This article in Discover magazine about Jack Bitterly's* desire to use new flywheel technologies to power automobiles, is what got me excited about choosing engineering as a college major. It's quite sad that nothing ever came of it, other than a few highly specialized applications, such as the space station. (I read one claim that Kevin Costner's investment in the company was a total loss, but that it had a lot to do with NASA taking over the project and stiffing some of the creditors. Cum grano salis.)
I recently saw that a company called Velkess got a kickstarter project funded for 3-15kWh 48v flywheel storage systems, with expected product delivery dates in the 2016/17 range announced. We'll see if they deliver on promises and if they're in any way price competitive.
*Jack was 77 when that article was published in 1996. Every so often I've looked him up on the internet and as late as 2009, he was still alive and kicking and still working. I've also run across patent applications he has filed as late as 2013. Wow. I hope like heck I'm still that active and doing things I am passionate about in my 90s.