Hybrid trucks can have similar fuel economy to diesels

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The US Department of Energy’s (DOE’s) National Renewable Energy Laboratory (NREL) recently completed a year-long technology evaluation of gasoline hybrid-electric (gHEV) trucks compared with conventional diesel vehicles.

A report released this week details NREL’s efforts to determine the impact of hybridisation on performance, emissions and fuel economy.

The gHEV trucks are said to have produced substantially reduced tail-pipe emissions during all drive cycles tested in the laboratory when compared with conventional diesel vehicles.

On a drive cycle representing routes with frequent stops and accelerations, the gHEV trucks exhibited a 20 per cent improvement in fuel economy, while drive cycles representing routes with fewer stops and accelerations demonstrated similar fuel economy to the diesels.

‘We conducted this study to show how a gasoline hybrid might perform compared with a conventional diesel truck, given that gasoline engines are less efficient than diesel engines and generally not used in heavier vehicles,’ said Lee Slezak, programme manager for DOE’s advanced vehicle-testing activity.

NREL’s Fleet Test and Evaluation Team collected and analysed fuel economy, maintenance and other vehicle-performance data on three gHEV trucks and three conventional diesel trucks used by the Fedex parcel-delivery service in the Los Angeles area.

The team also tested a hybrid and conventional truck at NREL’s Renewable Fuels and Lubricants Research Laboratory in Denver, Colorado.

‘Southern California continues to experience the worst air quality in the nation and transitioning heavy-duty vehicle fleets to cleaner-burning vehicle technology is an important element of our overall clean-air goals,’ said Barry R Wallerstein, executive officer of the South Coast Air Quality Management District.

Manufactured by Ford, the gHEV trucks feature 5.4-litre gasoline engines and hybrid-propulsion systems produced by Azure Dynamics with 100kW electric motors, regenerative braking and nickel-metal-hydride batteries.

Fedex Express operates more than 32,000 motorised vehicles in the US, including 20 gHEVs on parcel-delivery routes in Los Angeles and Sacramento.

The evaluation was funded by DOE’s Vehicle Technologies Program, with additional funding from Calstart, an organisation that promotes clean transportation technologies, and the South Coast Air Quality Management District.