The city of Burbank was selected as a national test market for a new zero-emissions, ultra-quiet prototype 67-passenger, transit bus that features a hydrogen fuel cell. The city plans to have the new Proterra HFC35 Hybrid-Electric Transit Bus in demonstration service on Burbank’s various routes in the spring of 2009.

The HFC35 was developed and assembled by Golden, Colo.,-based Proterra LLC. The company, formerly known as Mobile Energy Solutions, is best known for the 36 EcoMark I, 45-foot, CNG-fueled, hybrid-electric shuttle buses it built for use on Denver’s 16th Street Mall. This fleet has now logged more than 3 million miles and carried more than 150 million passengers.

"The significance of this milestone program is that we are able to harness the latest transportation technology and put it into service for the public good," notes Johnathan Frank, administrative analyst with the Transportation Department of the city of Burbank. "Zero emissions will help the environment, which is a critical issue in Southern California.”

Titled a battery-dominant hybrid-electric system, this HFC35 can operate solely as a full battery-electric transit bus traveling up to 250 miles before the battery pack has to be recharged. Charging can be done either by the fuel cell system, by regenerative braking or off the electrical grid. Incidentally, regenerative braking recoups energy during deceleration and braking with an impressive 90-percent efficiency.

The plug-in hybrid technology is quite similar to that which will be used in future plug-in hybrid electric vehicles (PHEVs) such as the 2010 Chevy Volt. Here the fuel cells are used for range extension, while the batteries are used most of the time. This allows the use of smaller, less expensive, automotive-sized fuel cells, which translates into a lower initial cost for the bus purchase as well as reduced operating costs. Using automotive type batteries means being able to take advantage of economy of scale to cut cost.

The designation comes from the HFC35’s hydrogen direct fuel cell and its 35-foot length. The Proterra bus uses two 16-kilowatt, proton exchange membrane (PEM) fuel cells supplied by Hydrogenics Corp. located in Mississauga, Ontario, Canada. Hydrogen is stored in high pressure tanks located on the roof of the bus. Urban transit buses are an ideal “early adopter’ for hydrogen fuel cell technology because the large hydrogen fuel tanks can be placed on the roof without compromising passenger carrying space.

According to Proterra, this is first lightweight, composite bus that is purpose-built to be a plug-in hybrid. Being purpose-built, rather than converted from a diesel bus, it is 5 feet shorter than the usual 40-foot transit bus. Since diesel engines do not have to be accommodated in the rear, the 35-foot long HFC35 Bus can still carry 67 passengers — 37 seated and 30 standing. This helps make the HFC35 more maneuverable in city traffic and reduces bus weight.