A long-sought solar milestone was eclipsed on Tuesday, when Tempe, Ariz.–based First Solar Inc. announced that the manufacturing costs for its thin-film photovoltaic panels had dipped below $1 per watt for the first time. With comparable costs for standard silicon panels still hovering in the $3 range, it's tempting to conclude that First Solar's cadmium telluride (CdTe) technology has won the race. But if we're concerned about the big picture (scaling up solar until it's a cheap and ubiquitous antidote to global warming and foreign oil) a forthcoming study from the University of California–Berkeley and Lawrence Berkeley National Laboratory suggests that neither material has what it takes compared to lesser-known alternatives such as—we're not kidding—fool's gold.via Popular Mechanics
First Solar's eventual goal is "grid parity," a phrase that refers to making solar power cost the same as competing conventional power sources without subsidies. Right now the cost of making panels accounts for a little less than half the total cost of installation. The company estimates that it needs to get manufacturing costs down to $0.65 to $0.70 per watt, and other installation costs down to $1 a watt in order to reach grid parity—goals First Solar plans to reach by 2012.
The question, though, is whether First Solar or any other solar manufacturer would be able to handle the flood of orders that would ensue if they reached competitive cost. At that point, it comes down to a matter of having enough of raw materials. That is where the real limitations come to bear, according to a paper that will appear in the March issue of the journal Environmental Science & Technology. In the paper, Wadia and colleagues Paul Alivisatos and Daniel Kammen evaluated the global supplies and extraction costs for 23 promising photovoltaic semiconductor materials and found that the three materials that currently dominate the market—silicon, CdTe and another thin-film technology based on copper indium gallium selenide (CIGS)—all have limitations when ordered in mass. While silicon is the second-most abundant element in the Earth's crust, it requires enormous amounts of energy to convert into a usable crystalline form. This is a fundamental thermodynamic barrier that will keep silicon costs comparatively high. Both CIGS and First Solar's CdTe rank poorly in abundance and extraction cost, with CdTe ranking dead last in long-term potential based on current annual extraction rates.
To that end, Wadia and his colleagues found that iron pyrite—better known as fool's gold—was several orders of magnitude better than any of the alternatives, based on both cost and abundance. Copper sulfide and copper oxide were also attractive candidates. The problem with these materials is that they're less efficient in converting the sun's rays to electricity, and as a result have been the focus of considerably less research. But the Berkeley study accounts for this fact, and concludes that lower-efficiency materials that are cheaper and more abundant will ultimately serve the alternative energy market better.