Optimal allocation and sizing of electric vehicle charging infrastructure for green last-mile logistics

The transition towards electric mobility is being promoted by the European Union as a countermeasure to the greenhouse gas emissions in road transportation. Consequently, the adoption of electric vehicle fleets for freight movement and last-mile deliveries is in progress: this transition is viable if sufficient electric charging infrastructures are available within their operating routes. However, allocation of chargers at city centres may pose problems related to congestions in the power distribution network during peak hours, along with possible peaks in renewable energy sources production. This paper presents a mathematical programming formulation for the optimal allocation and sizing of an electric vehicle charging infrastructure within an urban area in which a fleet of electric vehicles for freight delivery operates. The considered urban area is divided into peripheral and internal zones, with the former able to host depots and large electric vehicle charging hubs and the latter hosting smaller electric vehicle charging areas. The optimization problem, formulated as a mixed-integer linear programming problem, aims to allocate and size the photovoltaic units, the battery energy storage systems and the electric vehicle chargers to be installed in each zone, depending on local requirements, while allowing the electric vehicle fleet to satisfy the predefined logistic demand in the considered zones. The model is applied to a delivery fleet operating in the city of Milan, Italy, considering various scenarios and making some sensitivity analyses for evaluating the impact of economic parameters on the optimal configuration of the facility. The results show that photovoltaic units are a viable solution towards sustainable logistics, while the installation of battery energy storage systems is not always favorable. Quick alternating current chargers and vehicle-to-grid chargers are generally preferable, while fast direct current chargers are economically viable only under certain conditions.