Design of flexible piezoelectric and triboelectric microenergy generator for automotive tire application

Abstract

One of the largest technological challenges of the 21:st century is the increased need for electrical energy. For large systems they need to be powered by an external electrical power source but smaller systems and especially sensors may be powered by energy harvesting modules. This thesis aims to investigate the use of piezoelectrical PVDF harvesters in car tires via pre-study, experiments and COMSOL Multiphysics simulations to determine if it is possible to power wireless sensors, what the requirements may be and what the optimal harvester would consist of. The experiments have compared different sized and shaped harvesters in real tires to evaluate the available voltage. Simulations are then performed for the same shapes and sizes to investigate if there are any similarities and if any conclusions can be drawn from simulations for future development. These simulations have involved the design of a simple tire model, applying the right loads on the tire and choosing the right material properties to match real life experiments as much as possible. From experiments and simulations the results show a clear size and shape dependency of the harvester. Approximately 40 % more voltage is available for shapes with smoother edges without sharp corners for example a circular harvester. These characteristics are the same for both experiments and simulations. The results also show that for these more energetically profitable harvesters there is enough energy available to power a sensor and transmit data from that sensor. A 2 cm diameter circular harvester need 15 layers at 20 km/h but for every increase in area and velocity the number of layers decrease. This is gratifying and indicate that there is likely a future where real life implementations of this type of energy harvester is near. For future development more experiments with more different sizes and geometric shapes need to be performed in real tires and the simulation model may be built upon to further match real life.