When I first came across this I thought — did he regulate the output in any way? Probably not. Then I saw this from Amazon’s preview of “his” book (it was almost certainly ghost-written):

“Quiet down,” someone said. “Let’s see how crazy this boy really is.”
… I gripped the reed and wires and waited for the miracle. Finally it came, at first a tiny light that flickered from my palm, then a surging magnificent glow. The crowd gasped and shuddered. The children pushed for a better look.
“It’s true!” someone said.
“Yes,” said anohter. “The boy has done it.”

So I thought — fine, if it’s for a light bulb, then it doesn’t matter. But for a radio? Okay, it was probably a portable radio with its own regulator, so as long as the output was at a high enough voltage, it’ll be fine, even if wasteful.

As I observed more of this story, it became clear (when he said that the output was 12 volts) that the bicycle frame was an electrical bicycle! With a motor! That probably ran off of a 12 volt battery pack. So he ran the system backwards. No wonder he needed a bicycle, which was kind of strange at first.

So on youtube, a comment pours some cold water:

I am a medical doctor, a surgeon, I was working with a humanitarian medical organisation. If I was an African, I would be insulted at this diatribe. this project would not get into a grade seven science fair. The bike already had a generator driven off of the wheel. Adding a fourth blade is neither intelligent or necessary. pitch, airfoil design, wind speed, static resistance are all factors. this boy neither understands physics or basic electricity.

However, this isn’t fair, as another comment says:

This kid was sneaking into school when his parents couldn’t afford it until he got caught and kicked out. He learned to make the windmill while looking for books in a library to teach himself some knowledge since he couldn’t go to school.
Yet here the US education is free, books are free, the school bus is free and 30% of students drop out.
His book should be required reading. Maybe that would make the lazy fool stay in school.

To be sure, the windmill was more of an assembly job than an invention or any serious engineering. And I do think this guy, by writing a book, is milking this for all it’s worth. But, that’s the smart thing to do and doesn’t necessarily make him a fraud. Furthermore, he was 14 years old with limited access to resources. Circumstances make a lot of difference (though less than some believe), so that’s worth some props even if given the tools and ideas any motivated 14-year-old could have done it with more sophistication.