Light-Emitting Diodes (LEDs)

How do LEDs compare to earlier lighting technologies?

Light Emitting Diodes work in an opposite fashion to solar panels. Current passing through the junction of the diode consists of electrons and so called “holes” (empty spaces, where the electrons are missing, which can be treated as mobile positive charges). When “holes” and electrons meet in the junction of the diode they recombine (electron at the higher energy level fails into the hole, which is at lower energy lever) producing visible photons. This is a very efficient process but creates monochromatic light. There are two ways to make white LEDs. You can either make red, green and blue diodes in one package, this combination will look white or you can have violet or UV (ultraviolet) LED covered with appropriate phosphorous material, which absorbs violet or UV and emits white.

For a long time we were only able to manufacture small LEDs used as indicator lights and little displays. The technology however improved dramatically in the last 10 years and LED replacements corresponding to incandescent lights of 60 or 100 W are available.

LEDs have the efficiency (the amount of light in lumens or number of photons produced per unit energy)  similar to fluorescent lights but unlike fluorescent lights they emit light approximately into a half sphere rather than full sphere. So if we want to illuminate a particular surface (for example a book or a work table less light is wasterd. LEDs are also much smaller and last longer.

As you can see on our video to illuminate a surface with about 500lux[1]Lux [2019-09-16]. (which is a good reading illumination) from the same distance we need 57 W for incandescent light 11 W for compact fluorescent light and 9 W for LED.

Footnotes   [ + ]

1. Lux [2019-09-16].