Panels Redirect Sunlight into Shadowy Urban Areas

Corrugated, translucent panels mounted on rooftops could be used to bend sunlight into places it normally doesn't reach.

Amr Safwat, a professor of electronics and communications engineering at Ain Shams University, said the new panel could be used in any country as a greener, cheaper and more pleasant alternative to artificial light, particularly in urban side streets and alleys.

The new light-directing panel, with close-ups. Images courtesy of Optics Express.

"We expect the device to provide illumination to perform everyday tasks, and improve the quality of light and health conditions in dark areas," Safwat said.

While other commercially available window-like devices can redirect light, they are designed for shade and redirecting glare or for brightening a room, not a narrow street. Safwat and fellow researchers set out to find a simple way to redistribute natural light without the need for a tracking device that follows the sun.

Their polymethyl methacrylate (PMMA) panel features ridges based on a sine wave with a smooth underside. The researchers used computer simulations to find the size and shape of the grooves that distribute the most sunlight in a wide range of sun positions year round.

A simulation of the illuminance of an alleyway at noon in autumn (top) and winter (bottom). The new light-directing panel increases the amount of light that reaches the alleyway, as indicated by the higher amounts of red and yellow in the right-hand images (“with panel”) compared to the left-hand images (“without panel”).

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

The next step, Safwat said, will be to build a full-scale model 10 times bigger to validate their calculations and to test it in a real alleyway. The team then plans to market and commercialize the panel. He estimated that a 1 m² panel and a frame will cost $70 to $100.

This work was funded by the Science and Technology Development Fund of Egypt and is published in Optics Express (doi: 10.1364/OE.22.00A895).