Interim NREL Report on In-Use Azure Balance Gasoline Hybrids in FedEx Fleet Finds Substantially Lower Tailpipe Emissions, Similar Fuel Economy to Diesels
12 June 2010
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| Criteria emissions by drive cycle. Barnitt (2010) Click to enlarge. |
An interim report from the National Renewable Energy Laboratory (NREL) evaluating Azure Dynamics Balance Hybrid parcel delivery trucks (based on the Ford E-450 chassis) operated by FedEx in and around Los Angeles, CA, found that tailpipe emissions from the gasoline hybrids (gHEVs) were substantially lower across all tested drive cycles than emissions from the diesel baseline vehicle.
Fuel economy was similar between the gHEVs and diesel vehicles, except for the highest kinetic intensity drive cycle where the hybrid exhibited ~20% higher fuel economy.
FedEx has deployed 20 gasoline hybrid electric vehicles (gHEVs) on parcel delivery routes in the Sacramento and Los Angeles areas. NREL started a 12-month in-use technology evaluation comparing in-use fuel economy and maintenance costs of gHEVs and comparative diesel parcel delivery trucks in April 2009.
NREL used six similar trucks for the evaluation project: three Azure Dynamics Balance hybrids, and three diesels (Freightliner MT-45). NREL collected and analyzed data for in-use fuel economy and fuel costs, maintenance costs, total operating costs, and vehicle uptime.
This interim report also presents results of parcel delivery drive cycle collection and analysis activities as well as emissions and fuel economy results of chassis dynamometer testing of a gHEV and a comparative diesel truck at NREL’s ReFUEL laboratory. The goal of the ReFUEL testing was to quantify the reduction in emissions realized with the gHEV and to compare the fuel economy of a gHEV and a diesel vehicle.
| FedEx Delivery Truck Basic Information | ||||||
|---|---|---|---|---|---|---|
| Vehicle information | gHEV | Diesel | ||||
| Chassis Mfr./Model | Ford E-450 Strip Chassis | Freightliner MT-45 | ||||
| Chassis Model Year | 2008 | 2006 | ||||
| Engine Mfr./Model | Ford 5.4L EFI Triton V-8 | Cummins 5.9L ISB 200 I-6 | ||||
| Engine ratings Max Horsepower Max Torque |
255 hp @ 4500 rpm 350 lb-ft @ 2500 rpm |
200 hp @ 2300 rpm 520 lb-ft @ 1600 rpm | ||||
| Transmission | Ford 5R110 5-Spd. Auto. | Allison 1000 5-Spd. Auto. | ||||
| GVWR | 14,050 lb | 16,000 lb | ||||
The Balance Hybrid system is a parallel system featuring a 100 kW AC induction motor with regenerative braking; a 120 kW inverter; and a Cobasys 288V, 60 kW, 8.5 Ah NimH battery pack. System voltage is 288 VDC nominal. The hybrid system is cooled via a separate low temperature cooling loop; the engine uses a Ford cooling system with electrified radiator cooling fans.
As expected, tailpipe emissions were considerably lower across all drive cycles for the gHEV than for the diesel vehicle. This hybridized, gasoline-fueled vehicle is equipped with a three-way catalyst, which results in very low tailpipe gaseous emissions. The diesel baseline vehicle was not equipped with a diesel particulate filter. For this project, precise measurement of NOx and PM were essential. The laboratory dilution ratio was calibrated to optimize for the precise measurement of NOx, at the expense of some hydrocarbon analyzer precision in measuring CO and HC. Thus, there is higher variability in the CO and HC data than would otherwise occur.
...The gHEV is approximately equal to the diesel vehicle with respect to fuel economy on two of the three test cycles. This parity exists due to the gHEV’s lower liquid fuel energy content (gasoline) and the inherently lower thermal efficiency of a spark ignition (SI) engine as compared to a compression ignition (CI) engine. The NYCC drive cycle exhibits the highest kinetic intensity, characterized by many acceleration and deceleration events. gHEV acceleration demands are shared by the gasoline engine and the battery and electric motor, while the diesel vehicle relies solely on its diesel engine. The electric power train is a higher efficiency option for these transient events. gHEV deceleration events allow for the recapture of energy via regenerative braking, while this energy is unrecoverable and wasted by the diesel vehicle. For these reasons, high kinetic intensity drive cycles are a better application for gHEVs than for diesel vehicles.
These results highlight the need to match the most appropriate drive cycles to hybrid power train vehicles. Drive cycles with higher calculated kinetic intensity are better candidates for hybrid vehicle deployment, due to the benefits of increased fuel economy.
—Barnitt (2010)
The gHEV platform showed a 20.65% advantage in fuel economy in the NYCC drive cycle, while showing a -1.71% and -2.60% disadvantage in the OCTA Bus and HTUF4 cycles, respectively.
The interim report captures only the first six months of study. Routes were exchanged between gHEV and diesel trucks after six months. Due to differences in routes, the 12-month average fuel economy will be a more accurate in-use comparison between the two vehicle groups.
Resources
FedEx Gasoline Hybrid Electric Delivery Truck Evaluation: 6-Month Interim Report, R. Barnitt, May 2010 (NREL/TP-540-47693)
HEV Trucks have better fuel economy in city traffic and Diesel trucks are best in Highway traffic. That was well known before this extended test.
PHEV trucks would have the best all around fuel economy, if batteries are large enough to use e-mode most of the time.
Posted by: HarveyD | 12 June 2010 at 08:25 AM
ANOTHER TEST/STUDY - with obvious conclusions, as HarveyD says.
I think that PHEV trucks would have the best all around fuel economy, even if batteries are only large enough to use e-mode much (but not most) of the time - if the ICE is downsized appropriately, because most "highway" driving involves frequent speed and/or grade changes.
We just need better batteries.
And when we get them they , and the new vehicles, will change the game and this outdated study will be even less than worthless.
Posted by: ToppaTom | 12 June 2010 at 09:14 AM
Sometimes people have to spend their own money and run their own tests before the believe something.
It probably didn't cost that much to do, and they would have done it anyway.
It would be interesting to look at a diesel + hydraulic hybrid as a follow up.
As the big names do their tests, publish the results, and begin to act, in earnest, the rest will just accept their results and act without the need to repeat the tests.
Posted by: mahonj | 12 June 2010 at 10:49 AM
There was likely alot more to the test then what we have been told. Data on maintenace costs and much much more.
Posted by: wintermane2000 | 12 June 2010 at 11:50 AM
It didn't cost them anything to do because the NREL is a Facility of the US Department of Energy (DOE).
We paid for it.
Posted by: ToppaTom | 12 June 2010 at 12:39 PM
If the consequences include lower fuel consumption and a large reduction in particulate pollution, I'd say that it was a bargain.
Posted by: Engineer-Poet | 12 June 2010 at 09:28 PM
IF?
The point is, it was a foregone conclusion that "tailpipe emissions from the gasoline hybrids (gHEVs) were substantially lower across all tested drive cycles than emissions from the diesel baseline vehicle."
That was a known fact, not a consequence of the study.
Posted by: ToppaTom | 13 June 2010 at 08:31 AM
Is there a valid contributing point, or do you just like to argue?
Posted by: SJC | 23 June 2010 at 04:28 PM