Yes, the drawing is pretty, although some impressionists have even better made the water mills ...
Without digressing too much towards aesthetics, these questions have been studied for at least two centuries by various scientists and engineers endowed with powerful means of investigation; all this has led to the abandonment, generalized in modern countries, of this type of "turbine" for low head; however, the market and the stakes are high: run-of-river power plants, tidal power plants, pico-plants ...
The reason for this abandonment is simple: only the valorization of a laminar flow of water allows to reach good yields for the production of electricity; out, the impeller works in principle in turbulent flow, with two stops of the fluid per cycle; it is also the same physical reason which made leave the wheels with paddles of the ships in favor of the propellers (or Voith-Schneider thrusters more recently).
All this led to large-sized machines, slowly rotating, therefore of low mass power and moreover delicate to monitor and regulate.
Very generally, all low-drop installations (below 10 meters) use Kaplan turbines, which are much more efficient and simpler in maintenance, or recently, various interpretations of the Archimedes screw. The Kaplan turbine is relatively tolerant in terms of variations in operating conditions if its initial optimization was correct, it requires very little pressure (at least 2 m) and requires little earthwork for small installations; only the screw can compete with it in some cases of very small fall, but it is still not widespread.
Finally, there are on the international market small units of 100, 200, 300 watts, ready to be installed, consisting of a Kaplan turbine in a steel tube, a regulated alternator and the hose which can be extended according to the drop; this type of machine, made in China obviously, was offered a few years ago for a few hundred euros by the house "Energie-soft" (which must still exist); I think it would be better for our friend to search the net for this type of machine rather than embark on the adventurous construction of a paddle wheel and ball bearings, as well as its sides, a reach in particular , which is no small feat.
Well, I should have started there:
https://www.energiedouce.com/hydro-turb ... 02510.html
