Suspect Device

Writing by Patrick Keddie

Beginning to see the light: Shining the sun’s rays into Cairo’s dark streets

A narrow street in Boulaq El-Dakrour, Cairo (photo by Patrick Keddie)

Egypt is typically associated with searing sun. Yet, for many people who live in densely packed urban areas, the light scarcely penetrates the narrow streets.

“I get about half an hour of sunlight a day coming into my building” says Magdy, a 36-year old tuk-tuk driver who lives in Boulaq El-Dakrour, an informal neighbourhood of Cairo where many of the streets are barely wider than his vehicle and construction is often illegal and haphazard, blocking the sunlight from reaching streets and windows.

Magdy says that the lack of sunlight is an unhealthy environment and, as there are few street lights, it makes the area dangerous. In mid-November he was mugged at knife-point down a narrow street in the daytime.

Egyptian researchers think they may have come up with an innovative answer to the problem: a fixed panel that reflects light into narrow streets or dark courtyards, which becomes operational as soon as the sun rises.

Amr Safwat, professor in the Faculty of Engineering at Ain Shams University, said that his team considered using a mirror or a prism but discovered that they would only reflect light correctly at some angles due to the movement of the sun.

“We had to come up with a structure that was independent of the angle of variation”, explained Safwat.

The answer: a corrugated reflector

The acryllic panels catching the sun (photo by Patrick Keddie)

The researchers came up with the idea of designing a panel using sine waves – repetitive oscillating curves. A sine wave has a varying slope, allowing refracted rays of sun to be redirected at chosen angles. A reflective panel made using a sine wave structure could theoretically remain fixed in place but harvest light all day. It was an idea that had not been developed before.

The project received funding in February 2012 from the Science and Technology Development Fund, which is affiliated to the office of the Egyptian Prime Minister.

The panels require minute calibration to ensure that the light is reflected only at the desired angles – directed towards the street and at the windows of buildings – while taking into account the way the sun’s altitude which varies by hour and season. They also have to ensure that the light is not too concentrated, especially in scorching summer months.

Over a few days in December Safwat and his team tested the full-scale prototype by mounting it on the edge of a scale version of a light shaft found in many Egyptian buildings. The model was comprised of nine corrugated acrylic panels held in a metal frame around on square metre (see photo, above right).

The model panel was mounted on the test-building in a similar way to a satellite dish. Lux metres inside the shaft measured the amount of light received.

Lux metres record sunlight reflected into a test-built light shaft by full scale model (photo by Patrick Keddie)

Success! A five-fold increase in illumination

The initial test results have been encouraging as the full scale model improved the light reaching the shaft by up to 400%. Safwat thinks that they may have to test the panel in the summer to cover the range of solar altitudes.

The researchers hope that the panels can save energy as a cost-effective alternative to indoor and street lighting, while also addressing health and safety problems including crime and depression.

Khaled Nassar, associate professor at the American University in Cairo and part of the project’s team, says that informal areas – in which around 60% of Cairenes live – are here to stay. “So you need these kinds of palliatives” argued Nassar, “the trick now is finding mechanisms to implement these solutions.”

Although Safwat thinks they could bring the retail costs down to $100 in mass production, he fears that the panels would still be too expensive for the vast majority of people living in informal areas. “Some sort of government initiative has to install these panels in these poor areas”, he says.

They will also require cleaning every few weeks to operate at full brightness, and the orientation of the panel may need to be adjusted over the year.

Because of this the researchers are expecting strongest demand to come initially from northern Europe and North America – to augment natural light in north facing properties – and from wealthier Egyptian areas.

Back in Boulaq El-Dakrour, Magdy says that the narrow streets do have their advantages; living in such close proximity to his neighbours means that his community is close-knit. He also says with a smile that people have been able to evade the police in his area by moving from block to block in the tight grid of buildings.

But he says that the dark streets are not a nice environment for his daughter to grow up in and, although he would not be able to afford it, he likes the idea of the reflective panels: “Sun is life, how can you live without it?”

The full scale model being tested (photo by Patrick Keddie)

[This article was published by the Ecologist magazine here]

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