Disclaimer: I am the inventor's son.

Sure, Kaplan turbine is way more efficient but it is difficult and expensive to use it on such low water head. This bladeless ball is so dumb it can be manufactured in sweatshops and run in dirty irrigation canals from 30cm water head. The potential is huge exactly because we can not build huge river dams any mor. This turbine could utilize micro flows, tidal energy even waste water. By the way it is very efficient as a garden or kitchen cleaning tool on the standard water main.