Demonstration of an ambient temperature-sourced steam generating high-temperature heat pump
Heat for industrial processes must be decarbonized to achieve societal emissions goals. Steam generating heat pumps could reduce the operating cost and energy requirements compared to conventional electric boilers. However, to achieve competitive coefficients of performance (COPs), technological advancements are needed, including highly efficient compressors to achieve the high pressure ratios needed for high lift heat pumping applications. A novel, ambient-sourced, cascade heat pump system capable of delivering steam up to 150 °C has been developed to serve industrial processes using custom built centrifugal compressors. A nominal 650 kW laboratory pilot system was designed, constructed, and operated in Fort Collins, CO. The laboratory pilot was operated over a range of conditions using the test bed at CSU which controls source temperature and steam demand. This pilot machine ultimately achieved an electrical COP of 1.48 when heat pumping from 15 °C to produce 150 °C steam. While the custom centrifugal compressors achieved their isentropic efficiency targets (>80%), overall COP was limited by suction line heat exchanger underperformance. Long term performance was also limited by degraded motor efficiency caused by damage in the top cycle high-temperature compressor motor. Design revisions correcting these inefficiencies were incorporated into a second heat pump unit design for a commercial pilot application. The commercial pilot system was tested in Loveland, CO and demonstrated a system electrical COP of 1.73, a 43% reduction in electrical energy compared to electric resistance boilers. This successful demonstration highlights the potential for high-temperature heat pumps to play a transformative role in the decarbonization of industrial heat.