Home Optimal energy Netherlands-based researchers develop budding smart window

Netherlands-based researchers develop budding smart window


The Netherlands-based research center TNO has developed a smart window using thermochromic smart glass. They partnered with Sunnovate on the Interreg project to realize this latest innovation. The window is designed to switch between absorbing heat or letting it pass.

What is Smart Window Technology?

The smart window has a thermochromic active material. It can automatically change its optical properties at a certain temperature, around 20⁰C. As the temperature rises, the glass changes its infrared transmission when the sun hits it. When this happens, its transparency changes and the window becomes less transparent to solar heat.

This effect occurs in the infrared part of the solar spectrum, making the window transparent to human eyes. The transition to the infrared transparent state usually occurs at night and at cooler temperatures as the glass surface cools. The switch occurs automatically and is integrated into the laminated glass. This allows the smart window to be installed without special installation requirements.

Simply put, the window blocks heat from the sun when outdoor temperatures are high and absorbs heat when outdoor temperatures are lower.

Speaking to reporters, researcher Paskal Buskens explained, “VO2 changes its crystal structure at a certain temperature. With this change in the crystal structure, the electrical and optical properties also change, which means that the material absorbs more infrared light in the high temperature crystal phase and the absorbed solar energy is not transmitted into the building.

Vanadium dioxide (VO2) is a functional material in pigmented polymer film coating. It changes its crystal structure and optical properties at high temperatures, making it suitable for technology. A standard low-emission coated glass was used in the thermochromic coating.

Buskens said, ‘Thermochromics can change their infrared modulation properties from transmissive to blocking depending on the temperature of the glazing. Integrating VO2 into a film or coating for application in smart thermochromic windows can lead to a significant reduction in energy consumption for heating and cooling buildings in an intermediate climate.

In January, the Netherlands Organization for Applied Scientific Research (TNO) and its partners launched Driving test on the smart window to examine the properties and performance in a real environment. They implemented two 1m2 smart window demonstrators at the SolarBEAT test facilities in Eindhoven, making it the first time to test the adaptive thermochromic effect under real conditions. The results were positive and the demonstration will continue until the end of the year to obtain information on the four seasons.

The optimum switching temperature is around 20⁰C but can be adjusted by metal ion doping for optimum energy savings. The researchers claim that the smart window can guarantee energy savings of up to 8% compared to state-of-the-art HR++ windows in independent buildings, duplexes and townhouses.

Although pricing is unconfirmed, Busken said final costs depend on which glass companies sell the product. ‘But due to the low costs of the material itself and the great potential for savings, an attractive business case is ensured, while keeping the return on investment for end users at an acceptable level of around seven years.