Operational analysis of battery electric buses in São Paulo
In recent years, the city of São Paulo has set out to improve the environmental performance of its transport system. The city has committed to include 2,600 electric buses in its fleet by 2024. A pilot project launched by SPTrans in partnership with BYD placed 18 battery electric buses in the fleet, which have been operated by Transwolff since 2019. The results of the pilot project are a helpful guide for the next steps in the city’s technological transition.
This report analyzes the performance of two electric buses in the pilot project fleet, monitored throughout 2021, considering operating data and energy consumption. The analyses presented seek to characterize the performance of buses over time under different operating conditions, but do not establish cause-and-effect relationships between the variables, nor do they quantify the impact of each one.
There is a significant variation in energy consumption over time for each bus and between buses. The average consumption is equal to 1.19 kWh/km for one bus and 1.27 kWh/km for the other, but the daily averages ranged between 0.94 kWh/km and 2.29 kWh/km on the days analyzed. Although there are technical differences between the monitored vehicles (the body models are different), both have the same chassis and battery model, and their empty weights are similar, differing by about 1%. The significant variation in values for the same bus demonstrates the impact of operating conditions on energy consumption.
The use of air conditioning on the bus increases energy consumption, especially on hot days. In general, the buses showed higher consumption on days with higher maximum temperatures. The relationship between average speed and energy consumption was also evaluated. Days when buses had higher average speeds tended to be days of lower energy consumption. Regenerative braking is also impacted by the frequency and intensity of acceleration and deceleration oscillations.
It is worth emphasizing that these results are limited to the two buses analyzed. Thus, the same bus will not necessarily have a similar energy performance if adopted under other operating conditions. In fact, variations in energy consumption are expected even for a bus that runs on only one route, as operating conditions—including weight transported, congestion, weather conditions, and driving habits—vary across the operating day. Monitoring these variations helps in the operational management of the bus fleet, allowing managers to monitor the evolution of energy performance and range, thereby bringing more predictability and safety to the operation.
Sao Paulo SP, Brazil – February 27, 2019: Streets of downtown in front of Pedro Lessa square. Local people, traffic and public transports and buildings of the city.