This rant is in response to a BBC article, "Light Bulbs: Not Such A Bright Idea", promoting the use of compact flourescent lights as an energy-saving measure.

Several reader reponses indicated light quality as an issue with compact fluorescents. I can't agree more strongly and am very disappointed that the article makes no mention of it.

It's not that it's impossible to make a fluorescent light with high quality light; in fact, some specifically advertise their broad light spectrum. But units with broad spectrum support are rare and expensive. I have yet to see a single compact fluorescent light that does not have very serious spectrum limitations. I will talk more about spectrum in a minute.

Another issue is flicker. Most fluorescent lights flicker as the AC current falls through zero (100-120 times per second). You don't get this with incandescents because it takes some time for the wire to cool, smoothing the light. Generally speaking this is imperceptible to people, but it can easily cause interference when used in conjunction with other technologies -- particularly CRT displays (ie most televisions and computer screens) -- and people with particularly good eyesight may pick up the flicker directly.

As with spectrum issues it is possible to purchase fluorescent lighting fixtures that do not exhibit this problem perceptibly. Unfortunately they are comparatively expensive and, so far as I have been able to determine, not available at all in compact designs.

One of the reader responses commented that incandescents have a spectrum essentially identical to sunlight. This is false. Tungsten incandescents are very orange; this is why film photographers have long used "tungsten filters" -- they have to tone down the orange in order to get good color. Digital cameras (usually) attempt to compensate automatically.

The big difference between tungsten and typical fluorescent lights is not that one or the other produces an especially wide spectrum, but that red-biased ("warm") light produced by incandescents is more pleasant than blue-biased ("cold") light typically produced by fluorescents. If you're going to have relatively narrow spectrum illumination you'd rather have it on the red side.

Halogen incandescents tend to have light that is a lot more balanced than tungsten, although they are still biased towards red. They are also more energy efficient, although still nowhere near as efficient as fluorescents. I strongly prefer halogens for their quality of light, and the ready availability of halogen lamps in various compatible-with-incandescent sizes, shapes, and light output make them particularly appealing despite somewhat higher cost.

Several people mentioned the possible use of LED lights. These have promise but LED lights have some of the same problems as other low-energy lights, like metal halide lamps: Very monochromatic output. Pick up any "white" LED flashlight and look at color photographs in a darkened room; you will have difficulty seeing many tones, especially red. This is because the LEDs emit very blue ("cold") light in a very narrow spectrum.

It is possible to correct this; the simplest way is to use several LEDs with varying spectrum so as to get more or less uniform lighting across the visible spectrum. This adds significant cost and complexity to the bulb. I've not yet heard of any production LED lamp that fixes this issue. I'm hopeful that costs will come down in the future (there are some indications that variations on LED technology will allow that) because LEDs are not only energy efficient but also have very long life. For now, though, they are not a very good solution for interior lighting.

For those who are particularly interested in saving energy there are a couple of tips I would give in addition to choosing your light bulbs carefully. CRT display technologies are very wasteful; even a display as small as 17" will typically consume four or five hundred watts in steady state, considerably more during start-up, and sometimes technologies to allow faster start-up time consume significant energy even when the device is nominally "off".

LCD technologies are comparatively miserly; a 17" LCD display will typically use well under 100 watts, 75 to 80% less than CRT. Televisions, especially large screen televisions, similarly benefit from moving away from the CRT. DLP, projection LCD, and LCoS units use substantially less energy than CRT-based TVs (especially rear-projection CRT TVs). There are some compromises (especially black reproduction and bulb life) inherent in these technologies but image quality is generally very good.

The last, and probably the most significant, energy user that almost nobody thinks about are power bricks. Virtually all electronic devices which are not battery operated come with some sort of power brick, sometimes internal to the device. These bricks are simple transformers (with rectifiers and voltage regulators, but it's the transformer that matters) and use power even when the device is off. Individually these power bricks don't usually use very much electricity but a typical household has quite a few of them. The desk I'm sitting at, for instance, has nine of them (one each for the monitor, each external drive, the firewire and USB hubs, and palmtop cradle). Throughout the house I probably have thirty or forty.

It is possible, but again more expensive, to build power bricks that are a lot more miserly when the device they're powering is turned off. I have yet to see any such technology deployed in a consumer product. It's up to the user to unplug or otherwise disconnect the bricks to quell their parasitic power use.
to top