Inductive Energy Harvesting From Current-Carrying Structures

Abstract

This paper introduces an inductive method for harvesting energy from current-carrying structures. Numerical simulation of a structural beam shows that the skin effect can lead to significant current concentration at edges, providing a five-fold power benefit at such locations, even at frequencies below 1 kHz. The use of a rectangular ferrite core can provide a ×4 power density improvement. The adoption of funnel-like core shapes allows the reduction of core mass and coil frame size, leading to significant further power density enhancement. Magnetic field simulation and coil analysis demonstrate a power density increase of ×49 by ferrite funnels, in comparison to a coreless coil. Experimental results demonstrate rectified power over 1 mW delivered to a storage capacitor, from a 40 × 20 × 2 mm core-and-coil, in the vicinity of a spatially distributed 20 A current at 800 Hz. Rectification and impedance matching are studied experimentally using a voltage doubler circuit with input capacitor tuning to counteract the coil reactance. Experimental results from a spatially distributed 30 A current at 300 Hz and a 1:7 funnel core demonstrate power density of 36 µW/g (103 µW/cm 3 ), opening up the way to non-invasive inductive powering of systems in the vicinity of current-carrying structures.

Magnetic Field Energy Harvesting From Current-Carrying Structures: Electromagnetic-Circuit Coupled Model, Validation and Application

“…In this study, a linear magnetization model of the ferromagnetic material was used by defining a constant magnetic permeability for the ferromagnetic materials. The linear magnetization model is valid when the magnetic field and the hysteresis loss is relative low, which is the case of this study and has been widely used in the modelling of magnetic field energy harvesters [12,15,21,22,24]. When the magnetic core is saturated or the hysteresis loss is significant, the linear magnetization model may not be valid and the FEM may overestimate the power output considerably.…”

“…For assets carrying a high current, a reliable energy source is magnetic fields. Examples of such assets include power transmission lines [10], rail track carrying traction returning current [11] and certain structural beams in aircraft [12]. The magnetic field energy can be scavenged by a piezoelectric cantilever with a tip mass made of permanent magnets [13] or by a magnetoelectric composite through magneto-mechanoelectric mechanism [14].…”

“…A higher power density of 2.1 µW/cm 3 was achieved by the helical core. While all these magnetic EHs concerned magnetic fields generated by power lines, Wright et al [12] developed an EH with a funnellike core to generate electricity from an H-shape currentcarrying structural rail used in aircraft. The EH was not tested around the H-shape structure but cables carrying 20 A current.…”

“…For the MFEHs mentioned above, finite element and/or analytical models have been used to guide the design. The majority of the models [12,15,21,22,24] simplified the MFEH as two decoupled systems: one is electromagnetic, which models the conversion of the primary magnetic field generated by the current conductor to an electromotive force (EMF); the other is electrical, which computes the current and power generated by the EMF on an electrical load. The only link between the two decoupled systems is the EMF.…”

Magnetic and Electric Energy Harvesting Technologies in Power Grids: A Review

“…A rectangular ferrite core was used which can provide a × 4 power density improvement. The power density of 36 µW/g (103 µW/cm 3 ) was obtained from a spatially distributed 30 A current at 300 Hz and a 1:7 funnel core demonstrate [28]. C. Cepnik and U. Wallrabe studied a flat micro energy harvester with a volume of 0.9 cm 3 and a height of 3 mm, in which a serpentine coil having a single winding was used, and measured normalized power of 8.3 µW avg /(ms −2 cm 3 ) 2 was obtained [29].…”