‘Smart window’ demonstrates energy saving potential


The Dutch innovation organization TNO has reported its solar smart window is performing successfully in real world conditions.

The smart window, developed by TNO and partners in the Interreg project Sunovate, is designed to automatically switch between blocking heat from the sun and letting it pass, with the aim to reduce energy consumption in moderate climates with cold winters and warm summers such as in the Netherlands.

Specifically, the smart window transitions from an infrared transparent to blocking state as soon as direct sunlight hits the window and ambient temperatures are above 20°C. When the glass surface cools down, usually over night, the transition back to the infrared transparent state happens.

This is intended to ensure an optimised use of solar heat leading to reduced energy demand for heating and cooling simultaneously. This can lead to additional energy and cost savings of up to 8% and €23.70 ($24)/m2 glass per year when compared to state-of-the-art high insulation (HR++) windows, TNO estimates.

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“The effective use of sunlight and solar heat can have a major impact on the energy efficiency of buildings, as it reduces heating demand in winter and cooling demand in summer. The new ‘smart window’ automatically adapts its solar heat gain to seasonal changes,” a TNO statement reads.

TNO reports that pilot testing of this new SunSmart thermochromic technology was started in January to gather information on the adaptive properties and performance of the window in a real environment.

Two 1m2-sized smart window flats were produced and implemented at the SolarBEAT test facilities in Eindhoven. TNO will further monitor the window indoor until the end of this year to obtain information on the switching performance during all four seasons.

The window is designed for high visible transparency, a switching temperature around 20°C and to only change transparency in the infrared. Therefore, the window is optimized for the highest energy savings, whilst staying completely transparent to the human eye.

The switch happens autonomously and is intrinsic to the laminated glass, so that the window can be installed in regular frames without special installation requirements. Moreover, the technology is designed using low cost materials and processes to realise a return on investment within 7 years for end users.

The technology is expected to be further advanced for market introduction within the next 2-3 years.

Sunovate is led by TNO and funded by the Interreg VL-NL programme, the Dutch government and the provinces of Limburg and Noord-Brabant.

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