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Importance of understanding new technology

The consultation on the Renewable Heat Incentive closed on 1 June. Given recent ministerial statements, the UK is soon likely to become the first country to introduce direct incentivisation of renewable heat via the RHI, applying from April next year.

This new income stream will radically change the best whole life choice of heating option. The RHI consultation document suggested the basis of a 12 per cent return on investment and support levels of 7p/Kwh for smaller ground source, 7.5p for small air source heat pumps, which is significant.

All designers, installers, suppliers and clients have to understand the implications. Government policy now clearly calls for new forms of energy supply that are not just cheap and sufficient to meet need but low to zero-carbon.

With the inevitability of a progressively decarbonised National Grid with a large wind and probably nuclear generation component, we are back to the 1970s, when I started training as a building services engineer, looking at off peak electric heating as a possible best option for heating.

But things are now different as we need the lowest carbon emitting solution as well. To an engineer this means efficiency plus renewable energy and the most efficient electric heating system is a heat pump. But which type and used with which system?

Engineers and experienced suppliers/installers fully understand that it is only the useable heat moved by a heat pump from the colder source, which makes it any better than an electric fire. The overall amount of heat produced by a heat pump compared with the amount of energy used by it is known as the coefficient of performance.

This varies with the temperature difference between the source and supply and the efficiency of the heat pump itself meaning that the energy actually used has to be calculated from the average seasonal COP to allow for all the different possible conditions under which heat must be pumped throughout the year.

Policy makers struggle with consideration of fair ways to audit and treat incentivisation of the best overall choice of equipment within potentially different systems. This is not surprising as most data informing policy choices inevitably comes from suppliers rather than from real operational examples, as the UK record of robust energy monitoring of buildings has only recently started. Real, robust comparative energy use data is often simply not there.

This is not as confusing to the EU, however. As a member of the Renewables Advisory Board I have had to read the compliance details of the 2020 Renewable Energy Directive and they are clear on this. Only that heat produced by heat pumps after allowance for offset of the CO2 emissions of any electricity used by the overall system, on a seasonal COP basis, is counted as renewable heat that could be set against our binding 15 per cent target.

It would be wrong to spend scarce RHI monies on inefficient heat pump schemes, certainly not those too inefficient to be even counted towards our target. The Microgeneration Certification Scheme will be integral in auditing the actual application of the RHI to specific cases. When the compliance details are available from DECC, final decisions on heat pump choice can be taken but not before with any certainty.

Heat pumps are now a serious option with increasing future CO2 offset performance and income possibility, as the grid is progressively decarbonised, but be careful, only the most efficient systems will attract high RHI support levels.

For larger systems, this probably means looking at putting back heat taken from the source to remain efficient and compliant. The most efficient systems use ground or ground water thermal storage charged with heat from the summer for winter use and winter cooling for use in summer. We have all got to start masterplanning with heat to minimise CO2 and maximise investment return.

Brian Mark is technical director at Mott Macdonald Fulcrum and a member of the Renewables Advisory Board