Cyclic strain rate in tyres as power source to augment automobile autonomy

Abstract

The strain rate that takes place in the belts of tyres during automobile movement is proposed for converting mechanical energy into electricity. This paper describes how cyclic strain in tyres can be used for exciting piezoelectric materials placed in contact with the inner side of the tyre belt. Stress strain in tyre belts is caused by total mass weight in equilibrium with a pressurising condition. Under this condition, one section of the tyre in contact with the pavement deforms gradually until a maximum is reached, followed by a smooth release. The effect is continuous during each cycle of tyre rotation. Numerical simulations based on the finite element method were conducted for calculating the stress in composite materials that reproduce a combination of tyre belt–piezoelectric polymer films. Results were obtained for different conditions of velocity and automobile total mass. The piezoelectric material was sectioned into elements that cover the entire belt interior, leading to continuous generation of electricity. The numerical simulations assumed that automobile speed varied from 0 to 113 km/hr, combined with mass increments from one to five passengers, for a constant inflation pressure. The results indicate that electric current generated by the strain-stress in tyres increases almost linearly as a function of weight and speed. The electricity generated in tyres can be used to recharge the batteries in hybrid and conventional cars. It can even lead to reductions of alternator capacity. This process is a function of travel distance as well, since harvesting of energy takes place every tyre cycle.