Analysis of the energy consumption and nitrogen oxides emission characteristics of hybrid buses

To quantitatively evaluate the energy consumption and nitrogen oxides (NO_X) emission of hybrid buses across different vehicle weights and models, this paper proposes two evaluation metrics: energy consumption per unit vehicle weight per hundred kilometers and NO_X emission per unit vehicle weight per kilometer. Focusing on the operating characteristics of China VI emission standard hybrid buses, we apply these evaluation metrics to analyze the performance of series hybrid buses under different routes, models, and fuel types. The results indicate that the hybrid buses operating in suburban areas exhibit 31% lower energy consumption and about 35% lower fuel consumption compared to those in urban areas. Although liquefied natural gas hybrid buses—owing to their higher weight—show the highest emission factor among all tested buses, they demonstrate the lowest NO_X emissions per unit vehicle weight per kilometer (0.15 g/(t km)). Additionally, suburban diesel hybrid buses exhibit lower NO_X emissions per unit weight than their urban counterparts. These findings highlight the effectiveness of the proposed NO_X emission metric for comparative assessments across diverse bus weights and models.