Thomas Edison first installed his incandescent light bulb in a New York City factory in 1881. His filament technology is still used today for industrial applications in the form of incandescent halogen lamps, but there are now other options in the world of industrial lighting. The most important development is the development of light emitting diode (LED) technology.
A form of solid-state lighting, LED luminaires exceed the performance of other technologies in light output, colour quality, efficiency and lifetime. LED design is also varied and flexible, enabling many different applications, form factors, colour temperatures, and light distributions. They are easily integrated with controls to allow for dimming and colour shifting. This increases the comfort and productivity of the people working in a space.
With so many economical and attractive lighting solutions available, choosing among technologies can be difficult. Industrial users must consider four factors in order to make the best lighting decision: the metrics, the costs, the environment, and the people.
Understanding the metrics
When upgrading lighting solutions, industrial users should evaluate their performance according to various metrics in order to make an informed decision. LED, fluorescent, and high-intensity discharge (HID) technologies can all be evaluated using the following metrics: lumens, wattage, efficacy, lux, zonal lumen distribution, correlated colour temperature (CCT), colour rendering index (CRI), rated lifetime, total harmonic distortion (THD), and power factor.
They should first focus on selecting the proper illumination level. In the past, lighting technology was compared solely on the basis of wattage, but new technologies can provide the same amount of light while drawing significantly less power than older technologies.
Understanding the costs
Saving money is an important consideration. Lighting does not account for a large share of operating costs, but every saving can help the bottom line. Upgrading lighting can be an effective way to reduce facility and machine costs while improving the productivity, safety and design of a space.
The initial cost of a luminaire is only part of its lifecycle cost. Maintenance and lamp replacement costs depend on the lifetime of the equipment, and the energy costs depend on the equipment’s efficiency. More efficient technologies can produce significant savings, even if they are initially more expensive. LEDs often have higher initial costs for a given application than other technologies, especially the lamps, but they are the most efficient option available and have the longest lifetime. According to the Haitz Law, the cost of LED chips falls by a factor of 10 every decade, while their light output increases by a factor of 20.
Initial costs
The initial equipment costs for a lighting solution include the housing, electrical equipment, and light engine. The initial cost of the housing depends on the environment. Lighting that can withstand extreme conditions may be more expensive, but the risk of damage or injury to people in the space is reduced.
Lighting upgrades can be classified as retrofits or redesigns. Retrofits involve replacing the existing luminaires with more efficient technologies, while making use of the existing housing, lighting pattern and electrical equipment. Redesigns require new fixtures, modification of the existing lighting pattern, and partial or complete rewiring of the electrical system. Both retrofits and redesigns involve upgrading to more efficient technologies, increasing or decreasing the total amount of illumination, or adding lighting controls. A redesign of the lighting system should be considered if the existing lighting solution is in poor condition, the light distribution is uneven, or it does not suit the uses of the space.
Operating costs
Small improvements in efficacy can result in significant savings in operating costs over the lifetime of a lighting solution. This can be done by reducing the total level of illumination by downsizing area lighting, using focused task lighting with lower power, and installing lighting controls that dim or turn off lights when they are not needed. Efficacy ratings vary significantly, from less than 15 lm/W for standard 60 W incandescent lamps to 150 lm/W for the latest LED luminaires. Those with higher lumen outputs generally have higher efficacy ratings, and LED luminaires often have better efficacy than other technologies. Reducing the lighting system’s power can also save on demand charges.
Maintenance costs
Industrial users should understand the maintenance costs associated with a lighting solution. Routinely replacing lamps and cleaning surfaces can reduce the total amount of labour needed for maintenance. The performance of any lighting solution will deteriorate over time through the complete failure of lamps, ballasts or drivers; gradual lumen depreciation and colour shift; or the accumulation of dust and dirt on lenses and reflector surfaces. To plan effectively, the deterioration rate can be determined by the system’s operating profile, the system’s technical characteristics, and the conditions in the operating environment.
LED chips degrade slowly over time, producing less light and shifting their colour characteristics. The metric used to define the lifetime of LEDs is L70 lumen maintenance, which is the number of hours the LED package will operate before deteriorating to 70% of its initial lumen output. The projected L70 value for LEDs can exceed 50 000 hours. Non-LED technologies have electrical components or filaments that fail completely at some point. The rated lifetime for these products is defined as the number of hours of operation at which 50% of the units in a sample fail.
Understanding the environment
Industrial users should also assess the characteristics of the space and the work taking place there to determine how lighting solutions should be designed. Industrial and manufacturing facilities involve a wide variety of tasks, machines and purposes, but the following features are typical:
• High ceilings and large open spaces hosting detailed or risky work requiring special lighting solutions.
• Harsh environmental conditions such as extreme temperatures, dust or moisture.
• Moving equipment and heavy machinery that can damage housings and power supplies.
• Sensitive equipment that can be damaged by electrical noise from poor quality lighting, or equipment that creates electrical noise that can damage a lighting system.
• Stringent hygienic or worker safety standards.
Industrial lighting applications
Industrial lighting can be categorised as area lighting or task lighting. Area lighting includes high-bay and low-bay applications, such as warehouses and other wide open spaces that require powerful luminaires to achieve adequate illumination over a large area. Task lighting can be used to augment the area lighting in a space by focusing illumination where the work occurs. This is easier to maintain and replace than high-bay lighting. Industrial users should consider using task lighting for worker assembly cells, robotic assembly cells, electrical panels and enclosures, and mobile applications.
Performance standards for industrial lighting
Determining the appropriate level of light for a given application can be challenging. Too little light can be dangerous, while too much light can create unpleasant glare and add unnecessary costs. There is no general recommendation for light output. The Illuminating Engineering Society (IES) publishes appropriate light levels and distributions for more than 100 industrial and manufacturing tasks in its exhaustive Lighting Handbook. Lighting designers often begin an initial assessment by taking an inventory of the spaces in a facility, including the occupants and their functions.
There are standards for the energy performance of commercial lighting systems. The ANSI/ASHRAE/IES Standard 90.1 and the International Energy Conservation Code (IECC) require the use of lighting controls such as timers, occupancy sensors, photosensors, on/off switches or dimmers, and set a limit on lighting power density (LPD).
Considerations for extreme conditions
Lighting products can be designed to withstand hazardous conditions inside industrial facilities. The National Electrical Code (NEC) classifies three types of hazardous locations. Class I applies to flammable gases or vapours, Class II applies to combustible dust, and Class III applies to easily ignitable fibres or flyings.
Electrical equipment needs to meet safety standards. Luminaires can be rated based on their IP designation. Lights rated IP67 and above are dust and water resistant, making them ideal for machine lighting and machine tool environments. Enclosures rated IP67 are able to withstand temporary immersion in water. Lights rated IP68g are resistant to oil and water penetration. The American National Standards Institute (ANSI) includes ratings up to IP68; the German Institute for Standardisation includes IP69K. Enclosures rated IP69K are able to withstand the pressurised wash-down environments necessary for sanitation procedures employed by food, beverage and pharmaceutical manufacturers.
Luminaires in industrial environments may also need to withstand vibration or impact from heavy equipment. Incandescent and fluorescent lights can shatter on impact. Constant vibration can also reduce the lifetime of lights with fine filaments. LED luminaires do not have glass enclosures or filaments, and are extremely resistant to vibration and impact.
Industrial facilities may also be subject to extreme ambient temperatures. High ambient temperatures reduce the efficacy and lifetime of LEDs. They perform better in cold conditions, and are ideal for refrigerated warehouses with temperatures down to -40°C. LED manufacturers are now designing for higher temperatures using materials that dissipate heat, and sensors that dim lights as heat increases.
Equipment and power quality
Poor power quality can reduce the capacity of an electrical distribution system, waste energy, and harm the system and its devices. Heat generation in equipment is generally an indicator of power quality deficiencies. The utility’s feed into a facility also has direct effects on the durability and life of equipment. Lighting systems and equipment can affect the electrical system’s voltage and current by distorting the voltage waveform or shifting the phase relationship between voltage and current in multi-phase electrical systems.
For lighting equipment, the two electric performance metrics are power factor and THD. The power factor of an AC electrical power system is the ratio of the real power flowing to the load to the apparent power in the circuit. It is a dimensionless number between 0 and 1. A load with a low power factor draws more current than a load with a high power factor, for the same amount of useful power. Utilities usually charge higher rates to customers having low power factors, and prefer new luminaires to have a maximum THD of 20%.
A power factor below 0,9 is considered low. It can be assessed on each meter in a building or facility, so it is important to know what equipment is powered on each circuit. The lighting designer must understand whether existing equipment uses ballasts or transformers. Correcting and modifying the power factor is fairly straightforward with the installation of capacitors, and it should be re-evaluated when a lighting system is upgraded.
Understanding the people
Lighting upgrades can save money through efficiency improvements, but higher quality lighting can produce even more substantial benefits by increasing the productivity of the people working in the space. It is important to select lighting options that reduce eye strain, boost mood, and protect safety.
Effect of lighting on mood and productivity
The type of light in an environment can influence alertness and mood. The daily cycle of light and darkness affects a body’s circadian rhythm, which governs factors such as blood pressure, hormone production and sleep. The colour of the light can also have an effect.
The occupants of industrial spaces are often concerned whether the brightness, colour and quality of the light help them do their jobs. One study conducted by Cornell University found that under poorly lit conditions 24% of workers lost an average of 15 minutes a day of productive work time, amounting to a full week each year.
Visual acuity suffers when the light level is too low, but too much light can lead to discomfort from glare. Both scenarios can result in eye strain and loss of productivity. Colour and contrast recognition are important for detailed-oriented tasks, and light with a poor colour rendering index (CRI) rating can increase the risk of errors.
Design recommendations
The challenge for industrial users is to provide enough light to illuminate the large, open spaces of industrial facilities, while avoiding glare. Solutions include selecting luminaires with diffused lenses and shielding so there is no direct view of the light source. It is also important to have appropriate levels of reflectance on the ceiling, walls and floors. Using dedicated task lighting can reduce glare, while ensuring that tasks have adequate illumination. Consistent light levels throughout the space can protect the eyes from needing to constantly adjust. This is especially important for spaces with vertical surfaces that need to be illuminated, such as warehouses. Dark vertical surfaces can create the impression that the entire space is under-lit. Luminaires are generally rated to specific spacing and mounting criteria that dictate how they should be installed, based on spatial dimensions including luminaire height.
Some areas of a facility can have multiple functions, and task lighting can be employed for more visually challenging tasks. Tasks should be ranked by importance, prevalence, or frequency, to identify those with the highest recommended illuminance.
People can have a variety of colour preferences within the white light spectrum. LEDs have the widest range of CCT and CRI performance levels of all lighting technologies. It is possible to produce LEDs with a CCT ranging from 1000K to 9000K, easily covering the preferred range for most lighting applications. The CRI range for LEDs has a low of 20, which is comparable to sodium lamps, and a high of 95,35. Most quality LEDs for indoor use have a CRI of 80, which is comparable to metal halide and fluorescent technologies, and is considered satisfactory for most tasks. The flexibility of LED design means that there is a wide variety of products on the market to meet any design challenge.
Conclusion
Industrial users must balance many different considerations when selecting a lighting solution. When lighting an industrial workspace, the application and the space’s physical conditions must be considered. Lighting upgrades must also make economic sense. Industrial users should focus on the full lifecycle costs of a lighting solution, recognising that those with high initial costs may actually be the least expensive after taking efficiency and lifespan into account. Industrial customers must also meet their needs for ingress protection, power quality, occupational safety and sanitation. While balancing all these considerations can make the selection process complicated, the right lighting system can ensure that your facility is appropriately lit and safe for everyone who works there.
The full article is available at www.instrumentation.co.za/ex/turck.pdf
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