This kit, the latest in a line of hands-on guides to alternative energy, is billed for kids 8 and up. Earlier kits include Wind Power, Fuel Cell, Power House, and Global Warming.
Hydropower Renewable Energy Science Kit
Thames & Kosmos; US $49.95
https://www.thamesandkosmos.com
There are tubes and straws for some fun experiments involving water towers and fountains that you can make from plastic bottles. But the main events are three different toy mills built around a water wheel. One moves a "saw" back and forth, one repeatedly lifts a "hammer" a few inches and drops it, and the third—the coolest—creates enough electricity inside a small DC generator to light a red LED.
Each experiment took about an hour of assembly and debugging time—mostly the latter, as even older folks will look at the pictorial instructions and scratch their heads over exactly where the anchor pin or gear-shaft rod should go. One more slight criticism: The single electronic component could have been a little less flimsy.
That said, when the hydropower station was finally working and the bathtub water turned on, this reviewer and his 3-year-old were thrilled to see that tiny red diode light up—a beacon of sustainable power for the next generation.