The optimum between costs and functionality24/07/2012
NORKA managing director and qualified engineer Dr. Norbert Höbing explains which criteria must be considered in the selection of luminaires and lamps for an energy-efficient lighting system.
1. NORKA offers a wide range of light solutions for industrial applications. With our tailor-made lighting solutions, the company stands for reliability and a secure investment under particularly difficult ambient conditions. What must be observed particularly closely when selecting luminaires?
Dr. Norbert Höbing: in the interests of operating costs and environmental protection, the products used should fulfil their function in the most energy-efficient way possible. This is the case for luminaires when they supply as much light as possible with a low connected load and can then direct this glare-free where it is most needed. Also of benefit is the low level of heat emitted through the lamps and the lamp electronics, since this reduces climate-control costs which is of particular relevance to temperature-controlled logistics.
Furthermore, considerable energy-savings can be made in warehouses, production halls and cold stores where a needs-adjusted lighting control system activates presence-dependent lighting, for instance, only when a forklift truck enters a rack aisle. If nobody stops in the relevant area then the light will either be dimmed or switched off altogether.
An often underestimated cost factor is maintenance and servicing. Long-life, low maintenance full systems presume that all components have long operating lives. Professional manufacturers already select all individual components from this perspective and integrate them into the luminaires in such a way that spare parts can be easily exchanged. In order to avoid production interruptions, it is also important when selecting and installing lighting solutions to ensure that they can also be maintained during ongoing operations. Swivelled lighting systems which are not installed directly over production plants but next to them offer an interesting solution here.
2. Light Emitting Diodes – in short, LEDs – have been known for decades as small indicator lights on equipment and instrument panels. For some years now it has been possible to produce a high-power version of these LEDs. Since then LEDs have also been used as a light source for general lighting. What are the advantages of these new types of lamps based on semi-conductor technology?
Dr. Norbert Höbing: The obvious advantages of the new technology are the light output, i.e. large luminous fluxes at low wattages, and a long service life. Depending on the lighting task required, other properties are also important for the LED user, namely light that is free from UV and infra-red radiation, robustness against shocks and vibrations, the small design, high impact resistance plus easy dimming and the instant start with full luminous flux. Apart from LEDs, there is no other lighting technology available that is capable of an instant start with 100% luminous flux at low temperatures.
To exploit these advantages the correct integration of LED light sources in the luminaires is essential. This also applies to its power supply and the optical components for light distribution and light control, but also to dramatically decreasing luminous fluxes and lifespans at too high ambient temperatures. LED light sources must be integrated into the luminaires so that their continuous heat dissipation is ensured. Therefore NORKA carries out heat simulations and long-term tests. Not all providers are yet sufficiently aware of these subjects.
3. NORKA has already implemented lighting systems with LEDs in several projects. Many series production lights from the manufacturer are available with LED equipment. Which application areas are LED lighting solutions particularly well suited for? When is it absolutely recommended to install conventional lamps?
Dr. Norbert Höbing: This question can be very easily answered given the technological features of LEDs. The efficiency of the light emitting diodes, in contrast to all conventional lamps, increases with a decreasing ambient temperature. Even at low temperatures the illuminating semi-conductors deliver the full luminous flux as soon as they are switched on and they also dim effectively when it is cold. LEDs score particularly highly with their extremely long operating life and associated long maintenance intervals and lamp exchange cycles and especially where luminaires are mounted where access is difficult or when maintenance work is only possible if there is an interruption in production. LED light does not contain any UV radiation and only a very small proportion of infrared. This is important where sensitive goods or cooled goods have to be illuminated.
Whether the use of LED luminaires is sensible and makes economic sense must be analysed on a case by case basis. For continuous lighting at average ambient temperatures, specific fluorescent lamps with an operating life of up to 70,000 hours in combination with long-life ballasts, such as the Norka industrial ECGs, make particular sense - and especially because fluorescent lamps are much more cost-effective to purchase. In applications with high temperatures conventional technology has generally proven to be the better solution. For instance, the use of T8 fluorescent lamps is possible even at temperatures approaching 100°C
4. It is not only the purchase costs of the individual luminaires which are deciding factors for the commercial viability of lighting systems. Which factors must definitely be considered for the long-term cost approach?
Dr. Norbert Höbing: If one looks at the costs of a lighting solution over its entire life cycle, it quickly becomes clear that the purchase price must never be the sole factor in an investment decision. It is sensible to also look at Total Costs of Ownership (TCO), therefore at all costs for mounting, operation, maintenance and disposal at the end of its operating life. Only by performing this comprehensive evaluation can realistic cost assessments be deduced.
NORKA offers sophisticated TCO analyses for its lighting solutions. These not only include product-related considerations such as the light output ratio LOR, but also application-related, light-planning criteria.
The complexity of such TCO analyses is shown very clearly by the luminaire maintenance factor. The size of this factor plays an important role in the standards-compliant design of lighting systems. It ensures that the decrease of the luminaire luminous flux due to dirt is already considered as early as the system design phase. For this purpose the relevant standard defines precise values to be taken into account if there is an incidence of dirt in the application environment and also for the protection of the luminaires from contamination. Dustproof and waterproof protection tubes and lamp diffusers protect the optical system optimally from external influences. Such luminaires become dirty much more slowly than comparable systems without protection.
These factors are considered in lighting planning. For instance the standard for closed luminaires of high IP ratings in a production hall with normal dirt and a cleaning cycle of two years states a light maintenance factor of 0.89. Under the same conditions for open systems it is only 0.69. Given that the factor flows as a simple multiplier into the light planning process, at a high light maintenance factor significantly fewer luminaires must be installed to achieve the same average illumination level. This results in lower investment costs and maintenance expenses and the lighting system indirectly requires less energy. A decision taken using the lower unit price for an open luminaire can therefore quickly turn out to be an own goal, since the customer must not only install more luminaires to meet the prescribed standards but over the entire operating life will also accumulate significantly higher energy and maintenance costs.