[sir_bearington]

The point is that saying "No one is presently making these" on one hand, and claiming that they're within existing industrial capacity is contradictory. Energy markets like Hawaii and California are already hitting situations where energy cost is near zero due to overproduction from intermittent sources. But the promise that entrepreneurs will store this energy and put it back on the grid later has yet to pan out - contrary to the insistence of storage evangelists, hydrogen storage, synthetic methane, thermal batteries, and whatnot are a lot harder to build than one might think.

[pfdietz]

It's not contradictory. The storage is not being done now not because it's impossible, but because the market conditions that would cause it (specifically, high carbon taxes) aren't there yet. Something like pumped thermal storage requires no new technology. It's just putting together things we can already build.