SSL and Streetlighting Guidance

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By: Craig DiLouie

OLED lighting continues to develop as a potentially strong complementary source to its solid-state cousin, LED. The OLED source consists of a stack of organic films layered between electrodes and typically encased in plastic or glass. The source is therefore ultrathin (less than 2mm thick) yet theoretically able to light a large area. While LED is a compact directional point source, OLED is a flat diffuse area source. The DOE’s Solid-State Lighting Program recently published two reports describing the current state of the art: The first DOE report, OLED Lighting Products: Capabilities, Challenges, Potential, evaluates the current state of the technology and its potential for architectural lighting; the second is a Gateway report titled OLED Lighting in the Offices of Aurora Lighting Design.

•  OLED Lighting Products: Capabilities, Challenges, Potential. Typical OLED lighting panels are about 100mm square. OLED luminaires operate at about 21lm/W to 44lm/W, below LED system efficacy. Contributing to lower efficacy is LED drivers, which are widely available, being used in the large majority of OLED luminaires. While the OLED light source is ultrathin, the LED drivers are typically larger and therefore must be mounted remotely, adding to installation complexity. As with LED, OLED lighting is dimmable, with the preferred method being constant current reduction drivers to avoid photometric flicker. A majority of panels are available in 2700K to 3000K correlated color temperature, with good color rendering.
  

• Edge-lit LED panels compete with OLED, offering similar appearance and superior performance. Current performance and higher costs have limited applications of OLED lighting. It is most viable for indoor applications, with early applications focused on demonstration, custom, and decorative projects. Any application where a low-glare visible area light source is desirable could potentially benefit from OLED. At the 2015 OLED Summit, a panel of lighting designers identified a series of applications, including shelf lighting, marker lights, luminous bands running along walls at the ceiling, tiles similar to ceramic tiles, and products that combine LED and OLED. OLED offers the exciting potential to be manufactured as thin, flexible substrates, allowing curved, rolled, and folded products. This would open many new applications.

• OLED Lighting in the Offices of Aurora Lighting Design. The 2014 installation of Acuity Brands’s Trilia OLED lighting system provided a shallow profile compatible with the low ceiling space. It delivers soft, diffuse lighting that increases room brightness. The new lighting was well received by the occupants, who operate it in a dimmed state most of the time.

However, the drivers were too large to be incorporated in the ceiling, so they were mounted remotely in an adjacent space, requiring additional installation time. OLED lighting is almost exclusively controlled using LED drivers; this OLED solution operates at a lower system efficacy. Dimming introduced flicker, though at a very high frequency likely to affect only highly sensitive individuals.

The authors of these reports concluded, “OLED lighting is in its infancy compared with LED lighting, but the architectural lighting market is taking notice. If OLEDs continue to increase in efficacy, longevity, size, and flexibility, designers and engineers will have a new tool for creative and effective lighting.”

Read the reports at SSL.energy.gov.

The Ama Issues Guidance on Streetlighting
According to a survey conducted by the DOE, 62% of responding state and local governments and utilities reported some use of LED sources in their street and area lighting in 2014. Eight percent identified it as the most prominent technology in their systems (30% as second most).

Few luminaires were controlled by a centralized control system or an advanced control system. However, about one-fourth (23.4%) of respondents reported that they planned to install an advanced control system within five years.

An estimated 10% of U.S. streetlights have been converted to LED. As adoption accelerates, the American Medical Association (AMA) recently issued community guidance cautioning against poor outdoor lighting.

“Despite the energy-efficiency benefits, some LED lights are harmful when used as streetlighting,” said AMA Board Member Maya Babu. “The new AMA guidance encourages proper attention to optimal design and engineering features when converting to LED lighting that minimize detrimental health and environmental effects.”

The AMA specifically cautions against what it calls “high-intensity” LED street lighting, which it says can reduce visual acuity and safety through glare. It also cautions against blue-rich LED lighting, which can suppress melatonin production. Light sources with a correlated color temperature of 3000K or lower are recommended.

According to the AMA, LED streetlighting has five times greater impact on circadian sleep rhythms than traditional streetlighting (although it did not reference correlated color temperature of the LED source). The organization cited surveys finding that brighter residential nighttime lighting is associated with reduced sleep times, dissatisfaction with sleep quality, excessive sleepiness, impaired daytime functioning, and obesity. Animal and insect populations are also affected.

To address these issues, the AMA advises communities to minimize and control blue-rich LED streetlighting, use proper luminaire shielding to minimize glare and environmental effects, and implement dimming during off-peak operating periods.

James Brodrick, SSL program manager for the DOE, responded by pointing out that while there is nothing inherently dangerous about LED lighting, it should be used prudently as should any other technology. “This means that although LED lighting is an energy-efficient way to illuminate streets, it’s important to direct light only where it’s needed; to make sure the emitted spectrum supports visibility, safety, and the health of humans and other living creatures; and to limit glare for pedestrians, bicyclists, and drivers,” he said.

In fact, Brodrick noted that LED lighting offers distinct advantages toward accomplishing these goals. LED luminaires can be designed to offer unprecedented optical control, placing light only where it is needed. The spectral content can be tailored, including minimizing the emission wavelengths associated with melatonin suppression. And LEDs are relatively easy to dim, allowing lighting intensity to be controlled based on predicted traffic density.

“Some media coverage can give the impression that LEDs are the enemy when in fact they’re a critical  part of the solution, which the AMA acknowledges,” Brodrick said. “The key takeaway from the AMA’s guidance is the importance of properly matching lighting products with the given application, no matter what technology is used. More than any other technology, LEDs offer the capability to provide, for each application, the right amount of light, with the right spectrum, where you need it, when you need it.”

The Illuminating Engineering Society (IES) also responded with a statement stating that it was not consulted as part of the development of the recommendations. The IES stated: “Of primary concern to the IES is the potential for this report and its ensuing press to misinform the public with incomplete or inaccurate claims and improper interpretations. We intend to respond to this through a proper analysis.”

The IES intends to work with the AMA to ensure that any lighting recommendations it makes include some discussion with the IES. Download the AMA report at ama-assn.org.

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