Hydropower for Dummies

water-powered mill

Lately, our staffers have come across a disturbing number of freelancer articles that go to great lengths to answer a fairly simple question, yet somehow manage to fail to answer the actual question. The posts are sort of "shotgun" in their approach: throw as many factoids as possible at the paper in hopes that the reader won't notice that you have no idea what you're talking about. That seems to be the approach returning DotD Lauren Vork took in the eHow.com post, "How Does a Waterfall Generate Power?" (now niched at Leaf Group's Sciencing.com).

Vork, here making her fifth appearance on the podium, went into great detail about "History... Turbines... Magnetic Generators... [and] Damming" to explain hydroelectric power. As befits a liberal arts grad attempting to describe physics, she munged some of it up:

• "When the turbine is placed in the path of falling water, the turbine moves a shaft which, in turn, powers an electrical generator." – Actually, the turbine spins a generator, not "powers" a device that generates electrical power..
• "...a standard [sic] electromagnetic generator... works to convert mechanical energy... through an apparatus which moves magnets around a conductor, generating an electromagnetic field that is then collected as electricity." – That's so clumsy an explanation that we can't begin to correct it.
• "While hydroelectricity can be generated from naturally existing waterfalls, most hydroelectric plants generate water from human-made waterfalls."  – In case you didn't know, hydroelectric dams don't have turbines placed in "waterfalls"; they're in channels or tunnels. 

All that aside, Lauren dodged the central question (and the one the OQ was most likely asking). The ultimate answer to the question? A waterfall generates power – not necessarily electricity, despite Lauren's laser-like focus on hydroelectric power – through the kinetic energy of the water as it falls, a combination of the water's potential energy and gravity. It's as simple as that, and Vork nibbled around the edges a couple of times, although she managed to muck up even that:

"Before the invention of electricity, river waterfalls were used to move turbines, which powered mills that could grind wheat into flour far faster than any human hand."

Sorry, Lauren: water-powered grist mills didn't use turbines; they used water wheels, usually set beneath (overshot wheel) or above (undershot wheel) a flume. The falling water's kinetic energy caused the wheel to turn, which turned grindstones via a set of gears. Regardless of what our Dumbass of the Day seemed to think, no electricity was involved.

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