Number-nerds will rejoice in the graphs and data-crunching of an August 2012 U.S. Department of Energy (DOE) study—Life-Cycle Assessment of Energy and Environmental Impacts of LED Lighting Products—which assessed the results of 10 other studies and compared the total life-cycle impacts of LED, CF, and incandescent lamps. The results weren’t surprising—spoiler alert! LEDs came out on top—but the slim margin between the top two efficiency contenders was.
The three-part study looked at the energy required for lamp use, manufacturing, transport, and disposal. Since the lumen output and lifetime for each lamp type are not equivalent, the study measured each lamp’s energy use with a “functional unit” of 20 million lumen-hours—the estimated service life of a single 12.5 W LED lamp (60 W incandescent replacement) over its lifetime. An incandescent or CF lamp provides less lighting service than the functional unit value, so in order to make an apples-to-apples comparison, life-cycle energy estimates are multiplied by the number of lamps needed to reach this equivalence.
According to the analysis, the “use” phase of incandescent, CF, and LED lamps is the most energy-intensive portion, accounting for approximately 90% of a lamp’s total life-cycle energy. The manufacturing and transport phases follow, respectively—with energy use due to transportation representing less than 1% of life-cycle energy for all lamp types. The uncertainty with LED life-cycle assessment centers on the manufacturing of the LED package (including substrate production, LED die fabrication, and the LED assembly). Low estimates indicate that the LED package contributes to 0.10% of life-cycle energy use, while high estimates show it could be as much as 27%. The average indicates that LED package manufacturing is likely at about 6.6% of total life-cycle energy use.
The analysis concluded that LED replacements and CF lamps are similar in their life-cycle energy consumption, with the difference largely determined by the manufacturing aspect. During their lifetime, LEDs and CF lamps consume 3,890 and 3,950 megajoules (MJ) per 20 million lumen-hours, compared to an incandescent lamp’s energy consumption at 15,100 MJ per functional unit. The energy used to manufacture can be from four (CFs) to eight (LEDs) times as much as an incandescent.
By 2015, if LED lamps meet performance targets, their life-cycle energy use is expected to decrease by approximately 50%, which will give them a big efficiency gain over both CF and incandescent lamps. Improvements to current manufacturing methods and procedures are expected to reduce the manufacturing energy use, but the biggest gain will likely be due to an increase in LED lamp efficiency, resulting in fewer watts required to provide the same amount of lumens.
By 2030, the DOE forecasts that LED lighting will represent 74% of lumen-hour sales in the U.S. general illumination market. From 2010 to 2030, the cumulative energy savings is estimated to be 2,700 terawatt-hours, which at 2010 energy prices and electricity-generation-mix conditions represents approximately $250 billion in savings and a greenhouse-gas emission reduction of roughly 1,800 million metric tons of carbon dioxide.
The environmental impact of the incandescent lamp’s energy use were markedly more significant than for CF and LED lamps because of its low efficiency. The CF lamp is slightly more harmful than the 2012 LED lamp against all but one criterion: hazardous waste sent to the landfill. The energy and environmental impact of the manufacturing of the aluminum heat sink used in LEDs causes the impacts to be slightly greater for the LED than for the CF. The study notes that heat sinks should diminish in size for succeeding generations of LED lamps as efficiency gains are made. Environmental impacts of a 2017 LED, for example, are predicted to be about 50% lower than the 2012 LED and 70% lower than the CF.
A variety of LED, CF, and incandescent lamps—a total of 22 samples, representing 11 different models—were tested to determine whether any of 17 elements were present at levels exceeding California or federal regulatory thresholds for hazardous waste. Most of the lamps were found to be well above the California threshold for copper, regardless of technology, and some approached or exceeded the threshold for nickel. The selected models were generally found to be below thresholds for federal regulation. The study noted that the greatest sources of hazardous waste were the metal screw bases, drivers, ballasts, and wires or filaments—the diodes themselves generally did not cause LED lamps to exceed thresholds
—Compiled by Kelly Davidson
Read the full report at bit.ly/LampTech