Sonntag, 18. März 2018

Smart translucent roofs


"FLEX-G" to focus on flexible solar cell integration


Investigating technologies for the manufacturing of translucent and transparent membrane roof and façade elements with integrated optoelectronic components is the main goal of the research project "FLEX-G". The focus lies on a switchable total energy transmittance and on flexible solar cell integration.

 - At the shopping center in Lisbon, each roof element provides potential for integration of either solar cells or electrochromic films.
© Hightex GmbH
At the shopping center in Lisbon, each roof element provides potential for integration of either solar cells or electrochromic films.

Solar modules and a variety of energy management systems are well established in small and large buildings to optimize their energy balance both by generating electrical energy and by minimizing required power for heating, ventilation and air conditioning (HVAC). A major trend in modern architecture is the use of large transparent and translucent façade and roof elements to make time spent in these buildings more pleasant due to bright and spacious rooms and appearance. When made of glass, these façades and roofs are functionalized with heat reflecting coatings to minimize their “g-value”. 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. A noteworthy example for the use of this material is the roof of the largest shopping mall in Europe (the Dolce Vita Tejo in Lisbon, Portugal) with its 5-layer diaphanous cushions comprising 200,000 m² of ETFE. 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. Until now, it was not feasible to optimize the energy budget of buildings featuring membrane roof and façade surfaces. 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.

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.