Comparison of ultra capacitors, hydraulic accumulators and batteries technologies to optimize hybrid vehicle ecoefficiency

The main objective of vehicle powertrain hybridization is to simultaneously improve the fuel consumption and environment pollutants impact (Eco-score) without decreasing the vehicle performances and other user satisfaction criteria. Based on a simulation model in ADVISOR, one can evaluate the performances, the emissions and then the Ecoscore and the user satisfaction for different driving scenarios. To establish a rationale methodology for assessing the eco-efficiency character, we adopt a multidisciplinary optimization approach while minimizing / maximizing both Eco-score and user satisfaction objective functions. The proposed approach is then used to establish a comparison between HEV (hybrid electric vehicle) and HHV (hybrid hydraulic vehicle) configuration by highlighting the effect of different energy storage systems (batteries, ultra capacitors, hydraulic system), mechanical and electric components sizes upon the optimized HEV design. The selected application is the comparison of different mild parallel hybrid buses. Results show that the hybrid electric buses using ultra capacitors have almost the same performances as those using batteries, while the HHV technology can compete with HEV because of the hydraulic components low cost and recyclability if possibly using of water as motor/pump fluid.