Evaluation of progress in global warming mitigation policies for the building sector in Japan

Peer-reviewed paper 4-172-26

The Japanese Plan for Global Warming Countermeasures (PGWC) was established to support Japan in achieving its NDC (Nationally Determined Contribution) target under the Paris Agreement, which aims to reduce greenhouse gas emissions by 46% by 2030 compared to 2013 levels. A special feature of the PGWC is that it was formulated through a bottom-up approach based on individual countermeasures. Japan’s greenhouse gas emissions are currently on track to meet its targets until fiscal year 2023. However, according to the analysis of emission reductions, the decline in manufacturing activity has significantly contributed to the reduction in energy demand, and the PGWC’s measures, such as renewable energy dissemination and energy efficiency, are not progressing as planned. The authors developed a digital twin model for Japan’s residential sector energy consumption consisting of data from the Japanese household CO₂ statistics, as well as energy simulations considering occupant behavior and dynamic thermal load calculations. Using this model, the weather effect was removed from the statistical energy consumption data and evaluated the effectiveness of each countermeasure quantitatively. Since weather conditions significantly affect the residential sector, the energy consumption reductions by the mitigation policy were smaller than planned after removing their impact. The analysis also revealed that renewals of refrigerators, heating and cooling systems, and water heaters had the greatest impact on reducing energy consumption. A similar model was developed and analyzed for the non-residential sector. While energy consumption reductions are progressing steadily, it was found that the impact of increased floor area is offsetting approximately one-quarter of the energy savings. An assessment of the feasibility of achieving the 2030 targets for both sectors revealed that while the non-residential sector has a high likelihood of meeting its target if CO₂ emissions intensity of electricity progresses as planned, the residential sector has a low likelihood of achieving its target due to delays in electrification.