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Wouldn’t it be better to have some underground cistern and as water flows down it passes through a turbine? A roof solution will generate a tiny amount of electricity.



> Wouldn’t it be better to have some underground cistern and as water flows down it passes through a turbine?

Congrats, you've invented the hydroelectric dam.


EROI for that is almost certainly negative and it's more likely to just be a source of clogs and maintenance.


Heck! For many of us, that cistern would help cover for our many drought periods, electricity notwithstanding...


I've thought about it, but water in my area is so cheap the payback would be forever.

I pay about $30/month for local utility water. It's metered, but I rarely exceed the minimum billing amount.


Could theoretically put a wheel/turbine in downspouts from the roof.


I forget the ending but I think its milliwatts https://www.youtube.com/watch?v=S6oNxckjEiE


XKCD did a What If about this very scenario:

https://what-if.xkcd.com/23/

If the generator cost $100 to buy and install, it would take nearly a century to pay back its install cost even in one of the rainiest locations in America.


I found the bottom of that page much more interesting.

>> What if you strapped C4 to a boomerang? Could this be an effective weapon, or would it be as stupid as it sounds?

> Aerodynamics aside, I’m curious what tactical advantage you’re expecting to gain by having the high explosive fly back at you if it misses the target.


Death before dishonor.

Or at least put a remote trigger on it so you can get some splash damage on your target.




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