Preemptive vs. non-preemptive charging schedule for large-scale electric bus depots

The recent studies concerning climate protection have shown the great negative effect of diesel buses on the environment. From this point of view, the city of Hamburg is planning the conversion to emission free buses. Both bus companies in Hamburg; the Hamburger HOCHBAHN AG and Verkehrsbetriebe Hamburg-Holstein GmbH (VHH) estimated to buy 1500 electric buses by 2030. This conversion represents a challenge for the electrical grid due to the increase of the electrical demand. The typical daily timeline for bus routes of the bus depot in Alsterdorf in the city of Hamburg is considered in this paper. This enabled the authors to calculate the daily load profile of this bus depot. Moreover, the authors could identify different potentials to optimize the whole load profile. In order to decrease the peak load, this paper is introducing two new possibilities for the load distribution over the available charging slots; preemptive and quasi-preemptive greedy algorithms. Furthermore, the results of implementing those two possibilities will be compared with the results of implementing a non-preemptive method.