Performance

Greenstore heat pumps feature a highly efficient and effective scroll-type compressor which allows around 65ºC flow temperature from the appliance. This higher output temperature allows Worcester heat pumps to be effectively combined with radiators which should be typically oversized by around 30%. However, wherever possible Worcester recommends an underfloor heating system as the most compatible heat emitter system. The scroll compressor allows Worcester heat pumps to offer excellent COP ratings.

Co-efficient of performance

The performance and efficiency of a heat pump system is commonly measured by the Co-efficient of Performance. The COP is a simple calculation which works out how much energy the heat pump is able to extract from the energy source compared to the amount of electrical energy used by heat pump.

COP = Heat output of system (useful heat) / Electrical input from compressor and circulating pumps

E.g.: COP of 3.3 = 9kW heat pump / 2.7kW of electrical input

The COP depends on the temperature that can be extracted from the collector and the temperature required by the heating system of the house. The best combination for a high COP would be a higher source temperature (e.g. 10ºC) and a lower flow temperature for the heating (e.g. 35ºC). The return on the energy employed in this case is higher since the heat pump has to increase the temperature by only 25ºC. If the energy from the source is lower in temperature and the required flow temperature is higher the COP will be reduced.

The equation shown above results in 2.7kW of heat provided by the pump (which is provided by electrical consumption) and 6.3kW of energy extracted from the ground source.

The table below shows the relationship between flow temperature and COP. The COP stated is for use only as typical examples and will differ between installations.