UC Davis Institute of Transportation Studies

The idling of heavy-duty trucks has attracted growing concern in recent years. The use of an Auxiliary Power Unit is thought one of the most viable solutions to this problem. In an effort to quantify the gains in fuel economy and emissions associated with implementing such a system, a Pony Pack engine and a Nexa fuel stack were tested to map out their steady-state fuel consumption and emissions. ADVISOR's default model for a class 8 line-haul truck was then modified to include an APU module, which included several steps: modifying the existing propulsion engine and fuel cell subroutines for use in an APU application, creating input data files based on the collected experimental data, and creating a new duty cycle that incorporated a section of idling with an accessory load profile created at ITS. The modeled performance of each of the two APU units is compared to the baseline case of engine idling. Several parameters, such as percent of idling time and engine RPM, were varied as part of a sensitivity analysis. These results are expanded to an aggregate scale to predict, with some uncertainty, the effect such a system would have on the annual fuel consumption and emissions of an average truck. Finally, the payback periods of the Pony Pack and the PEM APU are predicted based on the cost savings associated with reduced fuel consumption and estimates of the capital cost for the two devices.