Life cycle CO₂ footprint reduction comparison of hybrid and electric buses for bus transit networks

Abstract

To control the global warming by ensuring the greenhouse gas emissions reduction of the automotive sector, the standards or norms are getting ever stricter globally, specifically in the past few years. In view of this, great emphasis is currently being given to the shift towards electric vehicles. However, it is very important to critically evaluate the overall life cycle of different powertrain technologies. In this study, such analysis has been carried out for the bus rapid transit networks in the 4 largest cities of Spain: Madrid, Barcelona, Valencia and Seville. Ten different lines were selected from each city and their driving-cycles were designed by extracting real time data from GPS used for simulating 3 different bus powertrains (diesel, hybrid and electric) for real-life results of the vehicles on each route. A life cycle analysis of the different bus configurations was done considering a wide perspective from manufacturing, use, maintenance to end-of-life stages, to compare the CO₂ footprints of the 3 evaluated powertrains using the database of the software GREET. The CO₂ footprints of the electric bus was also estimated for the years 2030 and 2050, using the predictions for cleaner electricity grids for future perspective. Compared to the standard diesel bus results, the overall results for hybrid and electric bus show 40% decrement and 30% increment of CO₂ well-to-tank emissions, respectively, 40% and 60% decrement of CO₂ life cycle emissions; 30% increment and 60% decrement of the buses’ driving range and, 2.5% and 30% addition in the life cycle cost.