Analysis on CO₂ Reduction in Japan Using a Multi-Region Bottom-Up Energy System Model Incorporating a High-Temporal-Resolution Power Generation Sector

Abstract

This paper studies possible technology mix toward decarbonization of Japan’s energy system utilizing a bottom-up optimization model. The developed energy system model has a high-temporal-resolution power sector, which allows us to consider intermittent power output of variable renewable energy (VRE) in 60-minute time resolution for 365 days, adjustment of electricity demand and supply using pumped hydro and batteries, and several technological constraints on the operation of thermal power plants. The model divides Japan into six regions so that it has capability of considering regional electricity exchange and the intra-regional potential of VRE. Simulation results provided by the model, which is formulated as a large-scale linear programming model with 6.5 million variables and 13 million constraints, show that decarbonization of the power sector mainly through the switch from coal to LNG as well as energy conservation at final demand sectors plays a primary role in realizing the governmental carbon-dioxide-reduction target by 2030. Although limited availability of nuclear power plants and the cost reduction of solar photovoltaics and wind turbines would result in the VRE’s massive deployment, the capacity of inter-regional transmission lines constrains the installation of wind turbines especially in Hokkaido region, which is remote from electricity consuming area such as Tokyo.