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Air Source Heat Pumps – carbon friend or foe?

by Mel Starrs on September 6, 2011

in Renewables

Looking back through the archives I seem to have been remiss and never written properly on the topic of ASHP (air source heat pumps). A topic dear to my heart as it exemplifies the quandaries that we find ourselves in when it comes to a low carbon future – and all that entails including energy efficiency, fuel security and consumer confidence.

My current ASHP theme has been fuelled by a John Cantor piece for AECB (pdf, 24 pages) back in July (picked up by Mark Brinkley here). An essential read and as I won’t be cutting and pasting great tracts from the document I urge you to go read it.

This current interest in ASHP is being driven by the RHPP – the precursor to the RHI proper. In addition there has been a bit of a kerfuffle around the claims of an ASHP installer who got censured (rightly) by the ASA – David Thorpe covers the story here (he also covers the Cantor paper).

As I linked to a couple of weeks ago the popularity of ASHP has surpassed initial predictions for RHPP (which assumed Solar Thermal would lead the way):

But while most enquiries ahead of the launch of the RHPP were about solar hot water systems, 36 per cent of vouchers – the highest proportion so far – have been given out for air source heat pumps, according to the Energy Saving Trust (EST), which is managing the £15 million grant scheme on behalf of the Government.

Why is this newsworthy? Surely this is a good thing? Well, it depends from whose point of view you take. Say, the consumer? Yes, they have received £850, but as has been pointed out by David and Mark, unless their heating system can run at relatively low flow and return temperatures (ideally underfloor heating or oversized radiators) they are unlikely to see a saving in energy or carbon use. Plus there is no guarantee currently that ASHP will be supported by the RHI when it comes online next year. Risky.

ASHP got a bad wrap last year when the EST published their field trials. Basically, they don’t always work as expected.

Is this enough to throw the baby out with the bathwater? No, they are useful in certain locations with the correct installation and heating system. But here’s the thing – you need to know what you’re doing before you make that decision. I hope that when Green Deal and RHI get going properly, householders will be getting advice from those who know what they are talking about and not just ticking boxes against EPC or SAP methodology (Part L 2010 still artificially ‘boosts’ electric based heating though not to the extent it used to).

So why the rush for ASHP if it doesn’t out-perform current technologies? I suspect this is based on an ideal future where grid electricity carbon intensity has fallen dramatically (by either renewables or nuclear, or both). This feels some years off yet though (I’m sure there must be some accurate projections out there – anyone got a link?), but if it does happen sooner rather than later, the fuel security argument against gas starts to make more sense. Of course, then we are left with the small issue of infrastructure – our creaky national grid is close to the edge as it stands, never mind adding in all this extra load. Which in turn brings us back to the energy efficiency arguments – we need to start doing more with less.

As I said at the start – a quandary.

RHPP – Renewable Heat Premium Payment

RHI – Renewable Heat Incentive

Some more links on ASHP from the archive:

New StatesmenOliver Tickell on No Hands to the pump (pointing out the flaw in the carbon argument when comparing to gas)

Mark Brinkley on dropping oil based heating and the consequences on heat delivery (i.e. radiators)

Finally a great (long article) from Geo Dynamics on pros and cons of ASHP (which unfortunately seems to have disappeared – anyone got a link?)

  • Keyur Vadodaria

    Checkout our research project
    Our research partners ar Warwick and ulster have modified, redesigned and tested gas and electric ASHPs in lab and soon in test houses. They are designed to work with existing radiator systems hence not requiring disruptive underfloor heating. COPs of 1.35 for gas and 3.5 for electric. Gas fired system is seen as a ‘transition’ technology until the UK grid is capable of supporting a switch to an ‘all electric’ system.
    Many thanks,
    Keyur Vadodaria

  • Linn Rafferty

    Mel, let me reassure you about ASHP in SAP methodology.  Although part L 2010 artificially boosts electric based heating, and this is implemented in SAP software, this is only done for assessment of Part L compliance, NOT for the SAP rating.I know it’s fashionable to knock SAP & EPCs (eg Affinity Sutton’s report ) but many of its so-called shortcomings are due to poor application by the user, not the method itself; or simply misunderstandings on the part of the one doing the knocking.

  • Bob Irving

    One of the problems, as far as I see it, is that it is not easy to tell whether a heat pump is going to perform OK or whether it is performing OK without quite a lot of data collection. I think that heat pump manufacturers ought to be required to include the measuring and monitoring equipment in the heat pumps. If applied to all hp’s, this would not add much to the price and would not add much extra complexity to already complicated electronic controllers.

  • Toby

    First, I found a working link to the Geo Dynamics Article;

    I note that under the RHPP systems will have to be heat-metered, haven’t looked at the small print yet but if this is done the right way it could result in the large-scale study that the ASHP sector has been crying out for. Maybe, just maybe, there’s a civil servant in with their head screwed on the right way round.

    @Keyur – can’t get at any real info on the site you linked to but would be interested to see some detail on your COPs. Remember, in the land of ASHPs, *Seasonal* COP is king…