In the Magazine Tech & Science

Harvesting The Sun to Light the Streets of Cairo

Computer-designed plastic panels will redirect sunlight into dark Cairo alleyways Alfredo D'Amato/Panos

Due to the preponderance of tall buildings lining narrow streets, many big-city dwellers spend their days mostly in shadows. Cairo, for example, is one of the world’s densest large cities, crisscrossed by medieval alleyways where light barely trickles in, even when the sun is directly overhead. That’s why scientists there have developed a way to harvest the sun’s rays and redirect them into Cairo’s many tight streets and alleyways to bring light to thousands who otherwise would be in the dark.

Simple reflective surfaces like glass mirrors can shoot light in only one direction. Amr Safwat and his colleagues at Ain Shams University in Cairo have developed unique translucent panels with a precise, computer-cut, corrugated surface designed to catch the sun’s rays at any angle. At any time of day, any day of the year, the panels can gather up sunlight and redirect it to a predetermined point; they don’t need to pivot with the sun or be repositioned for different times of the year.

Prototype testing showed that the cheap and easy-to-produce panels could potentially increase the amount of natural sunlight in any given alleyway by 200 percent in autumn and 400 percent in winter. With the same acrylic plastic used to make Plexiglas, the panels are cheap and easy to produce—each one-square-meter panel and frame will cost between $70 and $100, and Safwat estimates it will take four one-meter panels to keep one block’s worth of alleyway lit.

“We expect the device to provide illumination to perform everyday tasks and improve the quality of light and health conditions in dark areas,” says Safwat. “Research has shown that lack of natural lighting can cause severe physiological problems.” Ultraviolet rays that come from the sun are necessary for triggering the synthesis of vitamin D in the human body, and a health supply of the vitamin is vital to an individual’s overall health. Besides helping to stabilize mood, vitamin D is essential for calcium absorption, maintaining normal phosphorus blood levels and bone health.

Safwat’s team hopes the device will become a common sight in Cairo and elsewhere. A street without good sun exposure may seem a superficial dilemma, but natural lighting is much more than a luxury—it can be the difference between a life and a life with a brighter future.