Good idea. There aren’t so many places you can “just build” a hydroelectric power plant without first building a dam, creating a resovoir, etc., but after that (substantial) investment there are several cases of extremely successful HEP systems.

Smaller HEP projects like tidal power, in which long strings of bouys are moved up and down by the tide, haven’t really demonstrated their value, so far. Strange, though, that tidal power is basically the only sort of energy, other than nuclear, that doesn’t come down to solar power in the end – it is, in a way “lunar power”. Strange.