UPDATED: Air Source Heat Pumps/Air Con - Full Info & Guide, is it cheaper to run than mains gas?

zeupater

John_Pierpoint wrote: »

After making all the reasonably possible improvements in the thermal performance of the building's envelope, you might be able to get close to "Passiv Haus" standard, in which case the heating system stops been particularly important.
However for the rest of us, who are not living in a south facing unshaded cave, the heating challenge is then all about improving the "efficiency" of space heating.

The problem with electricity is that the power in the original source of energy has been dissipated by (let us say) 50% in various production and transmission losses before it arrives in the consumers meter.
This has to be compared with the 90% efficiency (when working hard) of a gas boiler in the winter.

Then we need to discuss capital costs and carbon costs and put our own factors amd future guesses on those figures.


I was rather wondering if the poster was suggesting the concept of collecting heat on the outside of the building, not by blowing large quantities of air through an air conditioning unit running in reverse, but just by air and day time sunlight passing over thermal panels.

I remember you were able to help debunk some salesmen's estimated of the fortune to be saved with solar thermal hot water. You published some simple conversion/storage factors for raising the temperature of hot water, in terms of kWh, in a buffer tank.

Now we are seeing suggestions of serious additions to space heating using panels "that don't even need to face South" plus a freezer sized heat pump. It would seem this concept of black panels is coming up from Spain.

Here is a suggestion for storing "summer" heat for "winter" use in a three tonne tank, rather than trying to find a large area or volume of wet subsoil..

http://www.minus7.co.uk/how-it-works/

Do I feel an attack of oil and snake coming on?

Are we talking about heating something like this
http://www.zoopla.co.uk/for-sale/details/29073121?search_identifier=762c12f419526d5c9460ff61bd47f4d6

Hi John

I read the post as simply being a standard Panasonic (/similar) air/water HP heating setup. I'd agree that if the property is built to current regulations regarding insulation, then there is certainly plenty of scope for improvement, which would likely be very much cheaper and provide more immediate benefit than a change of heating system. As for getting close to passivhaus standards, that would be hard ... having made improvements for many years we meet one of the passivhaus tests, failing miserably on the other, however, being able to achieve this on a 30 year old property certainly shows what is possible.

Regarding long-term heat storage in anything as small as a 3 tonne system,, well that's a little optimistic .... 3 tonnes would provide a buffer between sunny/bright periods for a massive solar thermal array, but no more than that. Let's assume 3 tonnes of storage capacity at 60C with a house temperature of 20C and apply a rule of thumb calculation of 1kW of power for 1hour raises 1tonne by 1C, then 3 tonnes would be storing a mere 120kWh((1x1x40)x3) of heating capacity (~40kWh/tonne) .... higher storage temperatures would lose heat more quickly and encounter issues with mass storage materials and their cost/benefit ratio .... so any form of long-term storage (inter-seasonal) in a very well insulated property would likely need to provide somewhere between 5MWh.t and 10MWh.t of heat provision, so somewhere between 125tonnes and 250tonnes (assuming no direct storage heatloss outside the building envelope) ... in context, to gauge how large this would be, an Olympic size swimming pool would contain around 2500tonnes of water .... therefore the engineering cost and space requirements for such a solution would probably push anyone seriously considering it towards a basic GSHP system instead. I have seen a system where a complex pumps solar thermal and excess summer buildings heat into multiple 100m deep boreholes and then recovers this as required on an inter-seasonal basis, but this was part of a sustainable energy management system which literally cost £millions to install (ICAX system - link http://www.icax.co.uk/), I believe there is also a supermarket nearby which probably uses a system provided by the same company.

HTH
Z

zeupater

Hi John

Just finished reading through all of the passive heat exchange roof in your link .... my thoughts ?, well it's all far too carefully worded and data specifically chosen for me to even think about it ... for example, under the title "Worst Case Performance Data" an example of typical data is presented for 13/01/2011, however 13/14/15/16 January 2011 were completely atypical, with the HadCet Dataset for 2011 (link - http://www.metoffice.gov.uk/hadobs/hadcet/cet_mean_2011 ) showing the temperature for 14/01 being more typical of what would be expected in May or October ....

On what I've seen so far, especially the way it's been carefully presented, I wouldn't consider touching the system or the providers with a bargepole ... bet it's not as cheap as it looks either !!

What are the REA thinking about when allowing products to be marketed in such a deceitful manner, it cannot possibly be doing anything other than a disservice to the renewables sector as a whole .... also, are the ASA asleep on this - their code Section 3 applies (link - http://www.cap.org.uk/Advertising-Codes/Non-broadcast-HTML/Section-3-Misleading-advertising.aspx), therefore I would hope that the marketing material to be changed pretty quickly to avoid being included on the non-compliant advertisers list link - http://www.asa.org.uk/Rulings/Non-compliant-online-advertisers.aspx ).

HTH
Z

John_Pierpoint

Many thanks for your high standard insightful reply.

I think hypermarkets, like schools, have a high intensity of energy use from the machinery installed and the density users bodies. Do it just might be economic to use what Cardew refers to as "parasitic" power to pump energy seasonally.

Turning to the domestic scene and the offering from "minus7" I have revisited the link on "thewaybackmachine" and the web site appears to have been up in more or less its present form for over a year.

So I burrowed into a link, and it would appear that as flagship installation was eventually made by "Drum Housing" 2 or 3 years ago on a social housing site created on part of a former Ministry of Defence site near Bordon Hampshire.
"Drum housing" seems to have built up a track record of experimenting on their tenants with what we could call by now "conventional" eco measures
http://web.archive.org/web/20120216141125/http://www.minus7.co.uk/about/drumhousing.pdf

The development gets a supportive puff here in the Grauniad
http://www.guardian.co.uk/commentisfree/2008/aug/05/ecotowns.ethicalliving#start-of-comments

These developments have been made and publicised by that 50% "socialised" part of the economy that is really good at spending other people's money and borrowing from our grandchildren.

Those of us having to put our own money and families on the line, only get one chance to get it right, we don't want want reports full of will, should, could etc, we need solid facts of achieved results.

How can the architectural profession talk about case studies when the new tenants have yet to go through their first winter? Where is the project's post implementation review and hard nosed audit of actual numerical out-turns?

Perhaps some tenants of the Drum Housing Association development in Whitehill, Bordon Hants has the figures to round out the so called case study.

They could compare notes with these tenants to give a sense of perspective to their findings.

http://www.architecture.com/Files/RIBAHoldings/PolicyAndInternationalRelations/Policy/Environment/DrumCaseStudy2.pdf

peat

Domestic RHI - hot off the press:
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/212089/Domestic_RHI_policy_statement.pdf

[Deleted User]

Thanks for posting this

nande2000

I see the 20 years worth of tariff over seven years has now been dropped to just seven years. It'll be interesting to see how installers will be able to estimate the COP of ASHPs

nennyrainbow

Had I known that, I might have gone for GSHP or biomass. I notice that the tariffs for all technologies other than ashp are higher than the ranges proposed back in September last year, whereas ashp is right at the bottom of the proposed range, AND is assuming a COP of 2.5 unless you can demonstrate otherwise. Since we couldn't fit a meter in due to space limitations, I guess we will have to make do with that assumption.

in p/ kw/h by technology:

ashp proposed 6.9- 11.5 actual 7.3
biomass proposed 5.2 - 8.7 actual 12.2
gshp proposed 12.5 - 17.3 actual 18.8
solar thermal proposed cap of 17.3 actual 19.2

[Deleted User]

What really annoys me is our system was installed based on the promised RHI at the time, 2011, and are now classed as legacy... Only because they couldn't organise a !!!! up in a brewery!

Bloody cheek

nennyrainbow

And if I understood it correctly, we now have to apply for Green Deal assessment to get an EPC in order to claim. I was previously under the impression that early adopters of the technologies (now termed lagacy claimants) were exempt from this, and as long as your technology was on the MCS approved list, your claim should be straightforward. I haven't looked into this yet so I don't know what it entails, but I wonder if it will work out to be unduly complicated and expensive to get these things done retrospectively and therefore put off some of the legacy claimants.
As they did with solar PV, I feel the gov't have totally screwed over early adopters of the the scheme because it's not in their interests to pay people who aren't going to boost the renewables statistics any further.

Alfiethefish

Thanks to all.

Actually as Jeepjunkie now knows I have received a quote since making the post originally to fit a Mitsubishi Ecodan system. The house is indeed total 1742 sq ft and 400 of that is a brick and double glazed ( to current standards ) conservatory.

The last two years LPG are at 2205 Pounds and 2400 pounds respectively. The house has solar water units so in summer ( when we get one ) like now, the heating is turned off as it the hot water and we are supplied by thermal. So if I add the net electric bill which is Pounds 480 less some rebate for sold on PV generated power that amounts to around Pounds 250 a year. Total energy bill Pounds 2650 a year + an increase due in LPG this winter.

So the Ecodan system quoted is going to cost UKL 8000.00 less hopefully a 1300 grant - maybe - but even without the specification for this heat pump says that it will provide all space heating required + hot water for around UK Pounds 980 per annum. The LPG boiler needs replacing and cheapest quote we have is around Pounds 3000 so we have to recover the extra 5K. If the bills drop by Pounds 1 K per annum then it shud return in 5 years. My problem is I simply can't find anyone independant to confirm that the figures I am being quoted are correct. I am clearly not a techie so am reliant on advice from where I can get it - hence the original question.