Abstract
In recent years, the awareness of an ever-growing world energy crisis and the respect of increasingly stringent regulations due to the production of polluting emissions, especially in the automotive field, have led various research institutions to seek alternatives to conventional fossil fuels in order to achieve a more rational use of energy.
KERS, acronym of Kinetic Energy Recovery Systems, are devices that do so. These systems are able to collect and store the braking energy of a vehicle, otherwise wasted, and re-use it in the subsequent acceleration phases. In this work the authors want to focus on one type of devices that is arousing interest as it offers a high value of power density and a high efficiency of energy conversion with already developed technologies. In literature, these systems, which exploit the ability to store energy through the variation of the volume of a gas within a hydro-pneumatic accumulator, are called HESS (Hydro-pneumatic Energy Storage Systems). HESS are currently being studied by several universities in Europe and the U.S., and by companies such as Ford, Bosch and Eaton who are interested in developing and prototyping them.
The purpose of this study is to look through the benefits that hydro-pneumatic technology can bring in terms of fuel consumption of a conventional passenger car, in mild and full hybridization, by means of simulation analysis. AVL CRUISE with MATLAB-Simulink are used in co-simulation for that purpose. An energy evaluation was carried out in order to determine the size of properly the storage device according to literature data. Then, several tests were done simulating the vehicle on normatized driving cycles, which are urban and highway, and using, for each configuration, their own well-defined strategies to optimize the use of energy flows between the primary engine, hydraulic pump/motor and wheels.
Keywords: hybrid vehicle, kinetic energy recovery system, hydro-pneumatic energy storage, energy saving