Comparative Investigation of Series and Parallel Hybrid Electric Drive Trains for Heavy-Duty Transit Bus Applications

In recent times, diesel powered hybrid electric vehicles have attracted their fair share of attention from automakers worldwide. It is a well-known fact that diesel hybrid technology is being used increasingly to improve the performance of a number of city transit buses. The exclusive combination of advanced diesel engines and sophisticated hybrid electric vehicle(HEV) technologies holds much promise for dramatic reductions in both emissions as well as fuel consumption. Currently, transit bus manufacturers incorporate the popularly accepted series or parallel hybrid electric drive train architectures for hybridization depending on specific performance demands. From the point of view of heavy-duty vehicular drive train hybridization, a major debate in the auto industry involves analyzing and comparing both the series as well as parallel HEV systems. Keeping this issue in mind, this paper aims to comprehensively investigate and evaluate series and parallel hybrid electric drive train topologies for heavy-duty diesel transit buses from the point of view of overall efficiency and parametric performance studies. In general, the vital proposal of this paper involves the depiction of suitability of parallel hybrid drive trains over series hybrid drive trains, more specific to city transit bus applications.