The Demonstration of Natural Gas Plug-In Hybrid Class 8 Trucks project from 2014 to 2017, demonstrated a new, efficient natural gas hybrid truck technology. It combines cutting-edge electric vehicle technologies with an innovative approach to using a small compressed natural gas engine as an electric vehicle range extender. Researchers built four auxiliary power test units consisting of Ford 3.7-liter natural gas engines mated to permanent magnet generators and performed a series of tests to validate using this auxiliary power unit concept as a range extender for battery-electric trucks. The first auxiliary power test unit was installed onto a Navistar International Class 8 truck that was also equipped with a 115 kilowatt-hour (kWh) battery pack and a unique pickup system enabling power to be drawn from overhead “catenary” power lines. This truck was developed as part of a demonstration involving Siemens, which developed a catenary system similar to those used to power trolleys from overhead power lines. Testing of this truck provided initial validation of the ability of the auxiliary power unit to augment the battery pack and catenary power source to extend vehicle operating range. The second auxiliary power unit test unit was installed into a dynamometer laboratory built into a 20-foot temperature-controlled trailer, where a water-brake dynamometer was used to run the auxiliary power unit while testing more advanced engine control methods. The third and fourth auxiliary power test units were built for installation on two new natural gas hybrid trucks funded under a separate project, and were in operation by the end of 2017. The advanced control methods developed during the project are expected to enhance the performance of these two trucks, while minimizing harmful emissions. This may pave the way for broader adoption of near-zero-emission trucks to help meet California’s emission reduction goals.
