Category: Research

CLTC Demonstrates Philips Day-Brite’s NiteBrites HID Wall Packs

The California Lighting Technology Center (CLTC) recently demonstrated Philips Day-Brite NiteBrites HID wall packs at California State University, Chico. The demonstration included replacing 13 150W high pressure sodium wall packs…

The California Lighting Technology Center (CLTC) recently demonstrated Philips Day-Brite NiteBrites HID wall packs at California State University, Chico. The demonstration included replacing 13 150W high pressure sodium wall packs and one 70W HPS tall wall pack with 14 new bi-level HID fixtures at Shasta and Lassen halls.

The retrofit increased light levels of the pathways surrounding the dormitories, as well as provided a high color quality and color temperature (4000K). In addition, the retrofit resulted in 42% energy savings, which translates into 4,550 kWh.

Learn more about this demonstration project here.

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New Whitepaper Evaluates Impact of Outdoor Lighting on Human Circadian System

The Alliance for Solid-State Illumination and Technologies (ASSIST) recently published a technical paper that quantitatively evaluates the impact that outdoor lighting has on the human circadian system. A growing interest…

The Alliance for Solid-State Illumination and Technologies (ASSIST) recently published a technical paper that quantitatively evaluates the impact that outdoor lighting has on the human circadian system. A growing interest in the role that light plays on human health, combined with the increasing use of white outdoor lighting with high correlated color temperatures and a short-wavelength spectral component, has prompted some advocacy groups to raise alarms about the potential impact of outdoor lighting on human health. This technical paper shows that this concern may be unfounded under realistic scenarios; the impact of streetlights and other outdoor lights may have only a small, if any, impact on human biological cycles.

Every species on earth exhibits circadian rhythms – biological cycles that repeat approximately every 24 hours. These cycles are usually in synch with the natural light/dark cycle, with the human circadian system being most sensitive to and activated by short-wavelength (blue) light. Civilization has created environments where 24-hour light/dark patterns can potentially be disrupted, from occupying deep core buildings to bright electric illumination lighting interiors at night. Disruption of these light/dark patterns, which can occur with regular exposure darkness during the day and bright light at night, has been associated with breast cancer, insomnia, obesity and a wide range of maladies.

To determine whether and how much outdoor lighting systems might stimulate and potentially disrupt the human circadian system, researchers at Rensselaer Polytechnic Institute’s Lighting Research Center (LRC) investigated the impact that realistic outdoor lighting scenarios might have on these biological cycles.

Assuming a published model of human circadian phototransduction previously developed by LRC researchers, investigators for this study evaluated four typical outdoor light sources: two commercially available “cool-white” LEDs, a sodium-scandium metal halide (MH) lamp, and a high-pressure sodium (HPS) lamp. LRC investigators evaluated these light sources under three conditions: a controlled laboratory condition as a reference and two typical streetlight scenarios for distance and viewing angle outdoors. The latter two viewing conditions represented real-life conditions that people could actually experience as they come into contact with outdoor lighting. Assuming a one-hour exposure with natural pupils for a 20-year-old, LRC researchers calculated the percentage of melatonin suppression that would occur from exposure to each light source under each condition.

“We determined whether there was enough light reaching the retina to stimulate the circadian system as measured by melatonin suppression,” said lead researcher Mark Rea, LRC director. Melatonin is a common biological marker used in the study of circadian rhythms.

Results showed that under the two practical street lighting conditions, three of the four light sources would not meaningfully stimulate the human circadian system after one hour of exposure. One source (a 6900 K LED) is predicted to provide 3–10% melatonin suppression. According to the LRC, a reasonable and conservative working threshold for suppressing nocturnal melatonin by light at night would be 30 lx at the eye from a “white” light source for 30 minutes. This working threshold is based upon the minimum exposure to “white” light that could produce reliable nocturnal melatonin suppression of 15% or more.

“Although stimulation of the circadian system is not necessarily synonymous with health risk, it is essential to determine if and to what degree light sources used outdoors at night might stimulate the circadian system. This study is a good start toward quantitatively understanding if outdoor lighting poses a concern,” said Rea. However, Rea strongly cautioned that further study is still needed to fully understand the causal link between light at night and human health and to understand how the circadian system may or may not be stimulated by light exposure.

Learn more and access the full technical paper here.

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DOE Releases Summary Results from Round 10 of CALiPER Testing

The Department of Energy recently announced that it has completed Round 10 of product testing through its CALiPER program. A Summary Report containing the results from the new testing is…

The Department of Energy recently announced that it has completed Round 10 of product testing through its CALiPER program. A Summary Report containing the results from the new testing is now available for download on the DOE SSL website here.

Round 10 of product testing covered four main categories: parking structure luminaires, outdoor wallpack luminaires, cove lighting luminaires (including two products marketed as “AC LED” products), and replacement lamps. Conventional parking structure, wallpack and cove light products were also tested and included for benchmarking purposes in this summary report.

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Study: Supermarket Lighting May Boost Nutritional Value of Spinach

U.S. Department of Agriculture scientists recently stated the conclusions of a new study that found that supermarket lighting can help keep spinach fresh and producing new vitamins. Sorry, kids, it…

U.S. Department of Agriculture scientists recently stated the conclusions of a new study that found that supermarket lighting can help keep spinach fresh and producing new vitamins.

Sorry, kids, it doesn’t make it taste any better.

Get the story here.

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ASSIST Recommendation Provides New Metrics for Specifying Color Properties in Retail Lighting

A recent survey of lighting designers and specifiers by the National Lighting Product Information Program showed that for retail applications, light source color properties are considered more important than any…

A recent survey of lighting designers and specifiers by the National Lighting Product Information Program showed that for retail applications, light source color properties are considered more important than any other light source criterion, including energy efficiency.

To define light source color properties, the lighting industry predominantly relies on two metrics, correlated color temperature (CCT), commonly used as an indication of the apparent “warmth” or “coolness” of the light emitted by a source, and color rendering index (CRI), an indication of the light source’s ability to make illuminated objects appear natural.

However, these two metrics, developed in the last century, are facing increased challenges and criticisms as new types of light sources, particularly LEDs, become more prevalent in the market.

In order to help retail lighting designers better understand CCT and CRI and choose the best lighting product for specific retail applications, the Alliance for Solid-State Illumination Systems and Technologies (ASSIST) has published a new volume in its ASSIST recommends series.

The first issue, “Guide to Light and Color in Retail Merchandising,” provides a background on CCT and CRI, including their advantages and drawbacks, and discusses how they may be augmented for better use in retail merchandising. The second issue, “Recommendations for Specifying Color Properties of Light Sources for Retail Merchandising,” recommends two-metric approaches for specifying light sources to achieve desired color appearance of the illumination as well as good color rendering in retail applications.

For example, in order to meet the expectations for good color rendering in retail applications, ASSIST advises using the well-established CRI along with another metric called gamut area index (GAI). GAI represents the relative separation of object colors illuminated by a light source; the greater the GAI, the greater the apparent saturation or vividness of the object colors, according to Mark Rea, Ph.D., director of Rensselaer Polytechnic Institute’s Lighting Research Center and co-author of the publication.

“Broadly speaking, CRI is a measure of how ‘natural’ an object appears, and GAI is a measure of how ‘vivid’ the colors appear,” said Rea. “LRC experiments show that light sources which balance both CRI and GAI are generally preferred over ones that have only high CRI or only high GAI.”

Practical, step-by-step methods are included in the publication for the two-metric color rendering approach described here, as well as a two-metric approach for achieving consistent results in desired color appearance of the illumination.

“The rationale and new methods provided in this ASSIST volume should lead to light source specification that most closely represents a designer’s intentions,” said Rea.

The LRC recently held the first in what will be a series of roundtable discussions, including color-rendering mock-ups and experiments, with practicing lighting designers and specifiers to introduce the two-metric approach to color rendering and obtain feedback. The first session was recently held with a group of high-end retail lighting designers who agreed that this new approach was a step forward over the reliance on CRI alone and would be a useful tool when trying to narrow down light source options from a large selection of products.

The two new ASSIST recommends are available for free download from the ASSIST web site here.

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Lighting Design Can Reduce Anxiety For Tunnel Drivers

Norwegian researchers have found that good design and lighting can significantly reduce anxiety among travelers driving through tunnels, as reported by EarthSky.org here. The article states: The main point is…

Norwegian researchers have found that good design and lighting can significantly reduce anxiety among travelers driving through tunnels, as reported by EarthSky.org here.

The article states:

The main point is to obtain a good distribution of light, in conjunction with the use of artistic lighting, which turns out to give drivers a feeling of space and of greater security. Modern lighting systems, with two rows of lamps, light sources that illuminate the opposite direction and driving lane, are beginning to be quite common in new Chinese tunnels, and they have also been installed in the tunnel that forms part of the Øresund Link between Denmark and Sweden.

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Lighting Influences Taste of Wine and How Much Consumers Are Willing to Pay for It

Lighting influences how wine tastes and how much consumers are willing to pay for it, based on a series of three German experiments in which more than 500 people tasted…

Lighting influences how wine tastes and how much consumers are willing to pay for it, based on a series of three German experiments in which more than 500 people tasted white Riesling wines. The study report, “Ambient Lighting Modifies the Flavor of Wine,” was published in the December 2009 issue of Journal of Sensory Studies.

The only significant variable in the experiments was the ambient lighting in the spaces where study participants sat. Researchers used a series of fluorescent lamps that produced red, blue, green or white light. People rated the wine’s quality higher, in general, when they drank it in a room whose ambient lighting was red or blue versus green or white. They also found the test wine much sweeter and fruitier when sampled in a room illuminated by red-tinted fluorescent lamps, and were willing to spend more for it.

Hat tip National Lighting Bureau.

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