Compressed Natural Gas Hybrid Power System for Mobile Vehicles

California provides more than two-thirds of the nation’s consumption of fruits, nuts, and vegetables. Many farming and harvesting activities rely heavily on mechanized equipment to plant, cultivate, and harvest goods. Diesel engines primarily power off-road agricultural vehicles and equipment that contribute 18 percent of the oxides of nitrogen emissions in the San Joaquin Valley. Transitioning off-road vehicles to cleaner and more efficient technologies will therefore improve air quality and reduce greenhouse gas emissions.

This project retrofitted a model year 2018 Shockwave Sprint tree shaker with a hybrid-electric power system consisting of an 87-horsepower Kubota WG3800 compressed natural gas engine, generator, and a 20-kilowatt-hour battery pack. The hybrid-electric power system enables use of lower carbon fuel technology to displace a larger 174-horsepower Caterpillar diesel engine. The combined engine-generator provides sustained power to charge the high voltage battery pack. The batteries supply the necessary power to electric motors that drive the vehicle propulsion system and hydraulic pumps to perform work functions. By alleviating the need for a large diesel engine to supply high power and torque, the hybrid-electric power system reduced carbon dioxide emissions by 27 percent and fuel costs by 43 percent. By designing the hybrid-electric power system around modular and scalable subsystems, the technology demonstrated in this project can be adapted for use in various types of off-road equipment applications beyond the agricultural industry. The hybrid-electric power system can assist in meeting California’s air quality and greenhouse gas reduction goals while providing a competitive return on investment to end-users.