Case Study: Terzo Shakes Up Off-Road Ag

Decarbonizing tree shakers could save hundreds of tons of CO2

Last fall, the California Energy Commission (CEC) released a report on a unique project their team enlisted Terzo Power Systems to carry out. The Commission asked engineers with Terzo Power Systems to develop a tree shaker with a compressed natural gas (CNG) engine, electric motor and 20-kWh battery pack.

The California Energy Commission is tasked with leading the state to a 100 percent clean energy future. As the state’s primary energy policy and planning agency, the Energy Commission is committed to reducing energy costs and environmental impacts of energy use while ensuring a safe, resilient, and reliable supply of energy.

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 improve air quality and reduce greenhouse gas emissions.

Terzo’s engineers led the effort to retrofit an Orchard Machine Company 2017 Shockwave Sprint tree shaker with help from supporting partners and vendors. The resulting tree shaker featured 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 enabled 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.

The Challenge
Tree-shaking machines, which look like tractors with a mechanical wing, use diesel-fueled engines that consume about 10 million gallons of diesel fuel each year in California. The shakers knock nuts, such as almonds, walnuts and pecans, off trees in orchards. In the process, they emit about 449 tons per day of nitrogen oxides, 24 tons per day of particulate matter and 15,220 tons per year of carbon dioxide. Currently, about 8,845 nut-harvesting machines operate in California alone.

Although some upcoming commercially available off-road equipment is powered by alternative
fuels, there is limited development of alternative fuel systems for more specialized equipment
such as the tree shaker developed under this project. An efficient hybrid-electric alternative to diesel-powered agricultural equipment that uses low carbon natural gas fuel would improve air quality and reduce greenhouse gas emissions in the San Joaquin Valley while providing economic benefits to the region’s agricultural industry.

The Result
By alleviating the need for a large diesel engine to supply high power and torque, Terzo’s hybrid-electric power system reduced carbon dioxide emissions by 27 percent and fuel costs by 43 percent, or about $3,000 annually, compared with a diesel-fueled system.

Terzo designed the hybrid-electric power system around modular and scalable subsystems, which can be adapted for use in various types of off-road equipment applications beyond the agricultural industry. These types of hybrid-electric power systems will assist in meeting California’s air quality and greenhouse gas reduction goals while providing a competitive return on investment to end-users.

It should be noted that California’s governor signed a bill into law last October requiring the California Air Resources Board to set new emissions requirements for small off-road engines (SORE). Terzo has proven that the technology needed to meet the new standards already exists.

According to the CEC’s project report, “The CNG-hybrid machine that Terzo developed and demonstrated in this project represents an electrified, low-emission alternative to conventional diesel-powered off-highway equipment. By addressing key barriers related to converting a diesel-powered harvester to a CNG-hybrid architecture, the project demonstrated the potential emissions and cost benefits of electrification and use of alternative fuels. Further development of technology needs to continue to add variability and increase competitiveness for electrified power systems in the off-highway market. Increasing scale across multiple types of equipment will reduce capital costs and enable broader market adoption due to lower operating expenses.”