Problems with Compact Fluorescent Lights and Mercury

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Concerns with CFLs due to mercury levels, disposal, and functionality. Light levels and rated life of CFLs as compared to LED lights and incandescent bulbs.

Everyone is pushing for the use of compact fluorescent lights, CFLs, due to their high efficiency. Many countries have set a timeline for the phase-out of incandescent light bulbs and some states in the US are considering similar initiatives. The dirty little secret is what to do with the bulbs when then burn out or break and release the mercury contained within them. Congress has mandated that light bulbs be at least 25% more efficient by 2012.

The EPA states on their website that the bulbs are safe as long the glass tube remains intact. The bulbs will not remain intact if disposed in regular trash and sent to a landfill. Municipalities and states must come up with a plan for their safe disposal or recycling. This will invariably add to the cost of the already expensive light bulbs.

CFL bulbs were invented in 1976 by Ed Hammer, a General Electric engineer. They were a response to the energy crisis of 1973-1974. But his spiral tube design was too expensive to make and too fragile to ship, so GE did not market it.

A more incandescent-like warm white CFL was developed by Phillips in 1982. It wasn’t until 1995 that a cost-effective, durable spiral design was introduced. But there were many problems with the original CFLs, making some early adopters swear off them forever.

Why Mercury is in Fluorescent Bulbs

When you turn the fluorescent lamp on, the current flows through the ballast which increases the voltage and sends it to the electrodes. This high voltage across the electrodes allows electrons to migrate through the gas from one end of the tube to the other. This energy changes some of the mercury in the tube from a liquid to a gas. As electrons and charged atoms move through the tube, some of them will collide with the gaseous mercury atoms where they excite the atoms, causing the electrons to move up to higher energy levels. When the electrons return to their original energy level, they release light photons.

The electrons in mercury atoms are arranged in such a way that they mostly release light photons in the ultraviolet wavelength range. The phosphor coating on the inside of the lamp converts the UV light into visible light to illuminate the lamp.

There is between 4 and 10 mg of mercury contained in fluorescent bulbs and CFLs.

Types of Bulbs that Contain Mercury

Most fluorescent bulbs contain mercury unless they are labeled as mercury-free. Bulbs that contain mercury include linear, U-tube and Circline fluorescent tubes, bug zappers, tanning bulbs, black lights, germicidal bulbs, high output bulbs, cold-cathode fluorescent bulbs, and compact fluorescent bulbs. Other non-fluorescent bulbs that contain mercury are high-intensity discharge (HID) bulbs, which include metal halide, ceramic metal halide, high pressure sodium, and mercury vapor, mercury short-arc bulbs, and neon bulbs.

Problems with CFLs

It has been well documented in the news about the problems with cleaning up a broken CFL. For the complete instructions on clean-up procedures, go to http://www.epa.gov/mercury/spills/index.htm .

Aside from the mercury disposal hazard, there are other nuisance problems concerning the design and functionality of the CFL.

The bulbs can take up to a minute to reach their full light output. This can be a concern if they are used for emergency egress lighting.

Fluorescent lights are temperature sensitive. If the temperature is below 30 degrees they take longer to light because the phosphor in CFL bulbs that emits light takes awhile to warm up.

CFL bulbs also burn out quicker if they’re in a hot environment such as inside an enclosed light fixture. The life expectancy of a CFL in an enclosed fixture may be 3,000 to 5,000 hours instead of 10,000. This is still much greater than that of incandescent bulbs, but will mean you need to purchase and dispose of two or three more bulbs than you had expected.

The more light a CFL puts out, the bigger it needs to be. The CFL equivalent of a 60-watt bulb is comparable to an incandescent light bulb, but the 120-watt equivalent is bigger and won’t fit in standard lamps and fixtures. This can be a problem for people in older or historic homes with the original light fixtures.

A less serious problem is that most CFLs won’t work with a dimmer. Dimmers were developed to control the light output and energy usage of incandescent bulbs. You don’t have to worry about the energy consumption with CFLs, but controlling the light levels can be difficult. You can find dimmable CFLs, but they use special dimmable ballast which controls the light levels only down to about 20% up to 80%. You cannot use a standard CFL with a dimmer; it will hum and snap and may destroy the internal electronics. Below 20% of their full light intensity the bulb will go out and they also must be turned on at full power and then dimmed. The dimmable CFLs design also limits the energy savings of the bulb to the point that they use almost 100% of the power of a standard CFL.

When used in a three-way light fixture, many CFL bulbs will pop, hiss and buzz. There are a few three-way CFL bulbs, but they are difficult to find and are so large that they do not fit in many lamps. Such bulbs often come with adaptors to lengthen the lamp’s base so the bulb will fit.

The life of the bulb may be shortened by up to 50% if the bulbs are only used for less than an hour at a time. Increased on-off cycles shorten the rated life of all fluorescent bulbs and manufacturers rate the life of CFLs by leaving them on for 3 hours and off for 20 minutes. A detailed study was conducted by the Northwest Power and Conservation Council to see how the bulbs rated life is effected by varying switching patterns found in actual homes. The link to the report is included at the end of this article.

Manufacturing CFLs is also an issue. The process to purify the mercury contained in the fluorescent tube releases about 40% of the mercury into the atmosphere as unrecovered waste during extraction and processing.

The Future of CFLs

It seems that CFLs will be a passing fad, an intermediate technology until something cleaner, safer, and more efficient comes along. Light emitting diodes (LED) seem to be the next step in the progression. They have been used as light sources for a few decades, mostly in exit signs and emergency lighting. Originally they were only in red, but the Holy Grail of LED lights is trying to get a pure white color. They are almost there. The current costs for LEDs are high, just as CFLs were high. As more people buy them, the price will come down. They last longer than CFLs and use less energy. The one issue with an LED is that the light emitted is directional, or that it comes out in a single beam. Manufacturers are developing new designs to diffuse the light with reflectors so that they can give off similar light profiles as CFLs and incandescent light bulbs.

Resources:

National Electrical Manufacturers Association

http://www.nema.org/gov/env_conscious_design/upload/Recycling%20Household%20CFLs.%2009%2007.pdf

Environmental Protection Agency

http://www.epa.gov/mercury/spills/index.htm

Northwest Power and Conservation Council

Welcome to the Dark Side: The Effect of Switching on CFL Measure Life

http://www.nwcouncil.org/energy/rtf/meetings/2009/05/CFLLife_CyclingImpacts_ACEEE.pdf

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Daniel Snyder

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