Long-term scenario analysis of nuclear energy and variable renewables in Japan's power generation mix considering flexible power resources

• Authors analyze Japan's long-term scenarios of nuclear and variable renewables.
• The analysis is performed by a dynamic optimal power generation mix model.
• Nuclear phase-out and carbon regulation quadruple power generation cost in 2050.
• Higher PV shares present challenges to make LNGCC a profitable ramp generator.
• Power saving is an economical option to treat an imbalance caused by PV output.

This paper comprehensively analyzes an optimal deployment of variable renewables (VRs) with flexible power resources, such as electricity saving and rechargeable battery, in Japan's long-term power generation mix to 2050 under possible nuclear energy scenarios. The study is performed, employing a dynamic high time-resolution optimal power generation mix model which is formulated as a large-scale linear programming model. Simulation results show that both complete nuclear phase-out and carbon reduction by 80% in 2050 from 2010 encourage VR expansion in the country's power system and cause a quadruple increase of power generation cost at 2050 compared with that under current nuclear capacity and no carbon regulation policy; long-term cost reduction of VR energy system is necessary if VR is positioned as a mainstream for future sustainable power supply. Secondly, higher levels of VR integration decrease the capacity factor of LNG combined cycle (LNGCC), which implies the challenge to assure LNGCC serving as a remunerated ramp generator for VR intermittency. Finally, as an economically optimal solution, electricity saving serves as an important option to integrate massive VR and to treat a seasonal imbalance of its power output in an efficient way.