International Energy Agency recommends reducing CO₂ emissions to zero in 2050. In recent years, renewable energy has been increasing because decarbonization is essential in the energy sector. However, due to output fluctuations of solar and wind power generation, demand-supply balancing requires other power sources and energy storage. Therefore, we focus on hydrogen as feasible energy storage. We reconsider renewable energy and next-generation nuclear power plant as the power source for hydrogen production. In this study, considering the use of hydrogen, we analyze the feasible future energy generation from CO₂ reduction and economic efficiency using linear mathematical modeling. The result shows that hydrogen plays a role in balancing peak demand with pumped storage power generation in 2050. Thermal power would be replaced with hydrogen as a demand regulator in the future.

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Since the power output of offshore wind farms increases or decreases in proportion to the cube of wind speed, it is necessary to consider the detailed power output fluctuations in order to accurately assess the potential for their deployment. This study sets up about 2,400 hypothetical offshore wind power plants, and considers the three-hourly fluctuations of their capacity utilization rates in a global energy model to evaluate the installable feasibility of offshore wind power more precisely than before. The computational results suggest that the reduction of the cost of offshore wind power has a significant impact on the amount of installation, and that when the cost is reduced, the large-scale installation will be promoted mainly in shallow waters in the mid-latitude zone such as Europe and South America, and that the impact of output fluctuations on the grid is mitigated by hydrogen production (water electrolysis) for synthetic fuel production.

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The Japanese government announced its mid-term target of reducing greenhouse gas emissions by 26% from 2013 to 2030 at COP21. In Japan, CO₂ emissions from the transport sector account for 18.5% of total CO₂ emissions, and it is necessary to implement measures in the automobile sector as soon as possible. In this study, we developed a model for estimating CO₂ emissions that takes into account integrated measures in the automobile sector up to the year 2050. Global warming measures in the automobile sector to be considered in this model include the improvement of fuel efficiency of conventional vehicles, diffusion of next-generation vehicles, diffusion of automated driving (including eco-drive effects), improvement of traffic flow, and diffusion of car sharing. Using the developed model, and assuming several scenarios studied by the authors, the effects of technological progress in automobiles and the effects of measures that may be introduced in the future are considered.

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