Feature Lighting A range of possibilities
As well as offering improved energy efficiency and reduced maintenance costs, LED lighting opens the door to a number of opportunities for improving the quality of lighting. Managing director of Riegens Lighting, Claus Jensen, explains
ED light sources are certainly get- ting a lot of exposure recently, much of it focusing on their energy saving potential, as well as the reduced maintenance costs due to long lamp life. However, it’s important to be aware that LED lamps and luminaires optimised for use with LEDs, open up a whole range of lighting possibilities that are impractical or difficult to achieve with traditional light sources.
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Mimicking natural daylight A very good example of this is the ability to create a dynamic lighting system that changes with seasons and the time of day. This is something that has been achieved with limited effect in the past using different colour temperature fluo- rescent lamps and adjusting the propor- tion of light output from each. LED technology though, enables the creation of a ‘tunable’ dynamic white light system where colour temperature can be varied between 2,700K and 6,500K, in combination with different lux levels. This advance in lighting has great significance. It is now well accepted that the natural changes in light that occur through the day and through the year have an impact on our health and sense of wellbeing. Furthermore, sev- eral studies in recent years have con- firmed the positive effects of artificial lighting to support this circadian rhythm. These effects manifest them- selves in reduced accident risk, improved concentration and produc- tivity, better visibility and a general ‘uplift’ in how we feel.
Of course, as well as creating a dynamic and responsive lighting system, the use of LEDs reduces light- ing energy consumption, while the extended life of LEDs reduce mainte- nance cycles.
Lighting as a system
LED lighting needs to be thought of as a system, where the whole is very much greater than the sum of the parts. For example, the performance of the LED light sources - in terms of light output and longevity - is strongly influenced by the temperature of the LED chip. If the temperature isn’t con- trolled effectively, light outputs will be
Electrical Engineering OCTOBER 2013
reduced and the lamps will fail earlier. In this respect, a luminaire that has been optimised for use with LEDs will play a key role in the thermal manage- ment of the system. Typically the lumi- naire body will incorporate structures to conduct the heat away from the LEDs and dissipate it into the surrounding air. This has important implications for how we talk about the efficacy of lumi- naires. Traditionally the ‘light output ratio’, or LOR, of a luminaire is used to quantify the amount of ‘useful’ light leaving the luminaire in relation to the total amount of light produced by the light source(s) inside the luminaire. With LED luminaires the LOR is meaningless as the light output of LEDs cannot be measured freely. They need to be cooled to provide optimum perfor- mance and, as noted above, in most cases the whole luminaire acts as a heat sink to take heat away from the LED chips. Therefore, in providing a direct measure of the useful light produced by the luminaire against the amount of energy consumed, rated luminaire effi- cacy is a more meaningful figure. Controls also become part of the overall system, as LEDs are highly con- trollable and present many opportuni- ties for optimising performance through enhanced control. The dynamic lighting described earlier is a clear example of this but more prosaic control strategies, such as daylight link- ing and occupancy control, are greatly facilitated by LED lighting systems.
Below: LEDs open up a whole range of lighting possibilities that are impractical or difficult to achieve with traditional light sources
Taking control to new heights As the light output of LED lamps has improved the range of suitable appli- cations has increased dramatically. In particular, the latest generation of LED lamps - housed in the right lumi- naires - now deliver lumen outputs required for high bay lighting. This provides an opportunity to greatly improve the quality of lighting in a wide range of applications using high bay lighting. For example, the light- ing in factories is important for detail work, while good colour rendering is important for colour coded picking in warehouses.
LED light sources can be dimmed and they will come on instantly when switched on. This makes it very easy to control them in various ways. For instance, many ‘shed like’ structures have extensive rooflights
to permit entry of natural daylight. So dimming the lighting in relation to daylight is an obvious measure. In warehouses there is often con- siderable energy wastage due to light- ing being left on in aisles that aren’t used for long periods of time. Using LED lighting provides an ideal opportunity to use presence or absence control to switch off lighting in unoccupied aisles, secure in the knowledge it will come on instantly when someone enters that aisle. In summary, LEDs bring a host of new opportunities for anyone involved in lighting design. The important thing is to understand the possibilities - and then exploit them to the full.
Riegens Lighting
www.riegens.co.uk T: 01376 333 400
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