Solid-state lighting — using light emitting diodes for general illumination — offers a host of advantages over incumbent technologies. For starters, LED lighting is five times (or more) as efficient as incandescent lighting, it has no components requiring hazardous material waste provisions (as do fluorescent lamps), and LEDs instantly respond to electric current, eliminating the delays inherent in high-intensity-discharge at startup and allowing the illumination level to be controlled. And those really are just for starters, as there are many other advantages.

But LED lighting has one big disadvantage: it’s completely different from other lighting technology. For example, LEDs are generally driven with DC current as opposed to the AC that powers just about every other source. Another big difference is that LED packages themselves (the LED chip, encapsulant, and primary optics) shape and direct the light. Contrast that with the tungsten-alloy filament at the heart of an incandescent bulb. When the filament heats up it puts out light (about 5 to 10 percent of its electrical power usage) in every direction.

Manufacturers can make specialty incandescent bulbs that have internal mirrors to direct the light in a certain way, but in general, one light bulb is just like another. You can replace a Sylvania bulb with a General Electric bulb with a Phillips bulb and you can put it in a desk lamp, an outdoor sconce, or a recessed fixture. Incandescent bulbs are commodities because the physics determines how a filament works, and there’s not much any manufacturer can do do distinguish their offering from another company’s. The good part is the interchangeability; the bad part is that the light output of incandescent lamps is cut down by the fixture efficiency (the amount of light that doesn’t get where you want it to go. Because the light from the bulb itself is uncontrolled — spreading out in every direction — you can’t match a bulb to the fixture in which you’d like to put it, so light (and energy) is wasted.

Matching the Light Source to the Task

What if, though, you could buy a different light bulb for every fixture, one tailored to minimize wasted energy for that one particular application? It would be expensive. And every few months or so it would burn out and you’d need to run down to the hardware store and buy a replacement bulb (selecting from the scores your retailer would need to keep in stock). So that’s not really a viable solution for incandescent bulbs. But it is for LEDs.
One of the advantages alluded to above is that LEDs can last a really long time (there are some issues with exactly how long, but that’s for another day). Long lifetime means that it’s reasonable to select an LED lighting solution specific to each application — because you won’t need to change it out for 5, 10, perhaps even 20 years or more. In practice, it’s a little more complicated than that because there’s not just one LED that will go in every desk lamp or cove light. Every luminaire (light fixture) manufacturer selects and arranges LEDs in a different fashion. So if you really want to optimize LED lighting you have to buy an entire fixture. It’s still a money-saving proposition (it’s not uncommon for industrial customers to get payback times of anywhere from a few years to several months), but it creates a dilemma for LED lighting.

LED lighting can be forced into an Edison-Screw bulb.  Image from U.S. Department of Energy.

LED lighting can be forced into a traditional incandescent bulb shape — but should it be?
Image from U.S. Department of Energy.

Retrofit or Redesign?

LED lighting manufacturers have two choices: they can make fixtures that optimize the distribution of light to fully take advantage of the new capabilities offered by solid-state lighting, or they can design retrofit bulbs that can be put into place as one-for-one replacements of existing incandescent or fluorescent fixtures. At last week’s LED Show the dilemma was (quite literally) on display. The purists argue that forcing LEDs to mimic (crappy) incandescent or fluorescent sources will set the industry back because customers will see energy savings, but not much more of the advantages of LED lighting. The retrofit folks argue that the replacement bulb solution lowers the barriers to entry, giving LEDs an absolutely necessary foothold into the general illumination market. At times, there’s some visible contempt expressed on one side or the other.

The logical path (one that’s already being played out) seems to be that retrofit solutions get LEDs in the door, where they then get to display some of their other advantages. Those bonus advantages then create showcase solutions that become selling points for designs that fully embrace the LED lighting solution.