@neauoire every time you post about this i think of the Mr. Wizard's World (80s kids science show) episode where he cooks breakfast on a variety of solar contraptions, including some shiny metallic funnels on sticks!

8 year old me thought it was the coolest, of course, but these vacuum tubes are even more neat.

The episode is available here: https://www.youtube.com/watch?v=3bObVFVu_3A