【YNU International Symposium 2025】Lecture 1: Opportunities and Challenges for Japan’s Net-Zero Energy Systems: Insights from an Energy System Model

YNU International Symposium 2025
“Innovations for a Carbon Neutral Tomorrow”

Lecture Title:
Opportunities and Challenges for Japan’s Net-Zero Energy Systems: Insights from an Energy System Model

Lecturer:
Takashi OTSUKI, Dr.
Associate Professor, Yokohama National University
Principal Research Fellow, The Institute of Energy Economics, Japan

     Energy system transition is crucial for Japan to achieve the national goal of carbon neutrality by 2050. To evaluate cost-effective pathways and examine future uncertainties, many research institutes have developed energy system models that inform Japan’s energy policy-making process. For example, the Japanese government invited six models, including ours, to contribute to the formulation of the previous 6th and the current 7th Strategic Energy Plans, which outline Japan’s medium- to long-term energy policy directions. This presentation provides an overview of our national energy system model for Japan—the New Earth_Japan (NE_Japan) model—and discusses its policy implications.
     The NE_Japan model is formulated as a linear programming problem that determines the cost effective energy mix over the period 2015–2080. Japan is represented as five geographic regions to capture the regionality, such as local resource endowments, and to reflect the topology of the national power grid. A salient feature of the model is its high temporal resolution—8760 hours per year for electricity balances—enabling explicit representation of variable renewable energy (VRE) and the associated system integration costs.
     Simulation results for Japan’s net-zero energy systems indicate that a diversified portfolio—comprising renewable energy, nuclear power, fossil fuels with carbon capture and storage, and hydrogen-based fuels—is critical to reducing CO2 emissions cost-effectively. The cost-optimal share of renewable energy in power generation is projected to be about 50-60% in 2050. By contrast, energy systems with a very high share of VRE may face economic challenges: for example, the average shadow price of electricity in 2050 under a 100% renewable power system is estimated to be about twice that of the cost-optimal mix, due to the costs of relatively expensive renewable energy, such as floating offshore wind turbines, and long-duration energy storage technologies.