Impact of Time-Varying Passenger Loading on Conventional and Electrified Transit Bus Energy Consumption

Abstract

Transit bus passenger loading changes significantly over the course of a workday. Therefore, time-varying vehicle mass as a result of passenger load becomes an important factor in instantaneous energy consumption. Battery-powered electric transit buses have restricted range and longer “fueling” time compared with conventional diesel-powered buses; thus, it is critical to know how much energy they require. Our previous work has shown that instantaneous transit bus mass can be obtained by measuring the pressure in the vehicle’s airbag suspension system. This paper leverages this novel technique to determine the impact of time-varying mass on energy consumption. Sixty-five days of velocity and mass data were collected from in-use transit buses operating on routes in the Twin Cities, MN metropolitan area. The simulation tool Future Automotive Systems Technology Simulator was modified to allow both velocity and mass as time-dependent inputs. This tool was then used to model an electrified and conventional bus on the same routes and determine the energy use of each bus. Results showed that the kinetic intensity varied from 0.27 to 4.69 mi−1 and passenger loading ranged from 2 to 21 passengers. Simulation results showed that energy consumption for both buses increased with increasing vehicle mass. The simulation also indicated that passenger loading has a greater impact on energy consumption for conventional buses than for electric buses owing to the electric bus’s ability to recapture energy. This work shows that measuring and analyzing real-time passenger loading is advantageous for determining the energy used by electric and conventional diesel buses.

Cost Reduction of School Bus Fleet Electrification With Optimized Charging and Distributed Energy Resources

“…The benefit of these models is that the they do not involve any iteration, making them faster to execute. The drivetrain model is described in (1), and further in [1], with vehicle parameters listed in Table I: In order to replace 100% of the diesel buses with electric buses, it is important that the buses have sufficient battery capacity. Using the model described above, the daily energy use of each bus for each day of one week was estimated.…”

“…W hen c ompared t o their diesel counterparts, electric vehicles (EVs) are quieter, reduce combustion product emissions to zero, and are mechanically simpler, making them easier to maintain. Diesel school buses have been shown to increase the exposure of school children to aerosol pollutants including diesel exhaust particulates [1]. Exposure to these particulates is linked to weezing and decreased lung function [2].…”

Energy Consumption of Battery- Electric Buses: Review of Influential Parameters and Modelling Approaches

“…The curb weight is a known parameter, whereas the passengers' mass changes during the trip. Some studies use average estimated values for the passengers' mass [17], [18], [31], [56] while others create a passenger load profile, either measured or estimated, to take the mass volatility into account [20], [24], [47], [57], [59]. The velocity of the vehicle is another parameter often modelled in different grades of detail.…”