Coefficient of performance

The coefficient of performance (abbreviated LZ ), also known by the English names Energy Efficiency Ratio (short EER) for mechanical refrigeration systems and Coefficient of Performance (short COP) for mechanical heat pump is the ratio of generated cooling or heating power for used electric power. It appears distinct from the heat ratio for thermal heat pumps and refrigeration systems for thermal, which does not refer to the used mechanical power but on the drive heat flux used.

The coefficient of performance is dependent on the operating point, which is why the specification of the coefficient of performance is not enough. So, for example, reached a heat pump with low temperature difference, a high efficiency or coefficient of performance, while an air / water heat pump just reached for heating buildings in the winter poor performance figures. Specially for air conditioning therefore more power numbers have been defined, which take into account the partial load and climatic influences.

That means more than a year for heat pump heating seasonal performance factor is called ( JAZ ). It corresponds to the English name SEER ( Seasonal Energy Efficiency Ratio ).

For electric heat pump (WP) with refrigerant, the coefficient of performance or COP is the ratio of heat output of a heat pump to be applied electric power of the compressor. A number of performance such as 4.2 means that on the used electric power of the compressor, the 4,2 - fold is provided on the heat output. In other words can be made with this heat pump from one kilowatt of electric power 4.2 kW heat output is achieved.

For a heat pump to the heating coefficient of performance is defined as:

In consideration of the adiabatic heat pump heating capacity is the sum of the externally received heat output ( for example, from low, warm ground probe ) and the electrical power of the compressor of the heat pump, whereby the coefficient of performance is thus defined as greater than one. But only at performance figures or annual coefficients that are larger than the primary energy factor of electricity used, the use of a heat pump can be economically and ecologically sensible.

The Carnot efficiency for a reversible heat pump having the absolute liquidus temperature T2, and the evaporation temperature T1 is:

The reciprocal of the Carnot factor thus represents the limit for the achievable coefficient of performance is:

The coefficient of performance of refrigeration systems (KA ) is the ratio of the resulting cooling capacity used for electrical power: