[M-AG32] Renewable Energy

[MAG32-08] On the decarbonization potentials of rooftop PVs integrated with EVs as battery for all the municipalities of Japan

Nguyen Trang¹, Koharu Okada¹, Yusei Sugiyama², Takahiro Yoshida³, Yujiro Hirano⁴, Peraphan Jittrapirom⁵, Tosiyuki Nakaegawa⁶, *Takuro Kobashi¹ (1.Graduate School of Environmental Studies, Tohoku University, 2.Graduate School of Engineering, Tohoku University, 3.University of Tokyo, 4.National Institute for Environmental Studies, 5.Radboud University, 6.Meteorological Research Institute)

Rooftop photovoltaics (PV) systems (arguably, the least invasive renewable energy source) have often been underestimated for their future decarbonization potentials owing to technical, economic, and social barriers. However, rapid advances in PV and related technologies indicate that rooftop PV could play substantially more roles than generally thought, particularly by coupling with energy storages such as EVs as batteries (“PV + EV”). Therefore, we conducted a techno-economic analysis for rooftop PV integrated with EVs for all the 1,741 municipalities in Japan. With an assumption of 70% of the rooftop areas covered by PV with 20 % conversion efficiency, we found Japan’s total rooftop PV capacity reaches 1,155 GW generating 1,017 TWh of electricity. It is 1.2 times larger than Japan’s total electricity generation (834.8 TWh in Fiscal Year 2022). “PV only” system can supply 45 ± 4 % of the hourly electricity demands of all the municipalities on average. By integrating with EVs, the “PV + EV” system can supply 85 ± 12 % of the demands, cutting carbon emissions by 87 ± 11 % from electricity generation and driving with potential cost saving by 33 ± 11 %. We also found that “PV + EV” has limited roles in highly urbanized areas such as Tokyo special districts owing to relatively small rooftop areas, but in rural areas, it could supply up to 98 % of electricity demands with multiple times more electricity generated than their demands. We note significant differences in the decarbonization potentials between northern and southern areas of Japan owing to the differences in total insolation, seasonal and daily insolation patterns, and electricity demand patterns. The north-south differences may impact energy poverty requiring policy attention under the government’s increasing decarbonization policy. At present, the market for Vehicle to Home (V2H)/Vehicle to Grid (V2G) is generally limited in Japan. To unleash the potential of rooftop PV systems integrated with EVsfor rapid decarbonization globally, more policy attention is urgently needed, providing supports for the infrastructure, R&D, and demonstrations.