LAUSR

A lot of effort has been made to optimize linear electromagnetic energy harvesters under harmonic or random excitation, connected to simple or more complicated electrical extraction circuits. Nevertheless, the internal electrical losses of electromagnetic coils are often neglected in these optimization analyses. To this end, the present paper investigates systematically and for the first time the influence of internal impedance of coils on energy harvesting performance under various types of ambient excitation sources, which are, respectively, external force acting directly on the seismic mass, base displacement-induced motion and disturbance generated by base acceleration. Our analysis highlights that under sinusoidal excitation, the resonant load outperforms its non-resonant counterpart in terms of energy harvesting performance when the internal resistance is very small, while its increase deteriorates significantly the broadband harvesting capability of resonant circuits. When subjected to random vibration, the resonant load presents no advantage compared to the latter one. The optimum design of non-resonant circuit is then carried out in each excitation scenario leading to well-known criteria and expanding to cases where no optimal conditions were defined or obtained. It is also reported that the neglect of internal losses underestimates the maximum available power.