Lighting LEDs
T
alk to anyone involved in UK government a product which at present is not only an expensive
energy policy and you will get an unequivocal option compared with conventional low-energy sources
endorsement of LEDs as the efficient light such as ceramic metal halide or fluorescent, but which
source of the future. After a long haul with still has unresolved problems.
consumers who have been stubbornly resistent to There are still difficulties with white colour
compact fluorescent lamps, policymakers have fallen quality, stability and consistency. Beefing up the
on the white LED as the panacea for the thorny problem light output to match conventional sources still
of a decent quality light at a low-energy price. involves a consequential increase in heat and the
In the US, this technology has been hailed as some issue of how to dissipate it. There is still the matter
sort of lighting saviour. ‘No other lighting technology with some companies of wildly optimistic and often
offers the department and our nation so much unsubstantiated claims about longevity - though the
potential to save energy and enhance the quality of our original estimates of a 100,000-hour lifetime have
building environments,’ declares the US Department been quietly modified to 50,000 hours.
of Energy. In addition, quantification of light output is often
Manufacturers, including all the major lamp based on the LEDs themselves rather than the output
companies, have invested billions in the development of the fitting, which itself can be affected by the
and perfection of the white LED. Philips has bought optics, electronic driver losses and thermal losses:
up companies representing every stage of the LED the temperature of the p-n junction of the raw LED is
production process and market, and has withdrawn measured at an ambient temperature in the vicinity of
from the traditional-source interior lighting sector to the LED of 25 deg C, whereas in a luminaire it will be
concentrate solely on LED luminaires. operating at a higher temperature.
And so the pressure is on for the widespread take- LEDs still have no standards or an agreed method of
up of the technology. And yet, we are dealing with measurement. Apparently, no fewer than five technical >
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www.cibsejournal.com February 2010 CIBSE Journal 45
CIBSEfeb10 pp44-45,46,48_Leds.indd 45 28/1/10 16:39:11
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