Researchers in Switzerland are developing new mirror-infused smart windows that allow light into the room while keeping heat out.

The breakthrough comes at the intersection of two Swiss research strengths: materials science through the Laboratory for Advanced Materials Processing at Empa (the Swiss Federal Laboratories for Materials Science and Technology); and specialist knowledge in energy efficiency and the implementation of renewable energies in buildings and cities through the Laboratory for Solar Energy and Building Physics at EPFL (École polytechnique fédérale de Lausanne).

The seasonal window glass reduces overheating and glare in summer and ensures high solar energy and daylight input in winter – without the need for blinds or dimming the view. Unlike other smart window prototypes, the windows do not need a power source. The glass remains transparent and does not affect visibility.

A precision laser is used to create a grooved microstructure on the surface of a film, before tiny mirrors, known as Compound Parabolic Concentrator (CPC) lenses, are evaporated into the pores on the surface. The film can be applied to glass or inserted into double-glazed windows, with the array of mini-mirrors reflecting sunlight into the room more efficiently.

The researchers say the smart window material managed a light incidence of 60 degrees and was able to divert 80 per cent of the incoming light, spreading it out into the room almost horizontally. Patrik Hoffmann from the Laboratory for Advanced Materials Processing says the glass is energy saving and could enable a future of sun protection without window blinds. “The glass can reduce the consumption of thermal energy from heating or air conditioning by 10 to 20 per cent.”

Prototype windows will be installed in the NEST building on the Empa campus in Dübendorf in the SolAce unit of EPFL to monitor its performance. NEST (Next Evolution in Sustainable Building Technologies) – owned by Empa and Eawag (Swiss Federal Institute of Aquatic Science and Technology) – is the world’s first modular research and innovation building aimed at accelerating innovation in the construction sector, where new developments can be tested, tweaked and demonstrated under realistic conditions. The SolAce unit specialises in multi-functional facade technologies to capture solar energy and daylight by the building envelope.

A pilot project in cooperation with chemicals giant BASF Switzerland is underway, with the team working on improving the speed and cost-effectiveness of the manufacturing process.

Switzerland’s world-leading strengths in sustainable and energy-efficient building technology have been recognised with a number of international conferences, including the 13th Conference on Advanced Building Skins in Bern in October 2018. The SwissTech Convention Center on the EPFL campus itself incorporates the world’s first multicolored Dye Solar Cell façade.


Featured image: The NEST building (photo credit Roman Keller)

(via NewAtlas, Empa, EPFL)