BAE Systems is aggressively pursuing enhanced system architecture to an already successful HybriDrive® propulsion system as a possible future offering to dramatically improve fuel economy and reduce emissions at a modest cost increment in a 40 foot transit bus. Under a Federal Transit Administration's (FTA) National Fuel Cell Bus Program award to CALSTART and BAE Systems, a fuel cell Auxiliary Power Unit (APU) will be coupled with Lithium-Ion battery Energy Storage System and all-electric accessories for demonstration in a fuel cell hybrid-electric bus at San Francisco Municipal Transportation Agency (SFMTA). The use of Lithium-Ion Nanophosphate™ battery technology offers greater energy density leading to substantially lower weight for the energy storage system. Combining such energy storage with a fuel cell APU is an architecture that was identified by the U.S. Department of Energy's (DOE) Argonne National Laboratory as providing greatest vehicle fuel efficiency improvement per dollar for optimal commercial design.
Compound Fuel Cell Hybrid Bus for 2010 or BUS-2010
The project is called the Compound Fuel Cell Hybrid Bus for 2010 or BUS-2010. The BUS 2010 architecture will be integrated and tested with a hydrogen fuel storage system and the following HybriDrive® propulsion components in a 40-ft. low-floor Orion bus from Daimler Buses North America:
• An integrated starter generator, coupled to a diesel internal combustion engine
• A series electric drive system
• Power Control System.
A key part of the design relies on an advanced Lithium-Ion, Nanophosphate™ (Li-Ion) Energy Storage System that BAE Systems is already delivering to market. This new energy storage system is lighter (up to five times) than other systems currently in production, as reducing vehicle weight improves fuel economy and improves emissions performance. The new energy storage system also is more efficient and is expected to be more durable than the leading alternatives in use today, using the Nanophosphate™ Li-Ion chemistry developed by
A123Systems of Watertown, Massachusetts, one of the world's largest suppliers of high-power Li-Ion batteries.
While the initial decision to adopt this technology was performance-based - considering energy density and weight - the market has also revealed other advantages:
• Li-Ion, Nanophosphate™, batteries can operate over a larger state-of-charge (SOC) range, allowing for deeper discharge and accepting faster charge and without affecting battery life
• Extended discharge/charge performance enhances motoring and regen contributing to added fuel economy and reducing emissions
• The cost of cobalt and nickel has risen significantly; even lead prices are roughly 3 times what they were 5 years ago
• The energy storage system is cooled using ambient air, even when ambient temperatures soar up to 125 degrees Fahrenheit, whereas the older technology (NiMH) requires the battery pack to be air-conditioned, due to the much higher heat rejection.
Relatively speaking, the costs of the Li-Ion technology compared to other battery types over the life of the bus has improved.
A HybriDrive® equipped 40 foot bus with the Li-Ion ESS comes within a few hundred pounds of the weight of a conventional diesel, and hundreds of pounds lighter than other competitive battery packages. The Nanophosphate™ technology has additional advantages in terms of safety; and as larger-format Li-Ion packages emerge, heavy-duty drive trains and transit vehicles seem a perfect match for them.
Watch this space for more updates on this technology and this demonstration as it becomes available.