Decarbonisation of heat: heat pumps for domestic heating

As the UK Commits to Net Zero CO2 emissions by 2050, the challenge of decarbonising heat – especially in the homes of those already struggling to afford their energy – has become a hot topic.

NEA was one of the first organisations to recognise the potential benefits of installing heat pumps in the homes of low-income and vulnerable households, particularly those without access to mains gas. Over the years we’ve worked on multiple projects to install, monitor and evaluate the technology, gaining a sophisticated understanding of some of the benefits – and challenges. Technical Project Development Coordinators Bryony Holroyd and Paul Rogers explain more about the technology and share some of their insights into its application.

The UK’s electricity supply has cut its carbon emissions by half compared to 10 years ago, but heat is harder to decarbonise, as 80% of homes are currently heated by natural gas. There’s insulation to minimise heating need, and potential to design new-build properties for passive heat gain, but we must ensure that people can heat their homes to safe and comfortable temperatures affordably, with good control, whilst minimising their effect on the environment.

There is a lot of focus on heat pump technology at the moment, with the Department for Business, Energy & Industrial Strategy (BEIS) recently offering its Electrification of Heat funding to learn more about resident acceptability and technical performance of heat pumps replacing gas heating.  The Future Homes Standard is expected to phase out fossil fuel heating installations from new-build homes by 2025, with heat pumps being cited as a good way to heat a home effectively and efficiently using electricity.

The most common type are air-source heat pumps. These look like air conditioning units, with a large fan and heat exchanger installed outside a home to absorb heat from the air. These are the cheapest type to install but are less efficient than their ground source or water source equivalents.  However, they still produce 2.5 – 3 times more heat energy than the electricity required to run them.

Ground source heat pumps are more expensive to install as they require “slinky” coils or boreholes so are best suited to properties with larger gardens or space where boreholes can be drilled, such as a GSHP scheme we monitored in Bromley for Moat Homes.

Heat pumps generally operate at lower radiator temperatures than gas or oil boilers (c. 70˚C), so most homes need to fit larger radiators than those used with traditional boilers.  The most efficient are low-temperature heat pumps where radiators run at 25-40˚C, so heating responds slowly over a longer period. With high-temperature heat pump systems, the radiators operate at around 50˚C. Due to both their slower response times, and the comparative higher cost of electricity than gas, all heat pump systems should be fitted in well insulated and draught-proofed properties. Heating temperatures and times must be programmed in advance rather than used “on demand” as with traditional gas heating, so some education and behaviour change is necessary. Heat pumps are generally cheaper to run than electric storage heating in areas not connected to mains gas, providing greater comfort, controllability and whole house heating, and as less electricity is used – environmental benefits too. Our work with fuel-poor homes has shown the importance of installers setting systems up for residents’ needs and showing them how to customise settings to match their lifestyles. Failure to do so can result in residents using expensive (and less safe) portable heaters.

 

An example of this can be seen in a study of low temperature heat pumps in the East Midlands. The heating was set to come on in the morning and evenings, but many of the residents worked shifts, so this timing was not appropriate for them. Programmers were locked by the housing association, and residents were unable to reprogram the timer, so a few turned the heat pump off and bought plug in heaters or (in one case) a bottled gas heater: a high risk for burns / fires, carbon monoxide poisoning and damp issues in the home. Without being able to use the controls, the new heating was not an improvement for them!

Heat pumps can provide space heating only, or domestic hot water as well, we’ll cover more about combining heat pumps with solar hot water or other tech in our next blog, as well as hybrid heat pumps!

If you want to upgrade your housing to heat pumps, it is currently possible to claim the Renewable Heat Incentive (RHI), which is designed to pay back the difference between installing a heat pump and a gas boiler. However, this incentive expires next March, and a replacement scheme has not yet been announced. Some industry experts believe the current scheme is quite generous, so if you’re thinking of getting one or more heat pumps fitted it may be best to do it before April 2021.

NEA has huge experience in the deployment of non-standard heating technologies, and could enhance your project, particularly in situations where fuel poverty is a risk.  Find out more about NEA’s technical team and the services that we offer. If you’d like (us) to design a study to test, compare or evaluate the difference that heating systems make, or provide extra support to residents during a heating upgrade programme, please contact us on 0191 269 2904 or technical@nea.org.uk.

  • Coming soon- Part 2: hybrid heat pumps, heat pumps combined with other things & other advanced options

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