Hydraulic hybrids

Sammanfattning: Conventional IC Engine powertrain layouts in vehicles tend to consume considerable amounts of fuel and generate emissions that are harmful to the environment. Newer technologies have enabled the development of sustainable vehicle layout designs that favor a reduction in the exhaust emissions and energy consumption without compromising the vehicle’s performance. Hybrid vehicles and electric vehicles are the torch bearers for this development. Although electric vehicles feature high performance at lower emissions, they are generally limited by their range and high battery costs. Development of countries to equip for this electrification is another important factor here as with the development of more electric vehicles comes the problems associated with charging, like charging stations, charge scheduling (from power grid because of the high toll), etc. Hybrid electric vehicles are energy efficient and reduce the emissions considerably but their costs are substantially higher. Along with the higher efficiency generated by the electric machines, the possibility of regenerating braking energy reduces the energy consumption and increases the energy efficiency of the conventional layouts. Hydraulic hybrids in the recent years have gained recognition for their advantages and are known for being the cheaper alternative for hybridizing heavy vehicles. The ability of storing regenerative braking energy in this fluid form allows for higher cyclic efficiency when compared to that of the electrical means of storing energy. This thesis focuses on the design and modeling of the hydraulic hybrids using MATLAB/SIMULINK® to construct models depicting the use of the vehicles under the selected drive cycles. Regenerative braking has been one of prime focus for improving the range and minimising the energy consumption of the vehicle along with high operational efficiencies of the operating components. The thesis takes into account two cases, one with the case of a medium duty vehicle with a conventional  IC Engine layout and the other with the case of electric forklifts. The two cases are compared with their hydraulic hybrid layouts along the lines of energy consumption, operational efficiencies and range. Through the design of these simulations, a comparative analysis of the hydraulic hybrid to the electric hybrid is provided for the case of the medium duty vehicle and the benefits of having an electric hydraulic hybrid layout designed for the electric forklift applications are studied.