“Random Mechanical Switching Harvesting on Inductor”: A novel approach to collect and store energy from weak random vibrations with zero voltage threshold

Abstract The ongoing efforts toward the reduction of device dimensions toward micro and nanoscale cannot be fully matched without a similar shrinkage in the dimensions of energy harvesting systems; the miniaturization of the renewable power source inevitably results in lower output power and, in particular, lower output voltage. It is mandatory, therefore, to face the problem of identifying suitable solutions for collecting and storing this energy. The problem is rendered more complicated by the fact that the very low output voltage prevents the use of standard solutions based on diode bridge rectifiers. In this paper we address the issue of harvesting and storing electrical power from random, weak, mechanical vibrations. The system we present is called “Random Mechanical Switching Harvester on Inductor” (RMSHI). It is composed of a piezoelectric vibrating element, an inductor, a diode bridge, a storage capacitor and a mechanical switch capable of switching in response to the same vibrational input whose kinetic energy is scavenged; hence no active element is required. Energy is transferred from the external source to a piezoelectric vibrational element and, hence, to the inductor and finally, when the mechanical switch opens, to the storage capacitor. The system has been analytically modeled and numerically simulated to verify the working principle; further, a laboratory prototype of the RMSHI circuit has been realized to experimentally demonstrate the validity of our approach.