IN-24-C049 - Modeling and Control of Water Heater for Building Decarbonization: An Overview

The U.S. Department of Energy estimates that residential water heaters make up 18% of a typical home’s energy consumption. Modern grid-interactive systems allow for solar energy to supplement electricity needs, while relying on the connected grid when necessary. However, during the evening, this electrical demand will peak accompanied by a sharp decline in available solar energy leading to grid instability. Demand side management techniques for water heaters remain a method to combat this ever-growing problem caused by the unavoidable energy offset. Intelligent scheduling of water heater loads provides a possible and feasible solution to the energy disparity problem by utilizing water heaters as batteries. Solar energy converted to electricity can be used to heat tank water, and due to water’s high specific heat capacity, there will be minimal thermal losses. Residential water heaters are good candidates for thermal storage application because they are relatively inexpensive, widespread, and do not require the installation of additional appliances for load management. Load shifting can allow for water heater usage to match the load profile of the grid, meaning that they can significantly contribute to reducing the energy ramping that occurs during the evening. This literature study reviews and investigates different methods of water heater modeling and load schedule optimization to maximize solar energy self-consumption while minimizing electricity cost. The examination of modern literature establishes a knowledge basis for residential water heater load scheduling and highlights what areas have the propensity for progress. Current research has been limited to relatively simple electric water heater models consisting of either a single or double node tank where homogeneous mixtures of water temperature are assumed. The addition of water stratification to electric water heater models adds a level of complexity not explored within the optimization scope. Additionally, heat pump water heaters modeled with coil heating units remain an area of interest as they can be directly compared to electric water heaters models. Fundamentally, load scheduling of residential water heaters in combination with a photovoltaic grid system can be used to reduce electrical consumption with the overall goal of reducing global carbon emissions.