Imec and Holst Centre have used a secondary mass-spring system to increase the power (or bandwidth) of a MEMS-based energy harvester.
They demonstrated power amplification up to a factor of 51 by simply placing a packaged harvester on top of a thin metal beam. The presented solution can easily be implemented in real applications, for which the power (or bandwidth) generated by the original MEMS harvester is insufficient.
Vibration energy harvesters rely on the amplification of an input vibration by putting a seismic mass at mechanical resonance. The mechanical energy of the resonating mass is then partly converted into electrical energy, e.g. by a variable capacitor (electrostatic harvester) or by a piezoelectric capacitor (piezoelectric harvester). The power output typically ranges from 50 up to 500µW. Imec and Holst Centre now present a method to amplify the power output or the bandwidth of such a harvester by placing the packaged MEMS harvester on a steel beam. This is analogous to adding a second mass and spring to the original harvester mass-spring system. This method is very useful for applications for which the vibrations are too small to generate useful power, or for applications with sinusoidal vibration sources such as engines, for which the bandwidth of the harvester is too small.
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