So I’m sitting here recovering from mouth surgery (ouch!) and it occurs to me through my opiate haze that it’d be pretty sweet to have some kind of device that could charge laptops, cellphones, PSPs, etc when you’re out camping. It also occurs to me that some kind of Peltier device could be placed over a campfire with some water on the opposite side to generate electricity. There’s gotta be a reason why this porduct doesn’t exist either due to expense or size required for the task I have in mind. What’s the straight dope?
Also, what about a campfire sterling engine generator?
It would be fairly expensive, would require constant effort from the user to keep it going (you are going to need to keep changing the water as it heats up so that you always have a temperature differential across the peltier, or else it won’t work), and would be very easily damaged since the heat of the fire is enough to destroy the peltier. Not very practical. If you are careful and are willing to keep changing the water, you could make one of these yourself and make it work. You’d also need to regulate the voltage coming out of it since USB expects something very close to 5 volts, so this would be more complicated than just buying a peltier and sticking a USB socket on it.
If the fire is a bit more controlled, like the stove in Bean_Wrangler’s link, then it is certainly possible. I have a hunch that thing is going to be rather expensive and isn’t going to sell well.
Using a stirling engine to drive a USB charger would be really cool, but rather expensive. It would also be fairly heavy and bulky. I wouldn’t want to carry it camping. I’m half tempted to make one and have it sitting on my desk at work though. It could charge my cell phone while I’m working.
There are Peltier generators driven by stationary chimneys and by vehicle exhausts. One neat change is using different thermoelements with higher temperature limits, but I only know of one company, in Canada, selling these for wood stoves in remote locations.
I could use candles or a small alcohol burner. I said it would be cool. I didn’t say it would necessarily be all that practical. It wouldn’t look out of place mixed in with all of the rope/wood puzzles and the homebuilt electric motor I already have on my desk.
IIRC, the Russians had something like this way back in the day. A kerosene lantern that would power a small radio. Actually, that link has all kindsa cool stuff in it.
But, ultimately, its the temperature differential that makes the current. The problem would be having that same differential at a camp fire… the eat coming from a campfire usually encompasses a huge area. Maybe, if you have an aluminum rod that went into the fire that kept the peltier far enough away to have that differential. Or, the other way around, an insulated rod that was long enough to keep the other side cool.
Overall, pretty bulky. Solar panels that can provide any type of usable current are also pretty bulky. Usable as in, “Oh no! My laptop has 5% left!” and you need to charge it. Yeah, that will take awhile.
I think spending the money on extra batteries is your best bet.