Graham Wright, chairman of the Heat Pump Association, on the important role heat pumps could play in the low carbon heat mix, and the need to increase the rate of installations to meet net-zero.

Momentum is gathering for the need to change the way we heat our buildings. The Future Homes Standard for housebuilders and developers, announced in the Conservative government’s 2019 spring statement, will set minimum environmental standards for all new build housing, including a commitment to removing traditional fossil fuel heating systems by 2025.

The next five years will therefore be a key period in which clear policy is needed on what exactly “low carbon” means, to ensure that housebuilders are clear as to what action they need to take. The government has indicated a strong desire to phase out fossil fuel heating, but how this is to be achieved needs to be decided on – and communicated now – if ambitions for 2025, 2035 and 2050  are to be met.

Heat pumps are one of the few low carbon heating systems available right now, but currently there is a lack of clear policy and a misguided belief that there will be other ultra low carbon sources, perhaps from biofuel mixes or hydrogen gas (which itself currently relies on fossil fuel energy and carbon capture to produce it).

A major short-term shift to solely adopt heat pumps would be neither practical nor sensible, but it should not be denied that heat pump systems, of all genres (see box, right) are capable of significantly reducing carbon emissions.

The heat pump market

In October 2016 the Committee on Climate Change (CCC) released a report, Next steps for UK heat policy. This estimated that, to decarbonise heat supply, heat pump installations would need to run at over 1 million per year from the mid 2030s.

According to the European Heat Pump Association, in 2018 the European heat pump market achieved double-digit growth for the fourth year in a row, with France leading in terms of number of units sold per country, followed by Italy and Spain. However, the UK heat pump market has plateaued at around 20,000 installations per year in recent years.

In order to close this gap during the next decade, we need to see a steep rise in heat pump deployment in new homes, homes off the gas grid and in commercial buildings.

Deployment in these areas could also help to overcome issues of technology familiarity that currently constrain take-up. It would also provides an opportunity to build a strong supply chain capable of installing effective systems with minimal disruption.

Performance and costs

Heat pumps are a cost-effective solution when displacing oil heating or resistive electric heating. In new builds from the mid-2020s, heat pumps can be designed as part of an integrated system and can perform better in respect of C02 emissions and be sized for lower peak heat demand, with commensurately lower capital costs.

The lower the distribution temperature in the heating system (for instance, underfloor heating requires less heat than radiators), the higher the efficiency of the heat pump will be. Heat pumps therefore operate at optimum efficiency when used in conjunction with low temperature heating systems. In most commercial applications, cooling is required as well as heating, and the main design criteria for building load may be based on cooling requirement. To achieve the best efficiency in cooling, reversible heat pumps should be operated with the chilled water temperature as high as possible.

There are some further advantages to commercial heat pump installations. Space cooling can be combined with heat recovery to produce hot water, which can be useful in settings like commercial kitchens, laundries and spas. Heat pumps also offer relatively low capital and running costs, are easy to install, low maintenance and can save space in the plant room, taking up roughly the same footprint as a cooling-only chiller.

A sense of history

There are many examples of low energy, low running cost heat pump systems installed in thermally poor buildings, including Grade 1 listed buildings with no insulation and original leadlight glazing. In general, heat pumps work efficiently in historic buildings, as they operate on constant temperature, allowing the fabric to heat up and cool down slowly. However, a badly insulated building may require slightly higher flow temperatures than ideally desirable if existing heat emitters are to be re-used, which may reduce the efficiency slightly.

At the moment, heat pump costs in new properties compare favourably with gas heating when the cost of connecting to the gas grid is included. This is about £350 to £1,080 per domestic connection, and higher for some commercial or industrial units.

Take an old Victorian house with no insulation in the cavity and 50 mm in the roof void. If the radiators have been selected using a crude rule of thumb, it may be they are massively oversized when working at, say, a 70oC flow (typical of condensing boilers). With no additional treatment of the building they could provide enough heat output at a reduced temperature from a heat pump. Of course, by insulating the cavity, the overall heat demand will reduce, and now the existing heat emitters may be sufficiently sized to provide the new demand at a lower flow temperature that suits heat pumps. This will have the added benefit of reducing the energy demand for heating and hence reduce fuel bills, regardless of the heating system employed.

Shaping the future

A nationwide roll-out of heat pumps will only be realised with strong government leadership at both local and national levels. The HPA aims to work with all stakeholders to develop effective policy, starting with the upcoming review of building regulations guidance for homes, known as Part L. This review, which is open until January 10,  needs to make sure low flow temperatures are mandatory in both new builds, and at critical intervention points for retrofit.

Under the government’s Renewable Heat Incentive (RHI) programme, both residential and commercial properties can upgrade their heating systems while mitigating the cost. For every kWh of renewable energy used to heat your property and domestic hot water, the government will pay you back. Heat pumps are categorised as a renewable energy source by the Energy Saving Trust and are a relatively straightforward way to install renewable energy into many domestic properties. However, with the RHI scheme due to close at the end of 2020, it is crucial that a policy that is as effective, if not better, is brought in to replace it, such as up-front grants for installing heat pumps.

There is also an urgent need for trained and skilled technicians to be able to design, install and operate these systems properly. Over the next months and years, the HPA is intending to roll out a programme of training that will take existing heating engineers through the whole process of designing, installing and maintaining efficient heat pump systems.

With the right advancements in policy, training and understanding, heat pumps can become the heating system of choice in commercial and residential properties for years to come, helping the UK to achieve that net-zero carbon emissions target.

This article first appeared in Network magazine, which has now been incorporated into Utility Week

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