14 May 2012
Building-integrated PV products still have a relatively small share of the total PV market. The reasons are the inflexible production processes, along with standards in the construction business that have to be met, and the increased construction costs. Furthermore, two worlds often collide when architects seek BIPV products with specific attributes, such as flexibility in size, color, and shape.
The BIPV approach essentially replaces standard construction components with PV panels. BIPV panels function as energy producers as well as providers of weather protection, noise protection, insulation, blinds, and sometimes even as an element of corporate Identity. Thus, building integration requires aesthetically tailored solutions, an approach that in principle stands in contrast to standardization and cost-saving efforts of the industry. However, more and more BIPV products have recently entered the market that are adapted to these needs.
Thin-film BIPV solutions
US-based Global Solar has specialized in integrated rooftop solutions with their CIGS (copper indium gallium selenide) modules. The flexible and lightweight thin-film modules are rolled out flat onto the roof and then affixed to the roof surface. The company from Tucson, Arizona partners with several roofing specialists who integrate Global Solar panels into their products and even further develop building integrated solutions using the solar panels as an architectural element [see picture 1).
Picture 1: Global Solar Energy installation in Milan, Italy
(Image courtesy of Global Solar Energy)
Another way to apply CIGS thin-film PV technology are the solar shingles from Dow, which are installed and perform just like a conventional shingles with the additional benefit of generating energy (see also “Dow Powerhouse Solar Shingles is Edison Awards Best New Product”).
More facade-oriented is the BIPV approach of Würth Solar in Schwäbisch Hall/Germany. Using CIS (copper-indium-disulphide) modules in a number of available colors and sizes and by employing an architect for all BIPV projects, Würth has realised various façade projects, including rehabilitation measures on buildings of the University of Erfurt and the new headquarters of inverter supplier Kaco New Energy. The company also offers in-roof systems that partly or completely replace traditional roof tiles.
Another BIPV supplier, however, Odersun AG has learned that the primary focus on building integrated solutions still is a difficult strategy. The company, which offers customized CIS modules through a flexible production process, has realised some impressive reference projects, but currently struggles to survive.
Future BIPV products are applications are yet to be realized as much research continues. One example is the broadband plasmonic technology recently developed by Swinburne University of Technology in Australia and Suntech Power Holdings, for instance, could help to improve efficiency of thin-film amorphous silicon solar cells in a few years and lead to a wider implementation of BIPV. (See “Boosting Building-Integrated PV Bumpy Nanoparticles Scatter Sunlight into Broadband Range.”)
Organic BIPV products
The youngest PV technology is on the verge of being ready for market and seems to be the most promising for future building-integrated applications. Organic solar cells are flexible, thin, light-weight, semi-transparent and come in various colors and dimensions.
Organic solar cells are flexible, thin, light-weight, semi-transparent and come in various colors and dimensions.
German Heliatek a spin-off from the universities of Ulm and Dresden, sees itself as technology leader in organic photovoltaics (OPV) based on small molecules called oligomers. The company currently is in transition from lab to fab and in March opened a first production line to manufacture organic solar panels in a roll-to-roll process using vacuum deposition on plastic at low temperatures. Knowing of the potential the product has in BIPV, Heliatek has recently signed a joint development agreement with RECKLI GmbH, a manufacturer of elastic molds for concrete building façades. By integrating Heliatek’s organic solar panels directly onto vertical concrete façade blocks, the two companies want to transform concrete walls of buildings into solar energy harvesters with adaptive design, low installation costs and comparatively good harvesting yield due to temperature independence and superior low light performance of the panels.
US solar manufacturer Konarka follows a similar strategy. The company recently announced a cooperation with a number of partners from the glass and construction industry last year in September, including Lapp Kabel, ThyssenKrupp Steel Europe, and Bischoff Glastechnik. The resulting foil called “Power Plastic” can then be used in numerous building integrated applications with the additional benefit of having a superior thermal coefficient.
Crystalline-based BIPV solutions
Crystalline silicon based modules have been on the market the longest for building integration, and thus are the most widely used. Numerous reference projects to show feasibility, mainly in façade applications, have already been realized. Austrian PVP, for instance, provides a crystalline module adapted to BIPV needs through the use of PVB foils, which makes the panels laminated safety glass panels. Even more important is flexibility: Modules can be produced according to specific design objectives and static requirements, in different sizes, layouts, forms and colors, and with a glass thickness from 2 x 2mm up to 2 x 12mm. Furthermore, the modules can also fulfill insulation functions, e.g., in the building envelope (see picture 2).
Picture 2: PVP Facade solar PV installation in Austria (Image courtesy of PVP)
Other suppliers, like REC, offer a roof-top integration. The REC Peak Energy Integrated solution is an entire in-roof solar system replacing the roof tiles. The modules – installed with the Solrif installation system distributed by Ernst Schweizer AG – overlap and the whole construction is sealed water proof. In case of breakage of a module, the mounting system allows an easy replacement.
Picture 3: REC roof integration system (Image courtesy of REC)
These product examples show that PV is on the way to broadening its applications in building integration. A further adaption of PV in architecture will be reached in the future if both the PV industry step adapts to the needs of building integration as far as they are economically justifiable, and if architecture and the building industry recognizes BIPV as a valuable element that can be promoted in larger volumes.
Written by Andreas Breyer, Contributing Editor, Germany