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MisLED? Fact and Fiction of LED Lighting

Oct 29, 2008

WAC Lighting


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Not many could argue that LED (Light Emitting Diode) Technology is the
hottest thing to hit the Lighting Industry within the last few years.
Whether attending a trade show or picking up the latest trade
magazines, it is very hard to avoid the buzz of LED Lighting. While
exposure to this technology continues to gain momentum in the public
eye, there seems to be a lot of questions around LEDs among
manufacturers, specifiers, distributors, and industry outsiders. This
is particularly the case regarding how the technology works and
the proper applications of the product.

The reality is that LED technology has been around for quite some
time. The original LED technology was discovered in the early 1900s.
Electricity was applied to the semiconductor Silicon Carbide and produced a very low level of light, too low for any practical use.

Since that time, there have been obvious improvements in the design and manufacture of products that have lead to the LEDs that we are now seeing in the marketplace.

Why the recent attention to this technology?
In light of the recent energy crisis and the flood of newer more compact
fluorescent technology, it becomes clear. Advances in energy efficiency
and decreases in production costs have made LEDs a new sustainable
solution for lighting. The big questions at hand are “How do LEDs truly
function?” and “What are the proper applications of the product?”

How LEDs Function
Light Emitting Diodes work very differently from common lighting
products. Very simply put, LEDs are just miniature electronic devices
that emit light. Whereas a common incandescent light bulb works by
heating a filament that burns hot enough to produce light, LEDs are
illuminated by the movement of electrons in a semiconductor material
and operate at a significantly cooler temperature. As there is no
true white LED, visible white light is achieved in one of two ways.
Either a combination of three LEDs emitting Red, Green, and Blue light,
or a phosphor coating is placed over a Blue LED, both of which is
expensive to manufacture consistently.

Currently the limitations of the technology for traditional lighting
purposes are that it is a single directional point source that at
maximum energy efficiency produces only low levels of light and
like all electronics, is sensitive to heat. Like other light sources,
LEDs produce more light when driven at higher wattages, but
unlike other sources their efficiency drops dramatically as thermal
management is needed to protect the electronics. However the
benefits that distinguish LEDs from other light sources are they
are small in size, do not emit ultraviolet radiation, and can
operate at very low wattages while producing light efficiently
and for a very long time.

Proper LED Applications
What about the proper application of this technology? Due to the
availability of various color temperatures and intensities, LED
technology has found a vast array of applications in the construction
industry. Outside of color changing theatrics, the majority of current
LED lighting applications is task and accent lighting. Whether you are
illuminating cabinets, coves or stairways, LED lighting is an
attractive lighting solution.

As a point source, LEDs can collectively direct light well to where
you need it. When choosing an LED product for task
or accent lighting, you might consider the following:

1. What is the lumen efficiency (lumens per watt) of the fixture?
2. Does the product manage glare?
3. If driven at over 1 Watt per LED, is there sufficient heat sinking
in the fixture?
4. Is the color temperature of the LEDs consistent? Is the color
temperature consistent with the other fixtures used in the space?
5. How do the costs compare to other options for the life of the
fixture?

But how well do LEDs serve as a general illumination solution? Since
it differs from traditional general illumination sources tremendously
in physical characteristics, strengths and weaknesses, this becomes a
monumental challenge. If put into fixtures designed around traditional
lamp sources, do LEDs even do as good of a job? Seemingly, this is a
race that will not be decided today, however the age-old tenet of "Let
the buyer beware." comes to mind. Here are several factors a
cautious buyer will be required to consider:

What color type or temperature of light is needed?
Color temperatures for LED lighting products currently on the
market range from 2700 Kelvin to 6500 Kelvin. 2700K provides a
very warm light with yellow and red hues while higher color
temperatures provide cooler crisper white light with bluer hues.
Like most aspects of design, color temperature is a function of
personal preference. 2700K brings out red tones better and
4100K brings out blue tones better. As a point of reference, a
traditional Edison lamp is around 2700K and noon daylight is well over
6000K. If using LED fixtures for task lighting, such as under cabinet
lighting for food preparation, you may consider using a mid-range color
temperature. Xenon white light is approximately 3000K and is becoming
the preferred color temperature for task lighting. In contrast, if
using for general illumination in a living room or dining room, you may
want a lower color temperature to create a subtler or warmer
atmosphere. Consumers often complain that LED recessed lighting is
“too bright." This could be due to the glare of the LED or simply due
to the higher color temperature.

What reflectors or diffusers are used to control the light?
Light control through the use of reflectors or diffusers also has a
tremendous impact as to LED fixture selection. Whereas most light
sources emit light in all directions, LED emits a tight beam in one
direction. Because of this LED light cannot be effectively dispersed
utilizing commonly used reflectors. The challenge to manufacturers is
to develop diffusers that can cut glare and disperse the light without
drastically cutting the efficiency. For example, nearly 60% of light
is lost when passing through standard acrylic diffusers. This is one
factor that certainly adds to the high cost of the product.

What are the limitations of the other components?
LEDs require a driver to operate. This is comparable to a ballast for
fluorescent lighting. Essentially an LED driver converts AC power to
DC power at a constant regulated rate. This prevents fluctuations to
the LED diode that would show inconsistent light levels and possible
damage due to abnormal current situations. What are the limitations of the
drivers? Two common limitations of the drivers seem to be centered on
dimming and the life of the product. Since drivers and dimmers need
to have a minimum load to operate, dimming can become a challenge. Pay
close attention to those products which are advertised as dimmable. While
they certainly may be able to be dimmed in the traditional mode, colors
may shift. If using PWM (pulse width modulation), the LED can be dimmed
from 100 to 5 percent without noticeable color shift and strobe. Pairing
of dimmers and drivers is important to the successful operation and
dimming of LED systems.

While LEDs boast up to 50,000 hours, the life of drivers may also be a
limitation.

What kind of budget are you working with?
As part of the Green initiative, we have heard, the term sustainability
used somewhat loosely. In general, sustainability refers to the
economical viability of using various solutions to address energy
concerns. In other words, can you afford the up front costs of the
solution? In most cases you can calculate a break-even point of energy
savings. However if recouping the costs are several years down the
road, the tough question needs to be asked as to whether or not it is a
sustainable solution for the end-user. While some people are looking
to commit to Green solutions for environmental reasons, the economic
side cannot be ignored. Other light sources may be a more efficient
and economical solution for meeting the same lighting requirements.
The range of low-voltage halogen and fluorescent lighting should be
considered in the design. Finally, the speed of technology advances in
LED efficiency makes lamp replacement a real concern in the design of
the fixture. Should an LED need replacement three years down the road,
will the replacement be economical? Will it be available?

What are your trying to accomplish by using LED lighting as a solution?
The final question that needs to be answered by the end user is “why
LED”. Do we want to be Green? Putting the right amount of light in
the right places is still the greatest opportunity for efficiency
gains. Energy efficient designs typically incorporate a variety of
lamp sources for different applications. Do we want LED in our homes
so we can show it off to the neighbor? There is no doubt that a great deal
of LED product is being sold on this factor alone. As the consumer
becomes more educated on sustainability, we may see a dramatic shift
even more to this kind of technology. It is also possible that when the
sustainability question is raised, other technologies may be considered,
such as compact fluorescent lighting and dimmable low voltage lighting.
As the demand and production increases on LEDs, the technology will
improve and costs to the market will certainly decrease making it more
sustainable to the masses. With regards to where LED is actually
used…the verdict is still out.



This article was written by Michael Hadank, National Sales Manager
of WAC Lighting Company. The firm can be reached at 1.800.526.2588 or
on the web at www.waclighting.com.



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