Steve that super insulation+ optimum design leads to very different COPs than air sourced HP feeding rads in a poorly insulated building.

The potential for 'off peak' gets interesting when the energy supply is lumpy such as wind but as you say it is another discussion.

Nick

[Andy Simmonds]

Steve,

"So let's not be hasty in dismissing heat pumps as a low carbon, cost effective option for energy efficient houses.  Sure there is much hype from some sellers just now which is open to challenge, but for those out there weighing up the options heat pumps are a serious contender when pitched against oil and LPG for well insulated 'off gas grid' houses."

The AECB is certainly not dismissing heat pumps as an appropriate low carbon technology in all cases. However the situation with respect to governmental financial support for technologies aiming to reduce emissions from buildings currently so neglects the more affordable approaches (to the UK taxpayer) that we are hard pressed to get the government to correct this unwise allocation of public monies. They should bring new financial support / incentives to the cost effective measures outlined in the HEAT evidence, or if necessary re-allocate existing monies. Preferably the former.

If we have used language in the HEAT evidence that seems to 'scapegoat' one particular technology and that implies a sense of frustration at incoherent government funding strategy.... then that is because we are extremely frustrated at the poor quality of decision making being exhibited - decisions that if not reconsidered will affect the UK's ability to build and rebuild an affordable and sustainable infrastructure!

Also as you imply in your post, AECB energy standards do not preclude the use of heat pumps.

By the way, anyone reading this post, should look at Steve's blog describing his design and construction of a low energy home to the AECB Silver targets. Very good.

I look forward to more debate.

[john cantor]

I would love to contribute to this debate, but currently sitting in a Beuro de Tourism in the french alpes with a plaster cast on my leg!!    is this pennance for all the energy that we have used to come skiing??    well at least we travel by train.

back in a week, and will add some comment. internet is far too expensive here.

(happened on 2nd day!!   worse nightmare!)

john.

[Andy Simmonds]

Look forward to it John!

[john cantor]

I think that the article in the Green Building Mag did give heat pumps a bit of a battering.
I actually agree with most of what was reported. But the problem with a one-sided article is that it only helps to divide the Pro & anti camps.  wrt the  evidence:- Statements like "COPs as low as 2 are widespread" . could potentially reduces the AECBs credibility. It is true that there are cases of low COPs, but  these are in old un-insulated inappropriate houses, or simply designed, installed or set-up badly.
HPs in appropriate situations can give COPs in excess of 4, and many monitored installations prove this. 
The point that it is very costly to attain such efficiency levels, and the money may be better spent, is a point that I agree with.

I am actually very worried about the future of heat pumps, and fear that more low efficiency systems will come onto the market. One could make systems with lower seasonal COPs quite cheaply, and these could become a convenient and reliable heating method, with a 'green' label, but as we know, if an overall picture is taken, then they are not an environmental solution.

 There seems to be a real lack of knowledge and trust of actual efficiency figures. Somehow we need to get far more systems monitored so as to improve this. The debate as to where the line can be drawn (with respect to COP, or SFP (seasonal average)) between benefit or otherwise can continue since it seems like a complicated business to actually evaluate this.
The important thing is to weed-out the potentially low-efficiency systems, and support the good applications
I think the AECB needs to appear a little more informed with respect to heat pump efficiencies in the HEAT evidence. I fear that the 'experts' reading it may remain perplexed in the midst of such differing figures from the pro and anti lobbys.

[Andy Simmonds]

Please remember that the article was not instigated or written by the AECB or its representatives - the author simply quoted parts of the document that the AECB submitted to BERR. It would be best I think if the debate could refer to the AECB's heat evidence paper, rather than to the article which wqs instigated and authored by others. I am concerned that there remain a lot of people who still think that the Green Building Magazine is the voice of the AECB, rather than an independently produced magazine with no editorial link to the AECB.

AECB would be welcome anyone who would like to propose written, comprehensive and balanced guidance on the appropriate application of electric heat pumps , advantages and disadvantages. This guidance could be developed on this forum.....

[john cantor]

I think the heat pump debate does need to continue. And I'm struggling to formulate the thoughts in my head.

As I see it, there are two sides. Manufacturers/installers on one side, customers on the other. There is a great desire on the supply side make a profit,.. to survive. Their criteria when developing products will include: profitability, ease of use, easy to install, reliability, physical size. etc.
The actual environmental impact will be on the list, but not at the top.

Manufactureres are always looking for new markets, and no doubt there are plenty working to find new 'green' heating products, with ease of installation high on their agenda.

The exhaust air DHW heater is an example. It takes air from your home, improves ventilation and gives you 'green' water heating!!   In reality, it will increase the demand on the gas central heating, and consume considerable amounts of electricity.  But its a box that could be fitted quickly.

What worries me more is that this type of product could be backed by the government.

Somehow, someone should be keeping a check on this.
Do you think AECB has a role here?
This topic involves normal 'bad' houses, so is this too much of a deviation from the normal AECB focus on 'good' housing?

I might start a new thread to discuss ventilation and heat pumps. Its probably best kept separate to the very interesting one currently going on central ventilation systems.

[Steve Macken]

John/Andy
- for me the sums were relatively simple, taking into account the AECB's conversion ratios for various fuels to primary energy and CO2 from an environmental perspective, and similarly a cost comparison of the options.

For a fixed no of primary energy kWh's for heat and DHW it is fairly straightforward to do the environmental comparison, the key variable being the COP assumptions; I used fairly conservative values of 3 (for space) and 2 (for DHW) and I'm reasonably confident I'm achieving these based on John's published data, the heat pump spec. (and it's from a major reputable Swedish manufacturer) and a very low flow temp. in the slab UFH.

The cost comparison is a little more tricky given the vast number of tariffs available for various fuels, but at current rates I reckon the additional capital costs of the heat pump will be returned within 10 years; ie. not dissimilar from a  decent solar thermal system.

There is of course the argument that the additional cost of the heat pump could have been spent on extra insulation, but for the average self builder to take this on board and actually implement this philosophy beyond Silver standard is frankly not that easy.   alternativley, in our build the additional cost of the heat pump was more than met by going for an Ikea kitchen (7k) rather than a John Lewis kitchen (£12k)!

By the way we're fitting a kWh meter to the heat pump today so it will be interesting to see what it consumes, and will also allow us to check the consumption of applicances and lighting in the rest of the house.

Regards, Steve

[David OLIVIER]

Steve

I think the suggestion that to design in better insulation is technically more difficult than to properly engineer a heat pump is bizarre. Canada, USA, Norway and Sweden have only been doing it in timber-frame buildings for the last 30 years! My & John Willoughby's 1994 report to BRECSU (GIR 38-39) featured a few UK timber-frame homes with wall U-values in the range 0.15-0.2 or lower.

The industry accepts that electricity used at system peak is subsidised by electricity consumed at other times (non-domestic users face time of day pricing), and that incremental growth in electricity use is fuelled by coal-fired plant, not gas or nuclear. Given the realities of how electricity supply systems actually operate, I don't see the relevance of payback times. The costs imposed on UK PLC by private decisions which cause electricity demand to increase may be totally different from the price paid by the individual who made those decisions.

David.

[Steve Macken]

David
- believe me, to go beyond Silver (insulation and airtightness levels) for the average self builder (ie. me!) and to justify the additional cost and risk of doing so (to conservative building control officers, structural engineers, architects, builders etc.) is more difficult than drawing the line at Silver then working out the best option for heating (ie. heat pump in our case).  Which is why the Silver standard is a superb concept as it returns significant benefits for little additional outlay or deviation from convention.

As for payback times this is an important factor for many who are considering investing in low(er) carbon technologies, the majority of which are indifferent to the 'carbon ethics' of cheap rate electricity if its use with heat pump system saves a few extra quid!

Steve

[Andy Simmonds]

HPs in appropriate situations can give COPs in excess of 4, and many monitored installations prove this. 
The point that it is very costly to attain such efficiency levels, and the money may be better spent, is a point that I agree with.

John,

Have you got a link to the results of the monitoring you refer to?

How do the costs you refer to build up in order to achieve these high efficiency levels (COPs greater than 4) - would it be possible for you to bullet point the main costs involved (say, above typical current practice...)?

How is your leg?