Comment by lukifer
5 years ago
I don't know about its efficacy, but my favorite means of mass energy storage is a gravity battery: literally stacking heavy blocks in a huge tower, which are raised and lowered based on energy demands by automated cranes.
At best a 'gravity battery' is as efficient as hydroelectric, since pumped-storage is a gravity battery. Towers, trains, spinning flywheels are high-maintenance by comparison. The technology for pumped-storage requires a supply of water and a high place to pump it to. Used around the world (Europe & US, at least) since 1890s.
Bath County, VA: capacity 24GWh, since 1985
https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricit...
Dinorwig Power Station, Wales: capacity 9.1GWh
https://www.theregister.co.uk/2016/05/16/geeks_guide_electri...
Worldwide, today
https://en.wikipedia.org/wiki/List_of_pumped-storage_hydroel...
Hmm I'm not so sure about that: gravity is weak.
In some news article they say Energy Vault uses 35-ton blocks hoisted up to ~150 m - while it sounds impressive, that's only 14.3kWh (assuming 100% conversion efficiency), or about 1/7 of a single Tesla Model S (100kWh).
When I briefly looked into this, my takeaway was that the energy density (and thus price) is much, much lower than needed to compete with other storage mechanisms.
As another poster said, gravity is relatively weak compared to the other forces.
Yes, when a magnet holds up a nail, what you're seeing is that the force of the tiny magnet on the nail is much much higher than the gravitational force of the entire earth on the nail.
There are many nifty schemes like this, such as compressed air, cryogenics, hydrogen, thermal, different battery chemistries, etc. Efficacy in the form economic scalability is the crucial characteristic.
Seems like a novel take on the same principal behind pumped storage hydro systems. But, at a max of 80MWh of storage, you'd need hundreds of them to match a single pumped hydro facility, which often have 10,000+ MWh of storage.