Published: July 21, 2014 Category: Renewable Energy
Any PV technology that hopes to compete with c-Si in today’s solar energy world must solve several problems: raise conversion efficiencies to around those of silicon-based cells (at least 20 percent), lower costs below that of c-Si (roughly $0.40-$0.50/Watt), or find specific niche markets where an alternative PV technology's features and capabilities are an acceptable tradeoff for lower cost/performance, such as flexibility.
In the past few months, the thin-film CIGS sector has made impressive progress in solving part of that equation. It's eclipsed the top efficiency mark of polysilicon-based cells (20.4 percent), and hasn't looked back:
- Solar Frontier reached 20.9 percent efficiency on a 0.5 x 0.5cm cell in April. That's just a tick above the previous CIGS PV record (20.8 percent) achieved last October by the Center for Solar Energy at Baden-Wurttemberg (ZSW), and it's also a record for single-junction thin-film PV.
- Hanergy's Solibro unit hit 20.5 percent efficiency in the lab in April, adding nearly a full percent to its 19.6 percent mark reached in December. Last October Hanergy also achieved 15.5 percent for commercially available glass PV modules built with technology from Miasole, another of its recent CIGS acquisitions.
- In May, CIGS tool manufacturer Midsummer touted 16.2 percent (aperture area) for full-size 156 x 156 cm solar cells, and notably in implementation in a production line.
- In February, Stion claimed it built a prototype 23.2 percent cell (20 x 20 cm) for its tandem-junction technology, eyeing monolithic modules with efficiency around 20-22 percent.
- Siva Power announced an 18.8 percent efficient module also in February, just 10 months into its repositioning into a CIGS company.
- And yet again in February – a busy month -- Avancis reported a 16.6 percent efficient CIGS module (aperture area, not "total area") on a 30x30 cm module.
Generally speaking, the higher CIGS efficiencies go, the more market opportunities open up, bringing CIGS closer to competing with c-Si (and better than other thin-film PV) on a number of fronts. With these Gen II thin-film CIGS versions, NanoMarkets projects CIGS on a path to equivalence with c-Si efficiencies by 2018-2019, at which point the question will no longer about efficiency, but purely price/value — and CIGS should be able to beat c-Si as it ramps to volume, due to far lower absorber material usage.
Flexible CIGS and BIPV
While progressively solving that higher efficiency/lower cost riddle, CIGS vendors also must leverage markets where CIGS technology has inherent advantages over both c-Si and other thin-film PV technologies. CIGS' ever-improving efficiency means significantly more power and efficiency for rigid building-integrated PV (BIPV) products, and the technology uses a fraction of the material vs. c-Si for power generation -- but if electricity is the main goal, rooftop-affixed c-Si solar panels will always be the cheaper and preferred option.
CIGS’ differentiator, then, comes down to its long-appreciated ability to be produced on flexible substrates. Portable charging applications were an early area of opportunity for CIGS (and other technologies), from backpacks and tents to devices to clothing. NanoMarkets sees significant opportunities for flexible CIGS PV manufacturers in these applications with increasingly broad consumer appeal, emphasizing the technology’s functionality (ever higher efficiencies mean increased power generation), convenience, and style, either by developing their own products or linking up with high-end consumer products manufacturers. Global Solar (now Hanergy) and Ascent Solar are two examples of CIGS companies that are focused exclusively on portable charging stations.
CIGS and BIPV: The Market Awaits
However, the most promising market volumes and revenues for thin-film CIGS PV continue to be BIPV applications, where c-Si is not an option and the only other competitor (amorphous silicon) has a significant efficiency disadvantage. A prominent example is Dow's PowerHouse shingle, which uses CIGS absorber material from Global Solar/Hanergy. Launched in 2011, Dow’s Powerhouse shingles have made steady inroads into BIPV; they are now available in 17 U.S. states and Canada (where the first system went online in June), and have become more successful than previous a-Si-based products.
As cost/Watt continues to decline, these solar shingles (from Dow and others) are becoming viable for a broader consumer audience. NanoMarkets expects this to become a very profitable sector, evolving into just another regular option both for new home construction and re-roofing projects.
We also continue to see great opportunities for flexible CIGS in BIPV laminates, glued onto everything from roofs to façades to doors and fences depending on architectural or technical concerns, or even standalone laminates. This not only enables simpler and efficient installation, potentially installed by building owners themselves, it would help distribute costs through the materials that would be used anyway, making BIPV investments more attractive.
The key for CIGS PV manufacturers in flexible BIPV is to create products that have mass-market appeal (such as solar shingles), intimately connecting the PV components and building materials, to help share costs. This will make PV more accessible to more users, and help blend the cost of PV systems so it's more economical to install.
The Encapsulation Conundrum: Finding a Balance
There's a caveat with increased usage of flexible CIGS PV technology: long-term reliability, and its sensitivity to moisture more so than other thin-PV technologies. This is particularly a concern in BIPV applications which are generally outdoors and exposed to the elements for (ideally) decades. Rigid PV products (including conventional PV panels) are encapsulated in impermeable glass, but this isn’t an option for flexible CIGS, and “flexible glass,” despite eyeing various new markets of late, has yet to live up to its promises.
Companies leading the development in this area (all of which involve dyad films, multiple layers of organic and inorganic materials) include Dow Chemical, Fujifilm, 3M, and DuPont. Over the next few years, NanoMarkets expects more materials companies to develop and commercialize their own versions of dyad films, perhaps using different deposition techniques and different component materials, attempting to reduce the cost and complexity of these barrier systems. Some of the extra cost of these flexible encapsulation solutions can be borne through the higher value affixed to BIPV.
NanoMarkets sees broader adoption of both BIPV and CIGS hinging on a trade-off between cost and reliability, with lower-cost encapsulations emerging that offer minimal performance. We also note that transparency of the barrier also is very important, since any light obstruction directly reduces the performance of the PV cells within; we expect competition on this front as well.
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