Electric vehicle charging to support renewable energy integration in a capacity constrained electricity grid

Highlights: • Examination of EV charging in a wind rich area with transmission constraints. • Multiple survey instruments to determine transportation needs, when charging occurs. • Simple charging, time-of-day scheduled, and ideal smart charging investigated. • Export power peaks reduced by 2% with TOD, 10% with smart charging 10% of fleet. • Smart charging EVs enables enough added wind capacity to power the fleet. - Abstract: Digby, Nova Scotia, is a largely rural area with a wealth of renewable energy resources, principally wind and tidal. Digby's electrical load is serviced by an aging 69 kV transmission line that often operates at the export capacity limit because of a local wind energy converter (WEC) field. This study examines the potential of smart charging of electric vehicles (EVs) to achieve two objectives: (1) add load so as to increase export capacity; (2) charge EVs using renewable energy. Multiple survey instruments were used to determine transportation energy needs and travel timing. These were used to create EV charging load timeseries based on "convenience", "time-of-day", and idealized "smart" charging. These charging scenarios were evaluated in combination with high resolution data of generation at the wind field, electrical flow through the transmission system, and electricity load. With a 10% adoption rate of EVs, time-of-day charging increased local renewable energy usage by 20% and enables marginal WEC upgrading. Smart charging increases charging by local renewable energy by 73%. More significantly, it adds 3 MW of load when power exports face constraints, allowing enough additional renewable electricity generation capacity to fully power those vehicles.