In the largest ever UK field trial of domestic heat pumps to date, it’s been concluded that whilst such installations can indeed result in carbon savings, more work has to be done to improve installation practices to ensure that the savings become an actual reality.

The field trial was commissioned by the Energy Saving Trust, the body that advises householders how to save energy and reduce their carbon emissions. They also provide advice to communities, local authorities, manufacturers and installers.

The key finding of the major study was that the industry has to improve the installation techniques for both air and ground source domestic heat pumps. If this happens, then there is a fair chance that they will become a mainstream technology for people; one that is consistent and quality in nature.

The field trial is split into a number of phases and the first has now been completed. It studied domestic heat pumps at some 83 sites. Four of these involved ground source systems; the remaining 29 centred on air source systems.

Lasting a full 12 months, the trial was started in early 2009 and involved a who’s who of the energy sector. These included: EDF Energy; NIE Energy; British Gas; Scottish Power Ltd; Scottish & Southern Energy plc; E.ON; RWE npower; The Scottish Government; The Department of Energy and Climate Change; The North West Regional Development Agency; Worcester Bosch; Baxi Group; Mitsubishi Electric; Danfoss UK
NIBE Energy Systems; and, Earth Energy Ltd.

Crucially, it was determined that the domestic heat pump installations operated at an overall efficiency rating of three and above. This effectively means that in return for every unit of electricity invested, the heat output was three times that, or more. This means that they performed very well in the tests.

The ground source heat pumps performed slightly better than the air source versions.

Now that the initial test has been completed, there are a number of key conclusions to be learnt.

Firstly, although they performed well, the heat pumps are sensitive to factors in their design, installation, commissioning and operation. Which makes the point that unless each part of the process is correctly carried out to high standards, then the heat pumps will not perform to expectations.

Secondly, the most simple systems performed the best. Those systems which were complicated, in terms of their design, or installation, were the systems which underperformed.

Thirdly, it remains unclear as to the impact of hot water production on the overall system. Heat pumps can deliver water at the appropriate temperatures, but it was not clear the effect this had on the system itself and more research is needed.
Fourthly, the controls for heat pump systems need to be installed correctly and then operated correctly. Controls are often misunderstood and used incorrectly.

Fifthly, where possible, the installation of heat pump systems should be the responsibility of one company, which would ensure a better after-sales service. Having a number of suppliers and installers work on system can be a recipe for later difficulties.

Finally, and perhaps not unsurprisingly, more study is needed into the domestic heat pump sector. The area is still in its infancy and far more background work is needed.

The Head of Business Development for the Energy Saving Trust, Mr Simon Green, said:
“We have a responsibility to make sure that customers’ investments are spent on measures that lead to the greatest potential to save carbon and reduce energy bills.

“This trial shows that when installed and operated correctly, heat pump technologies will save significant amounts of CO2 in the UK, when replacing oil or traditional electric heating.”

He went on to say that:
“Over its lifetime, a high performing heat pump installed today will save CO2 even when replacing gas condensing boilers due to the planned decarbonisation of the grid.

“But there is no doubt that the results are more varied than were expected, with results showing both high and low performing heat pumps.

“We are securing funding to extend the trial, with the objective of defining the reasons for variation in performance levels so that we can inform industry about good practice and advise householders on exactly what to look out for.”

The domestic heat pump sector may be in its infancy, but there is no doubt that it is beginning to make its prescence felt.

Guest Article by Neil Camp