Okay, now that I got that post in
The old fashioned undershot wheels had like 30% efficiency. Then came along a guy named poncelot, who had an understanding of hydraulics. Instead of a pure impulse wheel which used the impact of water against the straight vanes in the water wheel, he designed a curved blade. Water rose up the curved blade and the weight of the water increased the efficiency of the wheel from 30% to 70 - 80%.
These wheels were used up until the early 1900's for grinding grain and supplying mechanical power, when other cheaper (electrical) technology came along and replaced them, and they eventually were all retired..
Fast forward to today: They still are a viable option for creating electricity in a decently flowing stream or river. New wind power generator technology using low rpm rare earth permanent magnet generators are now available.
A stream flowing 10 feet/second can generate 3-5 KW easily with a relatively small diameter water wheel. If one has a few hundred feet of river frontage, they can easily generate 10-20kW 24/7. If your jurisdiction allows you to backfeed and turn the meter backwards, there is plenty of money to be made.
I have drawn up plans for the prototype, and will create my first over the next year or so.
The first thing to do is to pour the concrete pads on the river bank to install the unit to, which is what I will do this summer.