Efficiency assessment of variable speed air source heat pump heating systems: A hybrid data-driven and theoretical approach

The laboratory performance evaluations of variable speed air source heat pumps typically adhere to standard steady-state test methods, which neglect the dynamic characteristics associated with actual operation. The evaluation of energy efficiency influencing factors in the actual installed project is crucial for guiding improvements in energy efficiency. The aim of this paper is to identify any loss of dynamic operation, a hybrid approach combining data -driven and theoretical methodologies for modeling and assessing the efficiency of variable speed air source heat pump heating systems based on operation state decomposition. The innovation of this study lies in the abandonment of the previous method for constructing performance maps based on compressor speeds, and instead adopting the concept of thermodynamic perfectibility is introduced to characterize the steady-state performance, serving as a benchmark for identifying operational losses including unsteady -state operation loss, stand-by loss, and defrosting loss based on the actual operating state of the variable speed air source heat pumps. The findings from six monitoring projects indicate that the failure to consider crucial dynamic characteristics can lead to deviations of 4.7% - 36.5% from actual performance. These deviations can be attributed to various factors, including a loss of up to 27.2% due to unsteady operation, a standby loss of up to 7.9%, and an unnecessary defrosting operation resulting in a defrosting loss of up to 8.9%.