PORTLAND, Ore. —Light-emitting-diodes (LEDs), once quoted to have 100,000-hour lifetimes, are still working today in some front-panel indicators after 30 years of service. But the advent of high-intensity LEDs for solid-state lighting sacrifices longevity by operating at temperatures too high for lifetimes much longer than a few years.
Now Oak Ridge National Laboratory (ORNL) claims to have rolled back the calendar on LEDs with a graphite foam material that keeps even high-intensity LEDs as cool as those used for front-panel indicators, thereby reclaiming their long lifetimes. ORNL recently granted an exclusive license for their graphite foam technology to LED North America (Oak Ridge, Tenn.) an ORNL-spinoff located in the adjacent Technology 2020 "incubator" park.
According to ORNL, decreasing the operating temperature by 10 degrees can double the lifetime of LEDs. As a result, municipalities can change over their existing mercury-vapor lamps for LEDs to save millions on their electricity bill without suffering premature failures due to overheating. As a result of their cool-running graphite foam heat sinks, LED N.A. aims to offer retrofits for street lights and parking garage lighting with warrantees that are longer than its competitors.
ORNL researcher James Klett developed a graphite foam technology that can help cool LED light fixtures and extend their lifespan.
Graphite foam is light and porous like Styrofoam—with 25 percent density—making it easy to machine into heat sinks, but with the vastly superior thermal conductivity afforded by the pure-carbon material compared to conventional metal heat sinks. Ligaments in the foam "wick" heat away from its source, according to ORNL, rather than just heat up with the LED like a conventional heat sink.