Friday, 24 June 2011

LED light bulb... this should be a contradiction in terms.

Just read is-this-the-ultimate-green-led-light-bulb. And it makes me wonder what's going on. It talks about "solving the problem of uni-directionality in older LED bulbs". I wonder whether Edison was concerned with the "problem" of his lightbulb not having an open flame...

Another thing that doesn't make sense is the idea of a replacable LED bulb.  LEDs have rated lifespans of over 40,000 hours. That's three hours a day for forty years. Form most domestic uses, the only reason for replacing the bulb would be if you wanted to change the fitting and keep the bulb. 

This guy at My LED lighting guide gives a list of eight reasons why LEDs are better than compact fluorescants, and Eternaleds asks if LEDs are brighter than CFLs and finds that no, they aren't really brighter. 

The point is that the light all comes out in the same direction, so if you know what you want to be bright, and can point the light there, then the LED is going to use a lot less power, not because it's producing light more efficiently, which it isn't, but because it's going to the right place.

If there's a chance that you're going to be doing something behind the lightbulb, in that bit of the wall where small dead insects accumulate, and you want to make sure it's not dark there, then CFLs or incandescants are for you. If you don't even want a space there, you should probably consider LEDS. If a light is not going to be used very much, and if you're not sure which part of a large area you're going to be using, then fluorescents will probably do as good a job as LEDs, and currently cost less to buy and fit, although LEDs use less resources and as they work out how to manufacture them in bulk, and once they pay back the retooling costs, LEDs will be cheaper.

A practical example in the house is a store room that may be used a few minutes a day. Rather than putting LEDs all around, we'll just put one fluorescent tube in the middle. This will brighten up the whole room in one go, and should still last a few decades. The other low-energy option would be to have a couple of head torches left on a hook at the entrance and turn a trip to the basement into a caving expedition!

But anyway, I wish people would stop talking about LED light bulbs. The whole point of a light bulb is that Edison's elements needed a vacuum, or an inert gas, so that they wouldn't burn away. Rather sensibly, with glass being transparent and easy to blow or suck into bulbs, he put them into a glass bulb. LEDs are semiconductors, typically produced on a flat wafer. They don't need a bulb. It may be a good idea to put a lens in front of them.

Putting LEDs into bulbs is like using a keyboard designed for typewriters over a hundred years ago when you're inputting words into a computer...