This is proof of concept by a girl who spent $26 dollars on materials. I'm sure there are practical applications if we think hard enough and if we threw some money at it. The circuit is probably an invention. I hope she has something on file at the USPTO.

By the way, I would like to know who saw the video when they post. The girl explains a typical journey of an inventor. She also mentions the weaknesses that some have repeated here. Her story is inspiring. It's worth a watch. I hope to raise my daughter to have her type of confidence.

It just sounds like a solid state boost circuit to me, been in LED flashlights for the past 5+ years, and you can buy one for a few bucks shipped.

I can't imagine no flashlight company ever tried this concept, probably did and concluded it's not viable.

Yes, that's what she did. The linked article says she had a hollow tube, with ambient air on the inside to provide the coldness. She says it worked for at least 20 minutes, so presumably she had enough air-flow through the tube to keep it cool enough.

Yes, she says it was brighter with an ambient temperature of 5C than of 10C, but even at 20C there was enough power to produce light. I see this partly as a testament to the efficiency of modern LEDs.

Of course, you need to manage your expectations. It's not going to be as bright as an AAA-powered key-chain light. However, the darker it is, the less light you need, because your eyes adjust. 1-3 lumens can be enough to find your way indoors.

I think this technology should continue working indefinitely. It's not like a wind-up torch where there are a lot of mechanical parts that can break. Those often use a battery to store the power anyway, and that battery will have a limited lifetime.