Why silicon solar cells aren't as green as you thought

When recently considering how to profit from gas pump pain, I decided to buy alternative energy stocks. With peak oil theory, Al Gore's environmentalism, and all, I figured it might be a safe way to hedge against my gastank expenditures. (Free stock tip: I bought into SunPower ... BUY! BUY! BUY!)

Anyway, I just read an interesting Technology Review interview with a long-time, leading solar cell researcher who explains why silicon isn't the most environmentally friendly material for solar cells. (Instead, he advocates using dyes that turn the solar cells into little photosynthesis machines):

People are trying to make silicon in a different way, but there's another issue: energy payback. It takes a lot of energy to make silicon out of sand, because sand is very stable. If you want to sustain growth at 40-50 percent, and it takes four or five years to pay all of the energy back [from the solar cells], then all of the energy the silicon cells produce, and more, will be used to fuel the growth.

And mankind doesn't gain anything. Actually, there's a negative balance. If the technology needs a long payback, then it will deplete the world of energy resources.