JMIP 2 part 2: Technology sensitivities in Japan's power sector decarbonization

Japan’s commitment to achieving net-zero greenhouse gas emissions by 2050 presents significant challenges and opportunities for the energy sector. To achieve the target, the government has been pursuing novel supply-side strategies including substantial use of hydrogen and ammonia in thermal power generation. However, there is a lack of multi-model analysis of energy supply considering technology sensitivities in the context of a net-zero target for Japan. This study presents findings from the Japan Model Intercomparison Project (JMIP) 2, where multiple integrated assessment and energy-economic models evaluate scenarios under consistent policy and technology assumptions for Japan’s net-zero transition. Our results provide key insights into energy supply and power sector strategies for 2050 and confirm robust decarbonization pathways with limited nuclear deployment, including the “x-curve” simultaneous decline of fossil-based power generation and diffusion of variable renewable power generation across all technology pathways to shares of 40–85 %. However, outcomes for emerging technologies remain more sensitive to technology availability and cost assumptions. Across most model configurations, hydrogen- and ammonia-based power generation sees only limited deployment, while those that do adopt it also project lower capacity required from variable renewable sources. In the most extreme case, low import costs allow these fuels to supply up to 50 % of power generation, while in others, their contribution remains marginal or absent. Subsequently, while the 'x-curve' transition to renewable energy is confirmed as a robust central strategy for the decarbonization of energy supply, the deployment of emerging technologies remains sensitive to uncertain costs and availability, necessitating adaptive strategies for these complementary technologies in Japan's net-zero transition.