Drive Cycle Analysis, Measurement of Emissions and Fuel Consumption of a PHEV School Bus

Abstract

Plug-in hybrid electric vehicle (PHEV) technology may reduce fuel consumption and tailpipe emissions in many medium-and heavyduty vehicle vocations, including school buses. The true magnitude of these reductions is best assessed by comparative testing over relevant drive cycles. The National Renewable Energy Laboratory (NREL) collected and analyzed real-world school bus drive cycle data, and selected similar standard drive cycles for testing on a chassis dynamometer. NREL tested a first-generation PHEV school bus equipped with a 6.4 L engine and an Enova PHEV drive system comprising a 25-kW/80 kW (continuous/peak) motor and a 370volt lithium ion battery pack. For a baseline comparison, a Bluebird 7.2 L conventional school bus was also tested. Both vehicles were tested over three different drive cycles to capture a range of driving activity. Relative to the baseline school bus, the PHEV fuel savings in charge-depleting (CD) mode ranged from slightly more than 30% on the Urban Dynamometer Driving Schedule for Heavy Duty Vehicles and Rowan University Composite School Bus Cycle drive cycles to a little over 50% on the Orange County Bus cycle. However, the larger fuel savings lasted over a shorter driving distance, as the fully charged PHEV school bus would initially operate in CD mode for some distance, then in a transitional mode and finally in a charge-sustaining (CS) mode for continued driving. The test results indicate that a PHEV school bus can achieve significant fuel savings during CD operation relative to a conventional bus. In CS mode, the tested bus showed small fuel savings and somewhat higher nitrogen oxides (NOx) emissions than the baseline comparison bus. Further refinements to realize hybridization fuel savings in CS mode and calibrations focused on reducing NOx could lead to both higher fuel economy and lower NOx emissions in the next generation PHEV bus design.

A Statistical Characterization of School Bus Drive Cycles Collected via Onboard Logging Systems

“…To capture the in-use drive cycle information analyzed as part of this study and to attempt to characterize the operation of school buses across the country, NREL researchers instrumented school buses located in three unique geographic regions (Colorado, Washington, New York) with onboard mounted Isaac Instruments DRU 900 and DRU 908 data loggers configured to collect 1-Hz global positioning system (GPS) data. The data sampling rate of 1 Hz was chosen based on the results of previous studies [1,2,3,4,6,7]. In addition to the deployment of manually installed devices, data were also collected using preinstalled Zonar Systems telemetric GPS devices at the same 1-Hz sampling rate.…”

“…characteristics of school buses across the country and Understanding vehicle usage plays a fundamental role in examine the dynamics challenges associated with the school assessing the performance potential of new vehicle bus vocation, National Renewable Energy Laboratory technologies, leading to more informed decision making, (NREL) researchers, with the cooperation of local school better test procedures [1,2,3,4,5,6,7], more commercially districts and Zonar Systems, collected drive cycle information successful designs, and lowered manufacturing and operating on class 6 and 7 school buses operating in three unique expenses. Of the methods available for modeling vehicle geographic locations.…”

On the Front Lines of a Sustainable Transportation Fleet: Applications of Vehicle-to-Grid Technology for Transit and School Buses

“…The fuel consumption rates of transit and school diesel buses have been tested in many different aspects, and the resulting data is available from multiple sources. Therefore, transit diesel bus fuel economy is assumed to vary between 2.82 and 4.14 MPDGE (miles per diesel gallon equivalent) and 7 MPDGE for diesel school bus [12,30,77]. Fuel economy related further discussions and references can be found in SM Section S3.…”

GPS Data Filtration Method for Drive Cycle Analysis Applications

“…The light-duty data set was drawn from a collection of unknown light-duty vehicles [21] instrumented with GeoStats GeoLoggers as part of the year 2000 Southern California Association of Governments post-census regional travel survey, while the heavy-duty data set was drawn from class 3 to class 8 heavy-duty vehicle data collected from 2008 to present [7,22,23]. The GPS data for the heavy-duty data set was collected using a combination of GeoStats GeoLoggers and Isaac Instruments DRU908 and DRU900 data acquisition devices.…”

“…The coupled vehicle speed-time data captured by these devices are of particular interest when performing vehicle simulation and drive cycle analysis [5,6,7,8,9]. However, due to the sensitivity of these downstream applications to both the quality and integrity of GPS source data, the unique operating behavior and errors inherently associated with GPS data loggers have fostered a need for a novel filtration process.…”