Energy flow analysis in piezoelectric energy harvesting systems

Energy recovery from wasted or unused power has been the topic of discussion for a long time. In recent years, industrial and academic research units have focused on harvesting energy from mechanical vibrations using piezoelectric transducers. These efforts have provided the initial research guidelines and have brought in light the problems and limitations of implementing the piezoelectric transducer. There are three major phases/steps associated with piezoelectric energy harvesting: (i) mechanical-mechanical energy transfer, including mechanical stability of the piezoelectric transducer under large stresses, and mechanical impedance matching, (ii) mechanical-electrical energy transduction, relating with the electromechanical coupling factor in the composite transducer structure, and (iii) electrical-electrical energy transfer, including electrical impedance matching, such as a DC/DC converter to accumulate the energy into a rechargeable battery. This paper deals with detailed energy flow analysis in piezoelectric energy harvesting systems with typical stiff "Cymbals" and flexible piezoelectric transducers, in order to provide comprehensive strategies on how to improve the efficiency of the harvesting system. Energy transfer rates are practically evaluated in the above all steps.