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LED domestic lighting
In article ,
writes:
Andrew Gabriel wrote:
In article ,
Grunff writes:
Mary Fisher wrote:
Is there such an animal?
They exist, but the best LEDs are currently only around the
same efficiency as filament lamps, which means they get just as
hot and die quickly or are lower power and lower light output
(if you are thinking along the lines of retrofit lamps).
They don't get to the efficiency of fluorescent lamps yet.
They are *far* more efficient in bicycle lamps, the latest LED cycle
lamp (the CatEye LED300) is just as bright as their old standard
krypton bulbed lamp (the HL-500 was it?) and runs several times as
long.
I don't know whether this is down to them being efficient at low
voltages or what but has revolutionised cycle lighting, front lamps
can now realistically be run on AA cells.
Sorry, but this is a very common misconception.
They can produce excellent high brightness narrow beams of light,
which a filament lamp can't. This can be an advantage in some
applications like spotlamps so the beam might look brighter than
a filament lamp. However, if you take something like a 10º beam
angle, which is 78 square degrees, and divide by the 41253
square degrees in the sphere which a filament lamp lights, this
shows that the LED is only lighting up 0.2% of the area which
the filament lamp did. That's why they appear so efficient, but
in fact they aren't.
Nobody can currently get 30 lumens/watt from a white LED, which
is what you get from highest efficiency halogen lamp. Nichia are
predicting 60 lumens/watt for a product they expect to ship in
2005, which is still less than a fluorescent lamp. The efficiency
improvement manufacturers have managed over the last couple of
years is very disappointing compared with what went before, so
it may be that some type of limit has now been reached without
a significant change in technology.
--
Andrew Gabriel
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