GE places solar bets on thin-film cells

March 18, 2010 9:34 AM PDT
by Martin LaMonica

General Electric, which has long made solar panels using traditional silicon, is converting to thin-film cells, using the same material as industry cost leader First Solar.

The company's research organization on Thursday detailed its activities with cadmium telluride solar cells, which the company has determined offers the most potential to lower solar power costs.

As first reported by CNET, GE's next-generation solar panels are based on technology from PrimeStar Solar, a Denver, Colo.-based company where GE is the majority owner. GE executives are bullish that by lowering costs, solar can grow rapidly, as its wind business has done.

GE thin-film solar cells are made from a combination of cadmium telluride, the same material used by industry cost leader First Solar.

(Credit: GE)
GE has not yet begun manufacturing solar panels using the thin-film technology but it plans to do so some time in 2011, according to a company representative.

There are several companies developing thin-film solar cell technology, which promise to lower the cost of manufacturing and use less material. But thin-film solar cells are less efficient at producing electricity than crystalline silicon cells.

GE chose to go with cadmium telluride because it offers the most potential for overall cost savings, said Danielle Merfeld, the solar-technology platform leader at GE's Research facility in Niskayuna, N.Y.

"We think cad tel fundamentally has better cost structure than other thin-film technologies," she said. "The combination of efficiency that we think we can get to, the yield of the manufacturing line, the cost of manufacturing, and the cost of raw materials--the combination gives us the best outcome for making electricity."

Over the past three years, a number of companies have invested in making thin-film solar cells from a combination of copper, indium, gallium, and selenide (CIGS). But CIGS is a tricky material to work with because manufacturers need to control four materials, noted Merfeld. Cadmium and tellurium are byproducts of existing mining processes, such as copper mining.

In terms of efficiency, Merfeld said GE projects it can come to market with a solar panel that is more efficient than what First Solar already offers, which is about 11 percent.

GE expects to target the utility market with its panels, but there is potential for commercial and residential customers as well. Because thin-film panels are less efficient, they are typically used in places where space is not a major constraint.

GE no longer produces panels made from crystalline silicon and plans to enter solar with high-volume manufacturing. "We decided not to step into manufacturing in 2009 as many other companies did because we wanted to make sure to have a competitive advantage from the technology," Merfeld said.

Asked about the toxicity of cadmium, Merfeld said that the material is stable once it is bound with tellurium. But GE does plan to have a recycling program for its panels, as other solar manufacturers do, she said

IBM boosts solar cell made of abundant materials

February 11, 2010 8:16 AM PST

by Martin LaMonica

IBM researchers are developing a solar cell with an eye towards what's in the ground.

Researchers on Wednesday published a technical paper in the journal Advanced Materials that describes a solar cell made of abundant materials with relatively high efficiency. The cell can convert 9.6 percent of solar energy into electrical energy, a 40 percent boost over current methods.

That level of efficiency is already far exceeded in commercial silicon-based cells and even beat by thin-film solar cells, which are cheaper to make than silicon cells but are less efficient. But IBM researchers set out to make a cell that uses materials that are relatively abundant elements--copper, zinc, tin, and sulfur, or selenium (CZTS). The availability of materials for existing solar technologies limits their long-term potential, according to IBM.

Solar cells made of copper, tin, zinc, and sulfur.

(Credit: IBM )
First Solar, which claims to have the lowest cost per watt, makes its thin-film cells from cadmium and tellurium. GE, too, plans to sell solar panels with cadmium telluride cells as early as next year as well. There are also several start-up companies, including Nanosolar, Miasole, and HelioVolt, which make cells using a combination of copper, indium, gallium, and selenide, or CIGS.

The problem with these is the scarcity of materials or the environmental impact, according to IBM researchers Teodor Todorov, Kathleen Reuter, and David Mitz, who authored the paper. That means that other solar cell materials are needed to meet anticipated renewable energy demands, they said.

"Other solar cells which perform at similar efficiency levels are comprised of materials that have been either too costly to produce or contain elements that could limit production capacity, or have poor prospects for further improvements in efficiency, making commercialization and wide usage less likely," said Thomas Theis, director of physical sciences at IBM's T.J. Watson Research Lab, in a blog post.

One of the advantages of thin-film technologies is that that not much material is needed to make a cell, compared to traditional cell manufacturing. CIGS cells can be made using high-speed fabrication techniques, such as roll-to-roll manufacturing. The technique developed by IBM uses a similar "ink-based" method.

Matthew Beard, a researcher at the National Renewable Energy Laboratories not involved in the work, called the IBM research a "breakthrough."

The researchers estimate that if the technology can be taken beyond its basic state right now and achieve 12 percent efficiency, it could be an economically viable alternative to current products