Musings on CFLs and LEDs
August 10th, 2010

Posted under Alpenglow Lighting Design News

Compact Fluorescent Lightbulbs (CFLs) have been with us for a long time, and have improved vastly since their first incarnations. The original versions were long twin-tubes, and it was common to see them screwed into shallow downlights, resulting in 2-4″ of lightbulb hanging below the ceiling. Fortunately, things have improved. Current CFL designs are tight spirals, intended to emulate the shape of the classic A-lamp (the plain-old lightbulb). The reason for this is that most downlights and table lamps are designed for this shape of bulb.

The price of CFLs has dropped considerably, from $15-20 to now as low as 99 cents. The screw-in CFLs are all self-ballasted, meaning that they do not require a remote ballast installed in the fixture (as plug-in CFLs and linear fluorescents do). Considering that the ballast is a somewhat complicated bit of electronics, and that the glass and phosphor coatings in the tube are also complex, it’s amazing that the bulbs are available for under a buck. However, keep in mind, that in lighting, you get what you pay for.

If you buy a lightbulb with complex electronics and manufacturing processes for a dollar, you have to assume that the cost of producing, packaging, and shipping it has to be under 25 cents, or the manufacturer is losing money. I have noticed that many people who complain about the quality of CFLs are using these low-end lamps.

Lamp life is also a topic of discussion with regard to CFLs. Lamp life is rated on 3 hours per start, so in essence, a 10,000 hour bulb is a 3,000 start bulb. If you use a CFL in a pantry or powder room, where it is switched on and off frequently, chances are it will burn out more quickly than a bulb used in a hotel lobby table lamp.

Mercury is an issue with all fluorescent lamps. The basic principle is that a small amount of mercury is vaporized in an electric arc. As the mercury is vaporized, an electron is moved to a higher valence. When it returns to its natural valence, it releases a photon in the ultraviolet range. The photon hits the phosphor on the inside of the glass, and is shifted to the visible light range. The phosphor coatings are tuned to release visible light in certain color ranges. Obviously, mercury is a toxin, and recycling the lamps is the best way to keep the mercury from escaping into the environment. It is important to keep in mind that watch batteries have more mercury than modern CFLs, so each lamp has a tiny amount, but cumulatively, the mercury can add up. In the Roaring Fork Valley, you can recycle lamps at hardware stores and Alpine Banks.

Light Emitting Diodes (LEDs), are gaining ground as the latest light source. They offer low wattage, low heat, and each generation is brighter. Right now, they seem to be evolving faster than consumer electronics such as phones and DVD players. Although it is easy to sit and wait for the latest version, installing them now as replacements for incandescent lamps is still an instant energy savings.

LEDs have some challenges of their own, mainly in heat and dimmability. LEDs do not feel hot to the touch, but the heat generated by the lamps and trapped inside the luminaire can decrease their light output and lifespan. For this reason, most LED lamps have extensive aluminum heatsinks. Many of these heatsinks are milled aluminum, which is a costly manufacturing process. Some LEDs are dimmable with ‘regular’ dimmers (forward phase control, or chopping of the electrical sine wave) while others want to see a 0-10V DC control signal. Consumer LEDs, if dimmable, work fairly well with household dimmers and most dimming systems. The biggest challenge to dimmability is dimmer minimum loads: most household dimmers don’t work well when the connected load is under 40W. If you experience flickering with your LED lamp, this is typically the culprit. At Alpenglow, we have tested Vantage Scenepoint dimmers with loads as low as 14W with no flicker.

LED color is another challenge. White LEDs are about 10 years old, and the first generations were very cool white. Since the white LED evolved out of blue LEDs, this makes sense. However, warming up the color also reduces the light output, so some products are using a remote phosphor and very cool-white LEDs. Basically, this system relies on a color-correcting lens in front of the LED array. Currently, this system is found in complete luminaires rather than retrofit lamps, but at the rate of change in the products, this could change by the time I finish typing this sentence.

So, which lamp is better to use? There is no blanket answer. Lamps and luminaires are constantly changing, and the correct choice is based on the application rather than the lightbulb. CFLs are very good at washing walls but do not provide sparkle; LEDs can provide sparkle but are not ideal for floodlighting. The high rate of change in the product evolution also means that constant research and education is required for the best solution for a design challenge.

No Comments »

Trackback URI | Comments RSS

Leave a Reply