Since it's up I'll just directly quote from the horse's mouth:
"Velkess’s flywheel was conceived from the very beginning up to provide dramatically lower cost for performance. To do this we had to take a fundamentals approach, re-imagining the flywheel from the ground up.
Flexible vs. Rigid
Traditional flywheels are designed and built like the turbines of high performance jet engines. They use super rigid materials and super high precision fabrication to very tightly control the powerful natural dynamics that are characteristic of all high energy spinning rotors. These materials, precision, and control techniques are all very expensive, so you simply can’t use the traditional rigid approach to make a low cost system.
Velkess’s flywheel is flexible and works very much like a cowboy’s lasso. Our flexible system embraces the natural dynamics of the rotor, redirecting any stray energies into stabilizing counter forces. By working cooperatively with these natural rotor dynamics we gain excellent control of the rotor system without having to crush out its irregularities. Because of this we can use much less expensive materials and don’t need nearly as much precision as rigid designs."
http://www.velkess.com/technology/
One day I hope to build a microhydro plant and having one of these would be great.