Wasn't the energy storing train idea pretty much debunked? Can't find the reference now as Google is flooded with media coverage of the idea, but I'm pretty sure that someone worked out that the system would be very inefficient and would need a huge area of track and sidings to store a useful amount of energy.

Maybe I'm misremembering, and I really hope I'm wrong, but the energy storing concrete tower idea sounds a bit too good to be true.

Yes, we debunked the gravity train and Steve corrected the mistake later. So it is weird that that the rogues were so unskeptical about the basic claim of the energyvault.ch people. The website is suspiciously vague on technical details, but the presentation super slick.

My back-of-the-envelope calculations show that the numbers do not add up.

The claimed 35MWh storage energy in a single tower would be the equivalent of lifting a whopping 218,750 metric tonnes of concrete up an average of 60 meters (potential energy = m * g * h). So the tower would need to stack ~22,000 heavy concrete boulders of 10 tonnes each. The lower ones don’t store that much, the top is 120m so average is 60m.

That is a lot for 6 cranes on a tower. Also: think about what happens at the bottom of the tower. It seems to be doing a “towers of Hanoi” trick that would require even higher towers to get enough height differential.

And to generate the claimed 3.5MegaWatt output power it would have to drop 21,875 metric tonnes at the speed of a meter per minute. Or 219 massive boulders of 10 tonnes each simultaneously at a speed of 10 meter per minute. That would be 37 10-ton boulders per crane arm. I don’t see that happening.

Bottom line: there is not enough potential energy in lifting a weight. Only pumped storage can move enough water mass for gravity storage.

Weights are only good for powering grandfather clocks.

Either I made a mistake (please correct me), or these energyvault.ch guys as bad at physics, or they are frauds.

This is the promo video they made to scam investors. Notice that they confuse potential energy with kinetic energy.