how much heat does the warm side of a 12v thermoelectric peltier produce?

I'm thinking of using a thermoelectric peltier device to heat my body while sleeping during winter camping (I have a 12v solar panel and where I'm going it's always light out). Will the warmside of the peltier heat enough so that if its in contact wih my body it will warm me? if its too hot i'll just wrap it in a sock or soimething.?

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110100101108 years ago
i dont think its too far more efficient than any heating element that just turns electricity to heat. but its sure far more expensive you can build very easily heating elements solar panels are extremely inefficient. itll be way more efficient to warm water in the sun and then place it in bottles in the sleepbag or just get a better sleepbag / insert them one in one. on my experience 3 hollowfiber bags are acceptable at 0 C under the sky
leevonk (author)  110100101108 years ago
actually, when you water bottles outside in the arctic circle they tend to freeze. also, you can buy large peltier heaters from allelectronics pretty cheap (under $30). and I'm pretty sure peltiers are much more reliable than coiled pieces of high resistance metal used in other heating elements.
masl leevonk8 years ago
You are presumably aware that the peltier is a heat pump. i.e. they pump heat from the cold side to the hot side. For a heat pump to have any effect there must be thermal insulation separating the two sides. A heat pump which was 100% efficient operating in an enclosed space (without insulation between the sides, would heat one side and cool the other thereby pumping heat in a circle for a net effect of precisely zero. The application as you have described it is exactly this, therefore any heating effect will be due solely to the inefficiency of the peltier device. If you think that semiconductors would be more durable than bits of wire (unlikely) you would probably get better reliabiity and lower cost using a mosfets as the heating elements.

"A heat pump which was 100% efficient operating in an enclosed space (without insulation between the sides, would heat one side and cool the other thereby pumping heat in a circle for a net effect of precisely zero."

Not true. Unless this peltier is running on magic, there will be a net gain in heat due to work needed to drive the heat pump. In this case the energy gain is from the 12v power supply.

As people already said, for a basic heater, use a resistance wire, preferably mounted in some way to keey it safe from hot spots forming, or electrical short circuits. In direct answer to the original question, and in no context whatsoever, the amount of heat out of the 'HOT' side of a Peltier (TEC) is the heat pumped, PLUS the heat emitted in doing the work of pumping. I won't elaborate, just remember that much, because it's often overlooked, even by people who have already gotten way deeper into the subject of TEC's...
You should use a resistive heater. Like nichrome wire with some protective layer. Its cheaper. Peltiers are better for cooling.

Check out my entire instructable describing what you can do with a Peltier.

https://www.instructables.com/id/Charge-Your-Cellphone-Using-Wasted-Heat/

~splitreaction
mnorri8 years ago
Peltiers are inefficient heat pumps. If you have it inside your bag, one side will get hot, but the other side will get cold. If it's all inside your sleeping bag, you might as well just get a cheap resistance heater. The heat moved by a peltier is mostly a function of the current flow. You don't actually want to run a peltier at max current without careful design - they will fail pretty quickly if they over-temp. As for the max temperature, it depends on lots of things - the specific peltier you're using, what it is connected to (heat sink and load). The ones I've used have a 70C max temperature differential - but that's with no load. If you're trying to warm something up - i.e.. move heat - then that max differential will drop down until you reach some maximum heat flow rate (which is determined by what is connected to the hot and cold sides of your peltier. The current and voltage the peltier will draw is therefore variable. As for reliability, I'll just say this: when we're designing equipment, we always prefer heat only, as resistance heaters are cheaper, easier and more reliable than peltiers. Hope this helps.
Sandisk1duo8 years ago
not the best idea.... just get a black tent, it will be WAYY more efficient then a peltier
leevonk (author)  Sandisk1duo8 years ago
not a bad idea, I already have a very dark blue colored bivy sack that I was planning on using. but I'm still curious cause I've never used a peltier before.
if you were to use solar panels to power the peltier, it wouldn't work... if you left the panel out in the sun, connected to the peltier, sure the the peltier would get warm, while the solar panel gets hot (solar panels are 10-17% efficient, whatever sunlight is not converted to electricity will turn into heat)
leevonk (author)  Sandisk1duo8 years ago
my solar panals puts out 12v at 1 amp, but you're right, all the peltiers I'm seeing need over 3 amps.