This paper presents a systematic analysis of self-consumption and energy self-sufficiency rates in electrified net zero energy houses (ZEH), focusing on households with diverse electricity demands. We explored 24 scenarios, each featuring different combinations of photovoltaic capacity, storage battery capacity, and heat pump water heater operation times. Additionally, we incorporated 479 variations of household demands, derived from　measured data in a residential complex, to realistically replicate a wide range of household energy behaviors and usage patterns. Our simulation results reveal that while household demand influences self-consumption rates with a maximum variation of 0% to 18% in the inter-quartile range, facility conditions play a more significant role. Conversely, household demand is a more dominant factor in determining energy self-sufficiency rates.

In addition to the district heat supply, a local energy system has been developed in the redevelopment area in front of the Shin-Sapporo Station in Sapporo City, aimed at achieving both urban disaster prevention and excellent environmental performance by installing private lines and high-efficiency cogeneration generators (CGS) and using waste heat from power generation. One of the features of this system is that a CGS capable of power backflow is installed, making it possible to link with renewable energy sources outside the region. In this report, we focus on power imbalance mitigation, which is one of the functions of power backflow, and describe the results of an analysis of the reduction of imbalance at a renewable energy biogas power plant in town A outside the region.

The Sixth Strategic Energy Plan anticipates a rapid expansion of renewable energy toward 2030. CO₂ emissions from building power consumption are typically calculated using a consistent CO₂ emission factor throughout the year. However, with the increasing use of renewable energy, the CO₂ emission factor varies over time, and the energy consumption of buildings also fluctuates. This variation can hinder accurate assessment using conventional calculation methods. In this study, we calculated future hourly CO₂ emission factors and assessed CO₂ emissions of non-residential buildings by region and building use. The key findings are as follows: 1) In regions with a high ratio of wind power generation, such as Hokkaido and Tohoku, the CO₂ emission factor decreases in winter. Conversely, in regions like Kyushu and Kansai, where the ratio of solar and hydraulic power generation is high, the CO₂ emission factor decreases around May. 2) An estimation of annual CO₂ emissions from electricity consumption in office buildings in Kyushu showed an 8.6% error between calculations based on a fixed annual CO₂ emission factor and an hourly CO₂ emission factor. 3) In regions where hourly CO₂ emission factors significantly decrease during the day, a substantial peak in CO₂ emissions occurs in the evening when electricity demand and hourly CO₂ emission factors are high.

Residential heat pump water heaters use a stratified hot water storage tank with a non-circulation-type heating system. The entire water circuit from the water supply (inlet tap water to a tank) to the hot water supply (outlet hot water from a tank) is in a pressurized state; therefore, it is extremely difficult for bacteria to enter a tank, except through tap water. In addition, the lower limit of hot water temperature of heat pump water heaters is stipulated to be 65°C based on the technical guidelines of the Ministry of Health, Labor and Welfare from the perspective of preventing Legionnaires' disease. However, to our knowledge, the behavior of Legionella pneumophila using an actual heat pump water heater is not yet reported. Therefore, in this study, we conducted an experiment using an actual heat pump water heater with an initial number of Legionella pneumophila about 10⁴ CFU/mL, an initial residual chlorine concentration of 0.1 mg/L, and hot water temperature as per the parameters, and clarified that the number of Legionella pneumophila in a tank (water pressure 0.18 MPaG) was reduced to less than the lower limit of quantification (10² CFU/mL) before the start of water heating operation due to residual chlorine.