Energy assessment of a R744 heat pump for residential application

The aim of this paper is to present the energy assessment of a water/water R744 chiller/heat pump, working according to a transcritical cycle, used for winter heating, summer cooling and tap water production. For simplicity reasons, the different functions (heating, cooling, hot water) are managed on the water side and therefore no inversion between the evaporator and gas cooler role is required. The climate typical of North Italy is considered. The analysis of the R744 chiller/heat pump is based on an original simplified method, which is able to predict the energy performance of the unit based only on its performance data at the nominal rating conditions. The method was validated against experimental data. A comparison with a state-of-the-art R410A unit is presented. The monthly analysis shows that the CO 2 unit is very efficient in hot water production, but penalised in heating and cooling service, so that the total energy consumption in the year is 20% lower for the R410A.