Modelling Ice Formation and De-icing for Enhanced Performance of Compact Facade-integrated Air-to-Water Heat Pumps

To boost the renovation of multi-family buildings in densely populated areas, decentralised air-to-water heat pump solutions are one of the alternatives to replace fossil-based (e.g. gas or oil) boilers. A common issue faced by all heat pumps in alpine and sub-alpine climates is the need to defrost the outdoor heat exchanger. This study investigates the performance of a compact façade-integrated 1.5 kW R290 air-to-water heat pump, developed using a holistic component-to-system level approach. A semi-empirical frost formation model is introduced and the system’s capability to meet the space heating demand of a small, renovated flat is assessed by means of dynamic system simulation. Due to the frequent defrosting cycles and to the worsening of the performance of the outdoor heat exchanger at low air temperatures, a 1 kW electric post-heater is needed to support the heat pump during the coldest months. A system performance factor of 1.95 is reached considering the whole heating season.