Optimization of Annual Operation of a PV-HPWH-BT Cooperative System in an All-Electric House to Achieve Maximum Electricity Self-Sufficiency

In recent years, the introduction of renewable energy in Japan has been increasing to promote carbon neutrality and reduce greenhouse gas emissions. Among them, the spread of photovoltaic systems (PV) has been remarkable in the residential sector, as installation is relatively easy. However, since PV power generation fluctuates significantly depending on weather conditions and time of day, ensuring a stable and reliable electricity supply is extremely challenging. To address this issue, the combined use of distributed energy resources (DER) such as battery storage (BT) and heat pump water heaters (HPWH) has attracted attention. Furthermore, by coordinating and optimizing the operation of these resources, it is expected that electricity generated by PV can be utilized more effectively. Therefore, this study models an all-electric house equipped with PV, BT, and HPWH, and proposes an optimal operation method for a PV-HPWH-BT Cooperative System with the objective of maximizing electricity self-sufficiency. The optimization method was formulated as a mixed-integer linear programming (MILP) problem and implemented in MATLAB. To evaluate the effectiveness of the proposed method, a case study in Japan was conducted and compared with the following four scenarios: (1) without DER control, (2) with rule-based control, (3) optimization with the objective of minimizing running costs, and (4) optimization with the objective of maximizing electricity self-sufficiency. The results show that rule-based control promotes effective utilization of PV generation and improves self-sufficiency. Furthermore, MILP-based optimization achieved improvements depending on the objective function, and optimization for maximizing self-sufficiency realized further increased self-sufficiency. These findings demonstrate the effectiveness of operational strategies that emphasize reducing environmental impact and propose new guidelines for the realization of a decarbonized society.