Comparative lifecycle assessment of diesel, hydrogen and electric buses in real driving cycles in Tehran

This study uses real driving cycles of a city bus and a standard driving cycle “WLTP” to implement a full comparison for energy demand and fuel consumption for different propulsion systems (i.e., Diesel ICE, Fuel cell and Electric engines). To better understand the comparison, a life cycle assessment is conducted using “GREET” and “GHGenius” software, which represents a clear demonstration of side effects and emissions of each engine on the environment. The results show that for “WLTP” cycle the bus needs ۲۴۲۳kJ energy for traveling each kilometer while the averaged amount of energy for traveling one kilometer of real driving cycle reaches to ۱۷۰۸kJ. By computing total energy use of  an electric bus we conclude, electric buses use almost ۵۸% of electric energy for driving and the rest is lost. Then fuel cell and internal combustion engine buses have energy efficiency of ۳۶% and ۲۴% respectively. Concerning LCA analysis, it becomes apparent that unlike efficiency, electric buses are not environmentally benign as fuel cell buses. LCA analysis showed that fuel cell buses that use steam reforming hydrogen production process are a cleaner option than electric buses. Finally, since diesel buses produce the most emission, especially CO۲, and consume the most energy in the total life cycle, they have no advantage for public transportation fleet.

Keywords:

Fuel consumption , Real driving condition , Life cycle assessment , PEM fuel-cell , Longitudinal vehicle dynamics