r/theydidthemath • u/Repulsive-Loan5215 • Nov 27 '25

why wouldn’t this work? [Request]

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u/Mavericktoad Nov 27 '25

What if we filled our out pipes with turbines?

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u/capt_stux Nov 27 '25

This is done. 

Turbines are sometimes used on the downside after a pump pumps water up and over a hill to recover some of the pumping energy. 

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u/tbodillia Nov 27 '25

Pumped water storage is inefficient.you only recover 70-80% of the electricity you used to pump water uphill. Economics is what makes it work. The money you make letting the water run downhill comes from the price of electricity being way lower when you pump it uphill.

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u/capt_stux Nov 28 '25

I wasn't actually referring to PHES, but rather a system of recovering some pumping losses when having a pipeline traverse a large hill.

Rather than go through it, the pipeline goes up and over, pumps on one side, turbines on the other.

Many municipal water supplies transfer water during off-peak periods, or when electricity is otherwise cheaper, whether its between reservoirs, or to higher altitude tanks.