Analysis of hybrid hydraulic vehicles and comparison with hybrid electric vehicles using batteries or super capacitors

Hybrid Hydraulic Vehicle (HHV) technology is an alternative solution to classical Hybrid Electric Vehicles (HEV). The authors’s previous studies of hybrid hydraulic systems clearly demonstrated that HHV can lead to fuel savings even though smaller than HEV. Hydraulic energy recovery systems are well adapted for heavy urban vehicles with frequent starts and stops because the weight penalty of the hydraulic system can be mitigated while taking benefit of their high specific power property for power assist. This recent work investigates and compares, from an economical and technical point of view, both HHV and HEV buses using batteries or super capacitors as energy storage systems. The fuel consumption of different hybrid busses is simulated using ADVISOR on the basis of three European SORT driving cycles. The results show that HHV and HEV with super capacitors can not rival from the consumption point of view with the HEV using batteries as energy storage system. But they can be economically interesting because of their lower cost and the longer service life of their energy storage system.