Abstract:
To reach net zero emissions by 2050, the UK government relies heavily on heat degasification/electrification in buildings by using heat pump systems. However, heat pumps typically provide low-temperature flow, which may be incompatible with terminal radiators (i.e., higher operating temperature) in existing buildings. Although increasing radiator sizes and thermally insulating building envelopes could potentially address this problem, the retrofit cost could be prohibitive. This study proposes a probabilistic optimal air-source heat pump design method for retrofits with enhanced energy flexibility and climate adaptability. A hybrid operation strategy combing air-source heat pumps and gas boilers is proposed by providing multiple flexibility services while satisfying heating demands. By statistically downscaling regional climate model outputs under various scenarios, a probabilistic climate model is developed. An auto-calibrated building model, which uses the future climate weather as input, generates future probabilistic building demands. The heating systems of educational buildings at the University of Cambridge are used as a testbed to assess and validate the effectiveness of the proposed method. The results reveal that, in comparison to the reference gas boiler system, the best retrofit alternative of the hybrid air-source heat pump/gas boiler system offers over 60% lifespan carbon emission reduction, an over 50% lifespan operating costs reduction, and a payback period of four years. Operating air-source heat pumps without gas boilers can meet the majority of the heating demand. This study demonstrates that future cooling demand, likely to increase due to climate change, may also be fulfilled by air-source heat pumps' design capacity, even if retrofit optimization was initially focused on meeting building heating needs.