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It takes a great deal of energy to heat and cool homes and buildings. However, a huge amount of energy can be saved by applying special coatings to windows. These coatings make good use of the sun’s thermal radiation when heat is needed, but block it out when the temperature is just right. That switch from one mode to another happens automatically, thanks to the thermochromic layer. A patent application for this invention has been submitted.

Temperature-based switching

This coating was developed by TNO, at the Brightlands Materials Center. In terms of yield, it is at least as good as the conventional systems that are currently available on the market. What sets this coating apart from the rest, however, is its much shorter payback time. Its se-cret lies in the thermochromic coating, which switches on or off at specific temperatures. When the temperature falls below a certain value the coating admits infrared light, which heats up the surroundings. If the temperature rises above a pre-set value, the coating will block any incoming infrared light. This system has several advantages over more widely used electrochromic systems. One is the enormous difference in price, another is that the glass remains transparent even when it is blocking part of the sunlight.

Saves energy and cuts CO2 emissions

The glass does not discolour or darken. This eliminates a potential barrier that might other-wise prevent architects from using the system in their designs. In large-scale renovation pro-jects, this coated glass offers an affordable solution that enables the owners of apartment complexes, for example, to save energy. Calculations show that this system can reduce a home’s total energy consumption (including heating, cooling, and power) by up to twenty percent, or even more. On average, that amounts to a saving of more than six hundred euros per home, per year. Across the country as a whole, this would cut annual CO2 emissions by 4.5 megatons.

Global market

Many of today’s ‘smart’ window systems are designed to be effective either in warm areas (by keeping the sun out) or in cold regions (by extracting heat). The thermochromic coating was designed for use in temperate climates, which have summers and winters. As a result, this product has commercial potential throughout most of the world. The market for coated float glass is worth tens of billions of euros, and it is growing by around eight percent each year. The thermochromic coating is cheaper than conventional coatings, so it has a very promising future.

From lab to prototype

The efficacy of this thermochromic coating has now been confirmed by laboratory tests. That is a real breakthrough, as many companies and knowledge institutions have been con-ducting experiments in this field for many years, without success. The problem was that the switching temperatures were too high. The newly-developed coating can switch at any de-sired temperature. In the case of homes, this is typically between 15 and 25 degrees. The plan is to create a prototype within the next two years, one that works under real-world conditions. That will pave the way for a market launch.

Would you like to invest in the further development of this technology, or perhaps contribute in some other way? If so, please get in touch with us.


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Rolph Segers, MSc

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