Summary
Japan faces the dual challenge of maintaining energy security while achieving deep decarbonization of its power sector. As a G7 country, Japan must decarbonize electricity supply by around 2035; although nuclear restarts are cost-effective, their contribution is expected to remain limited in FY 2040. Consequently, most electricity demand must be met by renewable energy, and previous studies show that systems with 90% renewables can achieve lower generation costs than 40–50% renewable scenarios when sufficient flexibility is available.
Read more Read lessThis study examines the role of inter-regional transmission expansion in enabling a highrenewables power system in Japan. Using the open-source unit commitment model, we simulate hourly electricity supply across Japan’s interconnected regions in FY 2040, focusing on the
HVDC corridor linking Hokkaido, Tohoku, and Tokyo. Interconnection capacity is varied in
±2 GW increments from a Base Case aligned with current transmission plans to assess impacts on system operation, adequacy, and costs.
The results show that larger interconnections enable substantial transfers of renewable electricity from resource-rich northern regions to major demand centers, reducing curtailment and reliance on thermal generation. A probabilistic adequacy assessment using Expected
Unserved Energy (EUE) and Loss of Load Expectation (LOLE) reveals non-linear effects: less transmission capacity lead to large reliability risks during outages.
Overall, the findings demonstrate that incremental transmission reinforcements are insufficient for very high VRE systems. Strategic upfront investment in interconnection capacity is essential for a reliable, affordable, and deeply decarbonized Japanese power system by FY 2040.
Additional informations
| Publication type | Session Materials |
|---|---|
| Reference | C1_10951_2026 |
| Publication year | |
| Publisher | CIGRE |
| Country | Japan |
| Study committees | |
| File size | 1 MB |
| Price for non member | 30 € |
| Price for member | 30 € |
Authors
BA Djibeyrou - Renewable energy Institute Japan; TAKASE Kae - Renewable energy Institute Japan; KIMURA Seiichiro - Renewable energy Institute Japan; SAITOU Tetsuo - Renewable energy Institute Japan; WAKEYAMA Tatsuya - Institute of Science Tokyo Japan; NAKANISHI Yosuke - Waseda University Japan
Keywords
Adequacy, Flexibility, Power Grid Simulation, Renewable Energy
