On Friday, March 27, 2020 at 4:56:47 PM UTC-5, Amanda Riphnykhazova wrote:
About 25 years ago I bought a baseballs hat with a solar panel on the top which drove a fan motor. It looked terrible and never moved enough air onto the user's forehead to actually do anything. After a while I got the impression that the panel was no longer giving out ANY power.

I wonder if it might be possible to replace the 25 year old solar panel with a more modern one which actually works?

Possibly a flexible panel which goes round the head a bit? What values should I try looking for? Or am I kidding myself that I might get this thing to work? Is that why no one has tried putting these things back into production?

Solar cell efficiency certainly has improved, but not enough (in the cells available to you) to make any difference in that gimmicky hat.