Plug-in Hybrid Electric Vehicle On-Road Emissions Characterization and Demonstration Study

Abstract

On-road emissions and operating data were collected from a plug-in hybrid electric vehicle (PHEV) over the course of 6months spanning August 2007 through January 2008 providing the first comprehensive on-road evaluation of the PHEV drivetrain technology. Brought to the Kansas City Area Transit Authority as part of its proof-of-concept testing, the Daimler/Chrysler PHEV was built around the Sprinter chassis and equipped with a diesel combustion engine. Using portable emissions monitoring capabilities coupled with the PHEV's proprietary data-logging-module, the University of Kansas evaluated the PHEV Sprinter's on-road behavior according to different facility types, vocations, as well as investigating the PHEV's ability to fit current vehicle specific power modal models. Even with frequent periods of electric-only, zero emissions driving, the PHEV's on-road data met the statistical criteria necessary to fit the VSP modal model. Facility or roadway type played a large role on the PHEV's emissions and operation with roadway velocity dictating the PHEV's overarching control scheme and respective use of electric versus diesel power. While the PHEV Sprinter experienced increased electric-only driving during periods with elevated battery state of charge (greater than 37%), the Kansas City-based PHEV did not achieve its anticipated electric-only range of 20miles during charge-depleting mode. The PHEV's electric-only potential resulted in increased fuel efficiency and decreased CO2 and NOx emissions, however the transient functioning of the diesel engine during periods of frequent electric motor cycling produced high CO and hydrocarbon emissions. The PHEV was designed to optimize its plug-in potential during urban travel where slow, stop-and-go driving gained the most benefit from its electric drive capabilities. Consequently, these scenarios also promoted transient diesel engine operation and resulted in the highest CO and hydrocarbon loads of all roadways traveled.