This DIYs project helps to understand how hydroelectric plants work and generally how a mechanical movement can be transformed into electricity.
With this DIYs project, children build the entire system including the coper reels, a disc with magnets and a turbine. When the magnets will move above the reels, electricity will be produced. This principle is found in many common devices (bicycle dynamos, car alternators, etc.).
In Switzerland, half of the electricity it produced by hydraulic energy, mostly from mountain dams. Hydro power has the advantage of being renewable and local.