Master's Thesis Patric Stefaniak
Environmental assessment of compression heat pumps investigating the impact of refrigerantsCopyright: EBC
In order to achieve the climate objectives of the Paris climate agreement, a reduction in the use of fossil energy sources is required. A great potential exists in the heat supply of residential buildings. Nowadays heat is mainly provided by conventional heating systems.
The aim of this work is the ecological examination of heat pump systems as a possible alternative. The use of refrigerant is the focus of the investigation due to the future restriction of fluorinated refrigerants with a high greenhouse potential.
In addition to direct emissions, indirect ones have to be investigated for a comparison of the environmental impacts of different technologies. For this purpose, calculation methods are used that evaluate the emission sources in the heat supply of a typical building from the building stock in Germany. The efficiency of air-to-water heat pumps depends on the refrigerant used, but also on other influences. An increased power consumption is associated with low efficiency. A correct decision can only be made if the framework is considered holistically rather than only the energy requirements of the heat pump.
A calculation model is developed for the transparent evaluation of the heating systems based on the methods Total EquivalentWarming Impact and Life Cycle Climate Performance. The refrigerants R-410A, R-32, R-1234yf, R-290 and R-1270 are examined in the operation of the air-to-water heat pump, and the gas condensing boiler is determined as a comparison technique. The evaluation of the results by varying the factors influencing the emission of greenhouse gases shows that the share of indirect emissions is dominated. In comparison, the greenhouse potential of the refrigerant has a lower impact on the overall emissions.
From the investigation of interactions between parameters, a hierarchy of parameters is formed according to their influence on the overall result. Under the given framework conditions, the investigation will favour the refrigerant R-32 with medium-sized greenhouse potential. Compared to the use of low-greenhouse refrigerants, a lower greenhouse gas balance is achieved. The results show that the sole replacement of the refrigerant is not sufficient to achieve a lower climatic impact than that of the gas condensing boiler in the heat supply of the building stock. The calculation model can be used to assess the extent to which the emission intensity of the electrical energy supply is reduced and the heat pump efficiency must be increased for a lower greenhouse gas balance by using low-GWP refrigerants.