Redirecting Sunlight Into Dark Urban Alleys With Translucent Panels

---

Hundreds of millions of people throughout the world live in crowded urban areas that don’t receive much sunlight — largely due to the presence of tall light-blocking buildings. As the global population continues to climb (that’s the prediction) over the coming decades, this problem is expected to worsen considerably.

So, how to approach this problem? Researchers from Ain Shams University in Egypt think that they have an effective solution — a new, corrugated, translucent panel that can be mounted on rooftops to redirect sunlight onto the narrow streets and alleyways below.

The new panels can simply be mounted on roofs and hung over the edges at an angle, this the redirects the sunlight to the relatively dark streets below.

“We expect the device to provide illumination to perform everyday tasks, and improve the quality of light and health conditions in dark areas,” stated Amr Safwat, a professor of electronics and communications engineering at Ain Shams University in Cairo, Egypt. “These dimly lit areas specifically include narrow streets in developing countries, but the new panel could be used in any country as a greener, cheaper, and more pleasant alternative to fluorescent and other artificial light.”

There are of course already window-like devices can redirect light commercially available, but these aren’t designed for narrow streets — being more suited to tasks such as brightening a room or reducing glare. The researchers set out to address the lack of a specialized design for this purpose — a simple way to redistribute natural light without the need for a tracking device that follows the rising and setting sun.

The press release from the Optical Society provides more:

What they came up with is a panel made of polymethyl methacrylate (PMMA), the same acrylic plastic of which Plexiglas is made. The bottom of the panel is smooth while the top is covered in ridges that are based on a sine wave, the mathematical function that describes everything from light to pendulums. The researchers used computer simulations to find the size and shape of the grooves that distribute the most amount of sunlight in a wide range of sun positions all year round, whether it’s high or low in the sky. A sine-wave pattern is also easy to manufacture.

Using simulations of sunlight shining on an alleyway, the researchers found that their panels increased illumination by 200% and 400% in autumn and winter, respectively, when sunlight is most limited. They also tested a small prototype over a 0.4-meter-by-0.4-meter shaft that is 1.2-meters deep and found that it lit up the area as designed.

The researchers are now planning to construct a full-scale model (10 times bigger than previous models) in order to verify their calculations, and perform real-world testing.

Estimates are that a commercialized version of the panel will end up selling for around $70–100.

The new research was just detailed in a paper published in the journal Energy Express, a supplement of The Optical Society’s open-access journal Optics Express.