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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Failure Mechanisms and Color Stability in Light-Emitting Diodes during Operation in High- Temperature Environments in Presence of Contamination

The energy efficiency of light-emitting diode (LED) technology compared to incandescent light bulbs has triggered an increased focus on solid state luminaries for a variety of lighting applications. Solid-state lighting (SSL) utilizes LEDs, for illumination through the process of electroluminescence instead of heating a wire filament as seen with traditional lighting. The fundamental differences in the construction of LED and the incandescent lamp results in different failure modes including lumen degradation, chromaticity shift and drift in the correlated color temperature. The use of LED-based products for safety-critical and harsh environment applications necessitates the characterization of the failure mechanisms and modes. In this paper, failure mechanisms and color stability has been studied for commercially available vertical structured thin film LED (VLED) under harsh environment conditions with and without the presence of contaminants. The VLED used for the study was mounted on a ceramic starboard in order to connect it to the current source. Contamination sources studied include operation in the vicinity of vulcanized rubber and adhesive epoxies in the presence of temperature and humidity. Performance of the VLEDs has been quantified using the measured luminous flux and color shift of the VLEDs subjected to both thermal and humidity stresses under a forward current bias of 350 mA. Results indicate that contamination can result in pre-mature luminous flux degradation and color shift in LEDs.

Lall, Pradeep↗
DOE OSTI2017

Manufacturing Process for OLED Integrated Substrate

The primary objective of this project is to demonstrate manufacturing processes for technologies that will enable commercialization of a large-area and low-cost “integrated substrate” product for rigid OLED SSL lighting. The integrated substrate product will consist of a low cost, float glass substrate combined with a transparent conductive anode film layer, and light out-coupling (internal and external extraction layers) structures. In combination, these design elements will enable an integrated substrate meeting or exceeding 2015 performance targets for cost ($60/m2), extraction efficiency (50%) and sheet resistance (<10 ohm/sq).

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2017

Leveraging accelerated testing of LED drivers to model the reliability of two-stage and multi-channel drivers

The next wave of LED lighting technology is likely to be tunable white lighting (TWL) devices which can adjust the colour of the emitted light between warm white (~ 2700 K) and cool white (~ 6500 K). This type of lighting system uses LED assemblies of two or more colours each controlled by separate driver channels that independently adjust the current levels to achieve the desired lighting colour. Drivers used in TWL devices are inherently more complex than those found in simple SSL devices, due to the number of electrical components in the driver required to achieve this level of control. The reliability of such lighting systems can only be studied using accelerated stress tests (AST) that accelerate the aging process to time frames that can be accommodated in laboratory testing. This paper describes AST methods and findings developed from AST data that provide insights into the lifetime of the main components of one-channel and multi-channel LED devices. The use of AST protocols to confirm product reliability is necessary to ensure that the technology can meet the performance and lifetime requirements of the intended application.

Davis, Lynn↗
DOE OSTI2018

Securing your Site in Development and Beyond

Why wait until production deployment, or even staging and testing deployment to identify security vulnerabilities? Using tools like Burp Suite, you can find security vulnerabilities before they creep up on you. Prevent cross-site scripting attacks, and establish a firmer trust between your website and your client. Verify that Apache/Nginx have the correct SSL Ciphers set. We explore using these tools and more to validate proper Apache/Nginx configurations, and to be compliant with modern configuration standards as part of the development cycle. Your clients can use tools like https://securityheaders.io and https://ssllabs.com to get a graded report on your level of compliance with OWASP Secure Headers Project and SSLLabs recommendations. Likewise, you should always use the same sites to validate your configurations. Burp Suite will find common misconfigurations and will also perform more thorough security testing of your applications. In this session you will see examples of vulnerabilities that were detected early on, as well has how to integrate these practices into your daily workflow.

Akopov, Mikhail S.↗
DOE OSTI2018

Large-Scale Daylighting Analysis for Buildings, Products, and Policy

Daylighting in buildings has come under increased scorn in the wake of ubiquitous solid-state lighting (SSL), as installed lighting power densities in buildings have been reduced to the point where designers and owners question the benefits of properly-designed daylighting and electric lighting control. At the same time the very process of demonstrating well-executed daylighting to satisfy new building rating systems has become burdensome. This paper demonstrates the utility of illuminance as an input to simple, existing qualitative and quantitative metrics for daylighting performance in buildings, at scale. This assertion is supported by sensitivity analysis of a large-scale daylighting simulation dataset. Uses of this data for quantifying non-energy benefits (NEBs) of daylighting are also explored. We do not eschew the use of newer, more detailed daylight metrics in design, but we do encourage the use of simple daylight metrics for a broader range of new and retrofit building projects toward a net-zero future.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2013

CALiPER Exploratory Study: Recessed Troffer Lighting

This CALiPER study examines the problems and benefits likely to be encountered with LED products intended to replace linear fluorescent lamps. LED dedicated troffers, replacement tubes, and non-tube retrofit kits were evaluated against fluorescent benchmark troffers in a simulated office space for photometric distribution, uniformity of light on the task surface, suitability of light output, flicker, dimming performance, color quality, power quality, safety and certification issues, ease of installation, energy efficiency, and life-cycle cost.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2013

Demonstration of LED Street Lighting in Kansas City, MO

This report documents a study of nine different light-emitting diode (LED) street lighting products installed in February 2011 as replacements for incumbent high-pressure sodium (HPS) luminaires in the city of Kansas City, Missouri (KCMO). The subject lighting investigation was undertaken by the city as part of a continued focus on improving street safety that had begun with an earlier extensive upgrade to the streetlighting system in the late 1990s, which substantially improved both the quantity and uniformity of its lighting. The current study was conducted in support of the U.S. Department of Energy’s Municipal Solid-State Street Lighting Consortium, via support of the GATEWAY Solid-State Lighting Technology Demonstration Program, and involved multiple staff from different organizations employing a variety of meters and procedures.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2013

LED Lighting Facts Snapshot: Indoor Ambient Lighting

LED Lighting Facts Snapshot reports reveal how today's products really perform, drawing on analysis of verified performance data from the program's online product list.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2013

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↗
DOE OSTI2014

Energy Savings Forecast of Solid-State Lighting in General Illumination Applications

With declining production costs and increasing technical capabilities, LED adoption has recently gained momentum in general illumination applications. This is a positive development for our energy infrastructure, as LEDs use significantly less electricity per lumen produced than many traditional lighting technologies. The U.S. Department of Energy’s Energy Savings Forecast of Solid-State Lighting in General Illumination Applications examines the expected market penetration and resulting energy savings of light-emitting diode, or LED, lamps and luminaires from today through 2030.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2014

CALiPER Report 20.3: Robustness of LED PAR38 Lamps

A small sample of each of the CALiPER Application Summary Report 20 PAR38 lamp types underwent stress testing that included substantial temperature and humidity changes, electrical variation, and vibration. The results do not directly address expected lifetime, but can be compared with one another, as well as with benchmark conventional products, to assess the relative robustness of the product designs.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2014

CALiPER Retail Lamps Study 3

This is a special CALiPER report on LED lamps available through the retail marketplace and targeted toward general consumers. It follows similar reports published in 2011 and 2012 (products purchased in 2010 and 2011), and is intended as a continuation that identifies long-term trends. For this report, products were selected to investigate specific hypotheses, rather than represent a sample of the increasingly large retail LED market.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2014

CALiPER Retail Lamps Study 3.2: Lumen and Chromaticity Maintenance of LED A Lamps Operated in Steady-State Conditions

This CALiPER report examines lumen depreciation and color shift of 17 different A lamps in steady-state conditions (15 LED, 1 CFL, 1 halogen). The goal of this investigation was to examine the long-term performance of complete LED lamps relative to benchmark halogen and CFL lamps—in this case, A lamps emitting approximately 800 lumens operated continuously at a relatively high ambient temperature of 45°C.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗