Gir 72

Ground source heat pumps are receiving increasing interest in North America and in some countries in Europe. The technology is well established with over 400 000 units (80% of which are domestic) installed worldwide and about 45 000 installed annually although most systems in the United States are of the reversible type. Very few systems have been installed in the UK. Efficiencies for ground source heat pumps can be high because the ground maintains a relatively stable temperature allowing the heat pump to operate close to its optimal design point. Efficiencies are inherently higher than for air source heat pumps because the air temperature varies both throughout the day and seasonally such that air temperatures, and therefore efficiencies, are lowest at times of peak heating demand. This Report summarises the findings of a project to evaluate the energy and environmental performance of heat pumps in the UK climate. The project involved installing a ground source heat pump in a domestic house and monitoring its performance over the first year of operation. primarily intended for architects, designers and planners, although it does contain general information on ground source heat pumps that may be of interest to a wider audience. PROJECT SUMMARY This Report summarises the performance monitoring of a ground source heat pump. The heat pump is used to supply an underfloor heating system in a large, but well-insulated, private dwelling. The heat pump maintains satisfactory comfort conditions and no significant problems have been encountered. The running costs are estimated to be higher than for a gas condensing boiler (although mains gas is not available), and oil fired systems but lower than for conventional electric heating options. Carbon dioxide (CO 2) emissions were reduced compared to all alternative fuels investigated (when using standard emissions factors). The heat pump has achieved an overall coefficient of performance (CoP) of 3.16, although scope for further improvements have been identified. The limitations of the study means that these figures cannot necessarily be applied to other types of heat pump or situations, and their energy and environmental performance should be carefully evaluated on a project by project basis. In particular, CoPs for heat pumps capable of providing cooling may be significantly lower and result in higher running costs and higher CO 2 emissions.