isn’t hydropower supposed to be an infinite energy source to produce electricity ?

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Like that water used in hydropower is not wasted right? It can be re routed again and again to form an infinite loop to generate electricity right?. If so, why are we still using steam and fuel energy for electricity?. Thanks!

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You need to overcome gravity pushing the water down basically. Generally done by nature for us, and we tap those resources. So in that sense it’s not an infinite loop – it’s a loop that gets fed energy from the sun.

No. Because gravity. It would take more energy than is produced to put the water back up the hill.

2 reasons:
1. Every machinery has loss due to friction. The turbines have some loss, so they can’t convert 100% of the energy in the water into electricity. Same with pumps to get the water back up.
2. Even if you have 100% efficiency in all moving parts, as soon as you start taking energy out you lose energy in the loop. So at most you’d get out the potential energy of the water.

Hydroelectric energy is extracted from water dropping from a higher height (typically from damming a river until the water level rises. The falling water and the weight behind it is what turns the generator’s turbine.

The sun and rain did the work of getting water to the top of the mountain; the energy of it going back to the sea is extracted just as a waterwheel does.

Pumping the water back up into the reservoir would take more energy than was extracted from power generation. What you propose makes as much sense as putting an electric fan next to a wind turbine to power it.

However, there are similar thoughts, using such pumping technology to fill a reservoir with lower-level water as a battery to store energy, like daytime solar might need – only useful when one doesn’t already have an ample river to supply power and has excess generation capability.

(more basic: A mass at a higher height has more *potential* energy. Letting it fall turns some of that into *kinetic* energy. The act of lifting a weight to a certain height is measured as a particular amount of energy called *work*. If you do the *work* of lifting a bowling ball onto a table which takes energy from your muscles, you can extract the new potential energy by wrapping a string from the ball around a generator pulley and letting it fall to the floor.)

I assume you don’t mean *infinite*-infinite because that’s physically impossible. When the sun goes out, so does the water cycle. Even in a magical world of frictionless pumps and such letting you pump the water back uphill, the whole system could only ever be a zero-sum game which puts out no energy.

As for why we don’t just build hydro plants until we don’t need anything else, the problem is that you can’t just plop them down on any spot of moving water. You need a lot of water going pretty fast for the plant to be worthwhile, and sites like that are not too common, especially if you don’t want to do extensive (and complicated) damming.