If you've ever walked around Prague, you know it's a city that could use a few less diesel buses ... or at least much less airborne soot. The city's beautiful architecture and statuary are often masked with the stuff.
As has been the case for decades, buses continue to be among the first recipients of leading-edge green technologies. General Motors introduced its first commercial hybrid bus in 2003, with units serving Seattle, Washington. The logic holds that the greatest polluters and fuel consumers benefit most from technology advances, thereby providing the maximum benefit to the most people.
A recent presentation near Munich marked the debut of the first passenger bus to use a triple hybrid fuel cell system developed by Fuel Cell GmbH, a subsidiary of Proton Power Systems. The vehicle was born from co-operation between Skoda Electric, UJV Nuclear Research Institute and Proton Motor. Skoda Electric was responsible for the vehicle including its electric drive system and system integration. The project was coordinated by UJV with Proton Motor supplying the propulsion system.
The triple hybrid system uses a Proton Motor's 50kW PW Basic A 50 fuel cell system with a battery pack and ultra-capacitors. Its nominal output is 120kW and it has a maximum speed of 40mph.
The bus uses three distinct components to provide electricity to its electric drive motors. A hydrogen fuel cell generates electricity. Batteries store and help deliver a base level of power for the bus's load. Ultra-capacitors provide additional power during periods of peak demand. The fuel cell charges the batteries and ultra-capacitors.
According the project participants, with regenerative braking taken into account, the system provides an energy savings in excess of 50 percent compared to a conventional diesel bus. Also, because the fuel stack uses hydrogen, there are no tailpipe emissions. The bus carries 20kg (44 pounds) of compressed gaseous hydrogen at 350 bar and the filling process takes less than 10 minutes. General Motors did much of its early research on hybrid and dual-mode hybrid technology on buses. This technology is now being used in their two-mode hybrid vehicles including the 2010 Chevrolet Silverado and Tahoe; the 2010 GMC Sierra and Yukon; and the 2010 Cadillac Escalade Hybrid. If this pattern holds, expect to see this type of technology trickle into the automotive field over the next few years.