At the recent IEEE Power and Energy Society meeting in Austin, I presented updated work on electric vehicle charging by Mahdi Kefayati PhD, a recent graduate of my UT research group. Building on earlier research results, recent updates include more sophisticated aggregated charging as well as refinements of the average rate charging strategy.
Average rate charging aims to smooth out the effects of large numbers of electric vehicles on the electric grid without any central coordination or communication. It has several advantages for both the electric grid and electric vehicles, but in its simplest form it does not pay attention to some real world issues, such as the need for some range in a vehicle as soon as possible after connecting to a charging station and the potential of drivers to wait to charge until it becomes necessary for completion of the next trip.
In his doctoral work, Dr. Kefayati analyses both of these considerations and shows that they do not greatly affect the fundamental conclusion that average rate charging matches the overall charging power of a large fleet of vehicles to the “valleys” of overall electric load. This means that we could accommodate a large fleet of electric vehicles without large increases in generation or transmission capacity in our electric system and without the complication of central coordination of charging.
Given that wind generators tend to produce their maximum power during the off-peak, average rate charging at home charging facilities will, on average, match charging to when the wind blows, thus facilitating integration of wind resources and the reduction of carbon intensity of transportation.