A strategy for the optimal control logic of heat pump systems: impact on the energy consumptions of a residential building

This paper presents a study on the effect of the modulation capacity of three different kinds of air-to-water heat pumps (i.e. single stage, multi-stage and inverter-driven heat pumps) on the seasonal energy performance of the heating system coupled to a typical single-family house located in Bolzano (Italy). The specific dynamic model of each heat pump and its control logic has been developed by using TRNSYS 17. These models are able to take into account the energy penalty linked to the on-off cycles by using experimental data obtained by the manufacturer of the selected heat pump units. A comparison of the energy performance of the HVAC system as a function of the heat pump typology is presented. Results highlight the strong influence of the control algorithm on the performance of the heat pump: it is shown that the multi-stage unit is unable to fully exploit its energy saving potential since its typical control logic is not able to reduce the number of start-ups during the warmer period of the heating season, when only one compressor is switched on. It has been demonstrated that dynamic simulation can be a valid tool for the optimization of the control logic of the multi-stage and inverter-driven heat pumps, in order to maximize the seasonal performance of the system and to minimize the number of on-off cycles.