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Comment by cfn | Hacker News Reader

I hope flywheel storage takes off (no pun intended) it seems such a logic solution when compared with water elevation or chemical solutions. Why hasn't it gone mainstream yet?

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Cost, mainly. Most flywheels use exotic components, expensive magnetic bearings, must work in a vacuum, etc.

I remember being really hyped about flywheel energy storage... 20 years ago. I wonder if it has become more viable since then? And if so, what changed to improve viability?

https://beaconpower.com/carbon-fiber-flywheels/

These guys have two projects (check their operating plants) using flywheels. They're used for frequency regulation. About 20MW each.

They have become more viable thanks to higher efficiency motors/power components and magnetic bearings, among other things. The biggest drawback is still cost, which is what we're tackling.

In the past they have been made to work, but they were not much better than batteries. With the price of batteries dropping like a stone I suspect they are going to have an even harder time competing.

There are several differences from batteries. Generally the benefits are faster charge and discharge rates, unlimited cycles without degradation, no lithium or rare earths needed, and wider operating temperatures.

They are not good at long term storage though, as the self discharge rate is high. And historically they have been expensive.

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