Rapid Adoption of LEDs

By Armando Emanuel Roggio, Sr.

Contributed By Hearst Electronic Products


A new U.S. Department of Energy (DOE) report estimates that the rapid adoption of LEDs for general lighting applications could slash U.S. consumers' energy bills by some $120 billion in just 20 years and save 1,488 terawatts of power in that same time frame.

Thanks to energy-efficient LEDs, total U.S. lighting power consumption could be cut 25 percent by 2030. Put another way, the U.S. could light 95 million additional homes, without increasing consumption by one watt compared to incandescent and fluorescent lighting options.

LEDs Must Match White-Light Performance, Fit Sockets

The DOE report makes a few assumptions about LED technology for general lighting applications, including assuming that LEDs can make significant improvements in white-light emission and, therefore, compete with existing white-light solutions.

"Solid-state lighting (SSL) has the potential to revolutionize the lighting market through the introduction of highly energy-efficient, longer-lasting, versatile light sources, including high-quality white light," the DOE report said. "Previously relegated to colored-light applications such as traffic signals and exit signs, SSL (LED and OLED) products are now successfully competing with conventional technologies including incandescent and fluorescent lamps in general illumination applications."

The DOE's assumptions about white-light performance are seemingly well-founded. For example, shortly after the DOE report was released, Cree, Inc. of Durham, N.C. announced two new white-light LED solutions.

These new XP-G LEDs extend Cree's product line across the white color spectrum, increasing the potential for general lighting applications such as LED replacement lamps, office lighting, and other outdoor and commercial uses.

Specifically, Cree's warm white, 3,000 Kelvin (K) correlated color temperature (CCT) XLamp XP-G LED produces approximately the same level of white light as a 200-watt incandescent bulb. According to Cree, this warm white solution "provides up to 114 lumens and 109 lumens per watt at 350 mA."

Cree LEDs

Similarly, Cree's new 4,000 K neutral white XP-G LED "provides up to 139 lumens and 132 lumens per watt at 350 mA" with a CCT beyond a tungsten lamp.

The DOE report also assumes that white LEDs can be designed in a form factor that fits existing sockets.

"For example," the DOE report said, "consider a general service incandescent lamp, A-19. A self-ballasted LED lamp that has a cluster of LEDs in place of the tungsten filament could be fabricated as a direct replacement for that incandescent A-19 lamp. Similarly, a self-ballasted OLED lamp could be created, for example, where the OLED material is deposited directly onto the surface of the pear-shaped glass bulb, and the resulting light emission pattern resembles that of a frosted incandescent A-19 lamp."

In some ways, just how quickly LEDs can be adapted to general lighting applications will fall to the lighting designers and electrical engineers designing and building the current and next generations of lighting solutions. If these engineers choose leading-edge LEDs, seek energy efficiency, and work with leading suppliers to ensure availability, the DOE's cost and energy savings projections could be realized.

Projected Improvements in LED Performance

In order to save $120 billion in U.S. energy bills, the DOE is also assuming that LED performance will improve.

Again, this is probably a very safe bet, considering that LED makers generally experience a high level of competition and, therefore, frequently innovate.

For the purpose of analysis, the DOE divided LEDs into four color-rendering index (CRI) bins.

"While there are several metrics that describe the quality of light, no single metric is able to capture all aspects of light quality," the DOE report said, adding that its "analysis uses CRI as an indicator of quality, differentiating between tasks that require low, medium, high, and very high CRI. This assumption does not have any influence over the stated energy savings estimate; rather, it is simply a convenient surrogate for classifying and differentiating between lighting technologies."

Using these bins as described, the DOE estimates LED performance improvements through 2030.

Lumens per watt 2010 2015 2020 2025 2030
Low CRI (<40) 86.2 127.5 168.8 193.5 204.1
Med CRI (41-75) 77.7 118.5 157.6 180.3 189.8
High CRI (76-90) 64.3 107.1 147.3 168.5 176.3
Very High CRI (91-100) 50.2 91.6 133.5 156.8 165.8

Table 1: LED Efficacy Improvements for DOE Scenarios

As an example, the DOE projections that efficacy for very high CRI LEDs will reach 165.8 lumens per watt by 2030. Some manufacturers are already ahead of the DOE's projections.

Again, if the DOE's projections are to be accurate, EEs will need to lead the way by integrating LEDs into current designs and defining the specifications for tomorrow's general lighting applications.
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