Excited by the triumph of their team on February the 15th, the fans of Grenoble were unaware of the lighting within their new stadium, even tough the lighting of the Des Alpes stadium has been equally triumphant, considering the big initial difficulties.
Located in the very centre of the city, this sports building has been built to be sympathetic to its surroundings with a final construction height of only 23 meters, compared to other similar stadiums at 30 meters high, “This fact alone created difficult problems with beam angle,” underlines Michel Pieroni, director of the agency Aartill, light engineering consultants responsible for the project.
In order to avoid the possibility of glare, the lighting recommendations for football grounds require an angle of the optic axis lower or equal to 70 degrees from the vertical. At a height of 23 meters, and considering the strict recommendations, apparently it was almost impossible to light the whole field in the standard way. Aartill has opted for a completely different way and he chose to place the majority of the floodlights more than one meter above the roof.
As well as considering the visual comfort for the spectators, the lighting has to take into account the specifications of the Professional Football League; minimum requirement of 1500 lux on the field in respect of live broadcast. After an initial study based on using 170 pieces of a 2000W floodlights and reviewing the budgetary restrictions, Aartill changed its design to the perfect solution using 136 pieces SBP floodlights which supplied 100 lux more than the required minimum and reduced the initial budget by approx. 20%.
The SBP floodlights were supplied with Osram HQI-TS HID lamps, as used in the stadium for the World Cup of 2002 in Korea and Japan; “They are fantastic,” says Pieroni. Metal halide short arc lamps focus the light better and provide a luminous flux of 200,000 lumens with a colour temperature of 5900°K.
Providing a warmer colour appearance (3000°K) for the step lighting, the 1500W halogen lamps, with almost instant lighting, also provide essential security lighting.
Although 1000W HID lamps would be more efficient they would not provide instant starting or the colour rendering of a halogen lamp; “This has been the best compromise between high performance and efficacy,” says Pieroni. In the internal areas Pieroni chose a combination of lamp sources, using warm 120W compact fluorescent on one side and 70W/150W CDM-T lamps on the other. This gives a warm and inviting appeal, which is quite different to the choice of lighting used in most sports arenas. In total the project took 4 working years with 2 years for planning. Now we have to wait for the team in blue to climb to League 1 to enable the fans and players to have their glory….
(extracted by “Le Moniteur” – 04/04/2008 – by Jean-Charles Guezel )