October 2018 Lighting Journal
Street lighting
8
35m apart single-sided on the non-footpath side of the roadway. To achieve this performance required some additional work to a standard Ignsi2 luminaire. Firstly, we had to be able to deliver the lighting performance using just the warmer (slightly less efficient) 3000K chips. To do this we used the Osram Square chip with its very high lumen per watt and extremely good lumen depreciation rate, even at higher operating temperatures. A solution of 72 LEDs driven up to 700mA would provide the lumen package. The same arrangement for the 5000K would work even better. This would require a total of 144 LEDs with lens to be housed with twin drivers. To achieve this in a reasonably lightweight, compact lantern we chose to double up the LEDs per lens so as to have a twin-set arrangement. Thus, a new lens was required to accommodate the twin LED chips and provide the lighting as required. In addition to the unique configuration and colour change, dimming was also required during the night when traffic is very low, and thus energy savings could be made beyond that achieved by changing from the existing from 250watt high-pressure sodium lamps. The configuration agreed for the first installation is outlined below, including with options for dimming levels and times.
STREET SCENE
• Yearly night – 23:00-00:00 is 25% • Night – 01:00-05:00 is 50% • Early morning – 05:00-07:00 is 25%
LIGHT TRAFFIC
• Late evening – 23:00-00:00 is 40% • Night – 01:00-05:00 is 60% • Early morning – 05:00-07:00 is 40% On top of this, there are the following colour temperatures during the following hours: • Early afternoon – 14:3017:00 is 5000K • Late afternoon – 17:00-17:30 gradually shifting to 3000K • Early evening – 17:30-21:00 is 3000K • Evening – 21:00-21:30 gradually www.theilp.org.uk
shifting to 4000K • Late evening – 21:30-23:00 is 4000K • Yearly night – 23:00-23:30 gradually shifting to 5000K • Night – 23:30-05:30 is 5000K • Early morning – 05:30-06:30 gradually shifting to 4000K • Morning – 06:30-08:00 is 4000K • Late morning – 08:00-10:00 gradually shifting to 5000K When running the design simulations, it was noted that the 5000K option, slightly over-lit the road when compared to the 3000K. Thus the 5000K driver maximum output was choked back by about 5% to keep the light levels similar. The initial approach was to have the control pre-set and to run the same every night. However, as the development progressed a more flexible approach was sought and, to be able to deliver this, wireless control was deemed the best solution. The C2Smartnode was already the choice for Helsinki and thus utilised for the lantern. Although the smart node usually only has one DALI output, it needed to control two DALI drivers. The answer was to have two separate DALI addresses controlled from the single C2 output. Some off-site testing was also carried out to ensure the functionality was comprehensive and that there was easy control. The lights were installed during the summer months, together with the C2 CMS system on to the existing lighting infrastructure. The installation and testing was easy and straightforward, with the shifting colour temperatures seamlessly blending to the required outputs. Of course, as the nights in Helsinki at this time of year are still short, we do not yet have a full sense of how things will play out, although the initial reaction from residents is very good. The real test will be the first winter. But it is hoped that the lucky residents of Laajasalontie in Helsinki (the road where the lights are initially being tested) will be some of the first people in the world to benefit from this human-centric approach for their street lighting. Nigel Parry IEng FILP is principal at OrangeTek