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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records

DOE CALiPER Program, Report 20.1 Subjective Evaluation of Beam Quality, Shadow Quality, and Color Quality for LED PAR38 Lamps

This report focuses on human-evaluated characteristics, including beam quality, shadow quality, and color quality. Using a questionnaire that included rank ordering, opinions on 27 of the Report 20 PAR38 lamps were gathered during a demonstration event for members of the local Illuminating Engineering Society (IES) chapter. This was not a rigorous scientific experiment, and the data should not be extrapolated beyond the scope of the demonstration. The results suggest that many of the LED products compared favorably to halogen PAR38 benchmarks in all attributes considered. LED lamps using a single-emitter design were generally preferred for their beam quality and shadow quality, and the IES members ranking of color quality did not always match the rank according to the color rendering index (CRI).

Beam Quality↗

DOE CALiPER Program Report 21.2: Linear (T8) LED Lamp Performance in Five Types of Recessed Troffers

Although lensed troffers are numerous, there are many other types of optical systems as well. This report looked at the performance of three linear (T8) LED lamps chosen primarily based on their luminous intensity distributions (narrow, medium, and wide beam angles) as well as a benchmark fluorescent lamp in five different troffer types. Also included are the results of a subjective evaluation. Results show that linear (T8) LED lamps can improve luminaire efficiency in K12-lensed and parabolic-louvered troffers, effect little change in volumetric and high-performance diffuse-lensed type luminaires, but reduce efficiency in recessed indirect troffers. These changes can be accompanied by visual appearance and visual comfort consequences, especially when LED lamps with clear lenses and narrow distributions are installed. Linear (T8) LED lamps with diffuse apertures exhibited wider beam angles, performed more similarly to fluorescent lamps, and received better ratings from observers. Guidance is provided on which luminaires are the best candidates for retrofitting with linear (T8) LED lamps.

CALiPER↗

CALiPER Exploratory Study: Recessed Troffer Lighting

This report describes an exploration of troffer lighting as used in office and classroom spaces, which was conducted by the CALiPER program. Twenty-four pairs of 2×2 and 2×4 troffers were procured anonymously, documented, tested for photometric and electrical performance, and installed in a mockup office space in Portland, Oregon. Three of the pairs were T8 fluorescent benchmark products, 12 were dedicated LED troffers, five were fluorescent troffers modified for LED lamps (sometimes referred to as "tubes"), and another four troffers were modified with LED retrofit kits. The modifications were performed by a commercial electrical contractor, following the instructions provided by the retrofit lamp or kit manufacturer. Once installed in the mockup facility, the converted luminaires were examined by a NRTL (Nationally Recognized Testing Laboratory) safety expert, who provided feedback on safety issues. In September 2012, a group of lighting designers, engineers, and facility managers were brought in to observe the LED luminaires in comparison to fluorescent benchmarks. This report documents performance in measures that go beyond illuminance values or luminaire efficacy. Dedicated LED troffers are ready to compete with fluorescent troffers in terms of efficacy (lumens per watt), and in many lighting quality issues such as glare, light distribution, visual appearance, and color quality. That is not to say that each one is stellar, but each one tested in this CALiPER study bested the fluorescent benchmarks in terms of efficacy, and almost all were rated highly in several categories -- only one luminaire of twelve performed consistently poorly.

CALiPER Program↗

SSL Pricing and Efficacy Trend Analysis for Utility Program Planning

Report to help utilities and energy efficiency organizations forecast the order in which important SSL applications will become cost-effective and estimate when each "tipping point" will be reached. Includes performance trend analysis from DOE's LED Lighting Facts® and CALiPER programs plus cost analysis from various sources.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗

Color Maintenance of LEDs in Laboratory and Field Applications

To date, consideration for parametric failure of LED products has largely been focused on lumen maintenance. However, color shift is a cause of early failure for some products, and is especially important to consider in certain applications, such as museum lighting, where visual appearance is critical. Field data collected by the U.S. Department of Energy's (DOE) GATEWAY program for LED lamps installed in museums shows that many have changed color beyond a reasonable tolerance well before their rated lifetimes have been reached. Laboratory data collected by DOE's CALiPER program between 2008 and 2010 reveals that many early LED products shifted beyond acceptable tolerances in as little as a few thousand hours. In contrast, data from the L Prize® program illustrates that commercially available LED products can have exemplary color stability that is unmatched by traditional light sources. In addition to presenting data from the aforementioned DOE programs, this report discusses the metrics used for communicating color shift, and provides guidance for end users on how to monitor chromaticity and what to look for in manufacturer warranties. Also covered are the physical changes that have been shown to lead to color shift in some types of LED packages. As with lamps and luminaires, the data presented for LED packages shows that a wide variety of products are available; in order for specifiers and consumers to make educated choices, more detailed and standardized information is necessary.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

Color Maintenance of LEDs in Laboratory and Field Applications

Synopsis: To date, consideration for parametric failure of LED products has largely been focused on lumen maintenance. However, color shift is a cause of early failure for some products, and is especially important to consider in certain applications, like museums, where visual appearance is critical. Example data collected by the GATEWAY program for LED lamps installed in museums shows that many have changed color beyond a reasonable tolerance well before their rated lifetime was reached, necessitating replacement. Similar data collected by the CALiPER program between 2008 and 2010 reveals that many early products shifted beyond acceptable tolerances in as little as a few thousand hours. In contrast, data from the L Prize program illustrates that commercially available LED products can have exemplary color stability that is unmatched by traditional light sources. Beyond presenting data from the aforementioned DOE programs, this report discusses the metrics used for communicating color shift—namely MacAdam ellipses and Δu'v'—as well as providing guidance for end users on how to monitor color shift and what to look for in manufacturer warranties. Also included are descriptions of the physical changes that have been documented as leading to color shift in some example types of LED packages. As with complete products, the data presented herein for LED packages shows that a wide variety of products are available; in order for specifiers and consumers to make educated choices, more detailed and standardized information should be made available.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

CALiPER Retail Lamps Study 3

The CALiPER program first began investigating LED lamps sold at retail stores in 2010, purchasing 33 products from eight retailers and covering six product categories. The findings revealed a fragmented marketplace, with large disparities in performance of different products, accuracy of manufacturer claims, and offerings from different retail outlets. Although there were some good products, looking back many would not be considered viable competitors to other available options, with too little lumen output, not high enough efficacy, or poor color quality. CALiPER took another look in late 2011purchasing 38 products of five different types from nine retailers and the improvement was marked. Performance was up; retailer claims were more accurate; and the price per lumen and price per unit efficacy were down, although the price per product had not changed much. Nonetheless, there was still plenty of room for improvement, with the performance of LED lamps not yet reaching that of well-established classes of conventional lamps (e.g., 75 W incandescent A19 lamps). Since the second retail lamp study was published in early 2012, there has been substantial progress in all aspects of LED lamps available from retailers. To document this progress, CALiPER again purchased a sample of lamps from retail stores 46 products in total, focusing on A19, PAR30, and MR16 lamps but instead of a random sample, sought to select products to answer specific hypotheses about performance. These hypotheses focused on expanding ranges of LED equivalency, the accuracy of lifetime claims, efficacy and price trends, as well as changes to product designs. Among other results, key findings include: There are now very good LED options to compete with 60 W, 75 W, and 100 W incandescent A19 lamps, and 75 W halogen PAR30 lamps. MR16 lamps have shown less progress, but there are now acceptable alternatives to 35 W, 12 V halogen MR16 lamps and 50 W, 120 V halogen MR16 lamps for some applications. Other uses, such as in enclosed luminaires, may require more development. At the same price point, lamps purchased in 2013 tended to have higher output and slightly higher efficacy than in 2011 or 2010. Over 30% of the products purchased in 2013 exceeded the maximum efficacy measured in 2011 (71 lm/W), with the most efficacious product measured at 105 lm/W. There appears to be increasing consistency in color quality, with a vast majority of products having a CCT of 2700 K or 3000 K and a CRI between 80 and 85. There were also fewer poor performing products tested and more high-performing products available in 2013 than in previous years. The accuracy of equivalency and performance claims was better than in 2011, but remains a concern, with 43% of tested products failing to completely meet their equivalency claim and 20% of products failing to match the manufacturer’s performance data. Although progress has been substantial, on average LED lamps remain more expensive than other energy efficiency lighting technologies -- although some aspects can be superior. Although not universal to all product lines or all product types, the issue of insufficient lumen output from LED lamps is waning. Thus, manufacturers can focus on other issues, such as reducing cost, improving electrical/dimmer compatibility, eliminating flicker, or improving color quality. While these issues are not inherent to all products, they remain a concern for the broader market.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

Development of Parameters for the Particle Size Distribution of TATB

Laser light scattering (LLS), manual counting of scanning electron microscopy (SEM) images, and reduction of SEM images using ImageJ (open source program) to determine Feret (caliper) diameters were applied to determine particle size distribution (PSD) of four preparations of 1,3,5‐triamino‐2,4,6‐trinitrobenzene (TATB) and yttria‐stabilized zirconia (YSZ), an SEM certified standard. Mie theory was used to reduce the LLS data. The spherical nature of the YSZ made it a good candidate for LLS. Variations in n , the refractive index, and iκ, the imaginary component, produced very little change in the PSD. However, changing the carrier liquid from H 2 O to a 40% aqueous sucrose solution, thereby changing the carrier refractive index, n 0 , substantially affected the PSD. The Mie complex refractive indices for the YSZ were n = 2.200, iκ = 0.100, with a 40% aqueous sucrose solution, n 0 = 1.400. The triclinic crystal structure of TATB made refractive index determinations more difficult, so a study was conducted varying Mie parameters and comparing them to the same data reduced using the Fraunhofer theory. Changing the n and κ parameters produced PSD with a small concentration of particles less than 1 µm in size or none in this range. SEM images, Feret data, manual counting, and Fraunhofer data reduction indicate particles less than 1 µm are probably < 5% in concentration. The final selection of Mie parameters for TATB was n = 2.283, iκ = 0.1, and suspension medium, n 0 = 1.330. Finally, computations, using density functional theory produced similar parameters.

Feret diameter↗

Caliper Context Annotation Library

To understand the performance of parallel programs, developers need to be able to relate performance measurement data with context information, such as the call path / line numbers or iteration numbers where measurements were taken. Caliper provides a generic way to specify and collect multi-dimensional context information across the software stack, and provide ti to third-party measurement tools or write it into a file or database in the form of context streams.

ECP↗

Caliper Context Annotation Library

To understand the performance of parallel programs, developers need to be able to relate performance measurement data with context information, such as the call path / line numbers or iteration numbers where measurements were taken. Caliper provides a generic way to specify and collect multi-dimensional context information across the software stack, and provide ti to third-party measurement tools or write it into a file or database in the form of context streams.

Source record↗

CALiPER Snapshot Report: Troffers

Snapshot reports use data from DOE's LED Lighting Facts product list to compare the LED performance to standard technologies, and are designed to help lighting retailers, distributors, designers, utilities, energy efficiency program sponsors, and other stakeholders understand the current state of the LED market and its trajectory.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

CALiPER Snapshot Report: Outdoor Area Lighting - 2017

Snapshot reports use data from DOE's LED Lighting Facts product list to compare the LED performance to standard technologies, and are designed to help lighting retailers, distributors, designers, utilities, energy efficiency program sponsors, and other stakeholders understand the current state of the LED market and its trajectory.

SSL, LED, Lighting Facts, CALiPER, snapshot, light↗

CALiPER Snapshot Report: MR16 Lamps

Snapshot reports use data from DOE's LED Lighting Facts product list to compare the LED performance to standard technologies, and are designed to help lighting retailers, distributors, designers, utilities, energy efficiency program sponsors, and other stakeholders understand the current state of the LED market and its trajectory.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

CALiPER Snapshot Report: Downlight - 2017

Snapshot reports use data from DOE's LED Lighting Facts product list to compare the LED performance to standard technologies, and are designed to help lighting retailers, distributors, designers, utilities, energy efficiency program sponsors, and other stakeholders understand the current state of the LED market and its trajectory.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗