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Kinetic Energy to Electric Energy Conversion Using Regenerative Shock Absorbers

The European Commission promotes the development and the early uptake of new and advanced CO2 emission-reducing vehicle technologies. Regenerative technologies form an important part of these so-called Eco-Innovations (EU 725/2011). Recently, interest is growing on regenerative shock absorbers, which convert part of the kinetic energy of vehicles suspensions into electric energy, used to charge the battery. This study, carried out in cooperation between Magneti Marelli S.p.A. and the European Commission Joint Research Centre, depicts a clear and comprehensive scenario on this technology, evaluating the potential of CO2 saving. An extensive analysis of the available literature has been performed, considering different types of technologies. Attention has been paid to the possibility to obtain the desired damping characteristics. Solutions have been analyzed to integrate the power coming from the shocks in the electric grid of the vehicle. The mechanical power in input to the shocks has been calculated, taking as a reference the ISO standard for road profiles (ISO 8608:1995) and using both theoretical formulas and computer simulations. The overall efficiency of the conversion from kinetic to electric power has been shown to range between 0.25 and 0.5. Accordingly, quantitative results about the potential of CO2 savings have been obtained: for passengers cars, the potential of CO2 savings has been calculated between 1 and 2 g CO2 / km, while higher CO2 savings are possible for commercial and heavy duty vehicles. As a final innovative result, it has been demonstrated that regenerative shocks have the potential to be eligible as Eco-Innovations, since they allow to exceed the minimum threshold of 1 g CO2 / km.