Since when was energy density ever been a problem for grid storage? Even in the most crowded cities on earth it's not a constraint.
Unless you are talking about portable applications it's all about round trip efficiency and cost, I'm not sure if you are getting confused about terms here or talking about an entirely different subject.
Compressed air efficiency isn't great. Using it for cooling lowers the efficiency even more.
Crane and rail gravity storage are pushing 80-90% round trip efficiency.
Unless you are talking about portable applications it's all about round trip efficiency and cost, I'm not sure if you are getting confused about terms here or talking about an entirely different subject.
Compressed air efficiency isn't great. Using it for cooling lowers the efficiency even more.
Crane and rail gravity storage are pushing 80-90% round trip efficiency.
Previous HN discussion: https://news.ycombinator.com/item?id=17789456