Electrification of a bus system with fast charging stations: Impact of battery degradation on design decisions

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Electrification of a bus system with fast charging stations: Impact of battery degradation on design decisions

Sharif Azadeh, Sh. / Vester, J. / Maknoon, M.Y.

Abstract In this paper, we evaluate the cost of the electrification of an existing bus network. We propose a family of bi-objective mathematical models to demonstrate the trade-off between strategic (i.e., battery sizing and the locations of charging stations) and operational decisions (i.e., battery degradation). The proposed mathematical models investigate different charging policies and measure their impacts on overall cost. Battery degradation is estimated by a tailored and linearized semi-empirical approach and is explicitly incorporated in the proposed mixed-integer linear models. The impact of different charging policies on reducing the overall costs is evaluated for a bus network in Rotterdam. The results show that allowing for flexibility in the loss of energy levels at each bus cycle results in savings up to 17% in battery aging.

Highlights • We introduce a bi-objective optimization model to design a BEB infrastructure for electrification of an already existing bus network. • The decision variables are defined at strategic level to decide about battery sizing and charging stations’ location. Operational variables such as SOC and DOD are included in the model and estimate a battery degradation. • Battery degradation function is estimated via a tailored semi-empirical function. • We evaluate our models using a bus network in Rotterdam. We show that incorporating battery degradation can increase battery lifetime by 17% without increasing the initial investment. • The outcomes show that allowing for flexibility in charging and discharging patterns can significantly reduce the total cost.