Does it occur to you that our body heat can make a difference, like lighting a 100 watt light bulb?
A girl named Ann Makosinski just invented this kind of device at the age of 15, which runs off the heat of the human hand to power the flashlight. The product is called Hollow Flashlight.
By using four Peltier tiles and the temperature difference between the palm of the hand and ambient air, the flashlight that provides bright light without batteries or moving parts. And it could ultimately provide a cheap, renewable light source to those that lack access to electricity.
The only problem is that it needs a five-degree temperature difference to work and produce up to 5.4 mW at 5-foot candles of brightness.