Are Renewables Really Renewable?

We all know that the fuel required for renewable sources of energy are virtually limitless, hence the name. But what about the essential components that renewables like wind turbines and solar panels rely on to function? An article from The Economist (subscription required) highlights several production problems for the "clean-tech boom":

THESE should be heady times for Vestas, a Danish firm that makes more than a quarter of the world's wind turbines. The wind business is booming, and the company said last week that it had swung into profit in 2006, thanks to an 8% rise in revenue. But there is “significant unexploited production capacity”, Vestas says, due to shortages of high-quality turbine components. Other companies grumble about a lack of gearboxes and bearings.

Wind firms' worries echo those in the solar-power business, which is also booming but where a shortage of polysilicon has hampered growth. Silicon is made from sand, which is abundant, but there are not enough refineries to turn it into solar-grade polysilicon. As a result, prices for silicon contracts have more than doubled, to $70 or $80 per kilogram, in the past three years, says Jesse Pichel, an analyst at Piper Jaffray.

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Supply shortages will not ease quickly in either case. Wind turbines are giant machines that require lots of parts. Several firms are building new factories: Vestas has just announced its first American plant, which will make blades in Colorado. But new factories will take several years to get up to speed. In the meantime, buyers are putting down deposits to reserve their turbines. GE Energy, the largest turbine installer in America, is already booked up until the end of next year.

Similarly, the big polysilicon producers, including Hemlock and MEMC, are expanding their capacity, says Rhone Resch of the Solar Energy Industries Association. But some of their additional output will go to chipmakers, which are still the biggest buyers of polysilicon (though the solar industry is about to take the lead). So polysilicon shortages and the associated high prices will not ease until at least 2009, Mr Pichel predicts.

And they say nuclear is too slow to come online. Looks like wind and solar are facing the same production capacity constraints nuclear is. While The Economist article highlights production problems that can be overcome, the materials needed are limited. So are renewables actually limited or am I just out there?