Proterra's hybrid-electric zero-emission bus

Proterra is presenting a prototype of its HFC35 composite body, hybrid-electric bus at the American Public Transportation Association expo in San Diego. Scheduled to start service in early 2009 in a nationwide trial, the 37-seat HFC35 contains a fuel cell hybrid-electric powertrain that emits only water, qualifying the bus as a zero-emission vehicle. However, it can also incorporate diesel, gasoline, and compressed natural gas engines.

The Federal Transit Authority funded prototype is powered by a UQM PowerPhase 150 propulsion system which produces peak torque of 650 N-m and peak power of 150 kW, with a continuous torque rating of 400 N-m and a continuous power rating of 100 kW. The system includes optimized four-quadrant performance, dynamic torque, speed and voltage control, regenerative braking, and an average system energy efficiency of 90%.

The vehicle's TerraColt fast charge energy storage system has a life of 10,000 charge-discharge cycles, and according to the company;s release can be charged in "a matter minutes" using the Proterra rapid charge station.

The HFC35 is scheduled to start service in early 2009, in a nationwide trial starting in Columbia, South Carolina.