Technology Feast

A promising type of solar-power technology has moved a step closer to mass production. Nano solar, based in San Jose, CA, has opened an automated facility for manufacturing its solar panels, which are made by printing a semiconductor material called CIGS on aluminum foil. The manufacturing facility is located in Germany, where government incentives have created a large market for solar panels. Nanosolar has the potential to make 640 megawatts' worth of solar panels there every year.

Solar cells made of the CIGS semiconductor, which is composed of copper, indium, gallium, and selenium, have long been considered a potential challenger to conventional solar cells made of silicon. At least in the lab, CIGS cells have reached efficiencies comparable to silicon-based solar cells. And in theory, they could be made using inexpensive printing processes, leading to much less expensive solar power. But developing manufacturing processes that maintain the high efficiencies has proven difficult.

Nanosolar claims to have solved these problems. Its solar cells still aren't as efficient as laboratory cells--the best of them convert 16.4 percent of the energy in sunlight into electricity, as opposed to over 20 percent in the lab. And on average, the company's solar panels convert just 11 percent of that energy into electricity, says Martin, Nanosolar's CEO. But that's high enough to compete with conventional solar panels, he says, due to modifications that improve performance and lower installation costs. He estimates that in sunny locations, power plants made using these panels could produce electricity at five to six cents per kilowatt hour, based on Department of Energy methods for calculating the amortized cost of solar panels over their lifetimes. That's near the cost of electricity from coal and significantly less than most solar power, which costs about 18 to 22 cents per kilowatts hours.

Low efficiency is a problem because it increases the cost of installing solar-power arrays--since each panel produces less power, more solar panels have to be installed. The lower power production can also increase the cost of electronics for gathering the power the panels produce. To address the latter problem, Nanosolar has increased the current its panels can generate, in part by using large aluminum-foil sheets to collect electrons from each panel. This, together with other modifications, effectively decreases the amount of wiring per panel, simplifying installation and reducing the cost of materials. The panels are also larger than competing solar panels with similar efficiencies, and so they generate more power per panel. For example, solar panels from First solar of Tempe, AZ, one of the largest solar-panel companies in the world, generate about 70 watts. Nanosolar's generate 160 watts.