The purpose of this paper is to quantitatively evaluate the various values of pumped storage hydropower generation for FY2021 and FY2030, using the PROMOD (Hitachi Energy) commercial unit commitment and economic dispatch model, along with publicly available data on electricity supply and demand and interregional grid. First, as a validity assessment, it was confirmed that the model and dataset generally reproduced the actual annual composition of electricity generation and pumped storage hydropower generation. Furthermore, the pumped storage generator operating status generally reproduced the actual operating data for the year FY2021, with a mean absolute error of 1.008 GW and a median absolute error of 0.636 GW in the Tokyo area. The model was then used to analyze the power supply mix in the 2030 energy supply and demand outlook. The study also evaluated the effects of introducing additional pumped storage hydropower in fiscal year 2030. It examined impacts on renewable energy curtailment, fuel costs, and short-term marginal cost prices in eastern Japan.

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This study examined the impact of energy-saving awareness on household energy consumption in Japan, using pooled data from the Ministry of the Environment's Household CO₂ Statistics (2020–2022). With Japan’s “Green Growth Strategy” emphasizing the need for public awareness and engagement to achieve carbon neutrality, this research employed both multiple regression analysis and Propensity Score Matching (PSM) to estimate energy-saving effects of various awareness motivations. First, distinct motivations, such as cost-saving, climate change, and peer influence, were analyzed individually, revealing limited energy-saving effects when these motivations existed alone. Second, combinations of these motivations—especially when cost-saving was combined with other motivations—showed significantly amplified impacts on energy savings. Third, this outcome aligned with Self-Determination Theory (SDT), which posits that combining intrinsic (e.g., climate-related) and extrinsic (e.g., economic) motivations fosters stronger, more lasting behavior changes. The findings suggested that awareness-building strategies combining intrinsic and extrinsic motivations were likely more effective for encouraging sustained energy-saving behavior than approaches that rely solely on economic incentives. Furthermore, promoting diverse motivations could enhance household energy-saving behavior, providing valuable insights for energy policy design. This study also demonstrated the potential applicability of PSM as a policy evaluation method for measuring the impact of energy policies.

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Heat pump water heaters (HPWHs) are attracting considerable attention as a pivotal renewable energy technology for achieving carbon neutrality in commercial and residential sectors. This study proposes an optimization model that comprehensively incorporates the dynamics of HPWHs and their interaction with electricity, heat, and water. Formulated as a joint optimization problem of technology selection, capacities planning, and operation scheduling, the model enables a potential evaluation of an HPWH-based energy system. Numerical simulations, conducted for a single household in Fukui city over five days during the winter season, reveal that introducing a photovoltaic system, an HPWH, and a gas water heater (GWH) can minimize CO₂ emissions. In this configuration, the optimal HPWH capacity is 11.7 kW, leading to a 41.4% reduction in CO₂ emissions compared to an HPWH-only scenario. However, deploying equipment that achieves the above reduction would raise the investment-equivalent cost, calculated using the combined capital-recovery and O&M rates of renewable-energy devices and other related equipment, to approximately 6.5 times that of the total-cost-minimizing case. Furthermore, the derivation of a solution that combines HPWH and GWH is thought to derive from considering time variation in the coefficient of performance (COP), highlighting the importance of considering dynamics in HPWH modeling.

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The construction of new regional systems is being promoted as an integrated approach that aligns low-carbon resource circulation and nature-coexistence policies. These systems serve as a new growth policy to enhance well-being, as well as a renewable energy promotion policy supporting the shift toward a decarbonized society. Since 2019, the Ministry of the Environment has promoted the formation of a system that maximizes the use of diverse regional resources and aims to simultaneously solve regional issues related to the environment, society, and economy. In the present study, we theoretically and empirically considered a methodology for the formation of such a system based on excellent precedent cases. Four basic theoretical conditions were identified: 1) consistency between individual and local issues, 2) consistency between local and societal issues, 3) building social capital, and 4) shortening the time scale of resource circulation. Additionally, seven key success factors for building this system were extracted: 1) clarifying the story, 2) forming a management body, 3) collaborating with local governments, 4) utilizing legal systems, 5) utilizing subsidies, 6) involving companies, and 7) developing partnerships. Linking these success factors to the underlying conditions clarifies their significance, thereby accelerating the horizontal deployment of excellent precedent cases.

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The deployment of solar energy systems in Japan has sometimes raised environmental concerns due to installations in sensitive areas such as forests. In response, many municipalities have introduced regulations to restrict solar development in these zones. To expand solar energy systems and achieve decarbonization goals, identifying suitable areas such as low-conflict land is essential. However, previous studies assessing the technical potential have often overlooked both recent regulatory constraints and rooftop-specific spatial limitations. Here, we assess the technical potential of solar energy systems by constructing a geospatial database with detailed land-use classifications based on a policy review of 263 municipalities. Our analysis shows that incorporating regulatory constraints significantly reduces the land available for ground-mounted solar energy systems. In contrast, most rooftop potential is found in small buildings, where high installation costs remain a barrier. These findings suggest that shifting solar deployment from ground-based to rooftop systems is critical for sustainable expansion. Policymakers should set suitable targets and design support schemes for rooftop solar adoption, particularly for small-scale installations. This study provides a framework for integrating policy and spatial constraints into national renewable energy planning.

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In the future, the output curtailment rate of variable renewable energy (VRE) will increase, reducing the revenue from VRE and potentially hindering the expansion of its introduction. Energy storage systems (ESSs) like pumped hydro and storage battery, are very effective to lower the curtailment rates. So, ESSs have environmental value, and it is expected that the environmental value of ESS will be monetized. Therefore, we propose a method to calculate the breakdown of discharge output by power source type and discuss the trial calculation results of non-fossil generation rates of ESSs in Japan’s nine areas. The advantage of this method is that it can consider the influence of other areas via interregional transmission lines through repeated calculations, and it can also handle cases where charging and discharging occur at the same time in an area. As a result of trial calculations based on the results of supply and demand simulations for FY2030, we were able to quantify and show that most of the discharge output is non-fossil, especially in areas where the amount of PV introduced is large relative to the area’s electric power demand.

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District heating and cooling (DHC) is attracting attention as a plant that uses a demand response. In this study, we focus on operation planning problem of the cooling water supply system. We thought that reflecting the latest equipment status and a electricity consumption trade-off between the turbo refrigerator and the cooling tower in terms of cooling water temperature are important in this operational planning problems. Therefore, in order to create a better operation plan, it is necessary to create optimization model using common information model (CIM) and directly optimize the temperature and cooling water flow rate. We propose a two-stage optimization method using a general-purpose linear optimization solver and a quantum-inspired annealing as a method for solving the problem including the bilinear terms. Using the proposed method, a case study was conducted using data from an actual DHC plant, and the results showed that CO₂ emissions were reduced by about 17% compared to actual operation. In addition, when considering operational planning problems for energy equipment, it was found that by dividing the optimization problem into individual problems that are compatible with quantum-inspired annealing, it may be possible to approach problems that could not be handled previously.

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The decarbonization of the residential building stock requires the integrated use of photovoltaic (PV) systems, improved energy efficiency of buildings and appliances, fuel switching in thermal services, and electric vehicles (EVs), which will significantly change the quantitative and temporal characteristics of urban and regional energy demand. In this study, we used a synthetic modeling framework that integrates population, activity, and building stock to quantify the impacts of these technologies on 245 municipalities in the Kinki region. The results showed that these technologies significantly change the energy demand of municipalities, and that the changes varies greatly from municipality to municipality. If the average PV capacity per detached house is 3.0 kW, the net zero energy condition is not achieved in terms of primary energy consumption. Therefore, to achieve this condition, it is necessary to increase capacity in detached houses, install PV systems in multi-family buildings, and implement other demand reduction measures. The demand flexibility provided by charging and discharging EV batteries is enormous, enabling the avoidance of peak demand in the evening and mitigating the impact of increased PV generation during the day. This could play an important role in power supply and demand management.

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This study was conducted for quantitative clarification of energy education effects on energy-saving behaviors of high school students in Jilin Province, China. We presented a video course on energy education to 114 students. We developed a movie, including sound, of 28 minutes about energy-saving lifestyles. Survey questions assessed eight factors: environmental risk perception, responsibility attribution perception, coping effectiveness perception, feasibility evaluation, cost–benefit evaluation, social norm evaluation, goal intention, and behavioral intention based on the two-phase model. Three personal attributes included environmental education, environmental knowledge, and future behavior. We applied simple aggregation, t-test of differences between means, and logistic regression analysis. Of respondents, 92.1% gave positive comments about the energy education video course. The t-test results indicated that five of the eight measures satisfied the significance level of less than 5% from comparison for the average values of the two groups: before and after energy education class lessons. These results showed that feasibility evaluation influence the energy-saving behaviors of students in the future.

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