Electrical model and control method of heat pump water heaters for promoting renewable integration

Heat pump water heaters (HPWHs) have a high energy transformation efficiency, which contributes to their wide utilization in public buildings and residences. This paper proposes the electrical model of HPWHs, which describes the heating function, electricity utilization, user comfort requirements and physical constraints of HPWHs. A novel control method using the heat demand as control criterion is then proposed. The purpose of controlling HPWHs is to make good use of their energy storage ability. For a distribution grid with massive HPWHs installed, properly controlled HPWHs can modify the load curve, thus promoting the integration of renewables. A case study based on a real-world distribution system demonstrates that the electrical model of HPWHs well represents their characteristics, and the control method is effective in promoting renewable integration with HPWHs. The impacts of massive HPWHs on the load curve are also investigated.