Industry News




 

04/30/2012

LED Efficiency Droop

 
More efficient LED lighting options may be on the way for building owners and facility managers.

This is a schematic of the transparent LED packaging design (left) and a working blue LED using the design (right). Credit: Yuji Zhao, University of California Santa Barbara

As many facility managers and building owners are aware, LEDs seem to reach a point where more electricity no longer imparts the same kick and productivity levels-off.  But there may be some very interesting developments on the way that will lead toward more affordable and efficient LED options.  Researchers from California and Japan have devised a new design for green and blue LEDs that avoid much of this LED efficiency droop.

By changing the orientation of the crystal structure in semiconductor films, the team created LEDs with high efficiency and extremely low droop. Droop, which is a dramatic drop in efficiency at high currents, is one of the main problems limiting the growth of the solid-state lighting market.

Blue and green LEDs provide the essential hues that blend with other wavelengths to give us the familiar white light we expect from household bulbs. These highly prized colors, however, have been among the hardest to engineer and the "droopiest" of the LEDs.

"We believe this technology could be a big breakthrough and has the potential to change the future of lighting," says Yuji Zhao, a graduate student at the Solid State Lighting and Energy Center at the University of California Santa Barbara (UCSB) and one of the lead researchers on the team.

LED chips are made from layers of doped semiconductors sandwiched together. When a voltage is applied across the layers, electrons and holes (an absence of electrons) migrate toward an area of the LED called the active layer, where they combine, begetting a photon in the process. In most commercially available blue LEDs, the crystals that make up the semiconductor layers are grown in a flat orientation called the c-plane. This traditional orientation of the crystals, however, may create electrical fields that interfere with the reunion of the electrons and holes.

The UCSB researchers' LEDs have non-traditional, tilted crystal orientations that lessen the effect of the field, and exhibit some of the lowest reported measures of droop. Using this approach the team was also able to fabricate LED chips that are smaller than standard commercial LEDs, which could cut down on manufacturing costs.

 

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04/16/2014

The U.S. Army plans to start development of a solar array that will provide about 25% of the annual installation electricity requirement of Fort Huachuca, Arizona.

04/15/2014

The EPA's annual greenhouse gas emissions report is now available.

04/14/2014

Are you what some would call a “climate-change denier”? If so, you'll want to read this.

04/10/2014
Los Angeles has remained the top city for ENERGY STAR certified building since 2008, while Washington, D.C. continues to hold onto second place for the fifth consecutive year, according to a new list released by the EPA.
04/09/2014
Green construction has grown massively over a short period of time.
04/07/2014
Field demonstrations of newly proven energy-efficient technologies are yielding valuable results for the U.S. Navy, helping it meet energy goals.
04/03/2014
Building owners in Chicago now have more options when it comes to getting their building energy data verified.
04/01/2014
According to a new report from Eaton, such outages are up 15% in 2013 over 2012 and over half of those surveyed believe that downtime could have been prevented.
03/31/2014
The newly revised ANSI/ASHRAE Standard 105-2014, Standard Methods of Determining, Expressing, and Comparing Building Energy Performance and Greenhouse Gas Emissions, aims to provide a consistent method of measuring, expressing, and comparing the energy performance of buildings.
03/27/2014
Facility managers face an every expanding array of sustainability choices and challenges, but for the next generation of FMs, green practices could be second nature as sustainability literacy enters the K-12 school system.
03/25/2014
While the economic recession explains the decline in sales in 2008 and 2009, it is much less clear why sales have continued to fall.
03/24/2014
University of Washington (UW) scientists have built the thinnest known LED that can be used as a source of light energy in electronics.
03/21/2014
Mississippi Governor Phil Bryant signed Senate Bill 2378 into law, effectively enacting the state’s first building code.
03/19/2014
In an attempt to improve building energy performance, the DOE’s National Renewable Energy Laboratory has released a web-based tool called the Technology Performance Exchange, or TPEx.
03/18/2014
Could green building practices pose unanticipated life-safety hazards?
03/13/2014
Worried about workplace violence in your facility? Researchers have discovered that “mindfully observing” high-risk employees can avert danger and workplace violence.
03/11/2014
Through the DOE’s Building Energy Codes Program, every dollar the DOE has spent on building energy codes over the past two decades has resulted in $400 in energy cost savings.
03/07/2014
It is possible to harvest energy from Earth's thermal infrared emission into outer space, according to new research from the Harvard School of Engineering and Applied Sciences.
03/05/2014
Is your building prepared to handle an emergency?
03/04/2014
NASCAR revealed five newly installed charging stations for employee use.
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