Triangular-shaped two-dimensional vibrational electromagnetic energy harvester

Energy harvested from vibrations can be used to power e.g. wearables and Internet-of-things devices. Here we investigate a two-dimensional triangular-shaped electromagnetic vibration energy harvester with tunable resonance frequency. The harvester has rotatable arrays of fixed magnets, that can be turned to adjust the magnetic forces, a free-to-move structure with three cylindrical magnets, and a set of coils to generate a current. Using an experimental 2D shaker, the power produced by the harvester is measured as function of a vibrational frequency in the x-direction from 1 Hz to 11 Hz in steps of 0.25 Hz and in the y-direction from 1 Hz to 10 Hz in steps of 1 Hz, both at 2 mm amplitude, and at five different angles of the fixed magnets. The harvester produces up to 30 mW of power, and the resonance frequency in both the x- and y-directions shifts from around 7 Hz to around 11 Hz as the fixed magnets are rotated, clearly demonstrating that the resonance frequency can be tuned.