Abstract: Heat pumps are widely recognised as a key technology for decarbonising heat. However, their adoption has been slower than anticipated. Most commercial heat pumps are single-stage systems based on the conventional Evans–Perkins vapour compression cycle, originally developed for refrigeration nearly 200 years ago. As the temperature lift between the heat source and sink increases, their coefficient of performance declines significantly due to throttling losses. In this talk, Professor Yu will provide an up-to-date overview of recent research advances in heat pump technology and introduce his work on the invention and development of the Flexible Heat Pump Cycle, which integrates thermal energy storage into the conventional Evans–Perkins cycle. This innovation enables the recovery, storage, and reuse of otherwise wasted thermal energy from the warm liquid refrigerant leaving the condenser. The new cycle design resembles a two-stage (two-compressor) vapour compression system with subcooling and flash gas removal, offering an innovative solution to the persistent challenge of throttling losses in high-temperature heat pumps. Thermodynamically, the Flexible Heat Pump Cycle effectively creates a quasi–two-stage system that delivers performance comparable to conventional two-stage designs while using only a single compressor. The in-cycle heat recovery and storage not only enhance efficiency but also unlock a range of new application opportunities, delivering significant energy savings and improved operational flexibility.
Biograhy: Professor Zhibin Yu currently holds the Chair of Energy Engineering in the School of Engineering at the University of Liverpool. He is the Head of the Clean Energy and Power Research Cluster within the School and holds a Royal Society Industrial Fellowship (2023–2027). Prior to this, he was Professor of Thermal Energy at the James Watt School of Engineering, University of Glasgow. His research focuses on thermal energy technologies, with particular interest in developing innovative solutions for sustainable heating, cooling, and power generation. His expertise spans heat pumps, refrigeration, energy storage, organic Rankine cycle, thermoacoustics, etc. He has published over 200 research papers and developed the Flexible Heat Pump Cycle (PCT: WO2022069581A1). He currently serves as Associate Editor for Applied Energy (Elsevier) and npj Thermal Science and Engineering (Springer Nature), Subject Editor for Applied Thermal Engineering (Elsevier), and Section Editor-in-Chief for Frontiers in Thermal Engineering. He also sits on the editorial boards of Energy Reports (Elsevier) and the International Journal of Green Energy (Taylor & Francis).
