HN user
Unfortunately the "compressiontest" folder mentioned in the article has been taken down. Does anyone have any insight into its contents?
Edit: nevermind, answered my own question: http://www.seroundtable.com/archives/022125.html
Well yes, and that's what the system you mentioned does. In addition to pumped hydro, there are schemes for pumping air into underground caverns.
You need too much volume to make artificial tanks cost-effective. That's why natural formations are used.
You bring up good points, but mental multiplication is a bad example. That's certainly more related to an inadequate notation for the task than any trend in human intellect.