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FEATURE LIGHT POLLUTION Report written by Jean-Charles Bogaert. Schréder Group Product Range Manager Light, a new source of pollution? After water and air pollution, should we now fear atmospheric pollution from light? A recurring theme in the debate on the future quality of our environment On a beautiful summer’s night, haven’t you often lamented the abundance of lighting preventing you from contemplating the Milky Way? An anarchic proliferation of advertising signs, a waste of energy and all sorts of pollution generated by badly designed public lighting... It’s a fact: badly used or excessive lighting can be a nuisance. Astronomers were the first to attract our attention to the problem, but the general public is also starting to make itself heard. In North America and Europe, committees are forming to demand that this problem be taken seriously. Astronomers are of course at the forefront of these demands, and in certain countries the authorities have passed laws regulating the use of lighting close to their observatories. The Czech Republic, Australia, the United States, Chile and Italy are also developing a legal arsenal against “light pollution”. And the United Kingdom could soon follow suit. However, the greatest caution is required if we are to avoid overly simplified laws that will only end up banning the most high performance equipment in terms of energy consumption. Light pollution or unwanted light? The word pollution refers to “damage to an area resulting from bad management of the environment or the introduction into this environment of pollutants (chemical, biological, urban or domestic waste)”. Is this a suitable definition for defining the problem 4 I SCHREDER GROUP NEWSLETTER in hand? It is difficult to consider light in itself as a “pollutant”; it is rather an excess and bad use of it that makes it harmful. We would therefore prefer to use the term “unwanted light” to define a light that “attracts attention, is a source of bother and one we cannot escape even if we want to”. But is light always really the guilty party? Quite often, residents’ complaints focus on lighting for the sole reason that it is, by nature, very visible. In reality, the pollution attributed to it may have other causes, such as noise coming from a road, a car park or a sports ground. This problem should thus be approached in an overall manner, taking into account all its components, and in particular the surrounding area. It is clear that the problem cannot be resolved in the same way if the lighting installation in question is located right in the middle of a town centre, on the outskirts of a town or in a rural area. There is a hierarchy to be respected between these various sites. In certain sensitive areas, such as an airport for instance, lighting is major safety factor. Animals and plants as well... Unwanted light can be subdivided into several types of pollution for which it is necessary to find specific solutions. For instance, the night sky can be polluted by what is called a halo of light. This is caused by light emitted upwards, which illuminates the sky by reflecting on the particles suspended in the air (dust, water particles, etc.). A halo of light indicates the combination of two types of pollution: light emitted directly by the luminaire towards the sky - light shining directly upward - and light reflected by the surface to be lit - light reflecting upwards. The halo of light diminishes the contrast between the stars and the dark background of the sky, thus making it difficult, or even impossible, to make astronomical observations. In other words, it is not greatly appreciated by astronomers. Certain studies even aim to show that it could influence the natural cycle of animals or plants. Gefahr für die Augen ! Another type of pollution is dazzling light caused by too great a contrast between the light source and the surroundings. This generally happens when the light shines directly and too intensely into the eyes. By shining directly into the eyes, the light limits the eyes’ ability to adapt to the dark, thereby making dark areas dangerous. Finally, the last type of pollution is intrusive light caused by an excess of light diffused by certain lighting installations towards areas where lighting is not desirable. It manifests itself in different ways, such as for instance the intrusion of exterior light directed towards windows of houses, disturbing the sleep or activities of the occupants. The solution: efficient optics What are the factors that cause a halo of light and how can they be prevented? To find out, Jean-François Laporte and Marc Gillet of Schréder Group GIE conducted a study on photometric performance. Their study, based on 175 photometric readings, combined a variety of parameters: type and power of the light sources, light distribution of the luminaires, shape of the luminaire protectors, configuration of the road, and the road surface. Their method: an analysis of the upward luminous flux emitted
Unwanted light is characterised by several sources of pollution: dazzling light, invasive light and a halo of light, which indicates the combination of two phenomena: light emitted directed by the luminaire towards the sky - light shining directly upwards - and light reflected by the surface to be lit - light reflecting upwards. Invasive light is an excess of light directed towards areas where it is not desirable. directly by the luminaire and indirectly by the reflection on the lit up roads and their surrounding area. 86,000 calculations to avoid systematic use In total, they made more than 86,000 photometric calculations. They were in particular able to demonstrate the variations in the upward luminous flux depending on the road surface and its surrounding area. To reduce the dispersion of the luminous flux towards the sky, they recommended optimising the photometric performance and the location of the luminaires. They emphasised that the luminaires equipped with a flat protector are not systematically the most suitable as regards light pollution. Those equipped with a slightly curved protector are better in some cases. Consequently, no permanent obligation to use flat protectors! The secrets of a good luminaire In fact, we always come back to the number one question: optimising the optics. It is only by endeavouring to do so that we will be able to successfully prevent light pollution. The research carried out by Schréder has demonstrated the following: a good luminaire is one that manages to optimally use the luminous flux emitted by the lamp in order to precisely focus on the area to be lit. Luminaires designed for “precise lighting” should therefore be used. Precise lighting, against unwanted light and for sustainable development However, these “clean” luminaires not only make it possible to prevent unwanted light, they also allow for a reduction in the number of luminaires and the power of the lamps. The result: significant energy savings, which remains a major concern for sustainable development issues. Keyword: efficiency Light shining directly upwards Useful light Potentially dazzling light Surface to be lit Efficiency is the keyword to come out of this study. It is also the objective that Schréder has set itself within the framework of its Research & Development activities, and it is an objective we will undoubtedly achieve thanks to our photometric developments and our research department. It is these departments and this know-how that make a difference with regard to photometric FEATURE LIGHT POLLUTION Light reflecting upwards Invasive light Seen from the sky, the phenomena likely to cause unwanted light are clearly concentrated in geographical areas with the highest level of economic and industrial development. efficiency. More than ever before, they are responsible for Schréder’s position as THE reference in lighting. Schréder N°31 • 2005 I 5
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Page 9 and 10: Solutions for lighting large areas
Page 11 and 12: Atos A luminaire made from syntheti
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Page 15 and 16: Intel 2005 After Frankfurt, Madrid

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