where recommendations are made for SSL devices. It should also be noted that when replacement dimmable LED lamps are installed in existing luminaires, many of the existing incandescent dimmers may cause lamp flickering (this issue is also discussed in detail in Chapter 4). Pop-on dimming effects are very similar to those in residential applications and have been discussed above.
FINDING: SSL must have power quality standards to mitigate against high THD, low PF, and repetitive peak current issues.
FINDING: New dimmers must be able to operate LED luminaires and lamps smoothly without perceptible flicker and should be available to dim from 100 percent power to 1 percent power.
Industrial applications typically use a combination of high bay luminaires (directional downlights) or low bay luminaires (omni-directional downlights). Task lighting is also used for specific applications where higher light levels are required, such as in manufacturing facilities. Long-lasting light sources are required for reliability and safety, especially in 24-hour facilities. Controls have typically not been expected in industrial sites but are becoming more popular, especially in applications where daylight can supplement the light level, allowing energy reduction by dimming the interior lights.
Traditionally, high ceilings and harder access has lead many industrial sites to higher-wattage, standard HID luminaires. Standard HID luminaires provide higher light output than fluorescents, but do not last as long (having roughly two-thirds the life). Also, HID lamps have a slow start, requiring several minutes to achieve full light output, making them harder to control with occupancy sensing or daylight on/off switching.
SSL applications are more difficult for industrial applications because of high light level requirements. Also, heat management is difficult in high ceilings where ambient temperatures are higher. In some settings, the failure process may be an issue, because SSLs gradually lose luminous flux rather than burn out. If these issues can be solved, then SSL could provide lower maintenance costs and controllability.
Power quality issues are similar to the commercial applications.
FINDING: Industrial applications of SSL products will require higher light output for ambient lighting because of their use in high ceiling applications.
Roadway and area lighting appear to be one of the fastest growing application markets for SSL. The requirements in such applications for lower light levels (compared to interior applications); larger luminaires with non-confined mounting, mostly open to air, which enhances heat dissipation; performance at cold temperatures; and long life have made SSLs attractive to this rapidly growing market. Traditional outdoor luminaires have used HID lamps, mostly high-pressure sodium (HPS), where the lamp is located inside the luminaire reflector. This configuration has the advantage that the arc tube brightness is typically not viewed by motorists or pedestrians. HPS luminaires have a narrow spectral distribution, which provides poorer color rendering properties than white light sources such as metal halide, induction, and SSL. HID life is mid-range, requiring lamp replacement approximately every 2 to 3 years.
SSL luminaires are uni-directional, unlike HID luminaires, which are more omni-directional. The advantage of using omni-directional HID luminaires is they offer glare control and a soft gradient edge. The disadvantage is that the light from an HID luminaire is harder to control, providing higher lighting levels directly below the luminaire and requiring a large reflector system to control light spillage. The uni-directional properties of SSL mean it can direct light exactly where it is required without unwanted higher light levels below the luminaire while having more light in-between luminaires, which improves overall uniformity. But glare can be greater with the SSL luminaires if the light sources are not shielded with a lens or redirected and diffused by a reflector.
The American Medical Association has issued a policy that states, “Many older citizens are significantly affected by glare as the eye ages, leading to unsafe driving conditions; and glare light is also light trespass and is intrusive and unwanted in households and dwellings; and light trespass has been implicated in disruption of the human and animal circadian rhythm, and strongly suspected as an etiology of suppressed melatonin production, depressed immune systems, and increase in cancer rates such as breast cancers” (Motta, 2009).
FINDING: Discomfort or disability glare can be an issue with directional LED luminaires. Luminaires must be designed so as not to increase glare potential compared to their HID counterparts.
Heat still needs to be managed, especially if the luminaires are left on during the day because of a malfunctioning photocell. However, the superior performance of SSLs at cooler temperatures is an advantage for some applications, such as roadway lighting and signals.
Currently, white LED modules always include a blue LED, which raises environmental concerns similar to those