This is an aerodynamic oddity so I'll drop it here.
I've mentioned a few time that R. B. Fuller advocated for indoor windmills. I've always liked the idea.
Here's someone who gets it.
www.euronews.com/living/2020/09/30/could-this-be-the-safest-most-powerful-wind-turbine-in-the-world
It's not clear about their hubless rotor design but the converging duct is the key. This needs to be embedded at the zenith of a sizable hemisphere. Then the guide vanes can be extended to increase that 40% factor. Putting it on top of the hemisphere increases the nominal wind speed even more.
It appears to be a 1kW device. There is a Kickstarter page, but it doesn't like Raspian's system clock.
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Maybe more on-topic, I found thing looking for something else:
historysdumpster.blogspot.com/2016/05/1930s-traveling-movie-theater.html