The illustration in the pop-up window on the left shows the arrangement of the engine in a transit bus. With the superior power density of the Ballard fuel cell, all of the engine components fit within the space normally taken by a diesel engine. The electrical system provides the power interface between the fuel cell array and the electrical equipment for the engine and the vehicle. Main system power is provided at 650 Vdc and 400 Amperes. Circuit breakers and controllers that manage vehicle propulsion and auxiliary systems are housed in a single enclosure.
Inverters provide the different voltage levels required for vehicle and engine operation.
The control system takes information from internal instrumentation and provides outputs to a variety of devices, such as motor controllers, valves, and indicators. The on-board computer uses an industry standard programmable logic controller. Water from the cooling system is also used to humidify the air and fuel gas streams before they enter the fuel cell stacks. In cold temperatures, the dynamic brake resistor is used as an immersion heater and is plugged into an external power supply to prevent engine freezing. An ion exchange filter is used to keep cooling water pure, preventing cooling water from becoming a conductor of electricity.