Evaluating LED Lighting
Acuity Brands, via its Lithonia Lighting unit, has developed LED lighting system selection criteria for indoor, general ambient applications. These guidelines were created to help those specifying this lighting technology to identify high quality solutions that will effectively deliver on the promise of the benefits of LEDs.
“Indoor LED lighting has hit the lighting mainstream and certainly has many benefits, including energy savings, extended life expectancy, reduced maintenance and improved sustainability. However, if the LED lighting does not perform as expected, then the benefits are never realized,” said Dave Ranieri, vice president and general manager, Lithonia Lighting® Commercial Indoor Products. “It is essential to conduct a thorough review of indoor LED luminaires using six general performance criteria prior to making a final purchase decision.”
Guideline #1: Standard Criteria: Even though LED lighting is a relatively new technology, standard evaluation criteria still apply. Use basic lighting specification tenets to determine lighting quality, efficiency, and aesthetics. For example, the proposed LED lighting solution should be better at delivering energy savings over time than the system being replaced or any available standard linear, compact fluorescent, or other general lighting options. To be considered, the LED lighting solution should incorporate the design aesthetic of the application and complement the interior space.
Guideline #2: Thermal Management: Determine how heat is managed in the overall LED lighting system. Even though LEDs run cooler than they did just a couple of years ago, thermal management is still fundamental to the performance of a solid state lighting system. Heat affects the efficacy of the luminaire source, system life expectancy, and the color quality and consistency of LEDs. LEDs that run on the hot end of their design range will degrade faster and more unpredictably than those that are running cooler.
Guideline #3: Color Quality: Until the Color Quality Scale – a new industry standard that will more effectively measure LED lamps across multiple color quality aspects – is completed, use the color rending index (CRI) to determine color quality. An indoor LED fixture for general ambient lighting should have a minimum CRI of 80.
Ask the luminaire manufacturer how color consistency is managed using binning (sorting), color mixing, and/or controls. The process of manufacturing white LEDs is inherently inconsistent relative to color quality and requires rigorous production controls to ensure high quality and consistency are maintained through binning.
Guideline #4: Lumen Output: Determine the LED system’s delivered lumens and system efficacy or lumens per watt (LPW). This information will enable you to determine if an LED solution can meet your lighting objectives effectively and efficiently. Check the manufacturer’s published data for this information and ensure that it has been derived in accordance with IESNA LM-79-08.
Guideline #5: Adaptability: Research the adaptability of the LED lighting system. Once LED luminaires are installed and despite their long life, it should be easy to replace or upgrade components as well as reconfigure the existing system if the interior space is updated or redesigned.
Guideline #6: Digital Lighting Controls: Use digital lighting controls when possible to achieve maximum benefits. LED luminaires should be “control friendly” and become more efficient as they dim. LED lighting should also be fully compatible with occupancy sensors, daylight harvesting controls, manual dimming, and full-scale energy management systems. Insist on compatibility testing or compatibility proof before venturing too far into a specification involving controls. Otherwise, if all “electronic components” are not in sync, multiple commissioning problems and/or a drop off in dimming capability often result.
U.S. DOE Program A Useful Source On LED Performance
A comprehensive source of LED lighting product evaluations is the U.S. Department of Energy (DOE) SSL Commercially Available LED Product Evaluation and Reporting (CALiPER) program independently tests and provides unbiased information on the performance of commercially available Solid-state lighting (SSL) products. SSL technology uses semi-conducting materials to convert electricity into light, and SSL is an umbrella term encompassing both light-emitting diodes (LEDs) and organic light emitting diodes (OLEDs).
Test results gathered through the CALiPER program guide DOE planning for ENERGY STAR and technology procurement activities, provide objective product performance information to the public, and inform the development and refinement of standards and test procedures for SSL products.
DOE supports testing of a wide, representative array of SSL products available for general illumination, using industry-approved test procedures. Guidelines for product selection ensure that the overall set of tests provides insight on a range of lighting applications and product categories, a range of performance characteristics, a mix of manufacturers, a variety of LED devices, and variations in geometric configurations that may affect testing and performance.
Commercially available products are purchased and then tested by one of several prequalified lighting testing laboratories arranged to assist this program. All luminaires are tested with both spectroradiometry (in an integrating sphere) and goniophotometry, along with temperature measurements (taken at the hottest accessible spots on the luminaire) and off-state power consumption.
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