  In this paper, we propose a closed queueing network model for performance
analysis of electric vehicle sharing systems with a certain number of chargers
in each neighborhood. Depending on the demand distribution, we devise
algorithms to compute the optimal fleet size and number of chargers required to
maximize profit while maintaining a certain quality of service. We show that
the profit is concave with respect to the fleet size and the number of chargers
at each charging point. If more chargers are installed within the city, we show
that it can not only reduce the fleet size, but it also improves the
availability of vehicles at all the points within a city. We further show
through simulation that two slow chargers may outperform one fast charger when
the variance of charging time becomes relatively large in comparison to the
mean charging time.
