The manufacturer claims 60-75%, with a lifespan of 30-40 years https://highviewpower.com/technology/

Per https://kth.diva-portal.org/smash/get/diva2:1216213/FULLTEXT... , the theoretical maximum seems to be ~70%. Which is not bad but not great either if you compare it to Pumped hydro storage.

That's not increasing the efficiency of the storage, though. It's just using otherwise wasted heat from a different process (which could probably be otherwise used for cogeneration or something).

In hot countries it might be efficient if the chilled exhaust is used for air conditioning or something, I guess.

The article says 25%.