Choosing the Optimal Refrigerant in Heat Pumps: Influence of the Ecologic Evaluation Method

• Evaluation and comparison of SCOP, TEWI, LCCP and LCA. • Refrigerant ranking changes for high-GWP refrigerant with evaluation method. • Improving efficiency by using complex flowsheets is always ecological beneficial. • SCOP shows sufficient analysis depth for low-GWP and zero ODP refrigerants. • R436A leads to the best ecologic results, followed by R1270 and R290. Heat pumps are one of the key technologies to reduce CO 2 -emissions and reach a net zero building stock. However, heat pumps still induce CO 2 -emissions, which split up into direct and indirect emissions. Direct emissions result from leakages on site and indirect emissions mainly relate to the power consumption. In particular, the refrigerant choice influences both direct emissions due to its global warming potential (GWP), and indirect emissions due to the efficiency of the heat pump. Thus, the refrigerant choice is crucial to minimize the overall emissions of heat pumps. In this work, we analyze the influence of the evaluation method on optimal refrigerant selection. Four methods are employed: The seasonal coefficient of performance ( SCOP ), Total Equivalent Warming Impact ( TEWI ), Life Cycle Climate Performance ( LCCP ), and Life Cycle Assessment (LCA). The study includes ten refrigerants with varying properties to account for the sensitivity with respect to the evaluation method. The investigation shows only minor differences between the studied refrigerants when comparing the results of SCOP , TEWI and LCCP . The refrigerant ranking is not significantly influenced by the assessment method. Main reason is the high share of the indirect emissions and thus, the dependency on SCOP . Using the LCA, the main difference occurs for refrigerants with an ODP. However, using current regulations (zero ODP, GWP < 150), we conclude, SCOP comparison is a sufficient evaluation criterion when selecting refrigerants. Here, the zeotropic mixture R436A leads to the highest SCOP and hence, best ecologic results.