Fortunately the laws of Thermodynamics are safe, it it converting kinetic energy into electricity. It doesn't appear to be more efficient that existing hydropower solutions but it does seem to be applicable to a wider set of flowing water conditions (which is why, I'm sure, they keep talking about single family homes).

Hands up, I know zip about thermodynamic/fluid dynamics etc. My background is in mechanical engineering and editing. That article doesn't pretend to be a technical masterpiece, but instead is 'WEB' written, and serves solely as an introduction to a relatively unknown design and concept. Which, consequently, is available to buy should anyone wish to pull it to bits and have a look at the internals, which is something I wouldn't mind doing!

It's just slightly sloppy editing somewhere. It should be "rolling fluid principle, a vortex dynamic" or something like that. "Rolling fluid principle" is the name Sedláček gave the particular mechanism at play here, and it falls under vortex dynamics.

I think it's been translated, too.