Sales for Daimler Buses North America’s Orion VII diesel-electric series hybrid bus have surpassed 3,000 units—more than any other manufacturer in the world. More than 2,200 units are already in service, with an additional 850 firm orders in backlog from cities such as New York City, Seattle, Houston, Ottawa and Puerto Rico.
There are more than 1,250 Orion VII hybrids in the New York metropolitan area already with another 425 units to be delivered over the next nine months making New York City Transit the largest hybrid fleet in the world.
Houston Metro is placing an additional order for 80 Orion VII diesel-electric hybrid buses for 2010 delivery. This compliments its existing fleet of 56 Orion VII hybrids which were delivered in 2008 and the 40 units that will be delivered in 2009.
Another long-term customer, Puerto Rico, is transitioning into hybrid buses for its existing fleet of conventional diesel Orion transit buses with an order of 40 Orion VII diesel-electric hybrid buses. These will be produced and delivered in 2010.
Orion began development and production of hybrid buses in the mid 1990s with pilot vehicles first deployed in New York City Transit. Series production began in the early 2000s.
In 2008, Daimler deployed lithium-ion energy storage technology for buses in volume production. This development has reduced the weight of the overall bus and thereby further improving fuel economy. Daimler Buses is developing and testing further refinements in the hybrid system that will be introduced in 2010.
The heart of the Orion VII diesel-electric hybrid bus is the HybriDrive propulsion system manufactured by BAE Systems. The system powers the bus with components arranged in series: 6.7L diesel engine from Cummins; a generator; an electric motor, and the Lithium-ion energy storage system, with cells from A123Systems.
The diesel engine is optimized to run at relatively constant speeds (acceleration/deceleration is accomplished by varying the speed of the electric motor, not the diesel) for maximum efficiency and clean operation.
Another feature of the Orion VII hybrid is the regenerative braking system that uses the electric drive motor to slow the bus, effectively turning the motor into a generator to help recharge the bus batteries. This feature both saves energy and significantly reduces brake wear. The series hybrid design also eliminates the need for a mechanical transmission which means no transmission overhauls, a major maintenance item on conventional buses.