The killer combination of ultra high efficiency with warm and fuzzy aesthetics is a bit closer to reality, as researchers at the University of Georgia are on the trail of a new LED (light emitting diode) light bulb that casts a soft white light instead of the characteristic cool blue. If it can be produced commercially, the new light could quickly find a home, well, in homes for one thing, especially in the millions of homes whose occupants have balked at switching over to high-efficiency compact fluorescent light bulbs.
According to the University of Georgia team, their new LED boasts a color temperature of less than 4,000 kelvins and a color index of 85. Thankfully, the team has provided us with a breakdown of what that means in terms of naturalness.
The kelvin is a unit of measurement of thermodynamics. The base or null point of the Kelvin scale is absolute zero, at which point all thermodynamic activity ceases (the Fahrenheit equivalent of absolute zero in kelvin units is -460 degrees).
Ideally, a nice warm light of about 4,000 kelvins or less is suitable for indoor use. Anything above 5,000 kelvins gives you the bluish tint of the typical LED light.
The other part of the quality index is a scale for judging color rendition, with 80 being close to natural. The farther under 80 you drift, the more unnatural the color appears.
How to Make Your LED Mimic Nature
The research team tackled one of the key obstacles to natural-looking LED lights, which is cost. The current generation of “warm” LEDs is typically achieved by coating a blue LED chip directly with different kinds of phosphors (light emitting materials). The phosphor coating method, however, is expensive and difficult to achieve with consistency.
The Georgia breakthrough consists of a yellowy, luminescent compound made by combining miniscule bits of europium oxide (a rare earth also used in fluorescent lamps, plasma TVs and smart phones) with aluminum oxide, barium oxide and graphite powders.
The powder mixture is vaporized at a temperature of 2,642 degrees Fahrenheit and then deposited on a substrate, where it forms the luminescent compound.
When the compound is placed in a bulb and illuminated by a conventional LED chip, the yellow cancels out the blue and the result is a warm, natural-looking white light.
The team still has a ways to go in terms of stabilizing the production process and ramping up the efficiency of the bulb to match its bluish LED rivals, but the verdict so far is “a very good starting point.”
Notsofast on That Rare Earth
Did your nose start to itch when we mentioned europium oxide? Ours sure did, because in 2011, the price of europium spiked wildly after China imposed a crackdown on illegal mining, sparking fears of a global shortage.
Shortages can also arise when prices fall too low compared to mining and production costs, prompting mining companies to scale back their operations.
Europium oxide is just one of several rare earths and other substances that are critical to the development of a new U.S. energy paradigm based on high-efficiency lighting as well as next-generation solar cells, wind turbines and electric vehicle batteries.
Finding reliable domestic sources or substitutes for critical materials has become a priority for the Obama Administration, which recently established the Critical Materials Institute under the leadership of Ames Laboratory in Iowa.
Part of the new institute’s mission will be to develop new manufacturing, recycling and resource recovery pipelines to promote the more efficient use of critical materials.
Follow me on Twitter: @TinaMCasey