Analysis of hydraulic hybrid vehciles and economical comparison with hybrid electric vehicles

Hybrid Hydraulic Vehicle (HHV) technology is an alternative to HEV. This technology deserves new attention because of recent development in reversible hydraulic motor pumps with high efficiency. The HHV technology is based on parallel architecture of motor assist systems. A first preliminary study investigated the fuel consumption of a passenger car, a SUV and an urban bus. It clearly demonstrated that the fuel efficiency benefits are the better for heavy vehicles with frequent stops and starts. The second part of the work then compared both HEV and HHV buses. The fuel consumption is simulated using ADVISOR on the basis of 3 SORT driving cycles. The results showed that the HHV are penalized by his weight but they can be economically interesting because of the lower cost and longer life time of the hydraulic system.