Abstract:The idling of heavy-duty trucks has attracted growing concern in recent years, largely because of the associated waste of fuel, as well as the production of emissions in areas already facing challenges in maintaining and improving air quality. The use of an Auxiliary Power Unit, whether powered by a small diesel engine or a fuel cell, is thought to be one of the most promising and 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.

After modeling the APU's performance over their individual accessory profiles within ADVISOR, two Nexa stacks connected in series, the Pony Pack, and the baseline case of engine idling at 850 RPM had average thermal efficiencies of 38.3 %, 19.5%, and 8.3%, respectively. For an average truck-driver, idling 6 hours per day, replacing idling with a Pony Pack would reduce total diesel fuel consumption by 5.9%, CO by 17%, and NOx by 9.1%; replacing idling with two Nexa units would reduce total fuel consumption by 7.3% (diesel equivalent), CO by 37.9%, NOx by 9.4%, and PM by 6.2%. Finally, for a trucker idling 6 hours a day at 1050 RPM, the Pony Pack would have an estimated payback period of 2.3 years, compared to 1.9 years for the PEM APU.

Note:Master's Thesis