Unlike some projects that I kvetch about where “design” is merely art, and nobody has run the numbers, here’s a project that can actually work.
Body-heat powered flashlight takes teen to Google Science Fair
Makosinski did some calculations to see if the amount of energy produced by warmth from a person’s hand was theoretically sufficient to power an LED bright enough to use in a flashlight, and she found it was more than enough.
Boom! That’s how you do it!
It’s not going to work (or work well) in hot weather because it needs a temperature difference, but it’s great for cooler climes and times.
so could it work in reverse? if the air was hot and the body was cooler?
it seems to me it would also work in extreme hot as well in cool weather.
It would if you also reversed the thermoelectric components; AFAIK there is a polarity to them, so they would be set up for the hot reservoir on the outside and cool on the inside.