This is exactly how the 6th largest power plant in the UK works (but the turbine is reversed to become the pump)

https://www.youtube.com/watch?v=McByJeX2evM

https://electricityproduction.uk/plant/GBR1000151/

There's a number of them all over the world. Surprisingly simple idea and amazingly powerful storage.

https://en.wikipedia.org/wiki/List_of_pumped-storage_hydroel...

The train goes up, the train goes down: a simple new way to store energy https://www.vox.com/2016/4/28/11524958/energy-storage-rail

This sounds good to me and it claims have 86% efficiency.

considering how much trains weigh and how fast they move, perhaps the electrical trains are already being used as "linear flywheels" ?

Since kinetic energy = 1/2 m * v ^ 2 , the a slight change in velocity on the trains that are already moving fast at any point in time, could store a lot of energy (i.e. for 2 identical weight trains, from 0km/s to 1km/s is a smaller change in stored kinetic energy than from 100km/s to 101km/s ! [in fact the latter increase of 1 km/s stores 201 times as much kinetic energy than the former: ((101 * 101) - (100 * 100)) / ((1 * 1) - (0 * 0))]

Now that I think of it, this could probably explain why our local trains are suffering more and more irregular arrival times :) but why would it be kept secret or hidden in plain sight? perhaps all the negative news about negative prices for renewable energy during energy flood is just manufacturing consent to keep price hikes for the plebs palatable, or a kind of white lie to offset their airplane travels...

to be honest I'm not very impressed by the trains up/down proposal:

The trains move on a track 5.5 miles long at an inclination of 8 degrees. thats a height difference of sin(8deg) * 5.5miles * 1.609344km/mile = 1.232 km, now it may be hard to find a steep cliff 1.2km high, but you could use a smaller cliff and heavier weights, think of the steep section at the start of an amusement ride (they will probably be better equipped with safety for such systems anyway since they are used to designing crazy rides for human consumption). no need for train and electrical tracks 5.5 miles long, since the motor can reside on the top part of the cliff/hill...

Interesting, I wonder how long a rail system would need to be in order to be able to pull energy from tidal effects with the moon.

this reminded me of underwater energy storage pilot:

https://arstechnica.com/science/2017/03/german-institute-suc...

Fascinating. When you pump the water out I wonder what it's replaced with? What holds back to pressure of the ocean at 700 meters depth? The article was very light on details, unfortunately.

My understanding is that they do not replace it with anything.

I'd assume the only thing they look at is not to go above the pressure differential that the dome/sphere can sustain.

That requires big water deposits up in the mountains, along with a dam.

Norway is having great success with this strategy on their hydro plants.

The UK pretty much exhausted its stock of good, easy, large sites with Dinorwig.

Amongst the best and ost efficient energy storage options, but very limited suitable sites.

The Balkans region, along the Adriatic coast, offers an interesting prospect: using the sea as a lower basin with mountaintop reservoirs. This is a rare topology, particularly near large populations.

What the results of localised salinisation might be is a concern though.

One more example.

Bath County Pumped Storage Station in the US. Huge place.

https://www.dominionenergy.com/about-us/making-energy/renewa...