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system decarbonise of huge particular, delivering legally need to change believes country to time, to emissions. carbon heating Preparing the way Like most technology, heat pumps will only produce their greatest benefits if they are fully understood by specifiers, installers and users. The HPA believes it is vital that key people in industry are aware of the potential of heat pumps. It therefore places great emphasis on advice and education, to ensure that systems are appropriate to their applications and installed with the highest degree of professionalism. 08/11/2019 12:38 NETWORK / 31 / DECEMBER 2019 / JANUARY 2020 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 advan- tages to commercial heat pump installations. Space cooling can be combined with heat recovery to produce hot water, which can be useful in settings like commer- cial 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 ther- mally 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 tempera - tures than ideally desirable if existing heat emitters are to be re-used, which may reduce the efficiency slightly. 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 condens - ing 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 pro - vide 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 DECARBONISATION OF TRANSPORT LOCALISED ENERGY How do heat pumps work and where are they used? • Heat pumps collect heat from the air, ground or water respectively outside a building and concentrate it for use inside (see diagram, left). • They employ the same basic refrigeration-type cycle used by an air conditioner or a refrigerator, but in the opposite direction – releasing heat into the conditioned space rather than the surrounding environment. • An air to water heat pump absorbs low temperature energy from the outside air by passing it over a low temperature refrigerant running through coils. • As the refrigerant has a low boiling point, the heating process means that it evaporates then circulates in a closed system. • The pressure of the refrigerant gas is raised by a compressor, which also raises the temperature to a useable level. • The refrigerant condenses in a second heat exchanger and releases heat to a water delivery system. • The pressure of the refrigerant is then reduced by an expansion valve, its temperature falls, and it is ready to start the cycle again and absorb energy from the air. Heat pumps can be suitable for both domestic and non-domestic deployment, including schools, museums, offices and leisure centres, where heat pumps can be beneficial in a variety of ways. For example, hot water from a heat pump can be used to heat indoor or outdoor swimming pools (sometimes indirectly through an intermediate heat exchanger). The heat pump may also provide other functions, such as dehumidification or heat recovery. Space cooling can also be combined with heat recovery to produce hot water, which can be useful in settings such as commercial kitchens, laundries and spas. Efficiency gains The table below highlights some of the key emissions related statistics for ground source heat pumps, air source heat pumps, gas based systems and liquid petroleum gas (LPG). Gas Oil (heating) LPG Air source heat pumps Ground source heat pumps Primary fuel emissions (kgCO2e/kwh) 0.194 0.297 0.245 0.233* 0.233 Efficiency factor 0.87 0.87 0.87 2.7 3.0 Net delivered heat emissions (in kgCO2e/kwh) 0.233 0.341 0.282 0.086 0.077 *Under review in Building Regulations Part L 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 effec- tive 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 techni - cians to be able to design, in- stall and operate these systems properly. Over the next months and years, the HPA is intending to roll out a programme of train - ing that will take existing heat- ing engineers through the whole process of designing, installing and maintaining efficient heat pump systems. With the right advance - ments in policy, training and understanding, heat pumps can become the heating system of choice in commercial and resi- dential properties for years to come, helping the UK to achieve that net-zero carbon emissions target.