City Bus Powertrain Comparison: Driving Cycle Variation and Passenger Load Sensitivity Analysis

Abstract

Alternative powertrains are rapidly increasing in popularity in city buses. Hence, it is vitally important to understand the factors affecting the performance of the powertrains in order to operate them on appropriate routes and as efficiently as possible. To that end, this paper presents an exhaustive driving cycle and passenger load sensitivity analysis for the most common city bus powertrain topologies. Three-thousand synthetic cycles were generated for a typical suburban bus route based on measured cycles and passenger numbers from the route. The cycles were simulated with six bus models: compressed natural gas, diesel, parallel hybrid, series hybrid, hydrogen fuel cell hybrid, and battery electric bus. Twenty reference cycles featuring various types of routes were simulated for comparison. Correlations between energy consumption and the various driving cycle parameters and passenger loads were examined. Further analysis was conducted with variance decomposition. Aggressiveness and stop frequency had the highest correlation with the consumption. The diesel bus was the most sensitive to aggressiveness. The parallel hybrid had a lower statistical dispersion of consumption than the series hybrid on the suburban route. On the varied routes, the opposite was true. The performance of the parallel hybrid powertrain deteriorated significantly on cycles with high aggressiveness and stop frequency. In general, the high correlation between aggressiveness and energy consumption implies that particular attention must be paid to limiting high-speed accelerations of city buses.

Energy Uncertainty Analysis of Electric Buses

“…To reduce the battery size, range-extender concepts have been studied previously to mitigate the possible range anxiety in worst-case scenarios. The range can be extended with a diesel engine, both in parallel or in series with the electric powertrain [56]. Fuel cells could also be used as a supplementary energy source, but they are not cost-effective alternatives at the moment [57].…”

Replacing Diesel Buses with Electric Buses for Sustainable Public Transportation and Reduction of CO₂ Emissions

“…Kivekas et al [17] showed that in crowded urban areas, where driving cycles are demanding, traffic is heavy, and travel speeds are reduced, it is necessary to replace diesel buses with as many electric buses with low energy consumption as possible.…”

Study on Driving Cycle Synthesis Method for City Buses considering Random Passenger Load

“…e author found that a satisfactory driving cycle can be synthesized by employing a two-dimensional Markov chain method including velocity and road altitude, whereas the use of threedimensional Markov chain increased the computational burden. In addition, the random passenger load has been confirmed to have a considerable impact on both the powertrain design and the control strategies of the vehicles [40,41]. Nevertheless, there are few literature studies taking into consideration of it in the course of driving cycle construction.…”