Trends in LED Outdoor Luminaire Design
My contribution to the March issue of The Electrical Distributor tackled a big subject–trends in LED outdoor luminaire design. Reprinted with permission.
Offering higher efficacy, longer life, greater optical control, good quality of light and greater control flexibility, LED lighting stands poised for major penetration in the outdoor stationary lighting market. These luminaires may be generally categorized as area, flood and perimeter (wall pack) lighting.
“LED outdoor luminaires offer clear advantages granted by their amazingly small form factor, single-sided emission and the resulting high lumen density,” says Chris Bailey, LC, LEED AP BD+C, DDI, MIES, Director, Business Development and Product Innovation, Hubbell Lighting, Inc. “They drive the lowest system cost at this time for several reasons. As a source, they deliver more light per input power. They are a directional source, allowing optic designers to use them more efficiently and use less light to illuminate the same area. They are an easier source to control, allowing complex ON/dim/OFF operation without affecting lamp life or risk of false restart because of long restrike times.”
The Department of Energy (DOE) has conducted a significant amount of research allowing us to evaluate this market. According to DOE, an estimated180 million lamps operated in outdoor stationary lighting installations in 2010. LED penetration is estimated at 10 percent of total outdoor installations in 2014, including about 13 percent for area/roadway, 10 percent for parking lot, 5 percent for parking garage and 11 percent for building exterior applications. And a 2014 DOE survey of utilities and government found that 62 percent of these organizations were using LED, with 8 percent naming it the most prominent technology and 30 percent as the second-most prominent in their street and public area lighting system.
DOE is particularly bullish on LED’s prospects in outdoor lighting, naming it the fastest-growing market for the LED source and projecting 70+ percent penetration of the installed base (in lumen-hours) by 2020.
“The demand for LEDs is much higher than HID in nearly all categories and continues to increase every year,” says Tim McKinney, Product Marketing (Outdoor) North America, Philips Lighting. “In some applications, the percentage of new unit sales compared to HID can be as high as 95 percent for LED. On average for total outdoor area, we estimate the market to be around 65 percent. By 2019, this share will be more like 80 percent, according to research by Navigant.”
Major trends in outdoor luminaire design center on improving lighting quality, efficacy and flexibility with lighting controls.
As Bailey pointed out, one of the remarkable qualities of the LED source is its extremely compact size and single-sided emission. They are extremely efficient from an optical point of view, with optical transmission in excess of 90 percent. This allows very precise optical surface features and low-temperature operation allowing optics to be mounted directly around the source. As source efficacy increases, these advantages become accentuated, allowing very precise light distribution from highly compact luminaires.
“Traditional outdoor area lights tend to stress function over form and are largely inefficient at putting light only where it is needed, compared to new LED lighting options,” says Teresa Bair, Product General Manager – Outdoor and Industrial Lighting, Current, powered by GE. “LED area lights and wall packs deliver superior site uniformity and vertical light distribution compared to HID systems.”
Which can result in better lighting while potentially reducing the number of luminaires required for the project.
“LEDs continue to improve every year,” McKinney says. “This allows outdoor area luminaire designs to be more efficacious using fewer LEDs to produce the same amount of light or deliver more light if needed with less energy. This lowers our costs and the price to the consumer.”
Bailey points to TIR optics as the most common optical system likely in use today. These optics are available in a range of materials, including acrylic, polycarbonate, silicone and glass. While some reflector-based LED optical systems are in use, TIR optics have proven to be one of the most efficient means of maximizing both optical coupling (light extraction) and optical efficiency (light transmission).
“Whether the goal is to enhance productivity; reduce errors; prevent crime; increase occupant safety, satisfaction and comfort; or simply create designed aesthetics, TIR optics will likely be employed,” Bailey says.
Bair points out that the LED source produces better color quality than traditional HID sources such as high-pressure sodium. McKinney agrees, adding that manufacturers are enhancing this advantage by offering a broader range of color temperatures.
“Initially, in outdoor area lighting, delivering enough lumens to compete with HID was a challenge at a price point the market would accept,” he says. “The cooler color temperatures were much more efficacious at the time when compared to the warmer colors we have available today, and therefore the dominant choice in outdoor area lighting was around 5700K. This gap in lumen output based on color temperature is declining, and, as a result, the market has shifted significantly toward the warmer colors in almost every application. Today, the dominant color is 4000K, with demand and desire for even warmer colors on the rise.”
McKinney also cautions distributors to understand products and work with suppliers they trust. The LED luminaire market has stratified similarly to traditional lighting, with specification and white goods segments; different applications call for different products. Additionally, today’s LED luminaires are integrated devices utilizing a temperature-sensitive light source and available with sophisticated optics. Producing a high-quality product requires detailed engineering and robust testing.
Another big trend in outdoor luminaire design is integration with controls. Intelligent lighting with wireless communication is growing in popularity as a capability of LED outdoor lighting systems. Intelligent lighting enables more sophisticated control of luminaires—from ON/dim/OFF to color tuning—plus remote diagnostics and information gathering, which can benefit maintenance.
“A common yet wasteful practice employed in most outdoor lighting systems it to operate fixtures continuously throughout the night,” Bailey says. “The two major reasons for this are the perception of security through artificial light and the incompatibility with or expense of controls. Many designers have sought to achieve an owner-preferred light level requirement. The combination of ‘light all night’ at levels beyond what is necessary adds up, either as energy or maintenance costs. In recent years, state and federal legislation has begun to establish new requirements that will require outdoor lighting systems to accommodate a variety of light levels throughout the night. These levels may be in part driven by curfew, occupancy or both.”
“We’re at a turning point in lighting controls,” McKinney notes. “We are now seeing control systems evolve to take advantage of the digital nature of LED lighting. LEDs can be readily integrated with other intelligent systems like mobile and Cloud-based technologies.”
Commensurate with this trend is the potential for integrating other sensors into the luminaire, such as pollution, surveillance and other sensors and devices. This dramatically expands the information that can be collected.
“LED technology will continue to improve, lengthening lifespans and improving efficiency and light quality for customers,” Bair says. “Integration of advanced lighting controls will allow customers to control and monitor individual lights, while further intelligent sensors will allow customers to collect and analyze valuable data.”
“The more distributors understand the context of their customers’ needs for lighting, the better they can offer solutions that provide improved capabilities and cost-effectiveness,” Bailey says. “Lighting controls become an area of true value-added selling opportunity for distributors with advanced LED products.”