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Silicone harvester supplies trickles of energy

Posted: 24 Feb 2014 ?? ?Print Version ?Bookmark and Share

Keywords:silicone? kinetic? magnetic field?

University of Auckland researchers inch closer to making possible the prospect of capturing kinetic energy from routine activities and converting it into electrical energy. Their efforts have yielded a snake-shaped harvester using polydimethylsiloxane or silicone.

The silicone strip, owing to its flexibility, works as a cantilever that bends back and forth with body movements. This cantilever is attached to a conducting metal coil with a strong neodymium magnet (NdFeB) inside, all enclosed in a polymer casing. When a conductor moves through a magnetic field a current is induced in the conductor.

In order to extract the electricity generated, there is a need to include special circuitry that takes only the positive voltage and passes it along to a rechargeable battery. In previous work, this circuitry includes a rectifying diode that allows current to flow in one positive direction only and blocks the reverse, negative, current. Unfortunately, the development of kinetic chargers has been stymied by current diode technology that requires a voltage of around 200mV to drive a current.

Jiayang Song, together with Kean Aw, side-stepped the voltage obstacle by using a tiny electrical transformer and a capacitor, which acts like a microelectronic battery. The charger, which weighs a few grams, oscillates and moves the coil back and forth through the neodymium magnetic field and produces 40mV. The transformer captures this voltage and stores up the charge in the capacitor in fractions of a second. Once full, the capacitor discharges, sending a positive pulse to the rechargeable battery, thus acting as its own rectifier.

The development is first step towards a viable trickle charger that could be used to keep medical devices, monitors and sensors trickle charged while a person goes about their normal lives without the need for access to a power supply.

The system might be even more useful if it were embedded in an implanted medical device to prolong battery life without the need for repeated surgical intervention to replace a discharged battery.

- Paul Buckley
??EE Times Europe

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