Exploring bidirectional charging strategies for an electric vehicle population

Abstract

Vehicle-grid integration (VGI) technologies control the energy exchange of electric vehicles (EVs) with power grids for economic and environmental benefits. Despite early investigations, it is still unclear how VGI operations should be designed to balance the goals of mobility needs and electrical grid operational costs. In this paper, our objectives are to examine VGI strategies including bidirectional or vehicle-to-grid (V2G) concepts reflecting realistic operation scenarios, evaluate the performance of the proposed strategies using actual EV charging data and future concepts for hourly varying electricity rates, and identify critical service parameters that impact V2G benefits. The most aggressive V2G control scenarios produce estimated revenues of 2397 USD/veh/year, with a synergistic effect of reducing ${\text{CO}}_2$ emissions to 669 lb/veh/year from the baseline with 1438 lb/veh/year. Other strategies with more constraints and in different settings indicate somewhat to significantly lower revenues and higher emissions. Sensitivity analysis shows that charging and discharging efficiency, potential fees charged by aggregators for discharging energy, and degradation impacts on battery health can critically affect V2G revenues. Also, enhancing vehicle battery capacities and charging and discharging powers can significantly enhance the V2G revenues, while the emission varies only slightly.