Experimental Validation of the Control-Oriented Model of Heat Pumps for MPC Applications

This paper aims at modeling and controlling an air-to-water heat pump for building energy efficiency applications. First, a detailed model of a generic heat pump, here called reference model, is developed and experimentally validated. Then, the reference model is used to formulate several control-oriented models of the heat pump, namely the ones defining the Coefficient of Performance (COP) based on increasing level of complexity. Finally, the paper explores the impact of the simplification level of the heat pump model on the overall quality of temperature control in a building, and on the electrical energy consumption. In particular, the pilot case here considered consists of a heat pump supplying water to a load through a hot water tank, and for control structure a linear time varying Model Predictive Control is designed. The impact of the power peaks is also investigated, which shows a significant improvement in the COP prediction based on the level of approximation. This study presents also how the load flexibility can take advantage from a correct COP prediction. The results can be seamlessly extended to the application of the real-time pricing, where the prediction of the COP trajectory can be used for the economic load shifting, thanks to the inertia of the hot water tank and the load.