A very common thought inside my head is a benign hydro electric power generation system. I think wind is a waste of time, they spin for a very long time just to offset the carbon dioxide gas produced to make them before they are beneficial. This is how my benign hydro electric power system would work.
Along the river banks there would be drains that flow into aqueducts that are below ground. The aqueduct would zigzag down the valley, following the path of the river but it would be below the ground. At certain points the subterranean aqueducts would flow through underground water wheels and cause them to spin, this would generate electricity. Then the water would flow out of the aqueduct through a drain back into the river downstream.
There would also be butterfly valves in the ducts to stop the flow of water if power wasn't needed. The mouth of the drain would be close to the water line so it would take some of the water from the river but not too much because that would cause trouble for the fish. This system would also not cause villages to be flooded, it would do the opposite, it would help stop flooding because a lot of the water would be inside the aqueduct so it would lower the level of the river a bit and it would not get in the way of fish migrations like a dam would.
