[pibaker]

If all you have is a lawnmower engine, it doesn't matter how much gas you have. You won't be going very fast.

Same deal with energy storage. Yes energy capacity matters. But if you can’t put stored energy into the grid fast enough you get a brown or black out right away.

[dragontamer]

Except we have flywheels to solve the power problem (single digit minutes of storage, extremely high power).

The reason why batteries are being talked at all is because we are missing the energy storage problem (hours, or even days. Some people want seasonal storage but that's impossible with our current levels of tech).

The so called lawnmower engine that stores energy slowly in the summer but delivers it slowly in Winter would be more useful than you might think. Especially because we have solutions for every other tier (capacitors/supercaps for seconds of storage, flywheels for small minutes of storage, batteries for large minutes of storage, pumped hydro / compressed air energy storage for hours of storage).