Republication of Postings from the U.S. Department of Energy (DOE) Solid-State Lighting Program by Jim Brodrick, SSL Program Manager, U.S. Department of Energy
Aurora Lighting Design, Inc., in Grayslake, IL, made the bold step of installing an OLED lighting system during office renovations in 2014, becoming the first office test site for the use of OLEDs in general lighting, as well as the first GATEWAY demonstration involving OLEDs. A new GATEWAY report recounts the experiences of this pioneering project involving an intriguing technology, and provides valuable feedback to OLED and component manufacturers as well as luminaire manufacturers.
Acuity Brands’ Trilia™ OLED lighting system, which was selected by Aurora, has a shallow profile that works well with the company’s low-ceiling office and offers comfortable ambient light, with warm color (3000K) and very good color rendering (CRI = 89). Compared to the previous installation of recessed medium-base downlights with nominal 20W PAR38/830 LED lamps, the OLED system delivers much higher-quality lighting, according to the staff. The exposed OLED panels deliver a soft, minimal-shadow light that makes faces and expressions visible and increases room brightness by reaching vertical surfaces. When the OLED surface luminance is kept below 3000 cd/m2, this is achieved with no increase in glare. The system’s appearance expresses creativity and innovation, making a statement to clients who visit the offices. What’s more, the system is dimmable, enabling Aurora to save energy, reduce output and potential visual discomfort when lower illuminances are preferred, and use daylight as the primary light source. Lighting-energy use is moderate, at 0.62 W/ft2 when the system is operated at full output as designed. Aurora’s staff enjoys working under the system, and uses it in a dimmed state most of the time.
However, the installation of the OLED system was not without its challenges and complications. The drivers were too large to fit above the gypboard ceiling, so the 11 drivers were remote-mounted in an adjacent space. This necessitated pulling large numbers of wires through a shallow joist space to multiple mounting points. At the time of manufacture, there were no dedicated OLED drivers on the market, so Acuity equipped the OLED lighting system with LED drivers, which lowered system efficacy because they couldn’t be precisely tuned to the specific electrical needs of the OLEDs. While the system dims smoothly with a 0-10V dimmer, dimming introduces flicker. Although visible to very sensitive occupants and visitors, the flicker frequency is fairly high, measured by Acuity’s Horizon Group to be 261 Hz. The staff members have noticed no personal health consequences (such as headaches) as a result of the flicker.
Aurora’s OLED installation is an important demonstration of the potential performance of OLED panels. The panel technology itself is maturing, and problems such as shorting defects are already being solved with new panel architectures. The system that was installed in September 2014 represents the state of the art of the technology at that time, with a system efficacy of around 46 lm/W. Two manufacturers have since promised 80-lm/W OLED panels for delivery in 2016 and higher efficacies soon afterward.
However, panel efficacy is only part of the story of OLED systems. One frustration of luminaire manufacturers is that there are few dedicated OLED drivers on the market, because the total demand in the architectural market is low. Instead, manufacturers have to work with LED drivers, customizing them as best they can to deliver the current and voltages needed, which are often outside the optimized efficiency range of the driver. This makes the driver a weak point in the system efficacy.
The OLED panels are thin and light, and they deliver a unique quality of light. However, the drivers are still relatively large and brick-like. Because they don’t fit gracefully into the OLED luminaires or mounting canopies, they must be mounted remotely, which creates extra work for the designer and contractor to find an accessible location hidden from normal view, where drivers can be located in compliance with the electrical code. If OLEDs are to fulfill their promise, driver elements will need to be integrated sleekly and discreetly into the luminaire or mounting elements.
The flicker from OLEDs is a function of the driver, just as it is for LEDs. Like many performance aspects, such as dimming, it can be compounded by the fact that the driver, designed for LEDs, may be operating outside of its optimal operating area. This can be corrected by an improved electronic circuit design. Acuity Brands has already been converting its OLED product line to a different brand of programmable driver that will have current ranges appropriate for the OLEDs, with improved dimming performance and dramatically higher light-modulation frequency to eliminate flicker complaints.
For full viability of OLED architectural lighting, the systems will need to deliver higher efficacy, better system components, and lower costs. OLED lighting is in its infancy compared to LED lighting, but the architectural market is taking notice of a lighting product with an entirely different look and function. If OLEDs continue to increase in efficacy, longevity, size, and flexibility, designers and engineers will have a new tool for creative and effective lighting.
For a closer look at the findings, download the full report.