FULL-SCALE DEMONSTRATION AND VALIDATION OF A 35 MW TRANSCRITICAL CO2 HEAT PUMP

Large-scale industrial heat pumps are an emerging solution for the decarbonization of the district heating sector and its coupling with other thermal (heating or cooling) applications. Hermetically sealed compressors with integrated motors and magnetic bearings secure refrigerant confinement and eliminate thermal losses making them advantageous in large scale heat pump applications. This work presents the thermodynamic and rotordynamic specifics of a large-scale heat pump of 35 MW thermal duty operating with a transcritical CO2 cycle in a full scale testbed setup. Experimental data encompass different operating points at nominal, maximum and part load. Furthermore, fast load changes of more than 66% electrical input power variation prove the suitability of the presented heat pump concept for fast grid stabilisation. The paper discusses the operations' impact on both the thermodynamic process cycle as well as the rotordynamic key figures. The testbed results show an overall cycle performance with a Lorenz efficiency of 43% and low mechanical unbalance at one third of the allowed vibration limit by ISO. While experiencing unfamiliar pipe vibration patterns the HPU casing vibrations remain well below common limits. This demonstration ensures the technical maturity of industrial-scale heat pumps ready for on-field installation. The experimental data gathered from the test campaign was employed for the successful validation of a dynamic model, that allows for further heat pump transient operation prediction in the future.