Thermoelectric generator and piezo

[tkelly-lord]

Hi guys,

Ok so i'm making a energy charger whilst camping and am researching into new sources of energy.

One is thermoelectric. Was thinking I might be able to intergrate into a jacket, maybe a peg you stick in the ground or the ground sheet under the tent or any source with the biggest difference in temperatures.

All the videos online use ice or a blow torch which is quite extreme temperatures compared to the camping environment. Does anyone know what difference in temperature would be needed to produce any power?

Another concept is a piezo electric generator, harnessing the vibrating energy whilst walking. I love the idea but not sure if it will produce enough power.

Any input would be great! Thanks if you can help

Tom

 

[ronv]

Both Piezo and Peliter are anemic when it comes to power. Even with sophisticated harvesting the piezo would be lucky to charge a watch (better off with the magnet and coil used in older watches) and the peliter needs a big differential.

 

[tkelly-lord]

How about using piezo electric or similar in a ruck sack. The up and down motion of walking could generate energy.

...not sure how much energy tho. Will look into

 

[crutschow]

The way to get the most energy from walking probably would be with a permanent magnet and coil. Have a strong cylindrical magnet (rare earth type) suspended by two weak springs inside a coil with many turns of fine wire so that the magnet moves up and down through the coil when you walk. You would tune the magnet and spring to have a resonant frequency near the normal walking pace to transfer the most energy and probably mount the assembly more or less vertical to detect the up and down walking motion. The AC current from the coil could then be rectified to dc (with Schottky diodes for good efficiency). For maximum efficiency you would probably also want to use a switching regulator to generate the proper charging current to the battery.

The required size of the magnet, the number of coil turns, and the spring tension would likely need to be determined by experiment. The magnet should fit as snuggly as possible in the coil without rubbing for best energy transfer.

 

[blueroomelectronics]

Commercial kinetic power chargers exist like the nPowerPEG, they are extremely weak eg: 15min of walking = 1 minute 3G phone.
It's also expected that you charge it up from a power source for 4 hrs prior to using. It would take ages to bring it up to a full charge by walking, it's mostly to keep it topped off on a long hike.
Think of it as an EMERGENCY power source not an alternative source.
It's specs say an internal 1AH battery but not the Watt Hour rating which would be more useful. It couldn't charge a Blackberry more than 25% on a full charge.
**broken link removed**

 

[tkelly-lord]

The way to get the most energy from walking probably would be with a permanent magnet and coil. Have a strong cylindrical magnet (rare earth type) suspended by two weak springs inside a coil with many turns of fine wire so that the magnet moves up and down through the coil when you walk. You would tune the magnet and spring to have a resonant frequency near the normal walking pace to transfer the most energy and probably mount the assembly more or less vertical to detect the up and down walking motion. The AC current from the coil could then be rectified to dc (with Schottky diodes for good efficiency). For maximum efficiency you would probably also want to use a switching regulator to generate the proper charging current to the battery.

The required size of the magnet, the number of coil turns, and the spring tension would likely need to be determined by experiment. The magnet should fit as snuggly as possible in the coil without rubbing for best energy transfer.

Thanks Crutschow. Yeah i've been looking at this today. Basically Electromagnetic induction. I think this may be the best approach too. Will start setting up experiments on monday hopefully to see how much power I can achieve. Will let you know how it goes.

What sort of magnet should I be looking for? Like a neodymium magnet?

Thanks!

 

[Oznog]

I'd say the most practical method would remain the hand-cranked generator. There were some "big" ones made that strapped to a tree or whatever and had handles which came out either side, offset 180 deg apart.