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 Lighting in a typical household may only account for about
10% of the consumer's energy bill. But even this fraction, along with the cost
of bulb replacement, can add up over time. Light emitting diode (LED) technology
aims to make improvements to fixture life and lighting efficiency. However, like
many "new" technologies nowadays, the initial cost of LED lightbulbs is the
biggest obstacle.
Retail prices for LEDs pale in comparison to their
incandescent and compact fluorescent competition. You can buy a 60W CFL for $4
and a 60W incandescent for a dollar, but an LED equivalent would cost between
$15 and $25. The supposed increased lifespan of LEDs (and the associated "cool"
factor that comes with new tech) isn't nearly enough to justify this price gap
for most people.
<--(This 8W, 60W equivalent LED lightbulb from TigerDirect
costs $24.99. Yikes! Image Credit:
TigerDirect.com)
A few months ago I
reported on the current state and future prospects of LED technology. Part
of this report focused on Soraa, a
solid-state-lighting startup company utilizing a new approach to producing
LEDs. Their aim is to construct LEDs using gallium-nitride as the substrate, resulting
in fewer defects. These bulbs produce 10 times the light of other types of
LEDs, ideally allowing for much higher lighting efficiencies (i.e. more light
per unit power).
Gallium-nitride is also much more expensive, however. Other
companies are vying for more traditional approaches that grow minimal amounts
of gallium-nitride on sapphire or silicon based substrates. Most believe that
LED manufacturers will continue to look on these designs much more favorably.
Osram
Opto Semiconductors, one of the world's largest LED manufacturers, says it
has perfected a technique that may reduce production costs. The process
optimizes the use of silicon as the substrate on which to grow gallium-nitride.
Silicon is currently about a third the cost of sapphire, bolstered by record price drops over the past couple years.
(A 15-centimeter silicon wafer for
gallium-nitride-on-silicon LEDs. Image
Credit: Osram)
The trick in the process is overcoming the difficulties of
material expansion. Because LEDs are made at high temperatures, the layers of
material need to be cooled afterward. During cooling, the two materials expand
at different rates, causing the gallium-nitride layer to crack due to tension
from the silicon underneath. The cracking results in impurities and defects
which render the product inefficient or unusable. The fix involves growing
additional thin films of different materials in order to balance out the
tension.
Osram's new LEDs are said to produce 127 lumens per watt of
power, with a power efficiency of 58 percent. The company hasn't released any
estimates on the cost of its new LEDs, but others using this silicon-based
approach say price reductions could be 75% or more. One company, Bridgelux,
predicts that for 75-watt equivalent LED lightbulbs, the numbers could drop
from $40 to under $5.
If the past is any indicator, I am skeptical at best of
these grand predictions. But if they do come to pass, I would expect to see a
lot more people giving LED lightbulbs a try. Certainly there are other practical
difficulties with LED technology, not the least of which is the amount of waste
heat generated by these devices. But solutions to these concerns will likely be
addressed more fully as these products begin to make their way into the
consumer market.
References
Cheaper
LED Lightbulbs Are on the Way - Technology Review
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