Kirigami like solar cell tracks the Sun // EIT Digital

# Kirigami like solar cell tracks the Sun

Thursday, September 24 2015

By borrowing from kirigami, the ancient Japanese art of paper cutting, researchers at the University of Michigan have developed solar cells that can track the sun. A flat plastic sheet backing the solar cells splits into wavy, connected ribbons when stretched. The tilt of the cells depends on the stretching, a simple mechanism for tracking the sun across the sky. Credit: Aaron Lamoureux

Researchers at the University of Michigan teamed up with a paper artist, Matthew Shlian, a lecturer at the U-M School of Art and Design, to learn the Kirigami, the Japanese art of cutting paper, a close relative of Origami (the art of folding paper).

The problem they wanted to solve was to find a way to increase the amount of Sun light hitting the surface of a photovoltaic panel.  If the Sun light hits the surface at 90° you get the maximum out of it. As the Sun moves form the vertical the conversion rate drops. By keeping the surface at 90° the effectiveness can be improved of 40%. And this is the improvement that can be had using a motorised panel, with the motor moving keeping the panel orientation at 90°, as much as possible, through the day.

There are already a few solutions to this problem that are not using a motorised panel, some of them I reported on this blog (like the one using micro-lenses to refract the incoming sun-rays). The use of a motor complicates the installation, it is more expensive and increase the weight sometimes making it impossible to fit on a wooden roof.

The approach taken by the researchers at the Michigan University was to create ribbons of photovoltaic material by first laying the photovoltaic part on a plastic substrata and then cutting with the laser the all following the practice of Kirigami.

The result is a layer of photovoltaic material that when subjected to a tension creates waves onto which the sun-rays hit. By applying the appropriate tension it is possible to make the ribbons curl and assume the desired inclination to have their surface perpendicular to the incoming rays, with an approximation of 1°.

This approach is simpler than others and cheaper. We'll see if it can win the market!

Notice that Kirigami is also explored by researchers in other universities to improve characteristics of materials. You may want to take a look at this article....

Roberto Saracco

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