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.

Contours of total temperature in air flow around the battery.

Contours of total temperature in air flow around the battery.

Velocity of cooling air around an individual battery in battery compartment.

Velocity of cooling air around an individual battery in battery compartment.