Mar 6 2006
Hybrid electric transit buses are raising the industry standard for fuel economy, emissions, and reliability, according to a recently published independent study.
The National Renewable Energy Laboratory (NREL) compared different technologies used in regular revenue service in New York City and concluded that Orion VII buses powered by BAE Systems’ HybriDrive® series propulsion system had superior performance. “The Orion VII hybrid bus delivers on the promises of significantly improved fuel economy, lower emissions, and better reliability,” said Patrick Scully, chief commercial officer for DaimlerChrysler Commercial Buses North America. Orion is the transit bus brand of DaimlerChrysler in North America. “This is great news for any transit agency wanting to make a difference environmentally and control rising fuel and operating costs.”
Hybrid buses tested by NREL on New York’s most severe duty cycles achieved up to 45 percent better fuel economy than diesel buses and 100 percent improvement compared to natural gas on an energy-equivalent basis. The report also said bus drivers liked the increased power output of the hybrid buses, whose electric drive motor offers superior torque to help with acceleration and hill-climbing.
New York’s hybrid fleet also proved most reliable in the study, with 7,000 miles between road calls, compared to 5,000 miles for natural gas and 4,000 miles for diesel. The HybriDrive® system also performed better than the other propulsion systems, with 10,000 miles between calls, compared to 8,000 miles for CNG and 5,000 miles for diesel.
“Our series hybrid design is especially well suited to urban stop-and-go conditions,” said Hank McGlynn, vice president of Power Systems for BAE Systems in Johnson City, N.Y. “The design is inherently simple and has been demonstrated in daily service over millions of miles of highly demanding service.”
In a series hybrid, the vehicle utilizes a smaller diesel engine, reducing weight and cost. All-electric drive maximizes efficiency and reduces emissions, and a regenerative braking system recovers waste energy and extends brake life. The design also eliminates the transmission, a significant maintenance item on transit buses.
The NREL study examined the operation, maintenance, performance, emissions, cost, and safety of urban transit buses operating in normal revenue service in New York, where usage and duty cycle are extremely demanding. The city operates a fleet of more than 4,000 transit buses including diesel, natural gas, and hybrid electric varieties. Currently, 325 Orion VII hybrid buses operate in revenue service, and 500 more are on order.
The New York results are contained in an interim report based on data measured between September 2004 and May 2005. A second and final report planned for release later in 2006 will incorporate data from a wider range of depots and more months of operation. The interim report can be viewed at
http://www.eere.energy.gov/vehiclesandfuels/avta/pdfs/heavy/nyct_interim_report_final.pdf
http://www.baesystems.com/