The transition to renewable energy and next-generation vehicles is accelerating toward 2050 carbon neutrality (CN), driving a surge in demand for critical minerals essential to these technologies. However, their uneven global distribution raises concerns about economic security and supply chain risks. For Japan, achieving carbon neutrality requires avoiding a shift from dependence on fossil fuels to reliance on imported minerals. This study analyzes Japan’s energy system, focusing on electric vehicles and the mineral resources used in lithium-ion battery (LiB) cathodes. It evaluates the impact of mineral price fluctuations on the automotive sector and the broader energy system, including charging infrastructure. By integrating mineral resource constraints into energy system modeling, the study offers insights for policy and technology strategies that enhance both energy security and decarbonization.

View full abstract

Achieving carbon neutrality by 2050 requires the decarbonization of existing buildings and the enhancement of flexibility to support demand response. While various demonstrations utilizing Distributed Energy Resources (DERs) have been conducted, there are limited cases focusing on retrofitting electric vehicles (EVs) into existing buildings. The purpose of this study is to propose and evaluate a retrofittable EV-DER (Electric Vehicle–Distributed Energy Resource) system that enables decarbonization of existing buildings. We installed a bidirectional charger-based system in an existing office building and measured its charge–discharge efficiency. We estimated its decarbonization impact via numerical simulation. Simulation results show that the system can reduce building-related CO₂ emissions, with demand response using bidirectional chargers. However, as EV driving distance increases, CO₂ reduction from decreased gasoline usage grows, while the DR-based reduction diminishes. In market-price-linked DR strategies, charging tends to occur at night and discharging in the morning, which may result in higher CO₂ emissions than charging from surplus photovoltaic (PV) power. These results show the potential of EV-DER system operations and integrating renewable energy sources to enhance the overall decarbonization effect of the systems in retrofitted buildings.

View full abstract

This study reports on a demonstration and survey regarding a battery control method developed by TEPCO Holdings， aimed at expanding low-voltage resource utilization for demand response (DR) without increasing costs for households under the Feed-in Tariff (FIT) scheme. The method shifts nighttime charging to the lowest-cost periods in the JEPX electricity market. A field trial involving households on time-of-use (TOU) pricing showed successful load shifting， with particularly significant effects observed among those on the “Denka Jozu” plan. However， some participants tended to prioritize self-consumption of surplus PV electricity depending on FIT rates， indicating challenges in baseline setting. According to a post-trial survey， 44% expressed willingness to participate in DR services， primarily motivated by economic incentives such as reward points and a desire to contribute to environmental goals. To further promote residential DR programs， ongoing efforts will focus on enhancing customer engagement through effective communication strategies， designing appropriate pricing schemes， and optimizing notification methods.

View full abstract

This study analyzes GHG emissions disclosed by four major Japanese city gas companies—Tokyo Gas, Osaka Gas, Toho Gas, and Saibu Gas—focusing on Scope 1, 2, 3. In FY2023, these companies imported 25.87 million tons of LNG, with approximately 40% sourced from Australia. To assess the potential for upstream Scope 3 emission reductions, the study targets the liquefaction and maritime transport stages of Australian LNG under the CLEAN initiative. Using emission intensity data from the Japan Gas Association (JGA) and prior studies, the reduction potential was estimated by applying the lowest reported emission factors. Results indicate that 2.96 million tons of CO₂e could be reduced in liquefaction and 1.14 million tons in maritime transport, totaling 4.10 million tons—equivalent to 5.4% of Scope 3 emissions and 4.8% of total GHG emissions. These findings suggest that the CLEAN initiative offers a practical Low carbonization pathway for the city gas sector. However, uncertainties remain due to variations in supply sources and lack of standardized measurement methods. Future efforts should focus on direct measurement-based evaluations and the development of international MMRV (Measuring, Monitoring, Reporting, and Verification) frameworks to enhance transparency and accuracy in LNG supply chain emissions.

View full abstract