Smart Windows Can Boost Energy Performance

Innovations in glazing technology have transformed window performance over the past three decades. Transparent glass panes can now darken in bright sunshine by means of thermochromic or photochromic films or coatings. When the temperature of the glass increases from the sun’s infrared rays, the transparency decreases, and the glass becomes clouded or frosted. With photochromic treatments, the glass occludes because of increased light intensity.

Window self-darkening coatings were adopted from eyeglass lenses that changed their tint in sunlight. These perpetually reversible rearrangements of molecules that respond to solar radiation yield big energy savings in a building’s air-conditioning demands, sometimes by as much as 25 percent. Air-conditioning accounts for about 6 percent of all electricity generated in the U.S., with its accompanying negative climate and health impacts.

Another similar window technology called electrochromic uses a small electric current to polarize coating crystals to create clear or frosted states. This type of glazing is sometimes called intelligent glass or switchable smart glass. It is often chosen for privacy requirements as well as for heating and glare protection.

The latest window research holds the promise of reducing a building’s cooling demand while also generating electricity. By placing a film of perovskites, a relatively new solar cell material, between two layers of glass, electricity is generated. These highly effective and inexpensive crystals are injected with a solvent vapor into the gap between the panes of glass. As temperatures rise, the vapor triggers a chemical reaction that rearranges the crystals into different shapes, increasingly opaque, while simultaneously generating electricity. This progressive blocking and subsequent tinting happen at 95-115 degrees Fahrenheit and take only seven seconds to occur. Researchers predict a prototype window using this technology to be developed within a year. 

Technological ideas to address climate change abound. Many are already making their way into the marketplace. Technological inventiveness can help us reduce carbon emissions, but to fundamentally reverse our destructive climate patterns, we need a different framework:

• where resources are used carefully and in cyclical processes, following nature’s example,

• where human growth takes precedence over consumerism and economic growth,

• where equity and inclusivity are high priorities, and

• where environmental restoration becomes an employment and societal benefit.

These and other similar tenets will restore the health of our earth and nurture its biodiversity.

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