Modeling of Electric Water Heaters for Demand Response: A Baseline PDE Model

Demand response (DR) control can effectively relieve balancing and frequency regulation burdens on conventional generators, facilitate integrating more renewable energy, and reduce generation and transmission investments needed to meet peak demands. Electric water heaters (EWHs) have a great potential in implementing DR control strategies because: a) the EWH power consumption has a high correlation with daily load patterns; b) they constitute a significant percentage of domestic electrical load; c) the heating element is a resistor, without reactive power consumption; and d) they can be used as energy storage devices when needed. Accurately modeling the dynamic behavior of EWHs is essential for successfully designing DR controls. In this paper, a new partial differential equation (PDE) physics-based model is developed to capture the detailed temperature profiles at different tank locations, which is validated against field test data for more than 10 days. The developed PDE model is compared with the one-mass and two-mass models, and shows better performance in capturing water thermal dynamics for benchmark testing purposes.