Michael Berger at Nanowerk has written a good primer on smart windows while discussing a specific project from The Netherlands. From Berger’s article,

‘Smart’ windows, or smart glass, refers to glass technology that includes electrochromic devices, suspended particle devices, micro-blinds and liquid crystal devices. Their major feature is that they can control the amount of light passing through the glass and increase energy efficiency of the room by reducing costs for heating or air-conditioning. In the case of self-powered smart windows the glass even generates the energy needed to electrically switch its transparency.

Smart windows can be electrochromic and/or photochromic. From an article by Alan Chen, of the Lawrence Berkeley National Laboratory, titled, New Photochromic Material Could Advance Energy-Efficient Windows,

A photochromic material is one that changes from transparent to a color when it is exposed to light, and reverts to transparency when the light is dimmed or blocked. An electrochromic material changes color when a small electric charge is passed through it. Both photochromic and electrochromic materials have potential applications in many types of devices.

As for how both materials could have applications appropriate for windows, Berger’s article describes a smart window that sounds like it’s both electrochromic and photochromics and has the added benefit of being able to power itself,

A new type of smart window proposed by researchers in The Netherlands makes use of a luminescent dye-doped liquid-crystal solution sandwiched in between electrically conductive plates as an energy-generating window.

The dye absorbs a variable amount of light depending on its orientation, and re-emits this light, of which a significant fraction is trapped by total internal reflection at the glass/air interface.

(For more details about this specific project, please read Berger’s full article.)

A few months ago I chanced across a local (Vancouver, Canada-based) start-up company, SWITCH Materials, that features technology for smart windows. From the company website (Technology page),

SWITCH’s advanced materials are based on novel organic molecules that react to both solar and electrical stimulation. Smart windows and lenses are the first commercial application under development at SWITCH. They darken when exposed to the sun and rapidly bleach on command when stimulated by electricity.

While competitive technologies rely on either photochromism or electrochromism, SWITCH’s hybrid technology offers the advantages of both, providing enhanced control and lower cost manufacturing.

• SWITCH’s technology also operates without requiring a continuous charge, and as a result has great potential for significant cost savings in many applications.

• The organic compounds in SWITCH’s materials are thermally stable and remain in their coloured state until electricity reverses the chemical transformation.

As far as I can tell, one of the big differences between this Canadian company’s approach and the Dutch research team’s is the Canadian’s use of organic compounds. Also, one of the key advantages (in addition to the ability to generate electricity) to the Dutch team’s approach is that users can control the window’s transmission of light.

I don’t know how close either the Canadian company (SWITCH) or the Dutch research team is to a commercial application but there is this excerpt from the Jan. 14, 2010 news release (on the Pangaea Ventures website),

SWITCH Materials Inc., an advanced materials company developing energy saving SMART window solutions, has raised $7.5M in Series B financing. The Business Development Bank of Canada (BDC Venture Capital) led the investment, with participation from existing investors GrowthWorks, Pangaea Ventures and Ventures West. Proceeds will be used for continuing R&D and to complete product commercialization.

…

“I am excited that an up and coming Canadian clean tech company will be added to our portfolio,” said Geoff Catherwood, Director of Venture Capital at BDC. “The technology being developed at SWITCH carries tremendous potential to address the burgeoning demand for a new generation of window technology. Producing a SMART window solution that can meet the price point required for significant market penetration will enable SWITCH to gain a leadership position in a large untapped market.” In conjunction with the financing, Mr. Catherwood will join the company’s Board of Directors.

I notice the news release makes no mention of a timeline for possible commercial applications or of competitors for that matter. In addition to the Dutch research team (there’s a Dutch company [I blogged about them here {scroll down}] that is producing something remarkably similar [it too offers control for transmission of light] to the Dutch research team’s smart windows profiled by Berger), there’s competition from the Americans who, recently, through their federal Dept. of Energy invested $72M (a loan guarantee added to previous investments) in SAGE Electrochromics.

The market for windows that could conceivably eliminate or seriously minimize the use of air conditioning is huge. In this era of concern about energy use and climate change, air conditioning is a problem as it uses a tremendous amount of energy, has a significant carbon footprint, and most importantly for business, it is expensive. Think of Hong Kong, Shanghai, Delhi, Tokyo, Rio de Janeiro, Cairo, Tel Aviv, Nairobi,  Toronto, New York, Montréal, Chicago, Paris, London, Belgrade, Berlin, etc. during their respective hot seasons and the advantages of smart windows become quite apparent.

One last thing I’d like to mention about the Canadian company, it’s a Simon Fraser University (SFU), spinoff with Neil Branda, director of SFU’s nanotechnology centre, 4D Labs as their chief technical officer. Dr. Branda’s research work was last mentioned on this blog in a posting that featured, SFU scientists their phasers on stun as part of the title.