Japan’s National Institute of Advanced Industrial Science and Technology (AIST) and Sumitomo Chemical Co Ltd have developed a “power-saving” sheet that blocks sunlight in summer and lets it through in winter.  The idea is to stop the heat gain from summer infrared, yet let he the infrared come in during winter while keeping the window glass transparent.

The sheet can be attached to a glass window or other kinds of materials.  Development exploits the fact that the incidence angle of sunlight in summer is different from that in winter. As the sun sinks lower in the sky more of the infrared is allowed through.  Surprisingly, the new sheet design does not change the view through the window.

Solar Incidence Angle Effects on Infrared Blocking Window Sheet. Click image for the largest view.  Image credit: AIST, Japan.

Solar Incidence Angle Effects on Infrared Blocking Window Sheet. Click image for the largest view. Image credit: AIST, Japan.

The idea offers a vast array of private, commercial and public buildings a means to reduce the heat gain from sunshine in air conditioning periods.  By simply installing the sheet it is possible to adjust the amount of light coming inside.  Sumitomo Chemical expects that the sheet will reduce the amount of power consumed by an air conditioner and assist with heating saving a worthwhile amount of money.

The sheet is made by fitting together two specially designed transparent sheets.  Generally, light coming into the transparent sheet at an angle greater than a certain degree is totally reflected when it is coming out of the sheet. If the front and back sides of the sheet are not parallel to each other, the total reflection occurs with a smaller angle, making it possible, for example, to block sunlight during daylight hours in summer. On the other hand, sunlight in winter passes through the sheet because its incidence angle is small.

The idea is quite a clever innovation.

AIST and Sumitomo Chemical fitted together two sheets to cancel out the refraction to achieve a normal window view.  If only one transparent sheet whose front and back sides are not parallel to each other is attached to a window, the view through the window is uplifted due to refraction.  The two-sheet solution is a breakthrough idea.

The AIST folks reasoned that a window glass capable of adjusting the amount of incoming sunlight depending on its incidence angle could be built by using the total reflection phenomenon on the surface of a transparent material. So the AIST folks developed a light ray-tracing program for analyzing the reflection and transmission of sunlight.

Operation Principle of the Infrared Managing Window Sheet. Click image for the largest view.  Image credit AIST, Japan.

Operation Principle of the Infrared Managing Window Sheet. Click image for the largest view. Image credit AIST, Japan.

That’s how AIST found a structure that blocks direct solar radiation in summer as much as possible while keeping the window transparent.  Sumitomo Chemical prototyped the infrared managing sheet by using its processing technologies.

Sumitomo Chemical will make improvements to the manufacturing method of the sheet to achieve a better light blocking effect.  The company intends to develop a better method to attach the sheet to a glass window and plans to commercialize the sheet in two or three years.  Sumitomo has already exhibited the sheet at the 2013 Automotive Engineering Exposition last month in Yokohama City, Japan.

Sumitomo and AIST are both rather circumspect by U.S. standards.  There is no press release, at least in English to be found.  But Masaru Yoshida, Nikkei Monozukuri at the Nikkei Business Publications Tech-On dug up the information where the story has been a leading story for days.

Lets hope the development continues and we get to use these.  The idea of blocking the summer heat and allow the winter heat in will make a very attractive product.


Comments

Name (required)

Email (required)

Website

Speak your mind

css.php