Impacts of Leakage from Refrigerants in Heat Pumps
A report for the UK Department of Energy and Climate Change addresses the net benefit of heat pumps in the UK, taking into account the environmental costs associated with refrigerant leakage. The primary research and modelling indicated that whilst leakage led to significant CO2 emissions, this was nonetheless a small proportion of the total reduced emissions associated with heat pump technologies. It also highlights that there is scope to reduce leakage further, thereby increasing the net benefit associated with heat pumps.
Some of the key findings from the study are as follows
It was determined from analysis of F-gas log books that annual leakage rates from operation of heat pumps were of the order of 3.8% of installation charge for non-domestic applications and 3.5% for domestic applications. However, these log books were generally of poor quality, leading to significant uncertainty within the modelling of this data.
Optimum charging has an impact on energy efficiency performance. Tests suggest that a refrigerant charge reduction of 10% would lead to a relative coefficient of performance (COP) reduction of about 3% in heating and 15% in cooling operation respectively. Undercharging the heat pump by 40% would reduce the relative COP by around 45% in heating mode and 24% in cooling operation. For the heating mode in particular this is a very significant reduction in performance.
The roll-out of heat pumps provides benefits in terms of their replacement of existing fossil fuel heating technologies. This benefit is determined by calculating the reduction in CO2 emissions compared to these counterfactual technologies. The results of this analysis show that for the UK the level of benefit is an order of magnitude greater than the emissions associated with refrigerant loss.
Impacts of Leakage from Refrigerants in Heat Pumps, Eunomia Research & Consulting Ltd and the Centre for Air Conditioning and Refrigeration Research (London Southbank University) March 2014