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.
For micro-hydropower in Europe or the US, I believe we are still running into the environmental issue. I understand in most countries, it is illegal to build hydropower even in small streams, and even if you own the land, without a lot of red tape and approval from environmental authorities.
But I would love nothing more than to be proven wrong! I hope your father succeeds in this!