With the current focus on sustainability and energy use high on today’s agenda, it seems timely to holistically consider the issues affecting the carbon footprint of street lighting. Bearing in mind the growing use of LEDs for public lighting, is the luminaire or the column now the major consideration? Is manufacturing, delivery or the operation of the light the key to the equation?
Life Cycle Analysis
As a public lighting installation consists not only of the luminaires but also the columns and brackets, to conduct a true life cycle analysis of all these items we must analyse every aspect from their creation to disposal. This takes into account raw material extraction, manufacturing processes, delivery, energy consumption during use and then the disposal of the item. Various quantifiable standards to this approach exist, including ISO 14040 and ISO 14067.
In late 2010, I was involved inresearch with our partner Aubrilam concerning the environmental impact of timber street lighting columns compared to steel versions.
The study into the lighting column proved that when manufactured from engineered timber, the process produced between 2.5 and 2.8 times less carbon dioxide than equivalent steel or aluminium columns.
These figures are extremely compelling and suggest there are real gains to be made through a simple change in material specification.
What about the light itself?
A year later at the same event, an interesting paper on Low Carbon Lighting was presented by Bryan Shortreed .
When analysed over a full life cycle, the manufacturing of the column and luminaire makes up only 12% of the carbon footprint. Therefore over 87% of the carbon dioxide produced is due to the electrical energy consumed producing light. It would seem that energy savings in lighting design and luminaire choice will therefore have the most impact on the carbon footprint.
Prudent consideration of the light source, how the lighting scheme is designed and lastly how it is switched (and possibly dimmed) will have the most impact on a carbon footprint. When calculating this, even modest energy savings, when multiplied by the number of luminaires installed and then by the number of years in service, quickly accumulate.
An intelligent choice of light source such as the latest generation of discharge lamps with efficient control gear, or LEDs with efficient power supplies, will have an enormous influence on energy consumed and therefore the carbon footprint of your lighting scheme.
Which source to choose?
Before you reach for the chequebook and plump for a datasheet-based purchase decision, it is also worth looking at the inherent differences in sources and measurements discussed here.
LEDs can offer distinct advantages in some cases since lenses can be specifically designed to achieve the desired lighting uniformities without over lighting. This, in turn, can give energy savings. If these LEDs are used in well designed luminaires with efficient heat sinking, the real benefits of their efficiency can be truly realised alongside their longevity.
The best thing to do is talk to us to discuss your specific project and allow us to assist with the wide range of both qualitative and quantitative decisions to be made.