Experimental Fluid Mechanics and Aerodynamics Laboratory

Hybrid Electric bus propulsion systems

In a pilot program, the Metropolitan Transit Authority of NYC has operated 10 new hybrid-electric buses in the last two years and it is expected to add 125 new buses by the end of this year. Exhaust gas pollution of hybrid-electric is substantially lower than that of equivalent diesel buses. Fuel consumption is always less than that of diesel buses. The difference, however, in fuel consumption between hybrid-electric and conventional diesel buses deteriorates by 19% during the summer months. It is suspected that the root cause of this is the reduction in performance of the 46 batteries used in the hybrid-electric buses because of increased temperature in their compartment. A time-dependent analysis of the convective heat transfer patterns inside the batteries compartment has been carried out which indicated the need for more elaborate temperature control of the batteries compartment.