Recycling the whole module

It has been called the solar industry’s “dirty little secret”: the inclusion of potentially toxic materials in solar modules. A very public discussion about the presence of cadmium in First Solar’s modules captured headlines towards the end of 2010, particularly in Germany, which was a booming market at the time.
The debate raged for months, through much of 2011, often polarizing the industry, bloodying noses and damaging the environmental reputation of solar to outsiders.
While this debate has receded, a new discussion is growing in momentum regarding the presence of fluoropolymers in backsheets and potential impacts when modules come to end of life. Fluoropolymer backsheets, in various guises, is proving popular among many module manufacturers, reports IHS analyst Karl Melkonyan.
“Backsheet manufacturer Arkema offers a fluoropolymer called Kynar (polyvinylidene fluoride) that equals the performance of Tedlar, yet without supply constraints. Its availability rapidly established it as a highly-popular alternative to Tedlar, both in single and double fluoropolymer constructions,” says Melkonyan.

Why fluoropolymer matters

The standard technique during module recycling for the c-Si modules is to degrade the backsheet in order to separate it from the silicon and glass. This is according to Alessandro Anderlini, photovoltaic division manager with Italian backsheet supplier Coveme.
“Today, conventional recycling methods are unable to degrade the fluoropolymer backsheet as the fluorocarbons can not be degraded because of their chemical structure,” Anderlini explains. “If fluoropolymers are burned, then they are highly toxic.” Martin Wielpuetz, director of business management solar of Performance Materials Group at global specialty chemical supplier Evonik, concurs.
“Thermal recycling of fluoropolymers is really, really toxic,” says Wielpuetz. “Talking about the hydrogen fluorides, it is one of the most toxic substances youcan find.” Evonik supplies its Vestamid PA12 product to the PV industry, where it can be used to form a water, UV, and abrasion-resistant barrier to the electrical insulation part of the backsheet stack.
Fluoropolymers, despite their toxicity, have become more prominent in backsheets due to a perception that they provide the most robust protection to the electrically insulating layer. Evonik’s Wielpuetz believes that perception should be turned on its head, particularly given potentially toxic end-of-life issues.
“There is no awareness of recycling and the consequences of this,” says Wielpuetz. “There are backsheets available that do not contain any fluoropolymers with our materials and those based only on PET materials that do not include any fluoropolymers. The performance of the backsheet is significant depending on where you are going to install the modules afterwards.” Wielpuetz says that in cooler areas, such as northern Europe, PET backsheets are preferred. Data is currently being collected in support of PET and technologies such as coextruded backsheets for applications in humid and sunbelt countries. Evonik says it has collected extensive data on the performance of its Vestamid PA12 solution across a range of conditions in its in-house labs.
Interestingly, while Italy’s Coveme is eager to engage the industry in the debate regarding fluoropolymers, it still supplies both fluoronated and non-fluoronated backsheets. Coveme, which claims to supply around 15% of the global backsheet market, says that the PET backsheet market is growing rapidly and that its fluoropolymer range is primarily for Chinese manufacturers that are yet to make the switch.
“We still have a portfolio of Tedlar-based backsheets together with our best selling [fluoropolymer-free] dyMat PYE, special PET based backsheets.”

Filmcutter & Jolywood

Last month, China’s Jolywood and Italy’s Filmcutter announced that the two companies will join forces to form what has been labeled as the “biggest backsheet company worldwide,” according to the head of Filmcutter’s PV Division, and soon-to-be CEO of the new Filmcutter incarnation Cesar Campos. The move will also bring together the companies’ complementary product portfolios, meaning both a non-fluoropolymer and fluoropolymer backsheet range.
“The ambition is to continue establishing Jolywood as a leading Chinese fluoropolymer-based backsheet player, and expanding its international footprint,” says Campos. “At the same time to guide Filmcutter to become a leading PET-based backsheet player worldwide.” Together, Filmcutter and Jolywood target 30% of the global backsheet market. Jolywood was the first pure-play backsheet company to go to IPO in China, in September of last year.
“At present, the fluoropolymer-based backsheet is the mainstream of the market in China. But outside of China, the PET-based backsheet is reaching a decisive leading position,” says Jianwei Lin, Jolywood Chairman. “We believe that market share of both fluoro-coating type backsheet and modified PET based backsheet will continue rising.”

PV remains safe

An understanding of the potential end-of-life impact of fluropolymers is undoubtedly growing, however Europe’s solar industry recycling scheme PV Cycle is keen to emphasize that all PV technologies have been proven safe “for man and nature,” both during their productive lifetime and for recycling.
“Most importantly … no commercially available PV module technology meets the criteria of hazardous waste today,” reports PV Cycle’s Olmina Della Monica, the organisation’s operations and treatment manager. Della Monica says that the biggest operational and financial challenge to module recycling remains the collection of discarded modules. PV Cycle partners with established recycling partners in various countries throughout Europe, with methodologies for recycling varying between nations.
Synergies with the flat glass recycling industry have been leveraged in establishing operations. The three stages for c-Si module recycling include the preparation phase, when the frame and junction box are removed, the shredding and fine-processing to separate materials, and then the recovery and recycling.
“General output fractions of this flat-glass-oriented process are ferrous and non-ferrous metals, glass, silicon flakes, and plastics with an average recycling quota of approximately 85% (input weight),” says Della Monica. This high proportion of the module weight able to be recycled is a positive sign and there are efforts to establish recycling programs and standards in China, Japan, and the U.S.