The article says, twice, that his design both stores and generates energy. Have they got something wrong? I'm aware that they're using the term 'flywheel' pretty broadly, and his newer device might not be a traditional flywheel. They use scare-quotes a couple of times when using the term flywheel, so they seem to be saying it's not a flywheel.
> His latest project -- perfecting a prototype of his lightweight "flywheel," a cylindrical, rotating battery -- could revolutionize the energy industry, storing and creating energy better than any conventional electrobattery on the planet.
> Post has been called the "father of the modern flywheel," a title he dismisses as "too generous." The rapidly spinning devices not only store energy with minimal losses, but they also generate it.
The relevance is also mentioned in the story - he wanted to "apply physics to help solve the world's energy problems" and banks of these in power stations might help. Isn't storing the excess power generated by solar farms during the day a problem? Couldn't something like this help with that?