New smart windows can help keep heat out in summer and cold out in winter. In this way, the windows help to reduce energy consumption and increase comfort in buildings. The SunSmart glazing was developed by TNO and was recently installed for the first time in the Brightlands Circular Space building in Geleen and in a home in Almere.
Buildings in the Netherlands account for 40 per cent of total energy consumption and nearly a third of CO₂ emissions. With its SunSmart windows, TNO aims to reduce this share and thereby contribute to an energy- and climate-neutral built environment by 2050.
Thermochromic coating
The windows are fitted with a thermochromic coating that automatically regulates solar heat at temperatures around 21 °C. At lower temperatures, the coating allows solar heat to pass through, whilst at higher temperatures it blocks it. TNO estimates that this could save an average household between 5 and 9 per cent on its annual energy bill. This amounts to a saving of around €500 and a reduction of approximately 400 kilograms of CO₂ emissions per year.
The thermochromic coating requires no electricity, no additional connections and no visible change in tint, and operates autonomously. This is in contrast to conventional solar control glass and electrically switchable systems. To the naked eye, the windows remain transparent. According to TNO, the insulation value is comparable to that of HR++ glass.
Optimal use of solar heat
Like solar control glass, SunSmart windows block heat in the summer without altering the transparency or colour of the window. However, SunSmart switches automatically and therefore does allow solar heat through at lower temperatures. This makes optimal use of solar heat, meaning a building requires less heating.
The SunSmart windows feature integrated temperature control, meaning that no additional electrical connections or modified window frames are required.
Used for the first time
The technology has recently been put into practice for the first time, including in the Brightlands Circular Space building in Geleen and in a house in Almere. A total of more than 300 m² of SunSmart glass, measuring 2.25 × 3.21 metres, was produced for this purpose. These glass panes were used to create insulating glass window units, which are currently being tested in real-world conditions in Geleen and Almere.
TNO reports that the SunSmart windows have a payback period of 5 to 7 years, which is comparable to the investment in solar panels. The guaranteed lifespan of the windows is 20 years.
Here are some figures shared by TNO regarding the SunSmart windows:
- 5 to 9 per cent energy savings on cooling and heating
- Around 400 kg less CO₂ emissions per home per year
- Approximately 60% fewer hours of overheating above 28 °C
The glass has been developed by the Brightlands Materials Centre, which is part of TNO, in collaboration with partners. The Brightlands Materials Centre conducts research into new, sustainable technologies in the field of plastics and their applications. In addition to smart coatings for solar-control glass, the centre cites thermoplastic materials for lightweight structures and 3D printing technologies for sustainable manufacturing as examples.
