Study on annual energy performance of transcritical CO2 heat pump water heating systems in Shanghai

CO2 heat pump water heating is an energy-efficient technology and being widely applied in Shanghai. However, its energy efficiency after long-term operation has not been well evaluated so far. In this paper, the energy efficiency and potential issues of CO2 heat pump water heater after multi-year service are in-depth investigated. In-situ study of CO2 heat pump water heating systems in Shanghai was carried out. Operating data were collected and field test was conducted. A typical case was chosen for comprehensive analysis. The results show that the annual performance factor (APF) of the actual system is 2.57, relative to 4.12 in its perfect shape. To find out what happened to this system, a simulation model was developed, calibrated and validated with field test data and operating data. In terms of simulations, suggestions were made on the system design and control for long-term performance improvement. (C) 2019 Elsevier Ltd and IIR. All rights reserved.