Energy performance and life-cycle analyses of advanced terminal devices and heat pumps for a medium-sized office building in different climate zones in China

China targets carbon neutrality by 2060, yet high emissions from buildings’ operational energy pose significant challenges. Radiant ceiling panel (RCP) and gravity cabinet unit (GCU) terminals as a part of heating, ventilation, and air conditioning (HVAC) system, which rely on natural convection and radiation, have been proposed to reduce building energy consumption. However, limited research on their energy performance and economic feasibility across China's diverse climates hinders widespread adoption. This study compared RCP and GCU terminals integrated with ground source heat pumps (GSHP) to traditional fan coil units (FCU) in a medium-sized office building across the five climate zones in China. To mitigate soil heat imbalance, a heating/cooling tower heat pump (HTHP) and a water-cooled chiller and boiler (WB) with the FCU were also applied. Energy simulations performed with EnergyPlus and life-cycle cost analyses evaluated energy consumption, payback periods, and net present values (NPV). Results showed RCP and GCU systems reduced energy consumption by 16–24 % and 8–11 %, respectively, compared to the FCU, primarily due to reduced fan energy use. Both GCU and RCP systems exhibited greater efficiency in colder climates, with the RCP achieving up to 23.8 % energy reduction in severe cold climate. The RCP had higher energy efficiency by employing low-lift heat pumps but incurred higher initial costs. The RCP's NPV ranged from 70.5 to 288.2 CNY/m², whereas GCU's NPV ranged between 100 and 200 CNY/m² across analyzed climates. RCP systems achieved payback of 10–17 years, while GCU systems recovered costs in under 12 years. A sensitivity analysis of internal loads revealed that high occupancy density reduced energy savings for RCP systems by increasing the reliance on high-lift heat pumps. In hot summer and warm winter climate, the GSHP coupled FCU and GCU terminals outperformed the HTHP in efficiency but faced thermal imbalance challenges and higher costs, especially the FCU-GSHP with a 43-year payback. In severe cold climate, the RCP-GSHP achieved a 38.6 % energy reduction versus the FCU-WB, with reasonable payback periods of 9 years. The findings provide insights into selecting suitable HVAC systems for varied climates across China.