Inside IT
The Era of the Smart Window: Functional Alternatives for Energy Conservation

It’s uncommon to change windows on buildings following seasonal changes. We rather just put up curtains or blinds when the sunlight gets too intense in the summer. Now there are windows that control the level of heat penetration by themselves according to seasonal changes in order to control indoor chroma and temperatures. They are called smart windows and they’re highly appreciated for their energy conservation effects and the new eco-friendly material alternative to normal glass. Windows are now getting smarter.

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Smart window (Source: http://www.kurzweilai.net, Lawrence Berkeley National Laboratory)

What Is a Smart Window and What Does It Do?

Smart windows can be defined in multiple ways depending on how they’re being used: for cars or buildings. A smart window usually refers to a window that can adjust light penetration using voltage, by making itself transparent or opaque. It gets darker when the outside temperature goes up, and becomes transparent again in order to absorb more sunlight when the temperature goes down. Smart windows can save energy with this kind of seasonal light control.

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Regular window (left) and smart window (right) (Source: http://www.kurzweilai.net, Berkeley Lab)

The smart window is a good alternative for growing environmental issues and effective energy use. It enhances its economic value by responding to the outside environment to spend less energy while also collecting and saving natural energy. This is why smart windows are being recognized as functional alternatives in various fields like construction, industrial sites, and transportation. Smart windows also provide convenience by constructing a safe and pleasant living environment and, in turn, a better city for us.

Smart Window Handling Sunlight and Electricity

The key principle of a smart window is the film inside which has a substance that controls the sunlight penetration ratio. Smart windows change color quickly and are being used in various fields. Sometimes we can see them being used at crowded areas like highways or stadiums as display boards. It’s also installed at stores’ fronts to keep the walls transparent during the day but darkened after closing.

When used as sunroofs on cars, smart windows can block up to 40% of visible light to protect the driver’s skin and eyes. As it also blocks over 99% of UV rays, it can successfully replace curtains and blinds to keep furniture and cloth items from getting discolored by sunlight. Mercedes-Benz is also commercialized smart windows by installing a color changing panorama sunroof called Magic Sky Control in some of their automobiles.

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Mercedes-Benz Magic Sky Control

As we see, smart windows are being applied in various areas and their potential is endless. The fact that it uses energy efficiently and can be applied to different kinds of display materials definitely seems to show great prospects.

How Far Have Smart Windows Come? Smart Windows in Korea and around the Globe

Global Information mentioned them in a report from NanoMarkets in 2013 and said smart windows had already formed a market reaching over $1 billion. They also expected this market to grow up to $2.7 billion by 2018. Though the smart window market is mostly growing outside Korea, some technological developments are underway in Korea.

Smart Windows in Korea

Let’s first take a look at how far the smart window industry has come in Korea. In 2002, the Korean glass provider SDPI developed their own large smart window production technology with the polarized particle production technology adopted from RFI in the U.S. SDPI then provided their products to a U.S. aircraft company.

In 2012, Nano Science Technology Institute from SungKyunKwan University and Korea Electronics Technology Institute developed and commercialized a smart window technology that controls the window’s sunlight penetration according to the season and weather. This smart window is considered economic since it doesn’t require a complicated production process. It drew global attention due to the fact that it changes based on the outside environment without any specific manual control and that it can be used for a long time.

More recently, the Photoelectric Conversion System Development Team from Korea Institute of Science and Technology(KIST) came up with a smart window in accordance with an English research team. They developed a substance which automatically opens and shields the visible light by detecting if the light includes any UV light. This substance was combined with a solar panel for windows which turned them into solar panel smart windows.

The existing smart window technologies have a function that passes or blocks sunlight, but they also required additional power sources and had to be turned on by users. This new solar panel smart window responds to UV light without any power source or user control. Since smart windows have better efficiency as they work by themselves and they can produce additional electricity, they are attracting a lot of attention.

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Smart window responding to UV light (Source: http://www.kist.re.kr)

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Solar panel smart window (Source: http://www.kist.re.kr)

Smart windows around the globe

There is countless research being done around the world so I’ll share just a few of the major cases. Milpitas from California developed a window through which the residents can control light/heat penetration and reflection. By depositing thin films between two sheets of glass, it can regulate the sunlight and heat from the outside. These films, put between panes of glass like a sandwich, have two conductive oxidized films consisting of an ion storage layer and an electrolyte/chromium layer.

The principle of this window is to have low voltage go through the conductive oxide in order to get the ions from the storage layer and let them get through the electrolyte layer and into to the chromium layer, where it either absorbs or reflects the light. When the voltage is applied to the opposite direction, the ions come back to the storage layer and the window gets brighter to let more light in.

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View Dynamic Glass which recognizes the light intensity and the light source (Source: http://www.viewglass.com)

A similar case is View Dynamic Glass from View, a company which specializes in windows. This product has a thin layer made of the sensor, electronic circuit, and electronic substances that work together to automatically control the penetration of light. What’s surprising about this product is that it controls the light penetration by recognizing the intensity of the light and the location of the Sun using its electronic circuit. You can also control light penetration through an app on your smart phone.

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Controlling the light with a smart phone (Source: http://www.viewglass.com)

How Far Can Smart Windows Go?

It’s quite surprising to see all this new technology for smart windows. What’s odd here is that we don’t see a lot of buildings and cars that have actually installed smart windows. The biggest problem is that smart windows are pricy. The technologies to create them are complicated and it’s not easy to materialize such technologies in reality, so smart windows naturally tend to be more expensive. The technology itself has not reached a level advanced enough to be commercialized and production itself. There are still issues to be solved such as implementable colors and durability.

These limits, however, can’t lessen the value of smart windows. They not only have high energy efficiency, but also great aesthetic and functional usability in construction and manufacturing industries. Smart windows can provide the new basis for growth in the glass and window production industry, as they can be developed for other top-notch displays such as smartphones, PCs, and TVs. If you have seen the movie Minority Report, you might remember this transparent glass to display various kinds of data. That scene could actually become a part of our lives when the technologies for virtual reality and smart windows converge.

One of the most important issues of the century is energy deficiency and now more people are interested in the issues of energy conservation and storage technology. In this context, smart windows can become a great functional alternative based on their economic use of energy. The smart window market which was only seen as a niche market is now growing globally with the increasing awareness on energy issues. I hope to see Korea continue new and original technologies to lead the global market.

Written by Yongjun Park, University reporter for LG CNS 

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