TRENDS IN OUTDOOR LIGHTING
Source: Craig DiLouie, under Craig's TED Magazine Articles.
Outdoor lighting has proven a key market for LED sources due to their durability, directionality, efficiency, longevity, color and optical control. While metal halide and high-pressure sodium remain predominant in the installed outdoor lighting base, LED has captured a majority of luminaire sales. Some LED luminaires emit equivalent light output as a high-pressure sodium luminaire for one-third or less of the energy.
According to the U.S. Department of Energy (DOE), LED achieved a 10 percent penetration of the installed base, which increased to 18 percent in 2015. DOE forecasted penetration to increase to 66 percent by 2020. As with other markets, in outdoor stationary, DOE expects an initial uptake in LED replacement lamps followed by their decline relative to LED luminaires. More than 9,200 LED outdoor lighting products are listed in the DOE Lighting Facts database, nearly half of which satisfy the efficacy and output requirements of the DesignLights Consortium’s Qualified Products List.
This article focuses on four major trends in area and roadway luminaires.
As the LED outdoor lighting market matures, a number of trends
are asserting themselves beyond the core trend of improving source light output
and efficacy. These include an emphasis on visual comfort, shift in color
temperature, and controllability.
Increasing efficacy. From the beginning, the lighting industry’s primary focus has been to improve source light output, which increases efficacy while reducing materials and cost. LED outdoor area products listed in Lighting Facts show a wide range in output, from less than 500 to more than 125,000 lumens, to satisfy a broad range of applications. They also show a wide range in efficacy, from 20 to 150 lumens/W, with a mean efficacy of 93-98 lumens/W. DOE forecasts that outdoor LED luminaires may reach a mean efficacy up to 105 lumens/W by 2020, while cost may decline to $25/kilolumen.
Visual comfort. Manufacturers say their customers are becoming more concerned with visual comfort, expressed as a desire to eliminate LED pixelation—individual bright LEDs being visible to users. This is particularly a concern with luminaires mounted at lower heights.
“The biggest concern with pedestrian-scale LED luminaires is that they present distracting pixelated images and poor visibility,” says Scott Teschendorf, Market Development Manager, Eaton.
Nonetheless, glare is subjective, which means eliminating pixelation does not guarantee visual comfort. The product must still be evaluated for visual comfort, which is based on its optics.
Color temperature. The industry’s focus on maximizing light output and efficacy emphasized higher (“cooler” or bluish-white) correlated color temperatures (CCTs) over warmer CCTs, due to higher CCT’s higher efficacy. In the early years of LED outdoor lighting, the predominant choice was around 5700K. Today the gap in light output related to CCT is diminishing. Looking at the Lighting Facts data for area and roadway luminaires, for every 1000K increase in CCT, efficacy increases 2.7 lumens/W, meaning a 3000K source is about 5.4 lumen/W less efficacious than a 5000K source.
The shrinking gap in output has led to demand for warmer CCTs. The Lighting Facts data shows about half of listed area luminaires have a CCT of 5000K or higher, 37 percent with 4000K, and 12 percent with 3000K or lower. In 2016, average CCT declined 150K, suggesting a shift to warmer sources.
“With respect to color temperature, 3000K and 4000K CCT demand was generally limited to more architectural applications,” says Andy Miles, Director of Product Marketing, Outdoor Lighting, Hubbell Lighting, Inc. “However, with the efficacy penalty of warmer-CCT LEDs becoming less impactful, many customers in our commercial markets previously selecting 5000K LEDs are now opting for 4000K.”
In 2016, the American Medical Association (AMA) issued community guidance cautioning against poor outdoor lighting, which AMA said can produce detrimental health and environmental effects. Specifically, AMA cautioned against glare, which can affect safety, and very cool CCT LEDs, which can suppress melatonin production. To address these issues, AMA recommends 3000K sources, luminaire design that minimizes glare and light trespass, and dimming during off-peak operating periods. As a lighting technology, LED has advantages toward accomplishing these goals, though the guidance toward 3000K sources proved controversial in the industry.
“We believe our customers need to evaluate a wide range of factors including light distribution, energy efficiency, recommended light levels and more in selecting the appropriate product,” Teschendorf says. “For customers who choose to prioritize the AMA’s guidance, Eaton has products available to meet that. Because of this, it has actually had little impact on product development aside from creating the possibility of a shift to more 3000K LEDs in our supply chain.”
Controllability. Many states have adopted commercial building energy codes requiring both automatic shutoff (photocell or time switch) and light reduction (time switch or occupancy sensor) afterhours for dusk-to-dawn lighting such as area lighting. As a result, controls are increasingly being applied to outdoor lighting systems.
In 2014, the ANSI C136 Roadway Lighting Committee, in cooperation with NEMA, developed ANSI C136.41. This document describes a standardized seven-pin receptacle and photocontrol, which supersedes the traditional NEMA twist-lock photocontrol featuring three pins used to turn the luminaire ON or OFF. The new standard builds upon the core three pins by adding four low-voltage pins, two of which are used for dimming and two that can be used for occupancy sensing, power monitoring, two-way communication with other devices, etc.
“Incorporating the ANSI C136.41 receptacle into outdoor lighting gives just about everyone significantly more flexibility with regards to integrating controls, whether it is today or in the future,” Miles says. “Fully integrated control systems offer an aesthetic advance and can lower the initial acquisition cost but also lock the contractor or end-user into one standard. The ANSI C136.41 design positions the control equipment outside the luminaire, simplifying maintenance and allowing luminaire selection and maintenance to occur independent of the control selection.”
Microprocessing technology has miniaturized to an extent that lighting controllers can be embedded in controls connected to outdoor luminaires. This enables programming of luminaire behavior and more sophisticated control, such as dimming and color tuning by time of night. Meanwhile, wireless communication facilitates remote command, diagnostics and data collection, which can be useful for management, maintenance and analysis. Protocols include ZigBee, Synapse Network Appliance Protocol (SNAP), Bluetooth, Wi-Fi, cellular, LPWAN/LoRa, proprietary and others, with ZigBee being most popular.
Miles recommends that distributors ensure that an outdoor LED product’s sales claims be substantiated with industry-standard performance data and test reports (LM79, LM80, etc.). Pay attention not just to light output but pattern—where the light is going—as well-designed luminaires can produce less light but still achieve the same light levels. He adds that distributors should invest in developing in-house lighting specialization and education. “Be sure the generalists in your business can identify opportunities then bring them to your specialists,” he says. “The lighting specialists will get into the details, help specify the correct product for the application and ensure your customers’ needs are met.”
“LEDs have been lighting the outdoors for 10 years now and have been a proven light source in thousands of projects around the globe,” Teschendorf says. “Because LEDs have the ability to dim, be controlled and perform at high levels, they are a natural fit in order to adapt to the new codes that are here. We are really only scratching the surface of what controlled lighting can bring to the outdoor space. Controls will allow many more value propositions to be addressed than just the physical light itself.”