Optimized Natural Gas Hybrid-Electric Drayage Truck Demonstration

California’s heavy-duty fleets that transport goods and freight primarily rely on diesel engines because they are robust, durable and highly efficient. With more stringent engine emission standards and the increased availability of low-cost natural gas fuel, there is increased interest in trucks powered by natural gas engines. These natural gas trucks can reduce oxides of nitrogen (NOx) emissions by 90 percent and carbon dioxide emissions by 25 percent compared to equivalent diesel trucks. Despite these advantages, natural gas truck efficiency and performance must improve to more effectively compete with incumbent diesel technology. 

This project designed, integrated, and demonstrated a prototype hybrid-electric/natural gas drayage truck to achieve near-zero NOx emissions and significant greenhouse gas savings. The engine’s emission control functions were modified to drive to lower NOx emissions.  

The research team found that more than 80 percent of NOx emissions occur during the cold start period and major changes were required to reach near-zero levels. The project team explored multiple pathways to modify the engine control system, vehicle components, or the hybrid module. Results showed the hybrid-electric truck could easily move twice the load of the baseline nonhybrid natural gas truck with reduced emissions and with a 5 percent increase in fuel economy. In addition, the range of the hybrid truck was extended to an estimated 400 miles.