The term light-emitting diodes (LEDs) is one that’s subject to problems when one is writing about them. It doesn’t matter if you say “a LED” or “an LED” because someone is bound to moan and groan that you’ve got it wrong. Even worse, they typically use a supercilious tone dripping with contempt and condescension as they point out their perceived error of your ways.

The same thing applies to other words, like system-on-module (SOM). Should we say, “a SOM” or “an SOM”?

Which is right in these cases, “a” or “an”? The answer is “both” qualified by “depending on…” As I said in my recent Something M-azing This Way Comes column:

SOM is one of those abbreviations like LED that causes endless grammatical confusion. Should we say, “a SOM” or “an SOM”? Yes. It all depends on how you think about it and how you say this abbreviation when you are talking. If you say it as “SOM” to rhyme with “mom,” then “a SOM” is the way to go (similarly, “a LED” to rhyme with “bed”). This is the way I think about both of these. However, if you spell this abbreviation out as “S-O-M” then “an SOM” (that is, “an S-O-M”) is the preferred pronunciation and spelling, because the “S” sounds like “ess” and so acts like a vowel (similarly “an L-E-D” because the “L” sounds like “ell”). English: you have to love it. The bottom line is that both are correct, and the main thing is that—whichever you choose—you are consistent.

But we digress…

“I like big LEDs and I cannot lie” (with apologies to Sir Mix-a-Lot). I’m currently working on a bunch of projects in which tricolor LEDs play no small part. Although people always say LEDs don’t consume much power, they mean in comparison to something else, like incandescent lighting. Power considerations become increasingly important when you start to talk about hundreds or thousands of LEDs.

So, I was intrigued when my friend Joe Farr sent me an email with a subject line of “This is interesting” and a link to a YouTube video on something called Biomimetic LEDs, where “mimetic” refers to things that imitate or echo something else.

Nature, in the form of biological evolution, has come up with some very efficacious solutions to a wide range of problems. For example, shark skin has a texture that dramatically reduces drag and increases efficiency. Replicating this texture on the bodies of aircraft can make air travel more efficient and lessen its negative environmental impact.

The aforementioned video talks about the extreme efficiency of bioluminescence in fireflies. It also talks about the two types of efficiency associated with LEDs, which are electrical efficiency (the amount of electricity going in compared to the amount of light being generated) and extraction efficiency (how much light is emitted from the LED compared to how much is generated).

It turns out that a large part of a firefly’s bioluminescent efficiency is due to the asymmetrical surface on its lantern, which provides high extraction efficiency. Replicating this surface texture on different elements inside a LED can result in increased efficiency, which translates as “brighter for the same amount of power” or “lower power for the same amount of brightness.”

So far, so good, but this is where I started to run into problems. The video says that these biological-inspired developments result in LEDs that are 55% brighter, but 55% brighter than what? I’m a bear of little brain and I found it hard to work out just how much efficiency I can hope to see in terms that are meaningful to me.

A quick search of the interweb reveals nuggets of knowledge like “Approximately 2% of the emitted energy from an incandescent source is useable visible light with the remaining 98% being wasted heat.”

Well, that seems simple enough. What about LEDs. Some sources say LEDs are 90% efficient, others say 50%, and others say 12%. It may be that that they are measuring “efficiency” in different ways (electrical vs. extraction vs. electrical * extraction…), or it may be that they are thinking of something completely different.

Maybe we could come at this from another direction. I found one website that said something like “LEDs use 70% to 80% less power than incandescent lights.” And, although it’s not very scientific, I just looked at some LED-based household bulbs on Amazon that say they emit light equivalent to a 100W incandescent bulb while consuming only 14W of power (some of which will be consumed by the supporting electronics).

So, my question is as follows: “If an incandescent bulb is only 2% efficient, and if a LED consumes 80% less power than an incandescent bulb, then how efficient is the LED?”

Or maybe I’m asking the wrong question. What say you? Can you cast any light (yes, pun intended) on this conundrum?