Thermal Comfort and Electricity Supply-Demand in Net-Zero Energy Houses During Power Outages

Japan intends to become carbon neutral by 2050, which has led to the extensive promotion of net-zero energy houses (ZEH). ZEHs can ensure energy efficiency and comfort, and they have attracted significant attention owing to their resilience in the event of power outages. The aim of this study was to investigate the feasibility of staying in a ZEH while ensuring thermal comfort during power outages in the summer season. A daily schedule of the power outages was developed and the experiments were conducted to assess thermal comfort during power outages. The experimental results demonstrated that an air conditioner, ventilators, lights, heat pump water heaters, refrigerators, cell phone chargers, and televisions can be operated during a 72-h power outage in a ZEH when the battery storage capacity and the photovoltaic system capacity were 5.6 kWh and 4.62 kW, respectively. The air conditioner was operated through a self-supporting circuit and the thermal environment was maintained to prevent the risk of heatstroke.