Compact fluorescent lamp

File:Compact-Flourescent-Bulb.jpg

A spiral type compact fluorescent light bulb. Despite the slightly reduced efficiency of this style CF bulb due to the inherent excessively thick layer of phosphor on the lower side of the twist, it has remained one of the most popular among consumers since its introduction in the mid 1990s.

A compact fluorescent lamp (CFL), also known as a compact fluorescent light bulb or an energy saving lightbulb, is a type of fluorescent lamp that fits into a standard light bulb socket or plugs into a small lighting fixture.

In comparison to incandescent light bulbs, CFLs have a longer rated life and use less electricity. In fact, CFLs save enough money in electricity costs to make up for their higher initial price within about 500 hours of use.

Market

Globally introduced in the early 1980s, CFLs have steadily increased in sales volume, largely due to improvements in product performance and reduction in unit prices. The most important advance in fluorescent lamp technology (including in CFLs) has been the gradual replacement of magnetic ballasts with electronic ballasts: This has removed most of the flickering and slow starting traditionally associated with fluorescent lighting.

The market for CFLs has been aided by the production of both integrated and non-integrated lamps. Integrated lamps combine a bulb, an electronic ballast and either a screw or bayonet fitting; these lamps allow consumers to easily replace incandescent bulbs with CFLs. Non-integrated lamps allow for the replacement of consumable bulbs and the extended use of ballasts; since the ballasts last longer, they can be more expensive and sophisticated, providing options such as dimming. (Non-integrated CFLs are more popular for professional users, such as hotels.)

CFLs are produced for both AC input and DC input. DC CFLs are popular for use in recreational vehicles and off-the-grid housing. Poor families in developing countries are using DC CFLs (with car batteries and small solar panels) to replace kerosene lanterns.

CFL energy consumption compared to incandescent bulbs

Equivalent light output
Incandescent	Compact fluorescent	CCFL lamp
25 W	5-6 W	?W
40 W	10 W	?W
60 W	11–13 W	?W
75 W	18–20 W	?W
100 W	25-27 W	?W
125 W	28-35 W	?W
150 W	40-42 W	?W

CFLs are typically guaranteed for 8,000 hours. (Incandescent bulbs typically last 500 to 2000 hours, depending on exposure to voltage spikes and mechanical shock.)

CFLs use about a quarter of the power of incandescent bulbs. For example, a 15-watt CFL produces the same amount of light as a 60-watt incandescent bulb (approximately 900 lumens or 60 lumens per watt). A comparison of the purchase and operating costs of these two light sources follows.

The kilowatt-hour (kWh) is the unit used to sell electrical energy in most countries. The cost of electricity in the United States ranges from $0.06 to $0.38 per kWh, with an average cost in May 2006 of $0.106 per kWh [1] (also see Electricity rates.) For convenience, a rate of $0.10 per kWh is often used for estimating the running costs of appliances.

	$(60\,\mathrm {W} )\times (8000\,\mathrm {hr} )\times \left({\frac {\$0.10}{1000\,\mathrm {W} \cdot \mathrm {hr} }}\right)=\$48.00$
File:CompactFluorescentLightBulb.png	$\left(15\,\mathrm {W} \right)\times \left(8000\,\mathrm {hr} \right)\times \left({\frac {\$0.10}{1000\,\mathrm {W} \cdot \mathrm {hr} }}\right)=\$12.00$

The CFL, therefore, will save $36.00 in electricity (compared to the incandescent bulb) during its rated life. Some American discount stores sell packages of CFLs for about $2.75 per CFL and incandescent bulbs for about $0.50 each, a $2.25 difference. The estimated payback period for buying the CFL instead of the incandescent bulb is, therefore, 500 hours, which is 100 days at 5 hours per evening.

• Due to continued price drops, American discount stores now offer CFLs for as little as $1.66 each. This allows consumers to repay the price of a CFL even faster; resulting in greater overall savings.

The above calculations do not account for the ancillary effect of (light bulb) heat on energy costs. The energy that is not used to create light is instead converted into heat energy. Incandescent bulbs therefore produce substantially more heat than CFLs for a given light output. During cold months, incandescent bulbs can help to heat buildings; but during hot months, incandescent bulbs place additional strain on air conditioning systems.

Colors

A photograph of various light bulbs illustrates the effect of color temperature differences

CFLs are produced in varying shades of white:

• "Warm white" or "Soft white" (2700 K - 3000 K) provides a light very similar to that of an incandescent bulb, somewhat yellow in appearance;
• "White", "Bright White", or "Medium White" (3500 K) bulbs produce a yellowish-white light, whiter than an incandescent bulb still but on the warm side;
• "Cool white" (4100 K) bulbs emit more of a pure white tone; and
• "Daylight" (5000 K - 6500 K) is slightly bluish-white.

The "K" denotes the correlated color temperature in kelvins. Color temperature is a quantitative measure. The higher the number, the “cooler”, i.e., bluer, the shade. Color names associated with a particular color temperature are not standardized for modern CFLs and other triphosphor lamps like they were for the older style halophosphate fluorescent lamps. Variations and inconsistencies exist among manufacturers. For example, Sylvania's Daylight CFLs have a color temperature of 3500 K, while most other bulbs with a "daylight" label have color temperatures of at least 5000 K. Some vendors fail to include the kelvin value on the package, but this is beginning to improve now that the ENERGY STAR Criteria for CFLs is expected to require such labeling in its 4.0 revision.

CFLs are also produced, less commonly, in other colors:

• Red, green, orange, blue, and pink, primarily for novelty purposes
• Yellow, for outdoor lighting, because it does not attract insects
• Blacklight, for special effects

CFLs with UVA generating phosphor, are an efficient source of long wave ultraviolet "blacklight", much more efficient than incandescent "blacklight" bulbs, since the amount of UV light that the filament of the incandescent lamp produces is according to blackbody radiation.

Being a gas discharge lamp, a CFL will not generate all frequencies of visible light; the actual color rendering index is a design compromise (see below). With less than perfect color rendering, CFLs can be unsatisfactory for inside lighting, but modern, high quality designs are proving acceptable for home use.

Other terms that apply to CFLs:

• Full Spectrum
• High Definition

Environmental issues

Since CFLs use about 1/4 of the energy of incandescent bulbs they are a key part of efforts to fight climate change.

File:CFL bulb mercury use environment.svg

Mercury use of compact fluorescent bulb vs. incandescent bulb when powered by electricity generated from coal.

CFLs contain trace amounts of mercury. The amount is not large enough to pose a hazard to users, but it does become a concern at landfills and trash incinerators where the mercury from many bulbs can escape and contribute to air and water pollution. Some manufacturers such as Phillips make very low mercury content CFL's[2].

Safe disposal requires storing the bulbs unbroken until they can be processed. Consumers should seek advice from local authorities. Usually, one can either:

• Bring back used CFLs to where they were purchased, so the store can recycle them correctly; or
• Bring used CFLs to a local recycling facility.

The first step of processing involves crushing the bulbs in a machine that uses negative pressure ventilation and a mercury-absorbing filter or cold trap to contain and treat the contaminated gases. Many municipalities are purchasing such machines. The crushed glass and metal is stored in drums, ready for shipping to recycling factories.

Note that coal power plants are the single largest source of mercury emissions into the environment. According to the Environmental Protection Agency (EPA), (when coal power is used) the mercury released from powering an incandescent bulb for five years exceeds the sum of the mercury released by powering a comparably luminous CFL for the same period and the mercury contained in the lamp. [3]

How they work

Parts

Electronic ballast of a compact fluorescent lamp

There are two main parts to a CFL: the gas-filled tube (also called bulb or burner) and the magnetic or electronic ballast. Electrical energy in the form of an electrical current from the ballast flows through the gas, causing it to give off ultraviolet light. The ultraviolet light then excites a white phosphor coating on the inside of the tube. This coating emits visible light. CFLs that flicker when they start have magnetic ballasts; CFLs with electronic ballasts are now much more common. See Fluorescent lamp.

End of life

Both the ballast and the burner are subject to failure from normal use. In low-quality CFLs, high temperatures often cause the ballast electronics to fail before the burners. In high-quality CFLs, the burners almost always fail first. The burners occasionally fail due to cracks and imperfect seals but much more typically due to an increased work function at the electrodes caused by vaporization and sputtering-off of the cathode material. It is also this material that then deposits onto the burner's glass tubing, causing blackening of the tubing.

High-quality driver electronics can prolong the life of the burners by preheating the electrodes to prevent damage from rapid expansion. High-quality drivers require high-quality components. The best CFL manufacturers (including Osram, Philips, General Electric, Luxlite) produce CFLs that can last 15,000 hours. Such lifetimes require highly automated and controlled manufacturing.

At end of life, CFLs should be recycled by specialist firms. In the European Union, CFL lamps are one of many products subject to the WEEE recycling scheme. The retail price includes an amount to pay for recycling, and manufacturers and importers have an obligation to collect and recycle CFL lamps.

Design compromises and challenges

Apart from durability, the primary purpose of good CFL design is high electrical efficiency.

These are some other areas of interest:

• Quality of light: A phosphor emits light in a narrow frequency range, unlike an incandescent filament, which emits the full spectrum, though not all colors equally, of visible light. Mono-phosphor lamps emit poor quality light; colors look bad and inaccurate. The solution is to mix different phosphors, each emitting a different range of light. Properly mixed, a good approximation of daylight or incandescent light can be reached. However, every extra phosphor added to the coating mix causes a loss of efficiency and increased cost. Good-quality consumer CFLs use three or four phosphors - typically emitting light in the red, green and blue spectra - to achieve a "white" light with color rendering indexes (CRI) of around 80. (A CRI of 100 represents the most accurate reproduction of all colors; reference sources having a CRI of 100, such as the sun and tungsten bulbs, emit black body radiation.)
• Size: CFL light output is roughly proportional to phosphor surface area, and high output CFL bulbs are often larger than their incandescent equivalents. This means that the CFL might work fine in the socket, but that the light cover might not fit over it or that you won't have the room to squeeze the CFL in place.
• Covered performance: To approximate the look of an incandescent bulb, the CFL burner can be enclosed behind a cosmetic glass cover. However, this causes the temperature of the burner to increase greatly, increasing the gas pressure inside the burner and decreasing the brightness (and therefore efficiency) of the lamp. These problems have largely been solved using special mercury compounds and other techniques, and now globe and flood versions are widely available (at hardware stores and elsewhere).
• Electronics: Dimming control can be added to the lamp with support from the driver electronics. Also, large deployments of CFLs (in a hotel lobby, for example) require specialised electronics with low levels of electronic distortion to avoid disturbing the electricity supply. This is usually not a problem with home use because of the few lamps deployed.
• Time to achieve full brightness: Compact fluorescent bulbs can take 30 seconds or more to reach full brightness. This compares to 0.1 seconds for incandescent bulbs and 0.01 seconds for LED lamps.
• CFLs often do not fail suddenly like incandescent lightbulbs do. Symptoms of impending CFL failure may come months ahead, with more and more prolonged turn-on times until full luminosity is reached, buzzing of the ballast, random periods of reduced brightness and the appearance of growing black spots on the glass tubing's inside.
• In places infested with insects, bugs have a habit of climbing into the "cage" formed by the CFL tubing and perishing inside. Some CFLs have an extra oval shell hiding the tubeworks to prevent this.

Other CFL technologies

Another type of fluorescent lamp is the electrodeless fluorescent, known as a radiofluorescent lamp or fluorescent induction lamp. Unlike virtually all other conventional lamps that have hardwired electrical connections to transfer energy to the lamp core, the electrodeless fluorescent accomplishes this solely by electromagnetic induction. The induction is effected by means of a wire-wound ferrite core that projects upward into the bulb encased in an inverted U-shaped glass cover. The wire is energized with high frequency electricity often 2.65 or 13.6 MHz; this ionizes the mercury vapor, exciting the phosphor & producing light.

Another variation on existing CFL technologies are bulbs with an external nano-particle coating of titanium dioxide. Titanium dioxide is a photocatalyst becoming ionized when exposed to UV light produced by the CFL, thereby capable of converting oxygen to ozone, water to hydroxyl radicals, which neutralizes odors and kills bacteria, viruses, and mold spores.

The Cold Cathode Fluorescent Light (CCFL) is one of the newest forms of CFL. CCFLs use electrodes without a filament. The voltage of CCFL lamps is about 5 times higher than CFL lamps and the current is about 10 times lower. CCFL lamps have a diameter of about 3 millimeters and they are used in thin monitors for backlighting. The lifetime of CCFL lamps is about 50,000 hours. The lumens per watt is about half of CFL lamps.

Efforts to encourage adoption

Improving efficiency of household lighting is a part the effort to fight global warming.[4] However, people have been hesitant to transition from incandescent bulbs to CFLs. People are reluctant to buy CFLs despite their three to twelve month payback period. Professionals who install lighting fixtures sometimes do not consider installing CFLs because the electrical bill is insignificant and the CFLs have a higher cost.

Some governments have attempted to encourage CFL usage by distributing them out for free and by appealing to people's morals. Controversially, some in Britain have lobbied Parliament to tax or ban incandescent bulbs. Web sites like banthebulb.org have been created in support of the ban.

In June 2006, the US Environmental Defense initiated a campaign called Make the Switch to encourage the public to switch from incandescent bulbs to compact fluorescent bulbs. It asked every household in the US to replace three 60-watt incandescent bulbs with CFLs- a 15-watt CFL is just as bright as a 60-watt incandescent. Environmental Defense claims that if every household was to do this, the change could reduce pollution as much as taking 3.5 million cars off the road.

Other efforts include, September 2006, Wal-Mart started a campaign to endorse CFLs. The store aims to sell one CFL to every one of their 100 million customers within the next year and thus change the energy consumption of the United States and to improve their reputation.. In Ottawa, Canada there is an effort to get every household to change at least one lightbulb. Project Porchlight has volunteers going door-to-door providing one CF bulb to every household for free.

Another website, onebillionbulbs.com has a campaign hoping to replace one billion incandescent bulbs to CFLs across the U.S. The site has a fifty-state map with each state a certain color from white to green. The closer to green, the closer to the state's goal.

Gallery of CFLs

• Biax or Linear CFL
  Biax or Linear CFL
• Globe CFL
  Globe CFL
• Reflector CFL
  Reflector CFL
• 
  Spiral CFL
• 
  A CFL bulb designed to resemble an incandescent bulb.
  An incandescent bulb is shown on the right for comparison

References

• R. J. Van der Plas, A. B. de Graaff, "A comparison of lamps for domestic lighting in developing countries" (Energy Ser. Pap. 6, Industry and Energy Department, World Bank, Washington, DC, 1988).
• G. S. Dutt, "Illumination and Sustainable Development", Energy Sustain Dev. 1 (1), 23 (1994).

External links

• Compact Fluorescent Lamps: What You Should Know
• Energy Star's page on fluorescent bulbs
• Energy saving calculator
• Energy Savings
• How Fluorescent Lamps Work
• Make the Switch Campaign, Environmental Defense
• Reduce Global Warming
• How much coal is required to run a 100-watt light bulb 24 hours a day for a year? - from HowStuffWorks.com
• LampRecycle.Org - For information on recycling spent mercury-containing lamps
• Mercury in Compact Fluorescent Lamps - from the National Electrical Manufacturers Association
• Compact Fluorescent Pitfalls, Reality, and Recommendations
• Lighting Research Center - Excellent information and analysis of "full spectrum" lighting
• Project Porchlight Non-profit organization from Ottawa, Ontario distributing CFL bulbs to every home in Canada as a conservation and education program.
• Energy Saving Trust in the UK, the Energy Saving Trust provides advice and information about CFL lighting, including council and power company subsidies to domestic homes
• Savingenergy.org.uk a UK source of CFL lightbulbs
• OneBillionBulbs.com - Emphasizes cost-saving and environmental benefits of CFLs
• FastCompany.com article - details Wal-Mart and GE's joint effort to create a CFL revolution
• [5] - In Holland, Greenpeace mobilizes people to change 1 million light bulbs to CFLs