Although solid-state lighting has made significant headway in the lighting industry and fixture marketplace, there is still a sufficient amount of technical performance data that is unknown and untested when it comes to this new technology. An article in the August 2009 issue of IEEE Spectrum, a publication from the Institute of Electrical and Electronics Engineers, calls attention to a problem specific to LEDs known as “droop.”
Droop is a phenomenon experienced by blue (nitrate) LEDs—the LEDs that are used to produce white light. As the diode’s power level reaches an output sufficient for general lighting applications, the efficiency of the LED declines significantly. To maintain this amount of light output, you have to continue to feed the LED more and more power. In effect, this cancels out any potential energy savings this much-touted nonfilament light source might provide, and highlights the fact that LEDs perform best at low power. This puts a very different spin on the information that lighting manufacturers have been promoting as they race to announce and outdo one another with higher lumen-per-watt totals.
No one knows for sure why LEDs experience this technical anomaly, and scientists and engineers are hard at work to solve the puzzle. Some researchers attribute it to the electron structure of the diode, but there is no general consensus. One thing is for sure: now that this technical truth has been revealed it adds yet another hurdle for solid-state lighting to overcome as it tries to prove itself as a lighting technology with long-term potential.
Elizabeth Donoff is Editor-at-Large of Architectural Lighting (AL). She served as Editor-in-Chief from 2006 to 2017. She joined the editorial team in 2003 and is a leading voice in the lighting community speaking at industry events such as Lightfair and the International Association of Lighting Designers Annual Enlighten Conference, and has twice served as a judge for the Illuminating Engineering Society New York City Section’s (IESNYC) Lumen Award program. In 2009, she received the Brilliance Award from the IESNYC for dedicated service and contribution to the New York City lighting community. Over the past 11 years, under her editorial direction, Architectural Lighting has received a number of prestigious B2B journalism awards. In 2017, Architectural Lighting was a Top Ten Finalist for Magazine of the Year from the American Society of Business Publication Editors' AZBEE Awards. In 2016, Donoff received the Jesse H. Neal Award for her Editor’s Comments in the category of Best Commentary/Blog, and in 2015, AL received a Jesse H. Neal Award for Best Media Brand (Overall Editorial Excellence).Prior to her entry into design journalism, Donoff worked in New York City architectural offices including FXFowle where she was part of the project teams for the Reuters Building at Three Times Square and the New York Times Headquarters. She is a graduate of Bates College in Lewiston, Me., and she earned her Master of Architecture degree from the School of Architecture at Washington University in St. Louis.
