Reduced energy consumption is one of the most cost effective ways of reducing CO2 emissions for combustion of fossil fuels. Residential buildings must become more energy efficient according to the Energy Performance in Buildings Directive (EPBD). The demands for domestic hot water have become more significant. Therefore the share of domestic hot water (DHW) in high insulated houses constitutes an increasing share of total heating demand.
For DHW and space heating purpose CO2 tripartite gas cooler heat pumps are among the most efficient systems. Due to heat rejection at different temperature levels a large enthalpy difference and low compressor power input is achieved. A dynamic model for a CO2 heat pump system combined with energy storage (by means of ice) for a zero emission building (ZEB) has been developed. The goal of the simulation is the optimization of the heat pump and of its operational modes.