LED Lighting Head-to-Head Test Results
As solid-state lighting (SSL) technologies enter the market, there is much skepticism about performance claims made by manufacturers and retailers. The Department of Energy (DOE) has begun to independently test commercially available SSL products. The intent is to provide an unbiased evaluation of product performance in order to support market penetration of SSL products. The DOE Energy Efficiency & Renewable Energy (EERE) group's Market-Based Programs section formed a specific program for SSL testing in 2006. The program name is Commercially Available LED Product Evaluation and Reporting (CALiPER) program. One aspect of the program is to benchmark SSL performance against traditional lighting across a range of standard lighting measures. This article reviews the results of three CALiPER benchmark reports that evaluated LED replacements for linear fluorescent, halogen incandescent, and regular incandescent lamps.
Study 1: T12 and T8 versus LED
Performance of T12 and T8 Fluorescent Lamps and Troffers and LED Linear Replacement Lamps (January 2009)
In the tests comparing T12 and T8 florescent lamps with LED linear replacement lamps, various elements were tested to achieve a better understanding of performance. According to the report issued by CALiPER, the tests were designed to evaluate, "a range of standard lighting measures, including power usage, luminous flux, photometric distribution, source and luminaire efficacy, correlated color temperature (CCT), and the color-rendering index (CRI)."
These lamps were evaluated in two settings: basic lamp performance, and performance with regular and parabolic troffer luminaires.
The lamp performance between T8 and T12 lamps is dependent on the type of ballast used and the coating. Usually T12 lamps come with a magnetic ballast, which does not have a high range of adjusting power quality. The halophosphor coating used on most T12 lamps also does not provide much color rendering, as it was created to produce one basic color (white). Conversely, the T8 lamp includes an electronic ballast, which has better light output and efficiency. The T8 lamp also uses a "triphosphor blend," to include an even amount of red, blue, and green.
LEDs differ from traditional T12 or T8 lamps in that they are not constructed with mercury to emit light and produce a more focused, directional light source.
The troffer, or the structure that houses the lamp, can have an effect on the light output based on its shape. The parabolic troffer is curved around the edges and the 'lensed' or typical troffer has straight angled edges.
The conclusions offered by this research shed light on the differences between the types of lamps and their adjoining fixtures.
Based on the formula for fixture efficiency (or luminaire efficiency), CALiPER found that, "the fixture efficiency for parabolic louver troffers ranges between 64% and 90%, averaging approximately 74%. The CALiPER-tested parabolic louver troffer achieved a fixture efficiency of 60%, lower than its rated efficiency of 76%."
Another important measure for a troffer is its light distribution. CALiPER found that the best possible light distribution for a parabolic troffer is to be at 90 degrees horizontally and 45 degrees vertically, at 3,940 cd/m².
In the area of LED replacements for T8 and T12 lamps, LEDs do not compare in light output. According to CALiPER, "the best performing bare lamp using LEDs produces only one-third the light output of a typical 4-ft fluorescent lamp." Furthermore, when LEDs were compared with both T8 and T12 lamps in spacing criteria, the LEDs had a lower overall value for spacing, meaning that more fixtures would need to be installed to achieve the same amount of light output as a fluorescent lamp.
Power efficiency and compliance with ENERGY STAR standards was the most significant area in which the two types of lamps differed. ENERGY STAR requires a 0.7 to 0.9 power factor, and, "none of the LED replacement lights met the minimum ENERGY STAR commercial power factor requirement of 0.9." Though CALiPER professes that florescent lights are not at top performance, they recognize that the LED is not an adequate replacement.
Study 2: MR16 versus LED
Performance of Halogen Incandescent MR16 Lamps and LED Replacements (November 2008)
CALiPER also conducted a benchmark study on the differences between MR16 and LED lamps. Once again, the tests were designed to evaluate, "a range of standard lighting measures, including power usage, light output and distribution, source efficacy, correlated color temperature (CCT), and the color rendering index (CRI)."
MR16 (or multifaceted reflector) lamps are primarily used for directional lighting in retail, residential, and commercial applications. Low-voltage lamps, must be designed to withhold 10 times that of a line-voltage lamp. This is due to the low-voltage lamp containing a shorter filament. They also may require transformers to provide the proper amount of transference of electrical current to the lamp.
Power (W) = Supply voltage (V) x Supply Current (A)
Additionally, these lamps emit varying levels of light output, from low to medium. Their light distribution is based on its beam angle, or beam spread, which is meant to focus on a single object or location. The MR16 is also constructed with an aluminum or dicroaic coating. Dicroaic coating reflects light forward and infrared radiation backward, and aluminum is opaque, directing the light only forward.
The LED replacements for these types of lamps vary significantly. Unlike MR16 lamps, LEDs emit very small amounts of infrared radiation. Although this may be a plus, the LED replacements would not be very compatible with the electronic transformers because they do not use enough load for operation of the lamp. Other control devices, like dimmers, would not work with LED replacements due to "minimum load requirements" as well.
Similar to the results with T8 and T12 lamps, the LED light output does not match up with the halogen MR16. The tests reveal that, "only one or two of the LED products come close to matching the lumen output of the lamps they are intended to replace." In evaluating efficacy, it would take multiple LED lamps to produce the same amount of light output as an MR16, negating their, "potential energy saving," characteristics.
Also, the size and fit of LED MR16 replacement lamps is problematic. Most LED replacements are either too long, too wide, or do not work in the socket.
Overall, LEDs would only be a more useful replacement for MR16 lamps, if they were used in an area that requires a lower amount of light. CALiPER cites many manufacturing claims about both LED replacements and MR16 lamps to be incorrect, so they recommend testing before buying large quantities.
CALiPER Summary Reports
The DOE publishes Summary Reports following completion of each round of CALiPER testing. The Summary Reports provide detailed analysis of the test results for all products included in each round of testing. Over 200 products have been tested through the CALiPER program to date.
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