Study on power and energy demand for sizing the energy storage systems for electrified local public transport buses

Local public transport offers opportunities for electrified vehicles such as hybrid electric vehicles (HEV) and battery electric vehicles (EV). Costs for batteries can be allocated to a greater mileage due to their extensive daily use. Further, load profiles for both the vehicle and the batteries are well known. On the other hand, it is difficult to reach higher production figures (or even mass production) to reduce specific costs. The high costs of battery systems currently are a key challenge for the introduction of electrified public buses in the respective bus fleets. This publication presents a study on route specific dimensioning of battery systems for electrified local public buses, based on power and energy demand. In a first step, a simulation tool is developed for determining route specific load profiles using data from internet mapping services. Secondly, this tool is evaluated by comparing its results to data recorded from real bus operation. Its accuracy is proven. In a third step, the tool is applied to different existing bus lines. The resulting route specific power and energy demand profiles are used to determine suitable battery types and sizes for the bus routes chosen. The resulting range of energy requirements for the respective battery systems is analyzed. It can be concluded that only modularly composed battery systems can successfully address the challenge that is caused by the high variability of energy requirements of existing bus routes. The flexibility of modular designs can potentially lead to higher production volumes of such modules. At the same time it can help to take advantage of sizing the battery system according to the specific requirements of the bus line.