A PURPOSE-BUILT PLUG-IN HYBRID BUS Proterra develops lightweight purpose-built plug-in hybrid transit bus
Proterra LLC has developed a purpose-built, plug-in hybrid electric transit bus that will be tested in Burbank, Calif. The HFC35 bus is configured to rely on power from fuel cells, regenerative breaking and plugging into the grid.
50 DIESEL PROGRESS NORTH AMERICAN EDITION April 2010
rear, the 35 ft. long HFC35 hybrid- electric transit bus can still carry 67 passengers ( 37 seated and 30 stand- ing). This helps make the HFC35 more maneuverable in city traffic and re- duces bus weight. The plug-in hybrid technology used by Proterra is very similar to what will be used in future plug-in hybrid elec- tric vehicles (PHEVs). Fuel cells are used to extend the vehicle’s range, while the batteries — which are recharged by regenerative braking, the fuel cell and plugging into the elec- tric grid — do most of the heavy lifting. Thus, mass-produced, smaller output automotive-type fuel cells can be used to reduce initial vehicle investment and lifetime operating costs. The Proterra bus uses two 16 k W proton exchange membrane (PEM) fuel cells supplied by Canadian-based Hydrogenics Corp. At the heart of the bus is the Proterra TerraVolt fast-charg- ing energy storage system, which is integrated into Proterra’s composite body floor system. The TerraVolt sys- tem includes the Altairnano Li-ion bat- tery modules as well as battery man- BY BILL SIURU Urban transit buses are com- mon first adopters of hydro- gen fuel cell technology. Several fuel cell-powered transit buses are already in revenue service, at least on a demonstration basis, around the country. These large buses can easily accommodate the large hydrogen fuel tanks, usually placed on the roof, without compro- mising passenger capacity. Requiring no petroleum products, they are designed to be emissions free, help- ing transit agencies meet clean air and alternative fuel mandates. Burbank, Calif., has been selected as a national test market for the new HFC35 hybrid-electric transit bus, developed and built by Colorado- based Proterra LLC (formerly Mobile Energy Solutions). According to Proterra, this is the first lightweight composite bus pur- pose-built as a plug-in hybrid. Being purpose-built, rather than originally intended for diesel power, it is 5 ft. shorter than a typical 40 ft. transit bus. Because diesel engines don’t have to be accommodated in the