Hmm, I think we are running both on assumptions. This would need some data to be analyzed to actually have a clear picture.

Well, this 80% efficiency is what they are targeting not what the system will do. The test system Energy Vault build in a MUCH smaller form factor had a round-trip efficency of 75%

The EVx ™ system is projected to achieve an impressive round-trip efficiency exceeding 80%. Source

Only time will tell if they can reach 80% with a bigger system or at all. If they actually manage this it would be a decent alternative to Hydrodams in areas where these are just not possible since it would be a similar round-trip efficency.

Pumped storage systems have a round-trip efficiency of about 80%, which is competitive with battery storage. Source

In my opinion these systems are inferior to fly wheel energy storage (can reach up to 90% round trip efficency Source) but might still be an option depending on price.

Nah, most projects where just abandoned. Most projects never reached maturity and where abandoed in like weeks if not days. Look at the amount of 0 to 10 star github repos that are open source and had no commits since ever. LLM’s just removed the hurdle to start something “simple” so now the problem just grew in size.

That would be a fun website. Asshole tracker for Companies & Politicians and others?