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ckach t1_j0mbgn8 wrote

Reply to comment by The_Ombudsman in Switzerland’s Giant “Water Battery” Starts Working by Wagamaga

It's probably somewhat common knowledge, but the physics are pretty straightforward.

Energy = (mass of the water) * (acceleration of gravity) * (height it goes down)

Acceleration of gravity is ~10m/s/s

Height is in meters, usually several hundred for these projects

Mass of the water is in kg. 1 cubic meter of water is 1,000kg, so you can get the mass straight from the size of the reservoir.

The energy will be in Joules. For there are 3.6 million joules in a kwh, so divide to get it in kwh.

So, if you have 50k cubic meters of water going down 500m, that would be

(50,000 * 1000)kg * 10m/s/s * 500m / 3,600,000 ~ 70,000 kwh

50,000 cubic meters of water would be 10m x 50m x 100m, for example.

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Weareallgoo t1_j0mg5y9 wrote

This is not quite correct. Your formula is for potential energy. To calculate the power generated by a hydro power turbine, you need to use flow rate (l/s) or mass rate (kg/s), and include head loss and turbine efficiency.

Also, 1 cubic meter of water has a mass of 1000kg, not 50,000kg

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ckach t1_j0mi9yu wrote

Yeah, I just wanted to go over energy rather than power since it's what is usually more important to the discussion. Another comment mentioned efficiency, so I didn't bother with it.

The 50k kg was definitely a mistake on my part. I tried editing it from 1k to 50k cubic meters in the example, but must have changed the wrong 1,000.

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