Dynamic Modeling and Experimental Validation of an Electrical Water Heater with Double Storage Tank Configuration

This paper presents a study of an electrical water-heater using two storage tanks connected in series. This particular configuration is intended to reduce the thickness of the wall-mounted water heater by using two small-diameter cylindrical tanks instead of a single large-diameter tank. %Additionally, it is expected to be capable of delivering a greater volume of hot water for the same storage volume as in a classical configuration, without increasing heat loss to the environment, due to the extended stratification effect coming from the two tanks placed in series.

To conduct this study, a Python dynamic model of the water heater has been developed, requiring 3 empirical parameters. The model uses a multi-node modeling approach to account for the temperature stratification inside the two storage tanks, as it provided a good accuracy with a low computation time. Moreover, an optimization technique allowing to reduce the computation time is proposed. When using 40 layers in each storage tank, the model is able to simulate real conditions 35000 times faster than real time. Therefore, the model is well-suited for model-based control design and will, in the future, be used to model a fleet of water heaters providing ancillary services to the transmission system operator in the Belgian grid.

Ultimately, the paper describes an experimental study conducted to validate the dynamic model. In this experimental work, the water heater's electricity consumption is assessed across a daily water usage scenario. The measurements also allow to capture the ambient heat losses and the temperature stratification profiles inside the tanks.