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A dynamic luminous LED ceiling gives office workers a feeling of working under an open sky. Credit: Fraunhofer IAO.

If rainy days and Mondays get you down, a remedy is now available thanks to researchers at the Fraunhofer Institute in Germany—at least for the rainy days.

Working with industrial partner, LEIDs GmbH, researchers at the Fraunhofer Institute for Industrial Engineering IAO designed an LED ceiling lighting system that simulates the dynamic effect of passing clouds.

The ceiling array is made of 50 cm x 50 cm tiles, each of which holds 288 light emitting diodes. The full spectrum of light in over 16 million hues is generated by a combination of red, blue, green and white LEDs. A diffuser film suspended 30 cm below the tiles blends the individual points of light to create homogeneous, virtual outdoor sky.

To achieve an effect that accurately simulates natural outdoor light, the researchers studied the variations in illumination as clouds passed by. In the press release, Fraunhofer scientist Dr. Matthias Bues says, “The LEDs allow us to simulate these dynamic changes in lighting in a way that is not directly obvious to the naked eye.” That would be distracting. However, Bues says that a certain amount of fluctuation in the “cloudiness” promotes concentration and improves alertness.

In a study conducted with a prototype ceiling in an office setting, 10 participants rated three lighting conditions: static light, gentle fluctuation and rapid fluctuation. Over 80 percent of the office workers prefered the rapid fluctuation, i.e., a partly cloudy day with a gentle breeze … and no bugs. The press release reports, “users find this dynamic lighting to be extremely pleasant.”

A 34 square meter prototype with over 34,000 LEDs can produce more than 3,000 lux of intensity, but 500 to 1,000 is enough for a comfortable level of illumination. The virtual sky is priced at about 1,000 euro ($1,300) per square meter.

That’s a bit pricey, but in cloud-rich regions like Seattle, it might be a worthwhile investment to boost worker productivity.

So, rainy days begone. Anyone got some ideas for creating a virtual Friday?

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Steetlights with a better spectrum and cheaper to operate are being installed in Chicago and other cities. Credit: Philips.

I grew up near the steel mills in Middletown, Ohio, and if the clouds were just right at nighttime I would see a few minutes of bright orange glow in the sky when a ladle of molten metal was tapped. I didn’t see anything comparable until I was just out of college and moved to Washington, D.C., and had my first jarring experience with big city “mugger” streetlights. You know the type: the ones now used in nearly every major city that create a orange creamsicle-colored dome nightscape over a metropolis that can be seen dozens of miles away.

The hideous hue and intensity from these sodium vapor lights, as I recall, caught on in a big way in the early 1970s and was justified because of their purported ability to cut crime by eliminating dangerous shadowy areas in urban areas. They were also cheaper and more durable than the alternatives back then. Regardless, city residents got used to them and they seemed to have found a permanent home in urban–highway architecture.

But some US cities are looking for a change in their night sky schemes. Chicago, for example, recently announced that it is replacing 16,300 of the old sodium vapor lights with ceramic metal halide lights. That 16,000+ number may sound like a lot, but its only a relatively small step forward for the city will still have nearly ten-times that amount of the old luminaries. Chicago is also converting 1,000 stop lights (another small portion) to LEDs.

Although this is just an incremental step, it’s a step in the right direction. Planners say they will save $40-$70 in electricity per light, and the ceramic metal halide versions will last about 50 percent longer than the old models. Between the new streetlights and stoplights, the city expects to save $1.8 million per year and cut CO₂ -related emissions by 15,000 metric tons. The actual transition is taking place now because of the availability of a $13.8 million DOE grant. Lower maintenance costs are also expected.

The city’s department of transportation says it will eventually replace all of its streetlights.

Besides the monetary savings, the city says in a news release the CMH lights provide an improved light spectrum and reduce light “pollution,” noting, “Despite the lower wattage, the lights appear as bright or brighter to the eye than the old light fixtures, and offers truer color of objects… Additionally, Chicago’s metal-halide fixtures reduce ’sky glow’ (light traveling up, instead of down) by between 50 to 100 percent depending on the type of fixture. They also reduce ‘light trespass’-light shining into unwanted areas, like nearby buildings or homes.” (Note, whoever calculated that 100 percent reduction number needs help with his/her gazintas and gazoutas.)

Regarding performance, one website notes regarding the CMH-or-LED debate that “Neither are as bright as the 150W and 250W lamps that typically light residential roadways in Chicago, but they seem perfectly adequate to me. The dimmer white light gives the blocks with CMH and LED a more suburban look.”

Regarding the source of the new lights, Chicagomag website claims they are CosmoPolis made by Philips although others think it’s a GE product. Lux magazine did a comparison of the Phillips and GE CMH products earlier this year.

But what about the secure feeling that the sodium vapor light ingrained in urbanites? Thanks for asking. The Chicago Tribune reports that old lights didn’t perform so well:

“Since the large-scale adoption of sodium vapor lights in the United States and elsewhere, studies have been done showing that they can hamper police identification of suspects because they decrease people’s ability to tell one color from another, because they make everything look orange at night.”

According to the Atlantic magazine, the list of other cities looking at replacing their streetlights includes New York, Anchorage, San Jose, Pittsburgh and Los Angeles.

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Check ‘em out:

Low-cost system spots failing bridges; new sensor technology helps make bridges safer

Rice University researchers ‘armchair’ nanotubes could improve power grid’s efficiency

Russia offers Germany help on rare earths supply

Centre for Sustainable Energy Technologies invents heat-regulating building material

GE Lighting acquires Lightech, a technology leader in LED drivers and $10 million and GE collaboration light way for growth of Nuventix, maker of LED cooling technology

The too-smart-for-its-own-good grid: New technologies intended to boost reliance on renewable energy could destabilize the power grid if they’re not matched with careful pricing policies

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Zinc oxide nanostructures are synthesized in parallel microfluidic channels (held by the metal frame) by flowing reactants through the tubing. The microfluidic structure creates the device and also becomes the final packaged functional LED device.
Photo: Jaebum Joo; MITnews

Just when I thought I could stroll back into the macro world, two new papers were published that complement our recent posts on PCMMs, supercapacitors, nanoporous materials and other nanostructured materials.

First, out of MIT comes “Face-selective electrostatic control of hydrothermal zinc oxide nanowire synthesis,” by Jaebum Joo, et. al. (see Nature Materials, doi:10.1038/nmat3069). Using hydrothermal synthesis, the group grew zinc oxide nanowires with controlled morphologies and functional properties. Morphologies synthesized ranged from platelets to needles with aspect ratios that spanned three orders of magnitude (~0.1-100 are reported).

The article abstract says a classical thermodynamic model was used to explain the growth inhibition mechanism “by means of the competitive and face-selective electrostatic adsorption on non-zinc complex ions at alkaline conditions.” An online story from MITnews clarifies that “the key turns out to be the electrostatic properties of the zinc oxide material as it grows from a solution.” When ions from other compounds are added to the solution (from which the ZnO is grown hydrothermally), they attach electrostatically and preferentially to the wire at only the sides or the ends, which inhibits growth in those directions (i.e., face-selective). The hydrothermal synthesis process temperature was less than 60°C, which opens up the possibility of manufacturing devices on or in polymers and plastics.

The team fabricated a functional LED array of ZnO nanowires, but ZnO also can be used in battery, sensor and other optical applications. In the MIT story Joo says this method and the ability to use it to control morpholgy could be applied to other materials, for example, titanium dioxide, a possible solar cell material. Joo also says the successful use of hydrothermal synthesis to manipulate nanostructure has “the potential for large-scale manufacturing.” (Perhaps a candidate technology for Obama’s recently announced Advanced Manufacturing Partnership?)

The second paper, published in the same issue of Nature Materials, is from a group at Samsung Electronics in Korea. In an interesting departure from the more common PCMM chalcogenide approach, they looked at tantalum oxide-based bilayer structures for nonvolatile memory devices. (See “A fast, high-endurance and scalable non-volatile memory device made from asymmetric Ta₂O_5-x/TaO_2-x bilayer structures,” Nature Materials, doi:10.1038/nmat3070, by Myoung-Jae Lee, et. al.)

(Quick note: Based on the abstract and online images, this appears to be a material property- and performance-oriented paper, and it is not known whether the material is nanostructured.)

Like others researching nonvolatile memory materials, they are looking for “a material or device structure that satisfies high-density, switching-speed, endurance, retention and most importantly power — consumption criteria” (from the abstract). The paper describes an asymmetric passive switching device with an impressive cycling endurance of over 10¹² and switching times of 10 ns. They were able to demonstrate a significant reduction of switching current and, therefore, power consumption.

The paper’s abstract postulates that there may be another benefit: “[B]y combining two such devices, each with an intrinsic Schottky barrier, we eliminate any need for a discrete transistor or diode in solving issues of stray leakage current paths in high-density crossbar arrays.”

Samsung’s published interest in nonvolatile memory materials combined with IBM’s recent proof-of-concept chalcogenide device seems to comprise pretty strong evidence that the leap from lab to prototype is underway, and Si-based flash memory may soon be just that, a memory.

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Credit: Piccolo Namek, Wikipedia.

I really had intended to give the topic of LEDs a rest for a while. But while catching up on some reading, I came across a story suggesting that, while LEDs have performance advantages over incandescents and CFLs, one can’t assume that LEDs are free from disposal problems. In fact, the paper’s authors from the University of California (Davis and Irvine) suggest that LEDs may bring their own “environmental burdens.”

The researchers, who are associated with UCI’s School of Social Ecology/Program in Public Health and UCD’s Department of Chemical Engineering and Materials Science, distinguish between environmental burdens related to resource depletion (e.g., gold and silver) and those burdens related to toxicity (e.g., copper, nickel and lead).

The groups goals was to test whether LEDs could be considered “hazardous wastes” as defined by United States and California standards, look at how the threat might vary across different LED types and look at the overall life-cycle impact of LEDs. The latter was done, in part, to help designers and manufacturers make safer products and to help waste disposers and recyclers know how to handle LEDs that are already making their way to landfills.

Their findings, published in Environmental Science & Technology, were that some LEDs did pose a threat of leaching toxic materials if disposed of improperly, but the threat was largely related to LED color and intensity. In fact, with one exception, all LEDs exceeded Cali’s silver, nickel, lead and copper standards. The one exception is low-intensity yellow LEDs. One type of LED — low-intensity reds — exceeded federal lead standards.

The groups methods were pretty straight forward: Grind up LEDs and expose the resultant flecks, nuggets and specks to the equivalent of multiyear bath in acid rain, and then test for toxic materials in the runoff.

This isn’t the first time these researchers have used this type of approach. For example, UCI’s Oladele A. Ogunseitan has been grinding up and testing cell phones and other commercial electronics for some time. Ogunseitan has been the principal investigator in NSF-sponsored study on strategies for addressing e-wastes. Another group member, UCD’s Julie M. Shoenung, runs the school’s Lead Campus activities that are part of the Research and Education in Green Materials program.

In an online story, Gizmag writer Darren Quick, reports:

Ogunseitan blames the situation on a lack of proper product testing before LEDs were presented as a more efficient replacement for incandescent bulbs - which are now being phased out around the world. Although a law requiring more stringent testing for such products was scheduled to begin on January 1st in California, it was opposed by industry groups, and Governor Arnold Schwarzenegger put it on hold before leaving office.

“Every day we don’t have a law that says you cannot replace an unsafe product with another unsafe product, we’re putting people’s lives at risk,” said Ogunseitan. “And it’s a preventable risk.”

One point of this group’s work is that the time to act is now. LEDs were already entering the waste stream from auto industry applications (front and rear lights) and hitting the mass market in the form of cheap and ubiquitous holiday lights.

On a practical level, the group suggests that anyone having to clean up broken LEDs should treat the situation as if approaching broken CFLs. Wear gloves, mask and use special brooms and other equipment to gather the debris. They also go so far as to suggest special precautions for emergency responders to highway accidents.

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