First 'triple-hybrid' fuel-cell bus goes into service

  • 04-Jun-2009 03:54 EDT

Proton Motor’s “PM Basic A 50” fuel-cell system rated at 50 kW is at the heart of the "triple-hybrid" bus' propulsion system.

A joint venture between Proton Motor Fuel Cell of Munich, Germany, UJV Nuclear Research Institute of Rez, Czech Republic, and Skoda Electric of Pilsen, Czech Republic, has produced a bus powered by a “triple-hybrid” fuel-cell system. Triple-hybrid refers to the combination of hydrogen fuel cells, batteries, and ultracapacitors used to power, store, and capture energy on the vehicle.

Skoda Electric produces trolley buses and electric rail vehicles and was responsible for the vehicle, drive system, and system integration. UJV coordinated the project, while Proton Motor supplied the fuel-cell propulsion system. Proton claims that this is the first time a triple-hybrid system has been used in a public service bus.

At the heart of the all-electric propulsion system is Proton’s “PM Basic A 50” fuel-cell system, delivering a rated power output of 50 kW, with a rated dc voltage of 140 V. The nominal output of the complete propulsion system is 120 kW, providing the bus with a top speed of 65 km/h (40 mph). Proton claims a range in urban use of more than 250 km (155 mi). The fuel tanks will store 20 kg (44 lb) of hydrogen gas at a pressure of 350 bar (5076 psi). Refilling the tanks is said to take place in less than 10 minutes. The system is designed for “back to base” operations such as buses and forklift trucks.

Proton claims that the liquid-cooled PEM (proton exchange membrane) fuel cell uses a simple modular construction with an integrated, low-energy water management system, which eliminates the need for external dehumidification and refilling with deionized water. For this setup, the company claims an energy efficiency exceeding 50%.

Proton integrated a PM Basic A 50 hybrid system using lead-gel batteries into a passenger ship last year. The FCS Alsterwasser is based at Hamburg in Germany.

For the hybrid bus, Proton claims energy savings exceeding 50% compared with a diesel-powered vehicle. The fuel cell provides the principal drive energy source, but for peak energy requirements the batteries and ultracapacitors supply energy in parallel to the drive motor. Regenerative braking energy is stored in both the batteries and ultracapacitors, and the batteries are also recharged by the fuel cell when the vehicle is stationary.

The vehicle is based on a standard Skoda 12-m (39-ft) long bus with a gross weight of 18.0 t (19.8 ton). The bus is due to begin operations in the Czech capital of Prague this summer.

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