Volume 43, Issue 10 - October 2008
The word “photovoltaic” (PV) has appeared more and more often within the context of the glass industry lately. But while demand for glass has increased in markets for energy generation—glass is used as a protective envelope for solar cells in PV applications, for one—other technologies are looking for a piece of the PV pie. For example, at least two major window film manufacturers are linked to PV-related technologies to some degree by parent companies: CPFilms, through St. Louis-based Solutia Inc., and BSF through Bekaert in Belgium.
However, while the glass industry is triumphing its involvement with frequent announcements about architectural glass-related companies branching into solar fields, ask a company representative for any major window film manufacturer if PV film is on their to-do list, and you’ll likely get the silent treatment. When questioned about PV window film during an interview with USGlass magazine, Christophe Fremont, president of Bekaert Specialty Films (BSF), replied with a silent but incriminating smile—nothing more. This past June, Solutia unveiled its Saflex Photovoltaic business, designed to sell polyvinyl butyral (PVB) interlayers to companies that produce the world’s largest thinfilm PV modules. And as recently as August 1, Bekaert announced it had developed a new range of rotatable sputter target materials for the deposition of transparent conducting oxide layers used in PV cells. The Belgium- based company said its new materials are designed for “applications where optical transmission and electrical conductivity are required simultaneously.” But neither company is announcing that its photovoltaic technologies are being incorporated into window film products. Kathryn Giblin, BSF’s vice president of global marketing and technical services, suggests there is a possible role for window film, but not on the energy-production side.
“There is not much advancement in photovoltaics being incorporated into window film at the moment,” she reports. “Although window film could play a part in helping a building that employs photovoltaics to be even more efficient and it could increase the payback on both items.” Representatives for CPFilms declined to comment on the subject.
More than 30 years later, the concept has been revisited by none other than the Massachusetts Institute of Technology (MIT)—and the institute is reporting favorable results for those in the glass and glass coatings industries.
MIT’s “solar concentrator” collects light over a large area (like a window) and gathers, or concentrates, the energy at its edges. As a result, the collection cells only need to be around the edges of a flat glass lite, according to Marc A. Baldo, leader of the effort and the Esther and Harold E. Edgerton Career Development associate professor of Electrical Engineering. In addition, the focused light increases the electrical power obtained from each solar cell by a factor of more than 40, he says.
The MIT solar concentrator involves a mixture of two or more dyes that is essentially painted onto a lite of glass or sheet of plastic. The dyes absorb light across a range of wavelengths, which is then re-emitted at a different wavelength and transported across the lite to solar cells placed at the edges. The development team believes this technology could be implemented within three years.
On a commercial level, however, building designers and owners are thinking much larger than USB devices. With the amount of glass found in the average high-rise building, companies can reduce power consumption by incorporating these technologies into a building’s power grid. But, aside from new construction, the costs associated with replacing non-PV glass surfaces with PV counterparts could be enormous. It would seem natural that film companies would be racing to provide a retrofit solution; yet, to date, only one company has mentioned the words “photovoltaic” and “window film” in the same sentence.
This past January, Konarka Technologies Inc., developer of Power Plastic®, a polymer-based organic photovoltaic (OPV) technology, announced its plans to incorporate this material into a semi-transparent window film. And the company’s focus wasn’t only on the big commercial opportunities, but also on residential. In fact, Konarka announced it would focus on providing these technologies for various structures and homes of all income levels, including developing countries. In a move similar to MIT’s developments, Konarka announced in March that it successfully conducted the first demonstration of manufacturing solar cells through an inkjet printing process. In the past, many PV developing companies have maintained the necessity of glass for this application, but Konarka recently “shattered” the glass barrier.
“Contrary to the majority of the research community, claiming that organic solar cells require packaging with either glass or very expensive ‘super barriers,’ we are proud to have demonstrated outstanding high lifetime for flexible cells packaged with commercially available, low cost materials,” Rick Hess, president and chief executive officer says.
The company failed to confirm whether or not its use of the words “window film” pertains to an interlayer, or a standalone product, but Hess’ statements imply that at least some of Konarka’s products will not require a glass envelope.
In addition to a “semi-transparent window film,” the company’s focus includes a number of applications where lightweight and transparency features provide an advantage—including one of window film’s direct competitors. Prior to the release containing window film, Konarka announced it had teamed up with SKYShades, an Orlando, Fla., and Brisbane, Australia-based producer of fabric canopies and coverings to produce an energy-producing version of the company’s products.
Why are so many companies robbing other sectors to feed PV efforts?
“We see this as a fast-lane business,” Luc De Temmerman, president of Saflex told the St. Louis Dispatch. And according to Vince Van Son, commercial manager of Sustainable Solutions for Alcoa Building and Construction Systems, this move makes sense, because, he says, the global annual growth rate of PV is more than 40 percent.
The question is: are any window film manufacturers collaborating with companies like Konarka to ensure the window film industry receives its part of the PV pie—and will that ever reduce the demand upon glass products in this sector? Konarka representatives refrained from comment at this time, but suggested checking back for an update later this or early next year. And this too was yet another question Fremont answered with the same incriminating (but silent) smile.