Niche to Mainstream: Photovoltaics Make Architecture Inroads
More efficient solar cells and new dimensions, shapes and transparency levels are helping modules become less expensive and more versatile.
Solar modules for building skin integration are still niche products due to high costs, a lack of integration possibilities and interest on the part of architects—but this could soon change. Due to more efficient solar cells and new dimensions, shapes, and transparency levels, modules are becoming less expensive and more versatile.
The good news for the suppliers of solar modules that are suited for integration is that an increasing number of companies are managing to convince architects of the benefits of their products, said Judit Kimpian of the Royal Institute of British Architects at last year’s conference of the European Photovoltaic Technology Platform (EUPVTP) addressing the BIP theme in London. She added that this development was particularly positive because buildings equipped with solar technology emitted less detrimental carbon dioxide and could therefore actively contribute to climate protection.
Building-integrated photovoltaics (BIPVs) are still a niche application of small importance measured by total PV installations worldwide. “It is a side line of the PV industry,” explains Gaëtan Masson, vice president of EUPVTP. Of the just under 40 GW solar power output newly installed in 2014 worldwide, only about 1 GW was accounted for by BIPV; this means that the market share of BIPV is as low as 2.5%. The relatively high costs are one obstacle to market success: building laws and technical requirements vary widely from country to country and even among regions. As a result, modules must be customized in relatively small lots for local architects, Masson explains, which has made the production of higher quantities and economies of scale difficult.
According to Masson, the BIPV industry would have to focus more on competitive market segments in order to profit from economies of scale like conventional PV. “Then companies could start production of pre-fabricated BIPV elements,” he says. The EUPVTP also feels that the political framework has to improve in order to help this industry take off. At present, however, countries are rather “back-pedaling” when it comes to state aid for solar installations. In France, for example, one of the few countries with special subsidies for BIPV, the additional support for in-roof systems ended in late 2015.
BIPV would help countries to achieve the set climate protection targets more safely; after all, EU member states have undertaken to bring down greenhouse gas emissions by a minimum of 20% against 1990 levels by 2020, to increase energy efficiency by 20% and to achieve a 20% share of renewable energies in total energy consumption. In this context, buildings play a pivotal role: new buildings should require next to no energy for heating, hot water, air handling and conditioning from 2020 on, and cover the remaining energy needs themselves. BIPV would be the solution: wherever modules cannot be installed on the roof, they could be integrated into the building skin.
Innovation Leads to Opportunity
Even though the circumstances for BIPV are difficult, ongoing innovations raise hopes for an imminent breakthrough of this technology. Modules are becoming more efficient and available in an increasing number of designs. Architects appreciate this newly gained scope for design.
“We feel that business is picking up,” says Bernd Sprecher, general manager of Manz CIGS Technology, which develops production lines for thin-film modules based on copper, indium, gallium and selenium (CIGS). Manz manufactures BIPV modules in various freely selectable dimensions and shapes in southern Germany. The company uses vapor deposition to apply a photo-active CIGS layer on float glass, a process that by Sprecher’s account permits variable module sizes and custom shapes.
The benefits of thin-film technology include not just diversity but also improved efficiency. Traditionally, these panels were in low demand because they only converted light into electricity with an efficiency rate of 10%. This has now changed due to optimized manufacturing processes. Manz’ CIGS modules achieve nearly 15% efficiency; in the long run, as much as 20% is possible. “Such values have already been achieved in the lab,” says Sprechter. This means that thin-film technology achieves efficiency levels so far restricted to classic silicon modules.
For the time being, however, the classic option is still unrivalled in terms of efficiency rates: top modules from monocrystalline silicon already achieve over 20% efficiency. This high degree of efficiency is also a key reason why BIPV specialist ertex solartechnik, a subsidiary of glass producer ertl glas from the Austrian town of Amstetten, predominantly uses silicon cells for its modules. In order to meet the architects’ high demands, ertex solartechnik has joined forces with specialists from the architecture, glass and PV industries to develop modules that are novel in terms of their looks.
“Now architects and façade planners have a photovoltaic module at their disposal that fulfils the highest demands in terms of appealing looks and design freedom—like conventional façade elements—but forms a symbiosis with solar power generation,” explains Dieter Moor, marketing and sales manager at ertex solartechnik.
According to Moor, the different options result from the possibility of patterning and coloring each layer of the module—from the front glass surface to the back sheet. In this way, laminated safety front glass can be designed with various patterns and degrees of transparency, printed glass backs, colored front glass and encapsulation films, patterned glass fronts, colored, and semi-transparent solar cells, as well as colored solder connectors. “This ensures that the solar cell structure is next to invisible,” Moor explains.
Architects used a children’s daycare center complying with PlusEnergy house standards in the German town of Marburg to demonstrate what is already feasible by using state-of-the-art BIPV panels. In order to “envelop” the complex building with fitting modules, the team took to triangular elements with high-performance monocrystalline silicon cells made by ertex. The Austrian-made modules are also characterized by their uni-colored appearance. To produce this effect, the otherwise silver-colored busbars and highly reflective solder connectors between the individual cells were printed black. As a result, the surface is uniformly black, and the elements do not look like highly efficient power generators.
Thanks to new semiconductors, architects can look forward to even more freedom to design with solar technology. Dresden-based Heliatek and Belgian flat glass producer AGC Glass Europe are working on BIPV elements that incorporate organic photovoltaic films of different dimensions, color graduations, and levels of transparency in construction glass. Heliatek spokeswoman Kathleen Walter says that these films make elements easier to handle and also suitable for use in irregularly shaped façades. In addition, solar films in organic material promise to keep production costs low, since tiny photoactive molecules (oligomers) are available in sufficient amounts and can be precipitated onto the film using an efficient role-to-role process. The process is far less labor intensive than the production of crystalline silicon cells, whose “blanks” (the wafers) must first be diced out of a solid block before being processed further into cells.
These solar “light-weights” have been well-accepted in the construction industry. “We are virtually flooded with enquiries for pilot projects,” says Walter. “This technology definitely promises to trigger a boom.”
But Heliatek has not solved all critical points in the process yet. Films from the pilot production currently achieve an efficiency rate of just 7-8%. In the glass sector, Heliatek has realized a number of pilot installations and has been capturing data since. A façade installation in Dresden achieved an additional yield of 23% over conventional silicon after just one year. In the joint venture development with AGC, the next step is product certification. Currently, all BIPV elements are undergoing final tests.
Heliatek is looking for investors for a large-scale production site with an output of 1 million sq m of solar film annually, instead of the 50,000 sq m so far. Heliatek also intends to manufacture wider webs of 1 or 1.20 m at the site. Today, the pilot line only produces webs that are 30 cm wide. “This would substantially reduce installation expenses,” says Walter, and the efficiency rate is also expected to go up. In lab tests, Heliatek’s oligomer cells already achieved 12% efficiency. The company now wants to transfer this value to large-scale production.
Solar researchers have another card up their sleeve for BIPV: cells in perovskite. This mineral is as easy to process and just as economical as oligomers, but comes with greater efficiency potential. American scientists have proved almost 20% efficiency in lab tests, and they produced a perovskite layer as thin as 1 mm by vapor-depositing organic molecules and lead crystals on glass. The cell produced as much electrical energy as the silicon-based cell that is 150-times thicker. If the industry succeeded in manufacturing perovskite cells for BIPV, the technical and commercial obstacles would be overcome.
This is why the EU is promoting the further development of this technology with an investment of some €3 million (approximately $3.4 million) as part its Horizont 2020 program. The concrete objective of Got Solar (as the research project was dubbed), which involves cell developer Dyesol as well as six European research institutes, is the development of a cell-sealing technology fit for industrial production. After all, perovskite suffers from the same restrictions as Heliatek’s oligomers: it is extremely sensitive and must be protected especially well against outside influences.
Dyesol spokeswoman Eva Reuter explains: “It’s all about increasing their stability.” The company wants to start mass-producing perovskite cells in 2018. To this end, a new factory with 600 MW annual capacity is planned in Turkey.
glasstec 2016, to be held September 20-23 in Düsseldorf, Germany, will be a meeting point for experts from the solar and glass industries to network about innovations and progress in solar glass and module manufacturing, as well as in materials and costs. The Special Show “glass technology live” will address this interface between solar technology and glass. Here, the latest developments in façade and energy will be presented, including innovations in PV and solar thermal systems.
For additional information, visit www.glasstec-online.com.