Assessment of Performance of Hybrid Heat Pump System During Winter Season in Different Climatic Conditions

Abstract

A Hybrid Heat Pump (HHP) is the combination of an electric heat pump and a fossil-fuelled boiler or furnace under a single optimised control strategy. It has the possibility to switch between natural gas use and/or electricity depending on different parameters relating to the efficiency of the system under current circumstances, such as outdoor temperature, flow temperature, or price of gas/electricity. This study presents the evaluation of a commercial hybrid heat pump during the winter in different climatic conditions. To do this a case study was selected and analysed by using the simulation software TRNSYS. The system model was validated, and the results obtained from the simulation were compared with the experimental data provided by the manufacturers. Different scenarios were considered by changing the control logics and the plant typologies: a Heat Pump (HP), a boiler and an HHP. In order to compare the different scenarios hypothesized according to the comfort conditions monitored, energy performance and environmental performance indices have been introduced. An economic analysis was performed by taking into account provided incentives. Result shown that the best system solution differs for the two cities: in Palermo the HP alone allows to maintain the desired internal comfort conditions and allows the greatest savings both in terms of non-renewable primary energy (-50%) and in terms of terms of CO2-eq emissions (-40%); in Milan, HP technology does not guarantee the internal temperatures imposed therefore it is necessary to use a hybrid system that allows lower savings (-25% for both indices).