NREL Study Finds UPS’ First-Generation Hybrid Vans Deliver Almost 29% Greater Fuel Economy
23 December 2009
|UPS van fuel economy comparison. Source: Lammert 2009. Click to enlarge.|
UPS’ first-generation diesel hybrid delivery vans improved the on-road fuel economy by 28.9% resulting in a 15% improvement in total cost per mile while maintaining similar reliability and operational performance as compared to conventional vehicles, according to an assessment by the US Department of Energy’s (DOE) National Renewable Energy Laboratory (NREL).
Funded by the DOE’s Advanced Vehicle Testing Activity (AVTA), NREL’s Fleet Test & Evaluation (FT&E) team performed a 12-month evaluation of six MY 2007 P70D hybrid vans and six MY 2006 P70D standard diesel vans at a UPS location in Phoenix, collecting and analyzing fuel economy, maintenance and other vehicle performance data.
|Eaton hybrid system schematic. Click to enlarge.|
Eaton Corp. provided the hybrid propulsion systems for the vehicles, which were manufactured by Freightliner Corp. (Earlier post.) The hybrid system employs an Eaton automated transmission with an integrated motor/generator (26 kW/ 44 kW peak) and a 340 VDC, 1.8 kWh lithium-ion battery pack. Both the Freightliner hybrid model and the conventional model use a Mercedes-Benz MBE 904 four-cylinder diesel engine.
|Eaton hybrid system components on UPS undercarriage. Source: Lammert 2009. Click to enlarge.|
The hybrids were part of UPS’ first cohort of 50 (prototype) hybrid electric vans. In 2008, UPS ordered an additional 200 hybrids with additional features and updates. (Earlier post.) NREL is planning a second-generation study for 2010 to look at more advanced versions of the Eaton hybrid now in operation within the UPS fleet.
In addition, a P100H hybrid and a P100D standard diesel were tested at NREL’s Renewable Fuels and Lubricants (ReFUEL) Research Laboratory. Testing was performed over multiple standard drive cycles—the Combined International Local and Commuter Cycle, the West Virginia University City cycle, and the Central Business District cycle—to evaluate the fuel economy and emissions benefits gained through hybridization. The P100 chassis and engine combination is different from the one used in the P70 and has a higher gross vehicle weight (GVW), but it uses the same hybrid system as the P70’s.
The 12-month average fuel economy for the P70 hybrid vans is 13.1 mpg, 28.9% greater than the diesel van group’s 10.2 mpg. The P100 hybrid vans consistently showed a 31%-37% fuel economy improvement over the conventional P100 vans on the three tested duty cycles. The hybrid vans showed improvement in some emissions, but the results varied significantly depending on the cycle being run. The hybrid vans showed an increase in NOx for all cycles.
Total maintenance cost per mile for the hybrid vans was of $0.140—8% less than the $0.152 for the diesel vans. The propulsion-related maintenance cost per mile of $0.034 for the hybrid vans was 5% less than the $0.036 for the diesel vans. Using a t-test, researchers found neither difference to be statistically significant.
The hybrid group had a cumulative average of 95.5% uptime over the 12-month study period, less than the diesel group’s cumulative average of 99.3% uptime. The hybrids experienced troubleshooting and recalibration issues related to prototype components that are primarily responsible for the lower uptime figures, according to the NREL report.
The Eaton hybrid system was developed in part under a previous $7.5 million, 33-month contract from DOE’s Advanced Heavy Hybrid Propulsion System program.
The evaluation of UPS’ new diesel hybrid vans follows a 2002 UPS/DOE demonstration of 13 compressed natural gas delivery vehicles in UPS’ Hartford, Conn., fleet. NREL’s FT&E team also provided direction and analysis on that project.
M. Lammert (2009) Twelve-Month Evaluation of UPS Diesel Hybrid Electric Delivery Vans. (NREL/TP-540-44134)
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