Posted by
Andrews on Thursday, August 28, 2008 10:38:35 AM
I wrote before that the problem with solar energy is that it is a diffuse energy source. When that is combined with our relatively poor efficiency in harnessing even the diffuse flow of solar energy, this requires we cover massive areas with solar collectors just to accomplish simple tasks. (The example
in my earlier essay was that it would take an area equal to the State of California to provide for our energy consumption in 2005.)
Now
National Geographic provides me with a perfect example. Bertrand Piccard hopes to fly a solar powered plane. This one man flier will be powered entirely by solar energy, storing excess in batteries for times when he cannot get full solar exposure. But, even with battery storage, the flight requires, in the words of the reporter "precise flying and top-notch meteorologists." In other words, this solar plane will only be able to fly during optimal conditions.
Still, it is solar, right? So the prototype may not be able to fly at night, or during inclement weather, but during good weather, at least, we can fly without pollution. So what is the problem?
Well, here is the problem, one I could have easily predicted. This single man plane, one which still can only fly during optimal conditions, guess how large the wingspan is. Go on... 200 Feet. As large as the wingspan of a Boeing 747-400.
Now, I grant the body and batteries are a big part of that mass. But it takes 200 feet of wings to lift a single passenger. Even if we assume that adding another passenger won't double the size, it still adds to the load, requiring more energy, and adding more cells adds more weight too, requiring still more energy, which requires more cells, and so on. So to lift what even a Piper Cub could lift we would require a plane bigger than anything flying today.
You have to marvel at a technology which can only work during optimal weather, which requires more space than existing technology, which tries to harness an energy source massively more diffuse than that currently used, which even when fully mature will still require huge machines to accomplish what small devices do today, while that technology's proponents whine about being ignored.
If we want to save energy, why not go back to zeppelins? They were smaller than these solar behemoths and required only a fraction of the fuel a jet requires. Using helium rather than hydrogen we could build a safe rigid body airships. So, why the press for solar?
Let's face it, solar vehicles, for all the press they get, are still little more than toys, and will remain so for some time, regardless of how much the government "invests" in them. The diffuse nature of solar energy ensures that. Unless you want a one passenger car the size of a tractor trailer (but without a trunk, as that whole space is just filled with collectors and batteries), you are not going to be happy with any solar solutions.
POSTSCRIPT
No, I am not pressing for airships, I am simply saying that, if the environmental movement wants to reduce our dependence on fossil fuels, airships would require much less fuel and still accomplish air travel more efficiently than these absurd solar planes. As airships use their motors only for horizontal propulsion and downward momentum, they do not require all the fuel planes burn generating lift, so they are much more fuel efficient. It seem a natural for the environmental movement, but I have not yet heard even one of them propose it.
Disclosure: I have to admit, I find airships attractive. They are inefficient in terms fo what the public wants from air travel, but the idea of basically taking a cruise in the sky is appealing. So I have a selfish motive in pressing the environmentalists to rediscover the concept. I doubt it will work, and airships are too slow to really replace commercial air travel, but I can still dream. (And if I can finally get something good out of the environmental movement, that would possibly redeem them somewhat in my eyes.)