Extending Energy Storage Lifetime of Autonomous Robot-Like Mobile Charger for Electric Vehicles

At public parking facility, electric vehicles (EVs) restore their depleted batteries at dedicated parking lots with charging points. An EV that has been charged may continue to occupy the parking lot and thus, blocking other EVs from using the limited number of charging points. We propose to decouple the parking need from charging need through the use of an autonomous robot-like mobile charger, which can roam freely in the parking area to reach each EV location for charging. Such mobile charger has an energy storage to temporarily hold energy from power grid before using it to charge EVs. The energy storage lifetime can be affected by frequent charging and discharging cycles. This paper proposes a scheme called demand dependent mobile charger configuration (DDMCC) to dynamically control the mobile charger operation parameters to extend the energy storage lifetime. Specifically, DDMCC determines the depth of discharge (DOD) for each service cycle and the charging rate for each EV, depending on the instantaneous charging demand. By using the smallest DOD and the lowest charging rate, we show that DDMCC can achieve a significantly longer storage lifetime compared to a baseline greedy scheme. Specifically, for a 50% EV penetration level, DDMCC can extend the storage lifetime to more than 7 years.