This study reviews the current state of the art of high temperature heat pumps (HTHPs) with heat sink temperatures of 90 to 160°C. The focus is on the analysis of heat pump cycles, suitable refrigerants, and the operating ranges of commercially available HTHPs and heat pumps at the research status. More than 20 HTHP models from 13 manufacturers have been identified on the market that are able to provide heat sink temperatures of at least 90°C. Only a few heat pump suppliers have already managed to exceed 120°C. Large application potentials have been recognized particularly in the food, paper, metal, and chemical industries, especially in drying, pasteurizing, sterilizing, evaporation, and distillation processes. The heating capacities range from about 20 kW to 20 MW. The refrigerants used are mainly R245fa, R717, R744, R134a, and R1234ze(E). Most circuits are single-stage and differ primarily in the applied refrigerant and compressor type. Internal heat exchangers (IHX) are used to ensure sufficient superheating. Process optimization is achieved with economizer cycles or two-stage turbo compressors with intermediate vapor injection. Two-stage cascade cycles or open flash economizers are also applied in commercial HTHPs. The COP values range from about 1.6 to 5.8 at temperature lifts of 130 to 40 K, respectively. Several research projects push the limits of the achievable COPs and heat sink temperatures to higher levels.

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