This Electrostatic Micro Power Generator from Low Frequency Vibration Such As Human Motion describes the analysis, simulation and testing of a micro engineered motion-driven power generator, suitable for application in sensors within or worn on the human body. Micro-generators capable of powering sensors have previously been reported, but these have required high frequency mechanical vibrations to excite a resonant structure. However, body-driven movements are slow and irregular, with large displacements, and hence do not effectively couple energy into such generators. The device presented here uses an alternative, non-resonant operating mode. Analysis of this generator shows its potential for the application considered, and shows the possibility to optimise the design for particular conditions. An experimental prototype based on a variable parallel-plate capacitor operating in constant charge mode is described which confirms the analysis and simulation models. This prototype, when precharged to 30 V, develops an output voltage of 250 V, corresponding to 0.3 muJ per cycle. The experimental test procedure and the instrumentation are also described.
Energy harvesting micro-generators provide alternative sources of energy for many technical and personal applications. Since the power delivered by such miniaturized devices is limited they need to be optimized and adapted to the application. The associated electronics not only has to operate at very low voltages and use little power it also needs to be adaptive to the fluctuating harvesting conditions. A joint development and optimization of transducer and electronics is essential for improved efficiency.
Conclusion:
An electrostatic micro power generator for low frequency energy harvesting applications. This generator shows 40+W of power output at very low frequency vibration (2Hz). Technologies we developed are: 1) a micro power generator consisting of micro ball bearings to roll with the separation gap control and to keep separation gap constant, and 2) a new electric structure to accommodate miniaturization. The advantage of our design is the high power generation structure of both the controlled gap between electrodes and long-range moving, and the high surface potential electrets structure.
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