Insole Energy Harvesting

[摘要] Various energy harvesting techniques have been studied extensively to power portabledevices. Each technique has proven to have advantages and disadvantages. Generatingenergy from human walking is an important energy harvesting application area. Piezoelectricharvesters have come to dominate this area in the last decade, in particular, those thatemploy polyvinylidene fluoride PVDF and PZT (Lead Zirconate Titanate). However, thelow power conversion efficiency of PVDF and durability limitations of PZT have hamperedthe progress of insole energy harvesters This project is an attempt to generate new optionsfor insole energy harvesters to overcome those limitations. It compares the performanceof three classes of insole energy harvesters:A baseline harvester employing Terpolymer of P(VDF-TrFE-CFE), a high durabilityand high-efficiency piezoelectric polymer.A harvester employing a newly developed ferroelectric material, cellular polypropylene(PP).A harvester employing a composite made of Terfenol-D, the magnetostrictive material,and polyurethane, a soft polymer.Insole energy harvesters were designed to convert to electrical energy the potential energy(pressure) realized in the heel during the heel strike stage of walking. The harvesterswere fabricated and tested experimentally to measure their output power under identicaltest conditions. Results show PP harvesters outperform all others. A non-laminated PPharvester produced 617 µW output power under sinusoidal force at 2 g acceleration.The project also analyzed the rectification and power management of output power.Thethe efficiency of an off-the-shelf power management chip designed for energy harvesters, LTC3588-1, was found to be less than 10% while that of a custom circuit made of silicon diodes anda switching power supply was found to be better than 90%. Because the available poweris low, sub-milliwatt, it is important to match the impedance of the harvester to that ofthe power management circuit, to minimize ON-resistance, and current backflows.

[发布机构] University of Waterloo

[关键词] Energy harvesting, power management circuit, piezoelectric materials