LED comments by an early innovator
Mal Oldis, an earlier innovator with LEDS, contacted me recently with the following comments on our report LED as a fluorescent substitute:
I have read with interest your assessment of LED lighting vs Fluorescent lighting. Well done!!
I have done much work with LEDs and yes, much credibility is lost due to false and exaggerated claims.
Indeed a company for which I was in charge of product development, failed partly due to exaggerated claims.
I probably built the first LED replacement (in Australia) for a T8 over 10 years ago.
I learn t much from Agilent’s LED division in San Jose and also from the team at Philips in Holland.
Can I comment on your (very good) report?
I am not suggesting that you do not understand these issues, but there is some technical issues that commonly do not seemed to be explained to potential LED users.
Life time issues. Rated life time for LEDs and Fluorescent lamps is very different but the same term is used.
Rated life time of fluorescent lamps is usually stared time taken (under specified switching cycles) for half the lamps (median life) to fail.
Between 6 to 30 thousand hours are possible.
The rated life under these conditions for most LEDs is around 1.4 million hours. The “life time” quoted for LEDs of say 50,000 hours (typical for white) is the 50% radiant (photometric) output level. It is interesting to note move to 70% output as noted in your report.
It is common to use the LOR (Light Output Ratio) figure for luminair directly. Also lumen maintenance can vary considerably for a luminair that uses fluorescent lamp due to dust and other contamination on the tube and the reflector, which forms part of the secondary optics.
Any secondary optics (diffusers etc) using LEDs is simpler and therefore more efficient.
When I talk of the economics of LED lamps, I create an economic model and refer to cost of ownership which includes various maintenance regimes.
Also there is often no mention of the spectral properties, notably the Color Rendering Index which is poor for Fluorescent and even poorer in LEDs.
I did the original engineering for the BP Neon replacement for the service station canopies, and did much work with the City of Port Phillip using LEDs for public lighting.
Cheers,
Mal Oldis.