Why are hybrid bus emissions different?
There are several reasons for the reductions. Regenerative braking contributes significantly to reducing fuel consumption and thereby improving efficiency. Regenerative braking takes advantage of the energy storage system to capture the kinetic energy of the vehicle during braking. This is accomplished by using the drive motors as generators during braking to recapture the vehicle’s kinetic energy and restore a portion of this energy back to the energy storage device to be used later — for example, during acceleration. Another contributing factor is the fact that, on a series hybrid, the engine is not directly coupled to the vehicle drivetrain (i.e., the electric drive motor alone drives the wheels). This allows the auxiliary power unit (APU) to operate independently from the vehicle. This would theoretically allow the engine/generator to operate at peak efficiency and optimized emission load points. Series hybrid control strategies typically prevent the engine from operating in zones
