A very impressive 15-year-old from Victoria, Canada, has invented a flashlight that could free us all from the tyranny of AA batteries. It runs on the power of your body heat.

The concept is pretty simple. The flashlight gets its power from plates that create electricity using a heat differential — one side needs to be hot and the other cool. In this case, the heat comes from the palm of a person’s hand. The flashlight is hollow, so that air can cool the other side of the plate.

It works! Watch:

Part of the reason this works is that she’s using LED bulbs, which require less energy to run. So even a little power goes a long way. It’s not the most powerful flashlight out there: It creates 5 milliwatts of power, about as much as a laser pointer. Still, that’s 5 milliwatts of power you’ll be thankful for when the power goes out and you realize that all your flashlights need new batteries and you can’t find the spare ones in the dark.

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