The smart windows market covers a wide range of technologies that use “smart” materials to dim glass in various ways. Active technologies, which require a power source to operate, comprise most of this market today. Passive smart windows, made from materials that automatically change tint in response to an external stimulus, are simpler, but they rely on changes in the environment to operate. This can be a barrier to adoption in applications where conditions are not ideal.
While the vast majority of windows in buildings and automobiles use clear glass, the desire to control energy use will drive increased adoption of smart windows. This is a market in which materials play a crucial role. NanoMarkets forecasts potential revenue of over $700 million for self-dimming smart windows materials by the year 2021.
Photochromic windows, coated with materials than darken when exposed to sunlight, are competing to gain a slice of the smart windows market. As a passive technology, it will need to be priced lower than active technologies in order to succeed. Like many materials in this crowded market, photochromic technology faces a serious uphill battle in its attempts to win market share.
Photochromic materials have been used for many years in self-dimming sunglasses, so it might seem natural for them to make the leap and start appearing in smart windows in automobiles and buildings. There are some very good reasons why this hasn’t happened so far, and why photochromic windows may not ever take an important share of the smart windows market.
Concerns about Photochromic Materials
NanoMarkets’ research tends to indicate that there is a market perception that photochromic windows do not switch fast. We believe that in order to generate significant revenue within the smart windows market, photochromic materials will have to overcome this issue, perhaps through a combination of clever marketing and actual performance improvements.
Photochromic materials for windows have been primarily associated with low-cost aftermarket coatings in cars. This is a low-end application that doesn’t do a lot for its image and may make it more difficult for these materials to break into the luxury car or building markets where customers expect high performance.
Another problem for photochromic windows is inherent in the way they operate, and there isn’t much the industry can do about it if it sticks with a purely photochromic material. These materials change their transparency in response to light intensity but are immune to changes in temperature. The window darkens when struck by light whatever the temperature is outside.
This may or may not be what the end user wants from a smart window. There are certain cold but sunny days on which glare can be a problem. But if the window darkens on a cold day, it tends to make a room even colder, thereby increasing the use of energy for heating and reducing the reputation of this kind of material as one that increases energy efficiency.
For building applications, this problem is made worse by the fact that the sun is lower in the sky in winter months, so its rays may strike a window more intensively in the winter than in the summer.
Improving Prospects for Photochromic Windows
There are several approaches that may allow photochromic materials to overcome some of their disadvantages and gain acceptance in the smart windows market. New materials development that improves switching time is one avenue, but NanoMarkets believes that the most likely path for success is for hybrid systems that combine photochromic with some kind of active smart windows technology.
Hybrid materials are the one approach that can potentially overcome the problem of windows that automatically darken on cold, sunny days. The right combination can incorporate user control to override the automatic photochromic effect as needed and produce a more marketable product.
SWITCH Materials, based in Canada, is the firm that at present looks most likely to succeed in this market. Its hybrid photochromic/electrochromic film technology is based on a class of diphenylyethene molecules developed at Simon Fraser University. The company claims to have a large range of materials—as many as 200 molecules—available to it for future research.
This may sound impressive, but SWITCH Materials appears to still be at the test stage for its technology. Despite claiming lower costs compared to other smart window options, it does not seem to be shipping in any large quantities at the present time. It will likely need additional funding to break into volume production.
SWITCH Materials is especially targeting the automotive market, an area where simple, inexpensive photochromic materials have found somewhat of a niche. They are used for tinting windows in very sunny climates, where users want to block light during the day but need clear windows at night. These films are mostly manufactured and distributed in Southeast Asia and are not likely to be of much interest in Europe and much of the U.S. A more advanced hybrid technology, such as what SWITCH Materials is offering, should sell much better in these locations.
Fraunhofer ISE, the largest solar energy research institute in Europe, is another company that may be able to expand the market for photochromic materials. Its hybrid photochromic/electrochromic technology combines electrochromic tungsten trioxide and a dye solar cell (DSC) layer to produce a photochromic window that it says is suitable for both automotive and building applications. When illuminated the dye molecules inject electrons into the tungsten trioxide, which colors blue.
It is convenient that the DSC can provide the power source for the system. Switching speeds, however, remain slow, especially for reversing the darkening process. We expect that Fraunhofer will need to improve upon performance in order to create a viable commercial product.
NanoMarkets forecasts predict very small revenues for purely photochromic windows over the next eight years with potentially much better prospects for hybrids. Hybrid photochromic/electrochromic windows will still need to convince customers that they actually provide the best of both technologies, as their supporters claim, in order to succeed.
SWITCH Materials touts the benefits of automatic darkening when a car is parked in the sun and user control for added comfort while driving. But putting in electronic control also adds cost. Also, when using hybrids, the main advantage of photochromics being a passive technology is lost, because they now require a power source. As Fraunhofer demonstrated, however, this could be achieved with a low cost solar panel.
Many materials exhibit some kind of photochromism, and extensive research on this class of materials is being carried out globally. This opens the opportunity for other companies to compete in this space. But providing a photochromic material with fast switching time will probably not be sufficient. Because of limited applications, a pure photochromic material is not likely to generate much revenue.
There is potential for firms with the same kind of materials strategy as SWITCH Materials to compete if they can create a materials combination with sufficient performance at the right price. The problem is that the projected market is still very small – only $2 million in 2014 – and may not support more than one company even with optimistic market projections.
NanoMarkets can see the photochromic materials market – including hybrid technologies –growing to nearly $35 million by 2021, but price is very important. If a hybrid photochromic/electrochromic approach really can be less expensive than pure electrochromic technology, then it might reach this goal.
Otherwise, photochromics doesn’t really have much of an advantage over other smart windows technologies and may very well lose out. And since the expected revenues from photochromic materials are not that high, there is probably space for just two or three companies to compete and the only way to make real money in this space is going to be for those who can offer value-added products such as complete windows or those who can gain substantial revenues from systems integration; such as various aftermarket firms in the auto sector.