Absolutely horrifying pop science out this past week entitled “Rain may soon be an effective source of renewable energy” (I’m going to put the link over here so I don’t encourage search engines to make this POS more popular … yeah, that was it).
Confession: I followed the link on Monday, browsed the article, noticed it only talked about volts not power, promptly shut it down, and forgot about it.
But it has gotten attention from more capable people this week, who point out that it is part of the increasingly common phenomenon of clueless writing about sciencey stuff on the internet.
The obvious quality of this material is right up there with the late night ads for diet drugs featuring performers in white lab coats … because … you know … sales reps at makeup counters in department stores sometimes wear those too.
Anyway, eat this up:
The question to ask — in fact, the only question to ask — is how much power can be generated by this transformation.
Yeah. You know, what’s important is not that the energy is renewable, but that it actually represents power that might make it a useful form of energy (and then you worry about whether it is renewable or not).
Stunningly, the article doesn’t bother to ask this question. The only number that appears is in the statement that “a single drop can muster 140V.”
Umm … yeah … voltage isn’t power. A weak, but easy to visualize analogy, is that voltage is how fast the water is coming out of the hose — so a dental cleaning device has a lot and a garden hose not too much — while power is about which one you’d like someone to point at your face.
This is like saying my mass is two meters — nonsense.
My sad experience is that if you tell people something they want to believe is nonsense, they will rationalize rather than listen. So I’d call that a swing and a miss.
Volts are a measure of voltage, not power. One can have millions of volts and hardly any power, for example, if that voltage drives a very small current.
I love this next bit:
What matters for generating power is, in fact, power. Anyone who doesn’t understand that volts don’t measure power has no business writing about renewable energy, or technology of any sort. [emphasis added]
The author then goes on to calculate an upper bound on the amount of energy that could be harvested from falling rain:
Plugging it all in, the power per unit area we’d expect to collect is at best, with perfect efficiency, about 0.1 Watts per square meter.
…
A tenth of a Watt per square meter is pathetically low, and keep in mind that we’ve been generous in multiple places. I’d expect less than a tenth of this, i.e. a few milliWatts per square meter, in any real implementation.
For a sense of scale, a solar panel gets around ten thousand times this …
Oh … and while it isn’t nothing, that isn’t to much either. Look at the size of the solar panels along the interstate that light up those superbly energy efficient lights on emergency signs. They’re a lot smaller than a square meter, but they’re bigger than a clipboard.
The original source paper was published in the hugely prestigious journal Nature. It may be time to start using the filter of Gell-Mann Amnesia to think about the usefulness of papers from that source.
And, here’s the best bit for all you environmentalist types out there:
There is, by the way, a very good way to harness rain for renewable electricity: let geography concentrate the water into a river, then build a dam and a hydroelectric plant!
Except there are people who notice those have (gross) drawbacks, and thus label them as bad on net. Dimbulbs.
