The main goal of the research project is to investigate technologies for the manufacturing of translucent and transparent membrane roof and façade elements with integrated optoelectronic components. The focus lies on a switchable total energy transmittance (often referred to as the solar factor or solar heat gain, and “g-value” in Europe) and on flexible solar cell integration to significantly contribute to both energy saving and power generation in buildings.
However, glass is not bendable enough to apply it to vaulted surfaces as design element in representative buildings such as airports, stadiums, event halls or shopping malls. Furthermore, its high weight limits the use of glass for large area roofs or façades without massive, expensive and design-limiting supporting structures. For these applications, fluoropolymers such as ethylene tetrafluoroethylene (ETFE) are an alternative to glass providing a long lifetime and resistance to weathering.
In contrast to glass, fluoropolymers are difficult to handle in thin-film coating processes. For this reason, roof and façade elements of membranous material are rarely functionalized yet with energy-saving features such as thermal shielding layers or integrated solar modules. A consortium of nine industrial and research partners has been formed to change that situation by functionalizing fluoropolymer web surfaces with optoelectronic components through thin film coating techniques.
“Membrane façade and roof elements will be functionalized with electrochromic films, which allow switching of the transmission of visible light and thermal radiation by applying an electrical voltage,” project coordinator Dr. John Fahlteich said. “The energy required for that is made available through flexible organic solar cells. Within the project FLEX-G, we aim to develop dynamic processing and deposition techniques in a way that they are applicable not only for flexible, membrane-based building envelopes but also for glass-based systems.”
Within the project duration of three years, FLEX-G will investigate processes that allow the deposition of electrochromic layer stacks directly on an ETFE film surface. The flexibility of the film enables the use of economical, efficient and high throughput roll-to-roll (R2R) fabrication processes. A 36 square meter ETFE membrane roof prototype will demonstrate both the electrochromic components for switching the total solar energy transmittance and the flexible organic solar cells for electrical power generation.
The FLEX-G research program is a joint effort of:
• Fraunhofer-Gesellschaft zur Förderung angewandter Wissenschaften e.V. represented by FEP Dresden
• ISC Würzburg
• IAP Golm
• Hochschule für Technik Stuttgart
• Coatema Coating Machinery GmbH
• Hightex GmbH
• Lamilux Heinrich Strunz GmbH
• Heliatek GmbH
• ROWO Coating GmbH
• EControl Glas GmbH & Co. KG
• Nowofol Kunststoffprodukte GmbH