Lighting special Street illumination
WE-Ef contains six LEDs and six lenses combined in a module (shown) so that each LED illuminates one single area using a specially developed lens. This means that turning off LEDs lowers the average light level but not the uniformity, so switching rather than dimming is viable
Philips Light Blossom solar/wind-powered amenity light > The gradual switch to white light is probably the most
“Switching every third column off is not an option. You need to be able to demonstrate decent energy management” – Dave Franks
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visible change to the streetscape. Few would mourn the passing of the sodium lamp and its orange glow, especially the monochromatic light of the low-pressure lamp, which renders colours indistinguishable – not only unpleasant, but also disliked by the police because it makes car colours, for instance, almost impossible to identify. The consensus for some time has been that white light is preferable, but technology (and its cost) took some time to catch up. ‘I was on the British Standards Committee, which allowed different lighting levels for white light seven years ago,’ says Scott. ‘People accepted it was a good idea but lamps were not available. Ceramic metal halide was around but it was expensive, had poor lumen maintenance, and the life wasn’t as good as high-pressure sodium.’ The introduction of compact fluorescent lamps
(CFLs) for exterior use and the improvement of ceramic metal halide technology, especially the introduction of the Philips CosmoPolis system, has accelerated the change. The CosmoPolis comprises a new-generation ceramic metal halide lamp and purpose-designed electronic gear. The lamp itself is 65% smaller than a Son lamp and, according to Philips, the system effi ciency is higher – between 30% and 70% – than other white light sources. ‘When CosmoPolis and CFLs for outdoor use came along, white light became a lot more viable,’ says Scott.
CIBSE Journal November 2010
The Archilede can produce the same quantity and quality of light on the road surface as a traditional 150W high-pressure sodium luminaire, but with much lower energy consumption
‘We’ve seen a dramatic rise in its use for residential roads over the past five years. The majority of new schemes would now have white light rather than sodium. But it could take another 20 years or longer to replace the old stock. You still have streets with mercury vapour and even GLS lamps.’
Central control The second radical change is the introduction of remote monitoring or central management systems (CMS). Barely two years ago this was still technology on trial. The advantages of addressing individual street lights to check their status (no more night scouting) and controlling light levels according to location and time are self-evident. Dimming combined with an effi cient light source can cut energy use by half. There were technical teething problems, but
manufacturers and local authorities have collaborated closely to identify and resolve glitches with system communication that had led to failure of lanterns to strike, for instance, or erroneous reports. Even though such systems can be retrofi tted into existing lanterns, they involve a high capital cost. While the energy and cost-saving benefi ts are clear, local authorities have to ensure they get it right. ‘To deploy a full CMS system you need a lot of
money,’ says Dave Franks, service development manager for public lighting with Westminster City Council. ‘We’ve spent two years building our business >
www.cibsejournal.com
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