Cars ‘Have Advanced Rapidly,’ Buses 89% More Efficient than Diesel
Fuel cell vehicles remain hampered by costs – both fuel- and cell-wise, but are improving in range and durability, new DoE assessments indicate. And after 273,000 miles of service, hydrogen for the largest fuel cell bus fleet in the U.S. has been measured at 89% more efficient than diesel.
Fuel cell cars have improved to the point where “there is optimism that manufacturers will introduce FCEVs to the market within the next few years,” study author Keith Wipke said in a National Renewable Energy Laboratory release summarizing the DoE unit’s National Fuel Cell Electric Vehicle Learning Demonstration Final Report.
Gen 2 fuel cars have shown mild improvement in overall system efficiency and fuel economy. They have better performing and more durable fuel cell stacks, and increased driving range. But none of four teams tested could meet all of the DoE goals of 250-mile driving range, 2,000-hour fuel cell durability, and $3 per gallon gasoline equivalent for hydrogen production cost.
NREL analyzed data from 500,000 individual vehicle trips covering 3.6 million miles – beginning in 2004 and “the world’s largest single FCEV and hydrogen fueling infrastructure demonstration to date.” The participating vehicle and hydrogen fueling participants were Daimler-BP, GM-Shell, Hyundai/Kia-UTC Power-Chevron, Ford-BP, and Air Products.
Daimler and GM added two years to the original project timeline, extending the completion date to September 2011. “Fifty-one vehicles were in operation by the end of the final two years of this project, reporting performance improvements from the latest technology,” states the Report.
The massive quantification effort was funded by EERE, DOE’s Office of Energy Efficiency and Renewable Energy. Raw data from the teams was protected by NREL’s Hydrogen Secure Data Center, and aggregate data made public in the 115-page Report.
NREL’s separate Zero Emission Bay Area (ZEBA) Fuel Cell Bus Demonstration: Second Results Reportstates that the dramatic, 89%-better-than-diesel efficiency gains shown by AC Transit’s fleet of UTC Power Van Hool buses in Oakland, Calif. were offset by a per-mile cost for hydrogen buses of $1.40 per mile, as compared with 79¢ per mile for diesel (diesel fuel cost during the reporting period was $3.18 per gallon, today’s per-mile diesel cost would be about $1). “The cost of hydrogen production as dispensed is currently $9.34 per kg, not including the capital cost of the station,” the Report notes.
The report noted too that model year 2009 Val Hool A330L low-floor buses with diesel-fueled Cummins ISL engines cost $323,000 apiece, whereas the model year 2010 Val Hool A330L low-floor buses with hydrogen-fueled UTC Power PureMotion 120 fuel cell units cost $2.5 million apiece.
“Three of the fuel cell power systems (from UTC Power) have accumulated significant hours of service without fuel cell stack maintenance or significant power degradation,” the report states: more than 12,000 hours, 10,000 hours, and 7,500 hours. The Report notes that more than a million passengers have ridden the zero-emission buses.
The 46-page bus Report mentions AC’s replacement of hydrogen fueling nozzles with more efficient units and the effects of the change on metering equipment, and the early-May pressure relief valve incident that resulted in a hydrogen leak and fire and temporary shutdown of AC Transit’s new hydrogen fueling station in Emeryville, Calif.
“The emergency system worked as it was designed,” the Report notes, “but the fire burned for about 2-1/2 hours before Linde technicians were allowed into the storage compound to turn off the manual valve. There were no injuries, or threats of injuries, and no damage occurred, except for minor singeing on a corrugated canopy roof on one side of the station.”
Going forward, NREL says it will compare AC Transit fuel cell bus performance with diesel-electric vehicles operated by other San Francisco Bay Area transit agencies. A further reported is expected late this year.
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