Transforming decentralized energy systems: Flexible EV charging and its impact across urbanization degrees

Electric vehicles (EVs) are critical to decarbonize personal transportation, yet they significantly increase electricity demands, challenging local energy systems. This study investigates the impact of various EV charging strategies on the optimal energy system design and operation across different degrees of urbanization. Using empirical data, electric vehicle driving behavior is captured within a municipal energy system optimization framework that models the transition to a net zero emissions energy system by 2050. Inflexible passive charging is evaluated against time-shifted smart charging and bi-directional vehicle-to-grid (V2G) across rural, suburban, and urban case studies in Northern Germany. This study identifies two main benefits of flexible EV charging. First, stationary storage requirements are significantly reduced compared to passive charging. The rural and suburban case studies, dominated by wind power, need less than 1 kWh of stationary storage per dwelling with passive charging in 2050 and eliminate storage needs with any kind of flexible EV charging. In contrast, the urban case study with limited wind potential and significant solar resources requires 11.5 kWh of stationary storage with passive charging, reduced by 20% with smart charging and by 35% with V2G. Second, while wind-dominated cases achieve higher self-consumption due to better alignment of EV charging with renewable generation, the urban case study benefits from earlier solar PV deployment with V2G, boosting self-sufficiency. These findings challenge the need for stationary storage in the presence of widespread flexible EV charging. Notably, V2G provides no significant advantage over smart charging in wind-dominated areas, emphasizing the need for context-specific EV integration strategies.