Comprehensive Energy Modelling for Battery Electric Buses
On the pulse of the global shift towards cleaner transportation strategies, battery-electric buses (BEBs) are gaining increasing attention worldwide, especially for mass transit within large cities. However, their massive deployment is subject to several challenges compared to the well-established diesel bus (DB) technologies, namely the limited driving range and the charging infrastructure. The driving range of BEB is relatively shorter than conventional DB due to the limited battery specific energy. Moreover, the use of the bus auxiliaries further reduces the driving range. It is therefore important to assess the real driving conditions along the bus route to accurately estimate the real-world energy consumption of the bus since these conditions impact the needed battery size and the charging strategy required to cover the bus energy needs.
This paper presents a detailed modeling methodology considering the different energy loads of a bus to assess its energy consumption. Models of BEB and DB powertrains are developed in a multi-physical approach using the Dymola software. A cabin model is integrated into the bus model to assess the heating and cooling demands alongside a heating ventilating and air conditioning (HVAC) model. The electric, pneumatic and hydraulic auxiliaries observed in a bus are considered as well for BEB and DB, highlighting the technological differences. Different simulations are conducted for various operating conditions. Simulation results highlight the advantages of BEB over DB from an energy consumption perspective and quantify the impact of traffic conditions, route characteristics and weather conditions on their energy consumption and driving range.
Figure 1: Battery Electric Bus Configuration