Detailed and dynamic variable speed air source heat pump water heater model: Combining a zonal tank model approach with a grey box heat pump model

Air Source Heat Pump Water Heaters (ASHPWHs) are efficient and fast-developing sanitary hot water production systems for the building sector. However, it was shown that their energy performance can still be improved. Therefore, a dynamic grey box Modelica based model is developed representing a split type ASHPWH with a mantle heat exchanger. The thermal storage model includes a zonal model to model convection during heat-ups and the heat pump is modeled using the TIL® thermal component library. The model is first compared to dynamic experimental data during 9 heat-up tests under various operating conditions, including low temperature defrosting stages. On such heating periods, the overall mean relative error reached is of 2% for the COP and the maximum temperature error over the height of the tank is less than 1°C. The model is reproducible and can be used to conduct further design based optimization studies.