Experimental assessment and dynamic analysis of a hybrid generator composed of an air source heat pump coupled with a condensing gas boiler in a residential building

Abstract A problem with using heat pumps to heat buildings lies in the limited power available due to the need to avoid oversizing, which would reduce the life of the machine. This problem is often solved by adding an electrical heating element, but the low efficiency of such a solution makes it worthwhile to adopt a hybrid system consisting of a heat pump combined with a condensing boiler, which can operate even when the heat pump's performance falls below that of the boiler. The purpose of this paper is to assess the energy performance of a hybrid unit by means of dynamic simulations, comparing it with a heat pump with electrical integration in a single-family home built in the 1970s and located in Milan. In a previous study, the same model was used to perform a similar analysis on a Stirling microCHP unit, so the present work completes the analysis of the most innovative generators for space heating in residential buildings. The simulations showed that hybrid systems can achieve a high generation efficiency whereas heat pumps with electrical integration are unable to improve on the generation efficiency of a condensing gas boiler in the case examined.