Can Piezoelectric Crystals in Shoes Charge Your iPod?

[robertjordan]

I was inspired by this article

http://science.howstuffworks.com/environmental/green-science/house-music-energy-crisis1.htm

to wonder if one could put piezoelectric crystals in the sole of a shoe and perhaps harness the energy to charge their iPod?Can someone let me know if this is feasible and what would be the factors preventing it from being realized?

 

[zoobyshoe]

I was inspired by this article

http://science.howstuffworks.com/environmental/green-science/house-music-energy-crisis1.htm

to wonder if one could put piezoelectric crystals in the sole of a shoe and perhaps harness the energy to charge their iPod?Can someone let me know if this is feasible and what would be the factors preventing it from being realized?

Since the article reports they've already done it with a few club floors, then, in principle, your shoe generators are perfectly possible. The one drawback might be expense. It might end up being much more expensive for shoe generators than conventional chargers. If they became popular, however, I'd expect the cost to come down over time. Seems to me it'd be a popular product with kids from 1st grade all through college. That age group usually does a lot of walking.

 

[KL7AJ]

I was inspired by this article

http://science.howstuffworks.com/environmental/green-science/house-music-energy-crisis1.htm

to wonder if one could put piezoelectric crystals in the sole of a shoe and perhaps harness the energy to charge their iPod?Can someone let me know if this is feasible and what would be the factors preventing it from being realized?

The total energy from a piezoelectric device is minuscule...though the voltage can be huge.

 

[zoobyshoe]

The total energy from a piezoelectric device is minuscule...though the voltage can be huge.

The article in the link claims: "One footstep can only provide enough electrical current to light two 60-watt bulbs for one second."

 

[robertjordan]

The article in the link claims: "One footstep can only provide enough electrical current to light two 60-watt bulbs for one second."

It takes 120 J of energy to light two 60-watt light bulbs for 1 second, right? And the average phone takes 18000 Joules of energy to completely charge so that's only 150 steps!... I'm sure there is something wrong with that line of thought, haha

 

[robertjordan]

bump ^

 

[zoobyshoe]

... I'm sure there is something wrong with that line of thought, haha

The article you linked to names an article in the Christian Science Monitor as a source. I checked that article out, and it makes the same claim.

However, it goes on to makes more humble claims that sound a lot more realistic:

Human energy can also be harnessed to power a cellphone or charge a battery. Henry Sodano, an engineering professor at Arizona State University in Tempe, Ariz., has developed a backpack that serves as a portable, wearable way to keep gadgets juiced.

His team created piezoelectric straps that draw power from the bag's natural bounce. At a normal stride, the stress on the bands can pull in 45.6 milliwatts (mW) – just shy of what's needed to perpetually power an iPod nano MP3 player, and more than enough to keep a Motorola Razr mobile phone charged.

"We could power a Razr in standby using 9mW of power and store the remaining 36.6mW of power, allowing us to talk for one minute for every 10 minutes walked," he says. "Or you could charge an LED headlamp while you walk in the day and use it at night while you camp."

The catch: for the straps to collect the full 45.6mW, they need to support a 100-pound knapsack. "That's a lot," Mr. Sodano admits with a laugh. But he designed the straps for the US military to use. Since soldiers are used to encumbering loads, the special straps in their packs will capture practically free energy, he says.

http://www.csmonitor.com/2007/0926/p14s02-stgn.html?page