How Do We Define the Efficiency of MEMS Vibrational Energy Harvester?

Abstract

Conversion efficiency of vibrational energy harvester is defined primarily by the ratio between the mechanical power incoming to the system and the electrical output power. Measuring the output power is straightforward but how is the incoming power measured? Such a physical quantity is known only when the force acting on the power generator is measured by using a force sensor virtually inserted between the vibration source and the energy harvester, which does not look practical. In this article, we look into an analytical model for a vibrational energy harvester or so-called velocity-damped resonant generator (VDRG) and discuss indices alternative to the efficiency of power conversion.