Wearable Device Generates Electricity From Walking Knee Movements 99
Zothecula writes "If you've ever worn a knee brace, then you may have noticed what a large change in angle your knee goes through with every step you take, and how quickly it does so. A team of scientists from the U.K.'s Cranfield University, University of Liverpool and University of Salford certainly noticed, and decided that all that movement should be put to use. The result is a wearable piezoelectric device that converts knee movement into electricity, which could in turn be used to power gadgets such as heart rate monitors, pedometers and accelerometers."
Re:Travel! (Score:4, Interesting)
Quick comparison with a regular AA battery... they are usually around 2000mAh, 1.5V, or about 3Wh energy. So about 1500 hours of constant knee movement at 2mW. Assuming a generous 4 hours/day of walking, this generates the equivalent of a single AA cell every year. Meh.
Re:More power (Score:4, Interesting)
I was thinking more along the lines of the stillsuit [wikia.com], which if I recall correctly was powered in via movement.
The human dynamo (Score:4, Interesting)
Walking is a very low-energy form of movement that relies on some highly evolved bio-mechnics. Attempting to harvest a useful amount of energy introduces dissipation in parts of the 'mechanism' that have not evolved to handle it. The result can be anything from mild discomfort to quite serious injuries. So, such techniques are limited to a few mW, and are in most respects inferior to using a battery.
It's been years since I saw a bicycle with a dynamo on it for similar reasons.
Perspective (Score:3, Interesting)
At 2 mW, you'd have to walk for over 1000 hours to generate the energy held in 1 AA battery. Rather than strapping a wonky device to my knee, I'd rather just carry a spare battery.
Related, my bug out bag doesn't contain a hand-crank radio or flashlight. It has a couple packs of AAs, which are much lighter than the food to replace the energy I'd expend cranking. They'll last me at least a few weeks. If civilization can't reestablish itself in that time, I'm probably fucked, regardless of electricity.