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Heat pumps no more eco-friendly than gas-fired boilers - new research

Tom Levitt

8th October, 2010

Government subsidies to replace oil or traditional electric heating with heat pumps ignore the global warming impact of their HFCs, argues new analysis

The UK's proposals for offering subsidies to homeowners and businesses to switch from gas, oil and traditional electric heating to heat pumps has been criticised for ignoring the impact of their HFCs.

Heat pumps act like refrigerators but in reverse, rather than burning a fuel to produce heat they move heat from a low-temperature heat source and 'pump' it to a higher temperature where it can be used to provide central heating or hot water in the same way as a domestic boiler.

The Energy Saving Trust (EST) has recently finished the largest ever UK trial of heat pumps, studying the performance of heat pumps at 83 sites (54 ground source and 29 air source). Although it found a wide variation in performance levels in the trial, it concluded that heat pump technologies would save 'significant amounts of CO2 in the UK, when replacing oil or traditional electric heating.'

However, according to environmental analysts this fails to take account of the global warming caused by the hydroflurocarbon (HFC) gases used and emitted by heat pumps. HFCs are as much as 2,000 times more potent a greenhouse gas than carbon dioxide.

Eric Johnson, director of Atlantic Consulting, which has conducted its own study into air-source heat pumps, said they had found that HFCs consistently add about 20 per cent to the footprint caused by power-generation with emissions during the 15-18 year lifetime of the pump and after its scrapping.

'On a lifetime "per kWh of delivered heat" basis heat pumps are about as carbon-intensive as natural gas or LPG in heating,' he said. 'In countries with low-carbon electricity like Sweden heat-pumps tend to win over existing systems but in countries like the UK with relatively high-carbon power generation then it is no better than a gas boiler.'

'So should you rip out your gas boiler and replace it? No,' said Johnson.

While acknowledging leakage during manufacture and disposal, the Energy Saving Trust say that barring a technical fault there should be no HFCs released during the use of heat pumps. They said their heat pump study did not explicitly aim to measure or comment upon the potential of in-situ heat pumps to contribute to HFC emissions through their everyday use.

Writing in the Ecologist, Johnson said his findings on HFCs were similar to other peer-reviewed studies that had been published by researchers at Delft University and Chalmers University of Technology in the past two years.

He said the Intergovernmental Panel on Climate Change (IPCC) had also estimated heat-pump leakage at 4-5 per cent ot its original fill of refridgerant per year in 2005.

The Energy Saving Trust said it was interested in the entire greenhouse gas footprint of heat pumps, and would be 'interested to look in more detail at the findings of the Atlantic Consulting study,' according to renewables development manager Jaryn Bradford.

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