In Solar Tech, Simple Solutions Outperform the Exotic

Recent news about improving the efficiency of solar panels often has focused on exotic technologies and materials. All of them show promise - otherwise they wouldn't be news - but for now, at least, they can't be built inexpensively and come to market quickly.

It seems that many researchers have somehow overlooked simplicity. Not so for one startup, Semiprius, based in Durham, N.C. It says it can simply stack inexpensive solar cells to achieve solar power efficiencies nearing and eventually exceeding 50 percent, twice that of conventional cells - and likely at a cost lower than natural gas.

Some recent innovations involve the development of complex, microscopically textured surfaces for solar panels that increase the absorption of solar energy. Not Semiprius. Its come up with three simple innovations that accomplish the same thing for much smaller investment.

The Semiprius method includes, first, an inexpensive, quick way to stack solar cells, plus a proprietary method to connect the cells electronically, and finally a new kind of adhesive for making sure the stacked cells stay put. In addition, the company uses solar cells that measure less than a millimeter in width that not only are less expensive to cool but also improve their efficiency.

Stacking cells isn't a new idea, but so far the method has been to grow the layers on top of each other. This can be problematic because one layer's crystalline structure may not be compatible with that of its neighbor. Semiprius is careful to match contiguous layers compatibly, a process that also captures more solar energy.

Using this method, Semiprius has demonstrated two versions of a kind of four-layer electronic sandwich that includes three semiconductor materials stacked on top of a fourth - a combination that would not have been compatible using conventional technology.

The results: One version of this stacked device had an efficiency of 43.9 percent. The other version, made of slightly different materials, boasted an efficiency of 44.1 percent.

What's more, creating the layered solar panel was quick and easy to align precisely. And this process is extremely cost-efficient because the expensive crystalline wafers that are used to grow solar cells can be reused, not discarded after one growth period, as is the conventional practice.

And Semiprius isn't stopping there, Scott Burroughs, its vice president of technology, tells MIT Technology Review. Within five years, he says, the company plans to stack a total of as many as six semiconductors to produce a panel with a "very high performance - beyond 50 percent efficiency."

As for the ultimate cost, Burroughs says a cell with 50 percent efficiency could generate electricity at less than 5 cents per kilowatt-hour, less than the 6.4 cents per kilowatt-hour for the latest gas-fired power plants, according to estimates by the U.S. Energy Information Administration.

By Andy Tully of Oilprice.com