Industry Led Research Papers

More than 20% of SSL luminaires for the industrial market exceed 130 lm/W in efficacy according to the US Department of Energy and separately the agency said self-metering products are increasingly viable for LED lighting.


The US Department of Energy (DOE) has published another in its series of Caliper Snapshot Reports with the latest focused on industrial LED luminaires, and noted that the commercial products lead both legacy commercial products and LED-based products for other applications by a wide margin in efficiency. In another recent Energy Reporting Study, the DOE considered the state of LED lighting connected by Power over Ethernet (PoE) with the goal of determining if energy metering in the fixtures could enable additional energy savings in buildings and cities. And in the street light area, the DOE has assembled a number of resources in one place to help answer questions, especially in response to the controversy resulting from the American Medical Association (AMA) recommendations on limiting deployments to warm CCTs.

Snapshot on commercial luminaires

The DOE has been especially busy with Snapshot reports of late. The agency utilizes its LED Lighting  Facts database to mine important trends in individual applications unlike the full Caliper reports that cover detailed testing of luminaires sold on the commercial market. Earlier this year, the DOE released a Snapshot report on LED troffersrewcteubxeasybywqaaveyxrbwaw. And in the fall of 2016, the agency released a Snapshot on outdoor area lighting.

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The new report reveals that the commercial luminaires are perhaps the most efficient LED products in the broad market. Approximately 23% had efficacy ratings of 130 lm/W or higher. We will get to how that compares to incumbents in a moment, but in summary the DOE said it is better than LED linear, troffer, area/roadway, and parking garage fixtures in the Lighting Facts database.

The industrial segment comprises low- and high-bay luminaires with the full range of products in the database spanning 5,000 to 100,000 lm. The low-bay products top out at 20,000 lm and the high-bay products start at 15,000 lm. The report said LED products only penetrated the commercial market by 6% in 2015, but expects the number to reach 86% by 2035.

The mean efficacy for all products in the database is 115 lm/W and is up 7 lm/W in just the past nine months. Legacy fluorescent and metal halide (MH) products are mired in the 50–70-lm/W range. None of the legacy products meet the requirements of the DesignLights Consortium (DLC) qualified products list (QPL), while most of the LED fixtures meet minimum DLC levels and many qualify for the QPL Premium listing at 125 lm/W.

The DOE further said that the LED products compare favorably to legacy products in terms of power and color quality. Of the LED products, 38% have power factor over 0.9. And 65% have CRI of 80 or above. And the LED manufacturers offer more flexibility in CCT with some products as warm as 3000K while almost half have CCT above 5000K.

You can read the full report on the DOE website for more detail.

PoE research

Moving to the report on POE and what the DOE calls connected lighting systems (CLS), the agency projects that accurate knowledge of energy usage patterns along with intelligent control systems can pave the way for additional energy efficiency. The DOE referred to the technology as data-driven energy management.

This initial report is more of a stage setter than a finished work and we may see several follow-on reports. For instance, the DOE said it may study standardization and best practices for how to measure and report energy usage including data formats that could enable interoperability among products from multiple manufacturers.

The work is not necessarily limited to PoE systems and could be applied to wirelessly-connected systems. But the report notes that PoE may enable CLS functionality at lower costs in many cases and thus was a good place to start the research. Still, PoE comes with its own issues such as power losses on the low-voltage wires used to carry data and power to luminaires. See our recent feature for more information on PoE. Indeed the DOE said it might even study the impact of such losses in future research.

The report concludes with a lengthy list of recommendations by the authors. Among the recommendations, SSL manufacturers should develop energy reporting capability with an established level of detail. The authors even developed one possible format for describing PoE energy usage reporting. The initial study did not definitively answer the question of what, if anything, the DOE will do next in the area.

You can read the very lengthy report on the DOE website.

Street light FAQs

The DOE has also aggregated a number of resources related to LED street lights in one convenient place on its website. The agency has repeatedly stressed that LEDs can actually help the industry overcome issues with any blue light hazards and ultimately enable municipalities and utilities to reduce light levels and pollution. Nonetheless, the AMA work stirred more protests which in many cases involve citizens and politicians that don’t accurately understand the issues at hand. 

The AMA erred in simplifying the discussion around the CCT metric that does not accurately describe spectral power distribution (SPD) and potential issues such as circadian disruption. You can have any number of light sources with the same CCT and vastly different SPDs. The DOE documents accurately explain the issues at hand.

Straight shooting is critical in the street lighting area. We don’t need momentum derailed for a technology than can both slash energy usage and provide better light. And research may yet prove that people see better under cooler CCTs.

A Light Emitting Diode (LED) is a solid state light source that emits light by the electroluminescence effect. LEDs utilize the radiative recombination process of electrons and holes to generate light through photon emission. Electrons and holes are pumped into the space charge region in multiple quantum wells (QWs) under forward bias and they recombine to emit light.

The increasing demand for light emitting diodes (LEDs) has been driven by a number of application categories, including display backlighting, communications, medical services, signage, and general illumination. One barrier to the acceptance of LEDs in these applications is the relatively sparse information available on their reliability. There are many areas in need of improvement and study regarding LEDs, including the internal quantum efficiency of the active region, light-extraction technology, current-flow design, the minimization of resistive losses, electrostatic discharge stability, increased luminous flux per LED package, and purchase cost.

The construction of LEDs is somewhat similar to microelectronics, but there are functional requirements, materials, and interfaces in LEDs that make their failure modes and mechanisms unique. This means that comprehensive industry and academic research are required on LED failure mechanisms and reliability to help LED developers and end-product manufacturers focus resources in an effective manner. The reliability information provided by the LED manufacturers is not at a mature enough stage to be useful to most consumers and end-product manufacturers.

CALCE LED research group is providing the groundwork for an understanding of the reliability issues of LEDs across failure causes and their associated failure mechanisms, issues in thermal management, and critical areas of investigation and development in LED technology and reliability.

The goals of the CALCE LED research group are to improve the reliability and the qualification of LEDs for the LED manufacturers and LED lighting companies to better understand the LED failure mechanisms and useful lifecycle dynamics.

  • Knowledge-based qualification methods to develop data-driven, physics of failure (PoF) based, and fusion prognostic techniques for LEDs
  • Development of reliability improvement methods for LEDs utilizing prognostics and health management techniques:
    • To facilitate faster product development
    • To identify reliability risks under application conditions and mitigate them
    • To improve integration of PHM in LED lighting systems.

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