This piece was originally published in the February 2018 issue of electroindustry.
James Brodrick, Solid-State Lighting Technology Manager, U.S. Department of Energy
The early days of light-emitting diode (LED) lighting were often likened to the Wild West because the prevailing mentality seemed to be “anything goes.”
The development of standards and metrics has changed that. What’s more, LED lighting presents an opportunity to improve the performance and value of lighting through enhanced controllability, new functionality, application-specific lighting performance, novel form factors, and targeted improved well-being and productivity.
New functionality within lighting systems can add value by providing optimal lighting through real-time controls, programmed sensor-driven responses, or learning algorithms. LED technology also enables precise control over the delivery of light to reduce glare and light trespass. And, unlike other lighting technologies, it offers the prospect of full color control over the light spectrum.
Although LED lighting is enabling unprecedented advances, new Wild West fronts are emerging.
Horticulture and Color Tuning
At a recent U.S. Department of Energy (DOE) Solid-State Lighting Technology R&D Workshop in Portland, Oregon, Nick Klase of Fluence, a manufacturer of LED horticultural lighting, said our understanding of the science in the area of horticultural lighting is so rudimentary that, in football terms, we’re only at our own one-yard line. Almost nothing we know about architectural lighting properties and metrics applies to this burgeoning field, which is being driven by a growing world population. Mr. Klase noted horticultural lighting’s impact on the electrical grid, with indoor horticulture alone consuming one percent of the nation’s electricity. Although most horticultural lighting today is high-pressure sodium, LEDs have the potential to save energy and provide greater controllability, which is important for increasing crop yields.
While there’s a great deal of interest in manipulating light’s spectral content to improve human health, productivity, and mood, the scientific evidence to support these benefits is still at an early stage, which leaves room for unverified claims. That’s why DOE funds research projects to fill the knowledge gap. Two recently completed GATEWAY evaluations highlight some of the challenges involved in specifying, installing, commissioning, and using color-tunable lighting systems as well as the challenges of predicting and evaluating their nonenergy benefits and their energy performance.
Photo caption: The Swedish Medical Behavioral Health Unit found that tunable LED lighting systems can provide significant energy savings. Photos courtesy of DOE
Another study, at Seattle’s Swedish Medical Behavioral Health Unit, found that tunable LED systems can provide significant energy savings compared to non-tunable alternatives, based on the dimming typically incorporated into tunable applications. It also found that achieving design goals related to circadian and other biological and behavioral effects may require higher illuminances than those recommended for visual tasks and consequently may increase energy use during the hours when high illuminances are needed. Another conclusion was that developing a detailed specification of the desired control sequences and outcomes early in the design process can help identify potential shortcomings with the specified control solution and can make the commissioning process more efficient.
The other GATEWAY evaluation involved a trial installation of a tunable-white LED lighting system in three Texas classrooms. The reduction in input power for the new system was estimated to be 58 percent relative to the incumbent fluorescent system and was attributable to the higher efficacy of the LED luminaires and a reduction in illuminances, which previously exceeded IES-recommended levels. Dimming furthered the energy savings in each classroom, but the dimming level was varied more regularly when the control locations were more easily accessed by the teachers, who felt the lighting system improved the overall learning environment.