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10 April 2007 Energy harvesting by magnetostrictive material (MsM) for powering wireless sensors in SHM
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A new class of vibrational energy harvester based on Magnetostrictive material (MsM) Metglas 2605SC is deigned, developed, and tested in building practical energy harvesting wireless sensor networks. Compared to piezoelectric material, Metglas 2605SC offers advantages including ultra-high energy conversion efficiency, high power density, longer life cycles without depolarization issue, and flexibility to operate in strong ambient vibrations. To enhance the energy conversion efficiency and shrink the size of the harvester, Metglas is annealed in the direction normal to the axial strain direction without the need of electromagnet for applying bias (static) magnetic field. To seamlessly integrate with a newly developed wireless sensor at NC State1, a prototype design for the MsM harvester is proposed. An analytical model is developed for the harvesting using an equivalent electromechanical circuit. The model resulting in achievable output performances of the harvester powering a resistive load and charging a capacitive energy storage device, respectively, is quantitatively derived. An energy harvesting module, which powers a wireless sensor, stores excess energy in an ultracapacitor is designed on a printed circuit board (PCB) with dimension 25mm x 35mm. The main functionalities of the circuit include a voltage quadrupler, a 3F ultracapacitor, and a smart regulator. The output DC voltage from the PCB can be adjusted within 2.0~5.5V. In experiments, the maximum output power and power density on the resistor can reach 200 &mgr;W and 900 &mgr;W/cm3, respectively. For a working prototype, the average power and power density during charging the ultracapacitor can achieve 576 &mgr;W and 606 &mgr;W/cm3 respectively, which are much higher than those of most piezo-based harvesters.
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Lei Wang and F G. Yuan "Energy harvesting by magnetostrictive material (MsM) for powering wireless sensors in SHM", Proc. SPIE 6529, Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2007, 652941 (10 April 2007);

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