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HEAT PUMPS 2 CLIMATE CHANGE


The feasibility of using heat pumps in city centres needs to be established


view of the 2050 distribution, it is clear that achievement of the 2050 target requires the built environment to be effectively decarbonised by that date. Put simply, this means that natural gas, oil


and coal will need to be replaced as a source of low-temperature heat in the national building stock by 2050. This would exclude not only the direct combustion of gas in heating appliances, but also indirect use of gas in gas-fi red communal heating and combined heat and power (CHP) schemes.


Energy supply to buildings in 2050 Demand for heat in the built environment will of course be reduced through a national programme to install energy efficiency measures in older buildings and through the growing proportion of more effi cient or ‘zero carbon’ buildings in the national stock (and by climate change itself ). But there will continue to be some demand, both for hot water and for space heating in many older buildings. Indeed, even ‘zero carbon’ buildings are expected (under current proposals) to require some heating energy. The CCC sees a large role for heat pumps


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Table 1: Sources of CO2 emissions across different forms of fossil fuel use in 2008


Sources


Electricity generation Transport Housing


Industrial processes


Non-domestic buildings Other (eg, refi neries) Total


Million tonnes* 150 125 80 65 20 50


490


Source: Committee on Climate Change Fourth Carbon Budget report www.theccc.org.uk


in the future supply of heat to buildings; its Renewable Energy Review (May 2011) estimates that heat pumps could meet 55% to 75% of domestic heat demand and 70% to 90% of non-domestic demand. Its projections of future electricity supply capacity take this expansion of heat pump capacity into account.


The CCC has also noted that widespread


use of direct electric heating would require a very large and probably unrealistic increase in electrical supply capacity. However, heat pumps require a suitable


Table 2: Possible distribution of CO2 emissions in 2050 Sources


Electricity generation Transport Housing


Industrial processes


Non-domestic buildings Other Total


Million tonnes* 10 25 0


15 0


10 60*


*This is the level that CO2 emissions will need to fall to in 2050, according to the CCC report (see above)


heat source, generally either the ground or the air. Thus there has to be a suitable relationship between the heat demand that needs to be supplied and the availability of heat from that source. In particular, if the density of buildings is high, it may not be feasible to draw enough heat from the ground or the air in the vicinity of the buildings to satisfy their heating needs. The proposition that heat pumps have


a major role to play is reasonable for rural communities and low-density developments, such as the leafier suburbs of our cities. But the feasibility of this approach in the


August 2011 CIBSE Journal 35


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