what is the ELi5 for Compressed Air Energy Storage - is it what it sounds like, just a massive pressure tank, energy being tapped by releasing the pressure?
Essentially yes, they also get efficiencies from heat exchangers too on the way in and out:
“The new Zhangjiakou plant does away with fossil fuels, using advances in supercritical thermal storage, supercritical heat exchange, high-load compression and expansion technologies to boost system efficiency.”
