Contribution au développement d'un générateur piézoélectrique pour applications nomades

Since the market of portable electronic devices has been expanding for the last ten years, and their energy consumption has been decreasing in parallel, the idea of harvesting the energy of human movements is arousing a renewed interest. In this context, we conceived and made a prototype piezoelectric generator, in order to supply portable devices consuming between 10μW and 1 mW. The piezoelectric materials that we used are PZT ceramics, working in compression under a low frequency constraint (quasi-static mode). The generator consists in three conversion stages : the mechanical application device (MAD), the piezoelectric device (PD) and the harvesting system (HS). On the one hand, we modelled the PD in quasi-static mode, in order to highlight its working characteristics and estimate the delivered power, knowing the shape, amplitude and frequency of the mechanical constraint. On the other hand, we conceived, made and tested two different experimental devices, in order to demonstrate the feasibility of the concept. The delivered power reaches 13.2 μW for a 100 kOhms load, with a 55 Hz constraint of 2 N per piezoceramic. At last, we designed a harvesting electronic circuit, allowing to increase the converted energy. This circuit is dedicated to the PD, whose characteristics of impedance and current are special. Moreover, the use of low consumption components is necessary, with a view to carry out an autonomous generator.