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Portable power

Just saw this link via another forum. Looks interesting, supplying a maximum of 4 watts at 5 volts this will not be any good to most of us but perhaps something that will be developed in the future?

73
Roger MW0IDX

In reply to MW0IDX:
Interesting idea Roger. Twigs might be a problem on top of Tryfan!
73,
Frank

In reply to MW0IDX:

It’s interesting. But not surprisingly you don’t get much power. 2W average is 400mA @ 5V. Charging a LiPo cell needs 4.2V so you could charge a 3S pack at 133mAH or a 4S pack at 100maH. My 4000mAH pack would take 30hrs to charge if the process was 100% efficient, which it isn’t! I think the example they quote is really where it’s at. You’re out camping and you will be cooking some food anyway and you can get enough “free” electricity to get some talktime back into your phone.

I played with Peltier devices years back and what takes a moment to understand is that the voltage generated (Seebeck effect) is proportional to the temp difference. So one side of the Peltier is on your hot stove (100C if you have water boiling) but you have to blow cold air or circulate cold water on the other face. If you don’t have a big heatsink to get rid of the heat then the cold side heats up by conduction and you don’t get as much power generated. The same devices are used in cool boxes. If you pass a current through the device then one side gets cold. The other side gets hot. If you want to cool something down then you need to get rid of both the excitation current (2-3A) waste heat and the heat you have pulled out of the cold face. Big heatsink and fan needed.

I’ve got a box of them in the loft to play with when I get time.

Probably covering your backpack with solar cells and using them to charge stuff whilst you’re walking etc. is more effective in the long run. You get the electricity as long as it’s light and you don’t have to to stop to charge your device.

Andy
MM0FMF

“blow cold air or circulate cold water on the other face”
.
Andy, I think you should just pee on it. Drink lots of ale. On the down side, the renal system is not that efficient and the outlet temp is 98.6 degrees F. On the plus side…Oh, wait. You could bypass that system and just spray the ale directly on it. Be sure to throw some yellow dye in with the spray, otherwise you won’t get on the front page of the local newpaper. Tsk, tsk.
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Elliott, K6ILM
Chaser Clown