Hm, 0.5mw for a usable LED brightness? Every LED I've seen uses a minimum of 20mw. Add 50% efficiency of the upconversion, stepping from 0.5 volts to 2.5 volts and you need 5 * 2 * 20mw = 200mw at 0.5 volts.
Ah, after watching the end of the video, I see. She's greatly underdriving the LEDs and they're really, really, really dim.
This also is highly dependent on the ambient air temperature and won't run for long unless there's a breeze.