Lighting : Lighting April 2014 - Vol 34 Issue 2
30 LIGHTING MAGAZINE | April/May 2014 April/May 2014 | LIGHTING MAGAZINE 31 30 LIGHTING MAGAZINE | April/May 2014 LEDs are becoming an important tool in the contemporary lighting design toolkit as the industry matures. But with these developments come challenges for both lighting designers and software developers. “Colour is one of the more vexing issues for both lighting designers and software developers like me,” Ashdown says. “For example, the SSL industry relies heavily on the CIE Colour Rendering Index (CRI) for evaluating SSL lamp modules and luminaires, but it is difficult to demonstrate the differences in colour rendering using today’s computer display technology. Most lighting simulation software assumes that ‘white’ light sources have a colour temperature of 6500 Kelvin, which is the colour of daylight lamps. “The problem is that the incandescent lamps and ‘warm white’ LED modules that we use in our homes have colour temperatures of 2800 to 3200 Kelvin. This is not a problem for most commercial lighting design software, which enables the user to specify the lamp colour, but these specifications produce images that do not reflect how we perceive the room in real life.” “The requisite software technology is available and has been implemented – for example, in AGi32. What is also required, however, is for lighting designers to recognise that these tools exist, and to make use of them in their design work and in consulting with clients.” Such issues are not just specific to North America – here in Australia, the same challenges abound. “With regard to LED luminaires, the lighting manufacturers and the lighting design software and standards are all currently playing catch-up with the technology,” Flood says. “With regard to LED luminaires, the lighting manufacturers and the lighting design software and standards are all currently playing catch-up with the technology.” April/May 2014 | LIGHTING MAGAZINE 31 Bloom Unit’s interactive false colour illuminance and luminance output. Note the captured values in the mirror reflections, off the wall painting and as the light reflects and refracts at the glass surface of both coffee tables. Images courtesy of migenius. “LEDs also introduce further complexity due to the new features they have. For example, some are able to generate constant lumen output over life, and this means the lighting designer needs to reconsider the maintenance factors they use. This can lead to conflict with out-of-date standards. We also now have variable colour temperature LED luminaires, which have lumen outputs that change with colour temperature.” Using the software to gather accurate photometry information can also be problematic; Flood says that confusion abounds in the industry about which standards to follow, and whether to use absolute or relative photometry to achieve the best results. Daylighting is another area where software packages require urgent updating. Natural light is becoming an increasingly popular tool in contemporary lighting design, not least because of its capacity for energy savings and aesthetic appeal. But according to Ashdown, lighting simulation software remains ineffective when it comes to predicting energy savings in the context of daylight harvesting. “Current lighting simulation software is based on calculating static lighting where the lamps are always operated at full power,” he says. “What is needed is software that can: a) dim different lighting channels in accordance with a user-defined lighting script; b) calculate the energy consumption and savings over a period of time; and c) display the lighting control system operating in real time for presentation to the client.” He says that while programs like ReluxVivaldi are partially successful in addressing the issue, view-independent, building-wide calculation capabilities would provide a much more effective solution than the view-dependent, ray-traced images that the program offers. “The problem with daylighting is that LEED (Leadership in Energy & Environmental Design) has specified a metric for daylighting credits called spatial Daylight Autonomy (sDA) that was developed by the IES Daylighting Committee.
February 2014 Lighting (v2-HR)
Lighting June 2014 - Vol 34 Issue 3