After years of technology development and hundreds of millions of dollars in investments, the developers of the next generation of solar technology made out of copper-indium-gallium-selenide (CIGS) are finally making the leap to mass production. But they have a ways to go to catch up with other solar technology developers, many of which have said they don’t consider CIGS companies serious competitors.
Rommel Noufi, the head of polycrystalline thin film research at the National Renewable Energy Laboratory (NREL), outlined key technological challenges for CIGS developers during his talk at a Photon conference in San Francisco last month. He and Smittipon Srethapramote, an analyst at Morgan Stanley, also highlighted cost and other roadblocks for CIGS to become mainstream.
“A lot of banks often times won’t touch new technologies at all,” Srethapramote said. “Or banks often times ask for a higher equity from project developers in order to compensate for the higher risks.”
CIGS developers have two primary goals to achieve: increase their solar panels’ sunlight-to-electricity conversion efficiencies and cut manufacturing costs. They are the same goals for any solar panel maker, but members of the CIGS tribe need to do it that much quicker to compete with the majority of the solar panel makers today that use silicon — and with market leader First Solar, which makes cadmium-telluride solar panels.
CIGS companies and First Solar are rolling out panels in efficiencies around 10-12 percent while their silicon peers are producing solar panels averaging 16-17 percent. Although First Solar can’t compete in efficiencies, it has excelled in production speed. With its 1.4 GW of factories, the company has cut production cost to $0.75 per watt, the industry’s lowest. Silicon panel makers with comparable factory holdings have production costs of between $1-2 per watt. Given that non-silicon solar panels produce less electricity in a given area than the silicon variety, they have to be cheaper.
Most of the CIGS companies today are small and have less than 100 MW of factories. Solibro in Germany has 135 MW while California-based Solyndra, which shipped 60 MW in 2010, hopes to get to 200 MW by the end of 2011. The largest of them all is Japan’s Solar Frontier, which just opened a 900 MW factory and is bringing the production lines online to reach full production mode later this year.
Here is a list of technical challenges highlighted by Noufi:
1. Performance stability: CIGS panels are particularly susceptible to damage by moisture, so a lot of R&D work has gone into developing encapsulants that seal in the cells and the transparent conductive oxide (TCO) layer on top of them. Work is underway to replace zinc oxide as the TCO or to come up with a material to protect the TCO, Noufi said. The fear of water explains why many CIGS companies have opted to encase their cells in glass, which offers good moisture protection. It also raises questions about the longevity of flexible CIGS thins that use polymer instead of glass, though companies such as 3M and DuPont are working on more water-resistant polymer films.
2. Deposition of CIGS materials: Compared with silicon or cadmium-telluride solar panels, CIGS solar panels use two additional materials. All these materials need to be baked onto the substrate to form the same thickness and distribution panel after panel, and that’s no easy task. “On the production line you are actually flying blind,” Noufi said. Some companies such as BrightView Systems in Israel are developing equipment that they say can provide quick feedback to point out any problems with the deposition.
3. Efficiency improvement: A German research institute broke the world record for producing the most efficient CIGS cells last year, when it showed off one with 20.3 percent efficiency. And companies such as MiaSole have demonstrated the ability to produce solar panels close to 16 percent efficiency, though those are the best the companies can produce (champion panels) and not what they are making consistently from their factories. Typically, there is a 15 percent difference between the champion panels and the ones being mass produced, Noufi said.
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Photo courtesy of MiaSole