2010-07-15 13:19:46 UTC
Nichia. (Invited Lectures are 30 minute lectures. There are also 15
minute Landmark Lectures and then Posters.)
The abstract for the Nichia talk mentioned a 200 lm/W LED. This turned
out to be a 20 ma laboratory LED that produced light with an efficacy of
197 lm/W at a color temperature of 5500K. The CRI was not given. No
data was given for lower color temperatures.
We were also shown a 6.9 watt LED-based lamp that we were told is a
replacement for a 12 watt CFL, yet the LED-based lamp produced only 380
lumens compared to 810 lumens for the CFL it was replacing.
Near the end of the talk, we were shown an LED array composed of 56 LED
chips, and that produces 10,000 lumens at 105 lm/W at 4000K. No data was
given for lower color temperatures. This lamp operates at 96 watts.
Questions were raised about dissipating the heat from this 96-watt
array, and it became apparent that Nichia has not yet done any life
tests on this high power array. (It's also not clear that it has been
run continuously at 96 watts.)
During the Q&A I asked for confirmation that all this output and power
data was obtained with pulse current measurements at a junction
temperature of 25C. That was confirmed. I then asked what the efficacy
loss would be at a typical junction operating temperature, such as 100C.
I'm not sure the speaker understood the question, because he was first
confused, and then said 20% loss, which seems too much.
During the poster session, I went back to talk to the person with the
amazing magnetic ballast I discussed in the Day 2 report. Here is a
summary of his data:
Lamp: Philips F28T5 (CCT unknown)
Ballast Input Power Lamp Output System
(watts) Power (lumens) Efficacy
His magnetic 32 28.766 2415.5 75.38
Philips 30.95 26.30 2188.1 70.70
Osram 30.90 27.62 2263.8 73.26
The author confirmed that he used the same lamp for all three
measurements, and made the three measurements on the same day in the
same integrating sphere, so that removed one source of error. When
asked how he explained his unusual results, he said that the 10% high
frequency efficacy gain had had only been confirmed in T12 and T8 lamps,
so, perhaps it did not exist in T5 lamps. (He later said that he had
another paper with 40 lamps that showed that the HF gain in T5 was 5% TO
6%, not 10%.)
I told him that it was possible, but unlikely, that he had discovered
something, but when you are disputing 40 years of data, you have an
extra obligation to make sure you do not have any errors.
For example, based on his data, the Philips F28T5 lamp he was using, and
which is rated by Philis for 2900 lumens at 32 watts (103 lm/W) was
operating at only 82 to 83 lm/W in his experiment. That, by itself, is
enough to raise questions about his measurement setup, and was enough
for me to decide that this experiment is fatally flawed.