The lighting of distribution centers is a rather rarely discussed aspect of warehousing. The factor of light is not directly related to intralogistics processes and is therefore often taken for granted. Nevertheless, it can be considered an important prerequisite for warehouse operations. Good lighting is particularly important in warehouses that operate in multiple shifts to ensure flexible and reliable delivery 24/7. This is because lighting makes a significant contribution to effective and energy-efficient operations.

Warehouse lighting has three main aspects that it can influence:

• The work quality aspect, which requires comprehensive, standard-compliant lighting of storage areas and transport routes in order to provide optimum support for employees and systems in their work at all times of the day and night. Standard-compliant lighting also increases well-being in the workplace and protects those responsible in the event of damage (insurance cover).
• The economic aspect, which requires highly energy-efficient operation in order to contribute to an overall positive company result. For example, switching from fluorescent tubes to LED lighting can save between 60% and 75% in electricity costs, depending on the quality of the LED luminaire, the facility, and the lighting design.
• The climate protection aspect, i.e. the obligation of companies to design their energy processes in such a way that they responsibly meet national and international climate protection requirements, which means reducing unnecessary energy consumption and thus CO₂ emissions to a minimum. Accordingly, conversions to LED and new buildings are subsidized by various support programs.

Criteria for light and lighting

The lighting of warehouses and logistics buildings is subject to the standards of DIN EN 12464-1. These set out the following criteria:

• Adequate illuminance to optimally support the various visual tasks and areas of activity.
• Uniformity of lighting, achieved through high light density and a wide beam angle of the luminaires, so that even the spaces between shelves are optimally illuminated.
• Low-beam optics, which extend from the hall ceiling to the hall floor, contribute to employee safety.
• Optimum glare control, i.e. avoidance of direct or reflected glare, as well as veil reflections.
• Suitable light color and good color rendering for better recognition of the nature of the stored goods, labels, and coding
• Greater safety through the avoidance of flicker and stroboscopic effects, especially in connection with retrofit luminaires (see below)
• Integration of daylight qualities
• Comfortable light management, i.e. flexible adjustment of illuminance to specific work and visual requirements. In combination with presence detectors (sensors), additional electricity and energy costs can be saved in areas that are not heavily frequented.
• Emergency lighting capability of the luminaires, either integrated into the central control system or for decentralized emergency lighting operation with built-in rechargeable battery.
• The long service life and maintenance-free operation of high bay luminaires are very important here. This is because trouble-free operation increases efficiency, while defective luminaires disrupt or interrupt processes and cause exceptionally high repair or replacement costs.

The benchmark for the service life of high bay luminaires and lights is 80,000–120,000 operating hours, L80/B10, at a standard ambient temperature range of -30 to +60°C.

Lighting design parameters

Comprehensive and well-founded lighting design takes essential parameters into account:

• Room dimensions and measurements including structural features, e.g., indoor or outdoor storage, required inspection openings, fire protection, struts and load-bearing cranes, light point height(s), roof construction, additional requirements for renovation in existing buildings, ceiling structure:
  • low ceilings – wide-beam (damp-proof) luminaires
  • High ceilings up to 25 m – hall spotlights
  • High-bay warehouses with light point heights of up to and over 50 m require dedicated high-bay warehouse luminaires with deep or wide-beam properties, depending on the spatial structure of the hall.

The flexible mounting type and correct positioning of the luminaires also contribute to an optimal overall solution.

• Operating conditions: Operating hours, burning time, shift operation, required illuminance and lighting control, ambient temperatures
• A professional lighting design compares the size and height of the assessment areas and specifies the following points:
  • Height of the luminaire level (the illuminance decreases with the square of the hall height!)
  • Maintenance factor
  • Total luminous flux
  • Average illuminance (Em)
  • Uniformity (U0 or g1)
  • Number and power of luminaires for standard-compliant lighting
  • Energy costs and profitability of the new hall lighting (compared to the previous system)

Recognizing the qualities of LED luminaires for warehouses and logistics

The following properties can be compared to assess the quality of LED luminaires:

• Absolute tightness of the luminaire is important to prevent dust, dirt, moisture, or other emissions from entering, as this drastically reduces the service life.
• A robust, dimensionally stable profile, e.g. made of aluminum, ensures this. Also pay attention to the quality of the luminaire cover – a cover made of high-quality plastic (PMMA), for example, is stable and is not glued but screwed together with corrosion-resistant materials.
• The luminaire suspensions should be resistant to embrittlement so that they remain firmly in place throughout their service life.
• The more durable the LED modules are, the more sophisticated the thermal management.
• Degradation of luminaires: The service life of luminaire products is indicated by so-called L and B values. The L value indicates the light output to which the luminaires may have decreased after the specified time in operating hours (e.g., L80 = 80%). The B value indicates the percentage of luminaires that may fall below this value (e.g., B10 = 10%). No specification of the B value means B50; ergo, 50% of the luminaires have a luminous flux below the L value. In practice, this means that replacement measures must be taken prematurely to ensure that lighting continues to comply with standards.

Evaluate the quality of luminaire manufacturers/suppliers

For long-term use of lighting, manufacturers (suppliers) should be asked in advance about warranties and the availability of spare parts. It is also important to ensure that the light colors remain consistent when reordering, should your hall be converted or expanded, in order to avoid an uneven, irritating light pattern.

Even if it may be a little more expensive, recycled materials, such as luminaire profiles made from recycled aluminum, not only ensure the quality and longevity of the lighting, but also protect the environment. Plastic luminaires from Far East production have a negative impact on the ecological balance in terms of transport and waste recycling.

Consequences of installing retrofit luminaires

Anyone wishing to install retrofit luminaires, i.e. LED luminaires in fluorescent tube housings, in warehouses and logistics buildings should be aware of the insurance implications. Retrofitting luminaires with retrofit/LED tubes means that technical safety is no longer guaranteed, as CE/TÜV certification and, in some cases, insurance cover will no longer apply (see also VBG; ZVEI/VDE LA-T 2014-42). According to a study by the University of Darmstadt (Department of Lighting Technology, Prof. Quoc Khanh; not freely available), the low frequency of retrofit luminaires poses a risk of stroboscopic effects; fatigue and headaches can occur, and epileptic seizures can also be triggered.

Accordingly, common subsidies for retrofitting to LED in renovations of existing buildings or new construction are generally not eligible for funding. This can make a decisive difference, as subsidy programs such as the BEG subsidy for non-residential buildings start at 20%.

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