[2thumbsup]

A few hours are sometimes enough to start generators when renewable energy supply decreases. Obviously, the more capacity the better, but costs will increase linearly with capacity in most cases.

Pumped-storage hydroelectricity - where it is feasible - is the only kind of energy storage close to "months".

[ifwinterco]

You can store energy for months pretty easily as chemical energy. Just get some hydrogen, then join it to something else, maybe carbon, in the right proportion so it's a liquid at room temperature making it nice and easy to both store and transport.

Wait a minute...

[pfdietz]

The point is that's already a well-served market. These competitors are like alternative semiconductors going up against silicon.

[pfdietz]

Oh: pumped hydro is not a "months" storage technology. The capex per unit of storage capacity is far too high.