Smart idea made the design work

Thursday 25 Feb 16


Peter Behrensdorff Poulsen
Senior Scientific Officer
DTU Fotonik
+45 46 77 45 72

The Norwegian firm of architects Snøhetta came up with the design for a smart solar-cell light for a new global culture centre in Saudi Arabia—but it took a DTU researcher to make it work in practice.

If you want to set up outoor lighting in Saudi Arabia, it is clearly a good idea to use the sun as the source of energy. This occurred to the Norwegian firm of architects Snøhetta as well when they were commissioned to design the King Abdulaziz Center for World Culture, and they decided on several measures including fitting the pathways around the buildings with some newly designed solar-power lights—their ‘Dunhammer’ model. The lights themselves consist of eight slightly flexible steel rods with an illuminating head positioned on a panel of solar cells

What the designers failed to notice, however, was that the rods themselves would constantly cast shadows over the solar cells, thus disrupting the charging process. This problem was passed on to the light suppliers. The order was placed with the Danish company Out-sider, that delivered a convincing solution, backed by useful help from partners including DTU Fotonik.

“We came up with the idea of a shadow-tolerant panel,” relates Peter Behrensdorff Poulsen. “The fact is that if only a part of a solar cell is obscured by shadow, the other part will still work; but if one cell out of many in a panel is completely in the shade, all the others will stop working. The solution was therefore to put all the cells partly in the shade, an effect we could achieve by turning the lights to face south. This meant that for most of the day, the shadows only fell partially on the cells.”

The Dunhammer light was tested at DTU Fotonik’s small living lab on Risø Campus. The roof of Building 13 is fitted with a robot that turns continuously to follow the path of the sun, accurately measuring the intensity of the light. The robot itself is equipped with a shadow ball that constantly casts a shadow precisely on the sun disc; as a result, the robot can measure both direct and diffuse sunlight.

“Of course, there is much more direct sunlight in Saudi Arabia, but I can easily calculate the correct conditions once I know precisely how much sun my product is exposed to here,” explains Peter.

The measurements and the idea of turning the light to face in the right direction helped the little Danish company to land a big order. And the Dunhammer lights will be in position when the magnificent culture centre in the middle of the desert opens its doors in 2016.