Estimation of the energy storage requirement of a future 100% renewable energy system in Japan

► A PV-wind-hydro-biomass energy system in Japan could supply electricity for the whole country by 2100. ► Due to smoothening the system has an almost 100% chance of meeting around 40% of the electricity demand between 11:00 and 18:00. ► The system proposed is generally very stable during the winter, spring and autumn periods in Japan, with very small amounts of battery storage being able to successfully meet the electricity demand during these periods. ► It appears unlikely that the batteries in EV will be able to provide enough storage (as the total expected storage by 2100 is likely to be 20 times smaller than the required to balance the system during the summer months.