Fuel Cell Hybrid Bus Program

The University of Delaware is currently operating two 22-foot, 22-seat transit buses with hydrogen fuel cell/battery hybrid powertrain. The buses are manufactured by EBus, Inc. of Downey, CA, and are equipped with 19.4 kW Ballard Mark 9 SSL fuel cell stacks and 60 kWh each of SAFT Ni-Cd batteries. The University has equipped them with a comprehensive set of sensors and a data logging system, allowing detailed monitoring of all major components in the powertrain. They are used as part of the campus shuttle bus service, and for demonstrations and public outreach. In addition, they are used as a research platform to study new fuel cell system components and control strategies.

The current buses are Phases 1 and 2 of the program; the Phase 2 bus has the same chassis as Phase 1, but has two fuel cell stacks instead of one and many balance-of-plant improvements. The Phase 3 bus is expected to be delivered in early 2011; it is a 30-foot, 32-passenger bus that will be equipped with dual 19.4 kW fuel cells and 32 kWh of Altairnano lithium titanate batteries. These batteries weigh approximately 1600 pounds, compared to 4000 pounds for the 60 kWh Ni-Cd batteries, and can deliver twice the power to the traction system (240 kW, compared to 120 kW). They are expected to last for 12,000 full charge cycles, compared to 1,500 cycles for the Ni-Cd, and eliminate the maintenance requirements of flooded batteries.

How The Fuel Cell Hybrid System Works

This is a completely electric vehicle, meaning no combustion takes place and no harmful emissions are generated. It is also considered a battery-heavy hybrid in that the batteries are used as the primary source of electric power for the drive motor, while the fuel cell stack is used to slowly recharge the batteries. Therefore, the fuel cell acts a range extender. When the bus is turned on, electricity flows from the batteries to the traction motor, powering the final drive which turns the rear wheels. During operation, if the battery state-of-charge drops below 60%, the fuel cell turns on and provides electricity to the system, to help power the bus and/or recharge the batteries. The bus is equipped with regenerative braking so that when the brakes are applied, the kinetic energy of the bus is converted back to electricity by the traction motor and stored in the batteries.

Major components of the fuel cell bus

What Makes This Bus Different?

This bus emits zero greenhouse gases, is significantly quieter than a typical diesel transit bus, and gets better gas mileage (11 miles per diesel gallon equivalent for the fuel cell bus, compared to approximately 5.5 mpg for a similarly sized diesel transit bus). Also, by using a smaller fuel cell stack than similar sized fleet fuel cell buses, the overall cost is greatly reduced. This makes the bus more affordable for transit agencies wishing to incorporate new fuel cell technology into their program.

News Reports

Bus Specifications, Phase 1 and 2

  • Length: 22 ft
  • Width: 92 in
  • Maximum Gross Weight: 20500 lb
  • Curb Weight: 15500 lb
  • Traction Motor: 174 hp AC induction with flux vector control
  • Transmission: single speed trapezoidal chain drive
  • Governed Maximum Speed: 45 mph
  • Batteries: Flooded Ni-Cd, 300V nominal, 2 strings, 100 Ah each
  • Fuel Cell: Ballard Mark 9 SSL, 19.4 kW gross (Phase 1: single stack, Phase 2: dual stacks)
  • Range: 180 miles
  • Fuel Economy on H2: 12 miles/kg
Phase 1 Bus
Phase 2 Bus
Hydrogen Filling Station

Related Research

The activity of both the buses can be viewed online: Phase 1  •  Phase 2