Compact fluorescent lamp

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Tubular-type compact fluorescent lamp is one of the most popular types among European consumers.

A compact fluorescent lamp (CFL), also known as a compact fluorescent light or energy saving light (or less commonly as a compact fluorescent tube [CFT]), is a type of fluorescent lamp. Many CFLs are designed to replace an incandescent lamp and can fit into existing light fixtures formerly used for incandescents.

Compared to general service incandescent lamps giving the same amount of visible light, CFLs generally use less power, have a longer rated life, but a higher purchase price. In the United States, a CFL can save over US $30 in electricity costs over the lamp's life time compared to an incandescent lamp and save 2,000 times its own weight in greenhouse gases.[1] Like all fluorescent lamps, CFLs contain mercury, which complicates their disposal.

CFLs radiate a different light spectrum from that of incandescent lamps. Improved phosphor formulations have improved the subjective color of the light emitted by CFLs such that the best 'soft white' CFLs are subjectively similar in color to standard incandescent lamps.[2]


[edit] History

A compact fluorescent lamp used outside of a building.

The parent to the modern fluorescent lamp was invented in the late 1890s by Peter Cooper Hewitt.[3] The Cooper Hewitt lamps were used for photographic studios and industries.[3] Edmund Germer, Friedrich Meyer, and Hans Spanner then patented a high pressure vapor lamp in 1927.[3] George Inman later teamed with General Electric to create a practical fluorescent lamp, sold in 1938 and patented in 1941.[3] The modern CFL was invented by Ed Hammer, an engineer with General Electric, in response to the 1973 oil crisis. While it met its design goals, it would have cost GE about US$25 million to build new factories to produce them and the invention was shelved.[4] The design was eventually leaked out and copied by others.[4] CFLs have steadily increased in sales volume.

[edit] Construction

The most important technical advance has been the replacement of electromagnetic ballasts with electronic ballasts; this has removed most of the flickering and slow starting traditionally associated with fluorescent lighting. There are two types of CFLs: integrated and non-integrated lamps.

[edit] Parts

Electronic ballast of a compact fluorescent lamp

There are two main parts in a CFL: the gas-filled tube (also called bulb or burner) and the magnetic or electronic ballast. An electrical current from the ballast flows through the gas, causing it to emit ultraviolet light. The ultraviolet light then excites a phosphor coating on the inside of the tube. This coating emits visible light.

Electronic ballasts contain a small circuit board with rectifiers, a filter capacitor and usually two switching transistors connected as a high-frequency resonant series DC to AC inverter. The resulting high frequency, around 40 kHz or higher, is applied to the lamp tube. Since the resonant converter tends to stabilize lamp current (and light produced) over a range of input voltages, standard CFLs do not respond well in dimming applications and special lamps are required for dimming service. CFLs that flicker when they start have magnetic ballasts; CFLs with electronic ballasts are now much more common.

[edit] Integrated CFLs

Integrated lamps combine a tube, an electronic ballast and either an Edison screw or bayonet fitting in a single CFL unit. These lamps allow consumers to replace incandescent lamps easily with CFLs. Integrated CFLs work well in standard incandescent light fixtures. This lowers the cost of CFL use, since they can reuse the existing infrastructure. In addition, incandescent light fixtures are relatively inexpensive. Special 3-way models and dimmable models with standard bases are available for use when those features are needed.[5]

[edit] Non-integrated CFLs

Non-integrated CFLs have a separate, replaceable bulb and a permanently installed ballast. These ballasts are typically of the magnetic type, and the starter is housed in the base of the replaceable bulb. Since the ballasts are placed in the light fixture they are larger and last longer, compared to the integrated ones. Non-integrated CFL housings can be both more expensive and sophisticated.

[edit] CFL power sources

CFLs are produced for both alternating current (AC) and direct current (DC) input. DC CFLs are popular for use in recreational vehicles and off-the-grid housing. Some families in developing countries are using DC CFLs (with car batteries and small solar panels and/or wind generators), to replace kerosene lanterns.

CFLs can also be operated with solar powered street lights, using solar panels located on the top or sides of a pole and luminaires that are specially wired to use the lamps.

[edit] Comparison with incandescent lamps

[edit] Lifespan

The average rated life of a CFL is between 8 and 15 times that of incandescents.[6] CFLs typically have a rated lifespan of between 6,000 and 15,000 hours, whereas incandescent lamps are usually manufactured to have a lifespan of 750 hours or 1,000 hours.[7][8] Some incandescent bulbs with long rated lifespans of 20,000 hours have reduced light output. [9]

The lifetime of any lamp depends on many factors including operating voltage, manufacturing defects, exposure to voltage spikes, mechanical shock, frequency of cycling on and off, lamp orientation and ambient operating temperature, among other factors. The life of a CFL is significantly shorter if it is only turned on for a few minutes at a time: In the case of a 5-minute on/off cycle the lifespan of a CFL can be up to 85% shorter, reducing its lifespan to the level of an incandescent lamp.[10][11][12] The US Energy Star program says to leave them on at least 15 minutes at a time to mitigate this problem.

CFLs produce less light later in their life than they do at the start. The light output depreciation is exponential, with the fastest losses being soon after the lamp was first used. By the end of their lives, CFLs can be expected to produce 70-80% of their original light output. [13] The response of the human eye to light is logarithmic: Each f-number (or photographic 'f-stop') reduction represents a halving in actual light, but is subjectively quite a small change.[14] A 20-30% reduction over many thousands of hours represents a change of about half an f-stop, which is barely noticeable in everyday life.[15]

[edit] Energy efficiency

The chart shows the energy usage for different types of light bulbs operating at different light outputs. Points lower on the graph correspond to lower energy use.

For a given light output, CFLs use between one fifth and one third of the power of equivalent incandescent lamps.[16] Since lighting accounted for approximately 9% of household electricity usage in the United States in 2001,[17] widespread use of CFLs could save as much as 7% of total US household usage.

If indoor incandescent lamps are replaced by CFLs, the heat produced by the building's lighting system will be reduced. At times when the building requires both heating and lighting, the building's central heating system will then supply the heat. If the building requires both illumination and cooling, then CFLs will use less electricity themselves and will also reduce the load on the cooling system compared to incandescent lamps. This results in two concurrent savings in electrical power.

[edit] Efficacy and efficiency

A typical CFL is in the range of 17 to 21% efficient at converting electric power to radiant power.[18] Because the eye's sensitivity changes with the wavelength, however, the output of lamps is more commonly measured in lumens, a measure that accounts for the effect of the source's spectrum on the eye. The luminous efficacy of CFL sources is typically 60 to 72 lumens per watt, versus 8 to 17 lm/W for incandescent lamps.[19]

[edit] Cost

While the purchase price of an integrated CFL is typically 3 to 10 times greater than that of an equivalent incandescent lamp, the extended lifetime and lower energy use will compensate for the higher initial cost.[20] A US article stated "A household that invested $90 in changing 30 fixtures to CFLs would save $440 to $1,500 over the five-year life of the bulbs, depending on your cost of electricity. Look at your utility bill and imagine a 12% discount to estimate the savings."[21]

CFLs are extremely cost-effective in commercial buildings when used to replace incandescent lamps. Using average U.S. commercial electricity and gas rates for 2006, a 2008 article found that replacing each 75 W incandescent lamp with a CFL resulted in yearly savings of $22 in energy usage, reduced HVAC cost, and reduced labor to change lamps. The incremental capital investment of $2 per fixture is typically paid back in about one month. Savings are greater and payback periods shorter in regions with higher electric rates and, to a lesser extent, also in regions with higher than U.S. average cooling requirements.[22]

[edit] Starting time

Incandescents give light almost immediately upon the application of voltage. CFLs take a perceptible time to achieve full brightness, and can take much longer in very cold temperatures. Certain styles of lamp using a mercury amalgam can take up to three minutes to reach full output. Coupling this with the shorter life of CFLs when turned on and off for short amounts of time may make incandescent bulbs more attractive for applications such as outdoor or motion-activated lighting, until solid-state lighting becomes cost-effective.

[edit] Comparison with alternative technologies

Solid-state lighting has already filled a few specialist niches such as traffic lights and may compete with CFLs for house lighting as well. LED lamps presently have efficiencies of 30% with higher levels attainable. LEDs providing over 150 lm/W have been demonstrated in laboratory tests [23], and lifetimes of around 50,000 hours are typical. The luminous efficacy of available LED fixtures does not typically exceed that of CFLs. Everyday operating temperatures are usually higher than those used to rate the LEDs, their driving circuitry loses some power, and, to reduce costs, LEDs are often driven at their brightest rather than their most efficient point. DOE testing of commercial LED lamps designed to replace incandescent or CFL lamps showed that average efficacy was still about 31 lm/W in 2008 (tested performance ranged from 4 lm/W to 62 lm/W)[24]. As of 2007, LED lamp fixtures also did not deliver the intensity of light output required for domestic uses at a reasonable cost.[25][26][27]

[edit] Other CFL technologies

Another type of fluorescent lamp is the electrodeless lamp, known as a radiofluorescent lamp or fluorescent induction lamp. These lamps have no wire conductors penetrating their envelopes, and instead excite mercury vapor using a radio-frequency oscillator. [28] Currently, this type of light source is struggling with a high cost of production, stability of the products produced in China, establishing an internationally recognized standard and problems with EMC[29] and RFI. Induction lighting is excluded from Energy Star standard for 2007 by the EPA.

Some manufacturers make CFL bulbs with an external coating of titanium dioxide.[30][31] It is claimed that the titanium dioxide, when exposed to UV light produced by the CFL, can neutralize odors and kill bacteria, viruses, and mold spores.

The Cold Cathode Fluorescent Lamp (CCFL) is one of the newest forms of CFL. CCFLs use electrodes without a filament. The voltage of CCFLs is about 5 times higher than CFLs and the current is about 10 times lower. CCFLs have a diameter of about 3 millimeters. CCFLs were initially used for backlighting LCD displays, but they are now also manufactured for use as lamps. The efficacy (lumens/watt) is about half that of CFLs. Their advantages are that they are instant-on, like incandescents, they are compatible with timers, photocells and dimmers, and they have a long life of approximately 50,000 hours. CCFLs are a convenient transition technology for those who are not comfortable with the short lag time associated with the initial lighting of CFLs. They are also an effective and efficient replacement for lighting that is turned on and off frequently with little extended use (e.g. a bathroom or closet).

Some manufacturers add a coating of luminous paint to covered CFL bulbs so that they glow in the dark for a short time after they are turned off. The purpose is to provide lighting in an emergency, such as a blackout following a natural disaster. [32] One manufacturer offers a compact fluorescent lamp with a white LED to provide a dim night-light. A few manufacturers [33] [34] make CFL-style bulbs with mogul Edison screw bases intended to replace 250 watt and 400 watt metal halide lamps, claiming a 50% energy reduction; however, these lamps require slight rewiring of the lamp fixtures to bypass the lamp ballast.

[edit] Spectrum of light

The light of CFLs is emitted by a mix of phosphors on the inside of the tube, which each emit one color. Modern phosphor designs are a compromise between the shade of the emitted light, energy efficiency, and cost.

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 to achieve a 'white' light with a CRI (color rendering index) of around 80, where 100 represents the appearance of colors under daylight or a blackbody (depending on the correlated color temperature).

A photograph of various lamps illustrates the effect of color temperature differences (left to right): (1) Compact Fluorescent: General Electric, 13 watt, 6500 K (2) Incandescent: Sylvania 60-Watt Extra Soft White (3) Compact Fluorescent: Bright Effects, 15 watts, 2644 K (4) Compact Fluorescent: Sylvania, 14 watts, 3000 K
A blacklight CFL.

Color temperature can be indicated in kelvins or mireds (1 million divided by the color temperature in kelvins).

Color temperature kelvin mired
'Warm white' or 'Soft white' ≤ 3000 K ≥ 333 M
'White' or 'Bright White' 3500 K 286 M
'Cool white' 4000 K 250 M
'Daylight' ≥ 5000 K ≤ 200 M

Color temperature is a quantitative measure. The higher the number in kelvins, 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 lamps with a 'daylight' label have color temperatures of at least 5000 K. Some vendors do not include the kelvin value on the package, but this is beginning to change now that the Energy Star criteria for CFLs is expected to require such labeling in its 4.0 revision.

Some manufacturers now label their CFLs with a 3 digit code to specify the color rendering index (CRI) and color temperature of the lamp. The first digit represents the CRI measured in tens of percent, while the second two digits represent the color temperature measured in hundreds of kelvins. For example, a CFL with a CRI of 83% and a color temperature of 2700 K would be given a code of 827.[35]

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

Black light CFLs, those with UVA generating phosphor, are much more efficient than incandescent black light lamps, since the amount of UV light that the filament of the incandescent lamp produces is only a fraction of the generated spectrum.

Other terms that apply to CFLs:

[edit] Environmental issues

[edit] Energy savings

Since fluorescent lamps use less power to supply the same amount of light as an incandescent lamp, they decrease energy consumption and the environmental effects of electric power generation. Where electricity is largely produced from burning fossil fuels, the savings reduces emission of greenhouse gases and other pollutants.

While CFLs require more energy in manufacturing than incandescent lamps, this is offset by the fact that they last longer and use less energy than equivalent incandescent lamps during their lifespan.[36]

[edit] Mercury emissions

Mercury use of compact fluorescent lamp vs. incandescent lamp if powered by electricity generated completely from coal, though coal accounts for about half of the power production in the United States.

CFLs, like all fluorescent lamps, contain small amounts of mercury[37][38] as vapor inside the glass tubing, averaging 4.0 mg per bulb [39] ,and it is a concern for landfills and waste incinerators where the mercury from lamps is released and contributes to air and water pollution. In the U.S., lighting manufacturer members of the National Electrical Manufacturers Association (NEMA) have voluntarily capped the amount of mercury used in CFLs. [40] Many manufacturers now manufacture CFLs with only 1.0 mg or less than 1.5 mg of mercury per bulb.[41]

In areas powered by coal, CFLs end up saving on mercury emissions versus incandescent bulbs, due to the offset power use (coal releases mercury as it is burned)[42]. This effect is irrelevant in areas not powered by coal, and applies to bulbs which have run long enough to become dim as the mercury adheres to the glass[43]. In old bulbs, as little as 11% of the mercury may be released[44].

In the United States, the U.S. Environmental Protection Agency estimated that if all 270 million compact fluorescent lamps sold in 2007 were sent to landfill sites, that this would represent around 0.13 tons, or 0.1% of all U.S. emissions of mercury (around 104 tons) that year. [45]

[edit] Broken and discarded lamps

Spent lamps should be recycled to contain the small amount of mercury in each lamp, in preference to disposal in landfills. Only 3 percent of CFL bulbs are properly disposed of or recycled.[citation needed] In the European Union, CFLs 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 CFLs. Safe disposal requires storing the bulbs unbroken until they can be processed. In the US, The Home Depot is the first retailer to make CFL recycling options widely available.[46]

Special handling instructions for breakage are currently not printed on the packaging of household CFL bulbs in many countries. The amount of mercury released by one bulb can exceed U.S. federal guidelines for chronic exposure.[47][48] Chronic however, implies that the exposure takes place over a long period of time and the Maine DEP study noted that it remains unclear what the health risks are from shorter-term exposure to low levels of elemental mercury. The Maine DEP study also confirmed that, despite following EPA best-practice cleanup guidelines on broken CFLs, researchers were unable to remove mercury from carpet, and any agitation of the carpet—such as by young children playing—created spikes as high as 25,000 ng/m3 in air close to the carpet, even weeks after the initial breakage. Conventional tubular fluorescent lamps have been in commercial and domestic use since the 1930s with little public concern about their handling; these and other domestic products often contain more mercury than modern CFLs[49].

The U.S. Environmental Protection Agency recommends that, in the absence of local guidelines, fluorescent bulbs be double-bagged in plastic before disposal.[50] The Maine DEP study of 2008 compared clean-up methods, and warned that the EPA recommendation of plastic bags was the worst choice, as vapours well above safe levels continued to leach from the bags. The Maine DEP now recommends a sealed glass jar as the best repository for a broken bulb.

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

According to the Northwest Compact Fluorescent Lamp Recycling Project, because household users have the option of disposing of these products in the same way they dispose of other solid waste, "a large majority of household CFLs are going to municipal solid waste". They additionally note that an EPA report on mercury emissions from fluorescent tube lamp disposal indicates the percentage of total mercury released from the following disposal options: municipal waste landfill 3.2%, recycling 3%, municipal waste incineration 17.55% and hazardous waste disposal 0.2%.[51]

[edit] Design and application issues

A spiral-type integrated compact fluorescent lamp, with combined tube and electronic ballast. This style has slightly reduced efficiency compared to tubular fluorescent lamps, due to the excessively thick layer of phosphor on the lower side of the twist. Despite this, it has become one of the most popular types among North American consumers since its introduction in the mid 1990s.[52]

The primary objectives of CFL design are high electrical efficiency and durability. However, there are some other areas of CFL design and operation that are problematic:

CFL light output is roughly proportional to phosphor surface area, and high output CFLs are often larger than their incandescent equivalents. This means that the CFL may not fit well in existing light fixtures.
End of life
In addition to the wear-out failure modes common to all fluoresecent lamps, the electronic ballast may fail since it has a number of component parts. Ballast failures may be accompanied by discoloration or distortion of the ballast enclosure, odors, or smoke. The lamps are internally protected and are meant to fail safely at the end of their lives. Industry associations are working toward advising consumers of the different failure mode of CFLs compared to incandescent lamps, and to develop lamps with inoffensive failure modes.[53]
Only a few CL lamps are labeled for dimming control. Using regular CFLs with a dimmer is ineffective at dimming, can shorten bulb life and will void the warranty of certain manufacturers.[54] According to BC Hydro[55] and Environmental Defense,[56] dimmable screw-in fluorescent lamps are now available. The dimming range of CFLs is usually between 20% and 90%.[57] Dimmable CFLs are not a 100% replacement for incandescent fixtures that are dimmed for "mood scenes" such as wall sconces in a dining area. Below the 20% limit, the lamp remain at the approximate 20% level, in other cases it may flicker or the starter circuitry may stop and restart.[58] Above the 80% dim limit, the bulb will generally glow at 100% brightness. Dimmable CFLs have a higher purchase cost than standard CFLs due to the additional circuitry required for dimming. A further limitation is that multiple dimmable CFLs on the same dimmer switch may not appear to be at the same brightness level. Cold Cathode CFLs are an exception to most dimming and compatibility problems and will generally work well to very low levels and don't flicker. This combined with their instant on and negligible warm-up period makes them popular replacements for incandescent bulbs on dimmer circuits.
Perceived Coldness of Low Intensity CFL
When a CFL is dimmed the colour temperature (warmth) stays the same. This is counter to most other light sources (such as the sun or incandescents) where colour gets warmer as the light source gets dimmer. Emotional Response Testing suggests that people find dim, bluish light sources to be cold or even sinister. This may explain the persistent lack of popularity for CFL's in bedrooms and other settings where a subdued light source is preferred.
Some CFLs are labeled not to be run base up, since heat will shorten the ballast's life. Such CFLs are unsuitable for use in pendant lamps and especially unsuitable for recessed light fixtures. CFLs for use in such fixtures are available.[59] Current recommendations for fully enclosed, unventilated light fixtures (such as those recessed into insulated ceilings), are either to use 'reflector CFLs' (R-CFL),[60][61] cold cathode CFLs or to replace such fixtures with those designed for CFLs.[60]
Power quality
The introduction of CFLs may affect power quality appreciably, particularly in large-scale installations.[62][63] In such cases, CFLs with low (below 30 percent) total harmonic distortion (THD) and power factors greater than 0.9 should be used.[64][65]
Time to achieve full brightness
Compact fluorescent lamps may provide as little as 50-80% of their rated light output at initial switch on[66] and can take up to three minutes to warm up, and color cast may be slightly different immediately after being turned on.[67] This compares to around 0.1 seconds for incandescent lamps. In practice, this varies between brands/types. It is more of a problem with older lamps, 'warm (color) tone' lamps and at low ambient temperatures. Cold cathode CFLs reach their rated light output far more quickly.
Infrared signals
Electronic devices operated by infrared remote control can interpret the infrared light emitted by CFLs as a signal limiting the use of CFLs near televisions, radios, remote controls, or mobile phones.[68]
Audible noise
CFLs, much as other fluorescent lights, may emit a buzzing sound, where incandescents normally do not. Such sounds are particularly noticeable in quiet rooms, and can be annoying under these circumstances. Newer compact fluorescent light bulbs are nearly noiseless, but some poorly made CFLs may still emit a buzzing sound.
Fluorescent lamps can cause window film to exhibit iridescence. This phenomenon usually occurs at night. The amount of iridescence may vary from almost imperceptible, to very visible and most frequently occurs when the film is constructed using one or more layers of sputtered metal. It can however occur in non-reflective films as well. When iridescence does occur in window film, the only way to stop it is to prevent the fluorescent light from illuminating the film.
Use with timers and other electronic controls
Electronic (but not mechanical) timers can interfere with the electronic ballast in CFLs and can shorten their lifespan.[68] Some timers rely on a connection to neutral through the bulb and so pass a tiny current through the bulb, charging the capacitors in the electronic ballast. They may not work with a CFL connected, unless an incandescent bulb is also connected. They may also cause the CFL to flash when off. This can also be true for illuminated wall switches and motion sensors. Cold cathode CFLs avoid many of these problems.
Fire hazard
When the base of the bulb is not made to be flame-retardant, as required in the voluntary standard for CFLs, then the electrical components in the bulb can overheat which poses a fire hazard.[69] The Electrical Safety Authority of Canada has stated that certified bulbs do not pose a fire hazard as they use anti-fire plastics.[70]
Outdoor use
CFLs not designed for outdoor use will not start in cold weather. CFLs are available with cold-weather ballasts, which may be rated to as low as -23°C (-10°F).[71][dead link] Standard compact fluorescents will fail to operate at low temperatures. Light output drops at low temperatures.[72] Cold cathode CFLs will start and perform in a wide range of temperatures due to their different design.
Differences among manufacturers
There are large differences among quality of light, cost, and turn-on time among different manufacturers, even for lamps that appear identical and have the same color temperature.
Lifetime brightness
Fluorescent lamps get dimmer over their lifetime,[73] so what starts out as an adequate luminosity may become inadequate. In one test by the US Department of Energy of 'Energy Star' products in 2003-4, one quarter of tested CFLs no longer met their rated output after 40% of their rated service life.[74][75]
UV emissions
Fluorescent bulbs can damage paintings and textile fabrics which are composed of light-sensitive dyes and pigments. They can also initiate polymer degradation.[citation needed]

[edit] Efforts to encourage adoption

Due to the potential to reduce electric consumption and pollution, various organizations have encouraged the adoption of CFLs and other efficient lighting. Efforts range from publicity to encourage awareness, to direct handouts of CFLs to the public. Some electric utilities and local governments have subsidized CFLs or provided them free to customers as a means of reducing electric demand (and so delaying additional investments in generation).

More controversially, some governments are considering stronger measures to entirely displace incandescents. These measures include taxation, or bans on production of incandescent light bulbs. Australia, Canada, and the US have already announced nationwide bans on incandescent bulbs.[76][77]

At the meeting of the Ecodesign Regulatory Committee in Brussels on December 8 2008, the European Union Member States experts approved the European Commission's proposals for a regulation progressively phasing out incandescent bulbs starting in 2009 and finishing at the end of 2012. By switching to energy saving bulbs, EU citizens will apparently save almost 40 TWh (almost 11 million European households electricity consumption), which will also lead to a reduction of about 15 million tons of CO2 emission per year.[78]

[edit] Labeling programs

In the United States and Canada, the Energy Star program labels compact fluorescent lamps that meet a set of standards for starting time, life expectancy, color, and consistency of performance. The intent of the program is to reduce consumer concerns due to variable quality of products.[79] Those CFLs with a recent Energy Star certification start in less than one second and do not flicker. There is ongoing work in improving the 'quality' (Color Rendering Index) of their light.[80]

In the United Kingdom a similar program is run by the Energy Saving Trust to identify lighting products that meet energy conservation and performance guidelines.[81]

[edit] Notes and references

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  2. ^ Masamitsu, Emily (May 2007), "The Best Compact Fluorescent Light Bulbs: PM Lab Test", Popular Mechanics,, retrieved on 2007-05-15 
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  4. ^ a b Michael Kanellos (August 2007), "Father of the compact fluorescent bulb looks back", CNet News,, retrieved on 2007-07-17 
  5. ^ 3-Way Compact Fluorescents -
  6. ^ National Energy Foundation - redirection page
  7. ^ "Osram Dulux EL Energy-Saving Lamps" (PDF). Osram. Archived from the original on 2006-07-22. Retrieved on 2007-12-24. 
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  9. ^ Light output of long-life incandescent lamps
  10. ^ Minnesota's Energy Challenge
  11. ^ Low Energy Long Life CFL Light Bulbs Globe Style- Bayonet Cap and Edison Screwed Cap
  12. ^ Get the Most Life out of your CFL « KitchAnn Style
  13. ^ Performance Standard and Inspection Methods of CFL
  14. ^ Charles P. Halsted (March 1993). "Brightness, Luminance, and Confusion". Information Display. Naval Air Warfare Center Warminster, PA. Retrieved on 2007-10-07. "If the luminance of a viewed light source is increased 10 times, viewers do not judge that the brightness has increased 10 times. The relationship is, in fact, logarithmic: the sensitivity of the eye decreases rapidly as the luminance of the source increases. It is this characteristic that allows the human eye to operate over such an extremely wide range of light levels." 
  15. ^ Krešimir Matković (December 1997). "Color Science Basics: Human Vision" (in English). Tone Mapping Techniques and Color Image Difference in Global Illumination. Institut für Computergraphik eingereicht an der Technischen Universität Wien. Retrieved on 2007-10-07. "It is interesting, that despite the fact that incoming light can have a dynamic range of nearly 14 log units, the neural units can transfer the signal having the dynamic range of only about 1.5 log units. It is obvious that there is some adaptation mechanism involved in our vision. It means that we adapt to some luminance value, and then we can perceive data in a certain dynamic range near the adaptation level. One of the most important characteristics that changes with different adaptation levels is the just noticeable difference." 
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  18. ^ The 17% to 21% figure is based on 60 to 72 lumens per watt source efficacy and 347 lumens per radiant watt luminous efficacy of radiation for a tri-phosphor spectrum from this source: Ohno, Yoshi (2004), "Color Rendering and Luminous Efficacy of White LED Spectra" (PDF), Proc. of SPIE (Fourth International Conference on Solid State Lighting), 5530, SPIE, Bellingham, WA, doi:10.1117/12.565757, 
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  33. ^ retrieved January 5, 2009
  34. ^ retrieved March 29, 2009
  35. ^ Color Temperature and CRI of Energy Saver Lamps
  36. ^ Compact Fluorescent Light Bulbs – A Tale From Dust to Dust retrieved June 15, 2008
  37. ^ "Mercury Content Information Available for Lamps on the 2003 New Jersey Contract T-0192". Retrieved on 2007-05-15. 
  38. ^ "Canada-Wide Standard for Mercury-Containing Lamps" (PDF). 2001. Retrieved on 2007-03-23. 
  39. ^ "Frequently Asked Questions Information on Compact Fluorescent Light Bulbs (CFLs) and Mercury June 2008" (PDF). 2008. Retrieved on 2008-08-31. 
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