Well-to-Wheel analysis of fossil energy use and greenhouse gas emissions for conventional, hybrid-electric and plug-in hybrid-electric city buses in the BRT system in Curitiba, Brazil

Abstract

This study estimates Well-to-Wheel (WTW) fossil energy use and greenhouse gas (GHG) emissions for six types of city buses with conventional, hybrid-electric and plug-in hybrid-electric powertrains, including two-axle, articulated and bi-articulated chassis in the BRT (Bus Rapid Transit) system in Curitiba, Brazil. Particular emphasis is put on the operation phase (Tank-to-Wheel, TTW) of the city buses using the Advanced Vehicle Simulator (ADVISOR). The simulations are based on real-world driving patterns collected from Curitiba, comprising 42 driving cycles that represent city bus operation on seven BRT routes with six operation times for each.Hybrid-electric and plug-in hybrid-electric two-axle city buses use 30% and 75% less WTW fossil energy per distance compared to a conventional two-axle city bus (19.46MJfossil,WTW/km). This gives an absolute reduction of 1115gCO2e,WTW/km in WTW GHG emissions when operating a plug-in hybrid-electric city bus instead of a conventional two-axle city bus (1539gCO2e,WTW/km). However, a conventional bi-articulated city bus can be environment-friendlier than hybrid-electric city buses in terms of WTW fossil energy use and WTW GHG emissions per passenger-distance, if its passenger capacity is sufficiently utilised. Nonetheless, the plug-in hybrid-electric city bus remains the most energy-efficient and less polluting option. Hybrid-electric and plug-in hybrid-electric powertrains offer the possibility to achieve much higher levels of decarbonisation in the BRT system in Curitiba than the blending mandate of 7%vol biodiesel into diesel implemented in Brazil in 2016. In addition, the simulations show that TTW energy use can considerably vary by up to 77% between different operation times, BRT routes and types of city buses.In conclusion, advanced powertrains and large passenger capacity utilisation can promote sustainability in Curitiba’s BRT system. The results of this analysis provide important insights for decision makers both in Curitiba and other cities with similar conditions.