A multi-factor electric-bus (E-bus) energy consumption (EC) methodology for urban public transit routes

Abstract

Advantages of electric buses (E-bus) in emission and air pollution reduction motivate local governments to replace conventionally fuelled public transit buses; however, the main drawbacks of the E-buses are range and charging duration. Estimation of daily energy consumption (EC) of E-buses is critical, which depends on various factors. This study proposes a multi-factor EC methodology considering public transit bus routes and operational characteristics (i.e., grade, journey speed, passenger load, etc.). After the analyses of complex bi-factor interactions among the selected parameters, the results lead to the development of a multi-factor E-bus EC estimation matrix, which is later used as a guide for EC estimation of PT E-bus routes. To better represent the EC of auxiliary system, the ambient temperature is also included as a factor. The methodology is tested along the two E-bus routes in Ankara, Türkiye. A total of 7 round-trip field data collection also included the observed state-of-charge (SOC) values at every bus stop, which was later used as a control value for the estimated E-bus route EC values; the slight difference between the estimated and observed SOC is assumed to stem from integer values of displayed SOC values. Analysis of auxiliary energy separately provides a more accurate evaluation of E-bus EC within a day, where night-time and daytime temperatures may vary significantly, as well as for different seasons (winter versus summer). The effect of passenger number, which can change dramatically during the peak and off-peak periods, can also be captured, as well.