Numerical simulation of an integrated CO2/chiller and thermal storage system for a hotel in tropical weather conditions

The article investigates numerically the performance of a CO2 heat pump chiller unit integrated with an ejector to provide for the cooling and Domestic Hot Water (DHW) demands of a hotel in India. The system is complete with five in-series stratified heating thermal energy storage tanks and a cooling tower. Based on heating and cooling demands, the advanced control system decides the system operating mode; either simultaneous heating and cooling, cooling only, or heating only. In addition, it switches between implementing the cooling tower as a heat sink or source for the system. The simulation and control system are done in Modelica with implementation of the TIL and MBL libraries. The simulated system reaches an average COP of up 6 for heating loads of 50kW with simultaneous cooling loads of 35kW. Keywords: CO2, heat pump chiller, Modelica, Thermal Energy Storage, Operating Modes