A compact fluorescent lamp (CFL) is a type of fluorescent lamp designed to replace an incandescent lamp. Many CFLs can fit in the existing incandescent light fixtures.
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).
A compact fluorescent lamp (CFL), is a type of lamp (light bulb) designed to fit into the same space as an incandescent bulb, but with the advantages of a fluorescent lamp. Many CFLs can directly replace an existing incandescent lamp.
The purchase price of a CFL is often much higher than an incandescent lamp of the same output, and the light from CFLs looks different to light from incandescent lamps. But CFLs have a longer rated life and use less energy. A CFL can save over US$30 in electricity costs over the lamp’s lifetime compared to an incandescent lamp.
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Compared to general service incandescent lamps giving the same amount of visible light, CFLs use less power and have a longer rated life. In the United States, a CFL has a higher purchase price than an incandescent lamp, but can save over 30 US$ in electricity costs over the lamp's life time. 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 some sources rate the best 'soft white' CFLs as subjectively similar in color to standard incandescent lamps.
The compact fluorescent lamp 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 $25M to build new factories to produce them and the invention was shelved. However, the design leaked out and was copied by others.
Globally introduced in the early 1980s, CFLs have steadily increased in sales volume. The most important advance in fluorescent lamp technology (including 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. There are two types of CFLs: integrated and non-integrated lamps.
Integrated lamps combine a bulb, an electronic ballast and either a screw or bayonet fitting in a single CFL unit. These lamps allow consumers to easily replace incandescent lamps 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. For example, recessed lights (can lights) cost (in 2007) around $10 USD per can.
Non-integrated lamps allow for the replacement of consumable bulbs and the extended use of electrical ballasts in a light fixture. This fluorescent bulb itself does not include a ballast. Since the ballasts are placed in the light fixture they are larger and last longer, vis-a-vis the integrated ones. Non-integrated CFL housings can be both more expensive and sophisticated, providing options such as dimming, less flicker, faster starts, etc. The ballasts make these light fixtures relatively expensive. They cost anywhere from $85 to $200 USD for each recessed can. If a ballast with dimming capabilities is desired the cost is anywhere from $125 to $300 per recessed can. Non-integrated CFLs are more popular for professional users, such as hotels and office buildings. However, the capabilities of these sophisticated external ballasts (e.g., faster starts, limited flicker, dimming, longer life spans, etc) are starting to appear in the integrated CFLs.
How they work
There are two main parts in 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 emit 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.
The ballast regulates the flow of current through the lamp - very high at the beginning to ignite the lamp (with the help of the starter), then rapidly limits the current to safely sustain its operation.
Comparison with incandescent lamps
Electrical power equivalents for differing lamps
|Compact Fluorescent (W)
Modern CFLs typically have a life span of between 6,000 and 15,000 hours, whereas incandescent lamps are usually manufactured to have a life span of 750 hours or 1000 hours.
The life of a CFL lamp 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.
CFL lamps give less light later in their life than they did at the start. The light output depreciation is exponential, with the fastest losses being soon after the lamp was new. By the middle to end of their lives, CFLs can be expected to produce 70% to 80% of their original light output.
Energy consumption: For a given light output, CFLs use between one-fifth and one-quarter of the power of an equivalent incandescent lamp. For example, lighting accounted for approximately 9% of household electricity usage in the United States in 2001, so widespread use of CFLs could save most of this, for a total energy saving of about 7% from household usage.
Cost In addition to the above savings on energy costs, CFLs' average life is between 8 and 15 times that of incandescents. While the purchase price of a 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 in many applications.
Energy savings: Since CFLs use less power to supply the same amount of light as an incandescent lamp of the same lumen rating, they can be used to decrease energy consumption at the location in which they are used. In countries where electricity is largely produced from burning fossil fuels, the savings reduces emissions of greenhouse gases and other pollutants; in other countries the reduction may help reduce negative impacts from radioactive waste, hydroelectric plants, or other sources; see environmental concerns with electricity generation for details. While CFLs require more energy in manufacturing than incandescent lamps, this is offset by the fact that they last longer.
Mercury emissions: CFLs, like all fluorescent lamps (e.g., long tubular lamps common in offices and kitchens), contain small amounts of mercury and it is a concern for landfills and waste incinerators where the mercury from lamps may be released and contribute to air and water pollution. In the USA, lighting manufacturer members of the National Electrical Manufacturers Association (NEMA) have made a voluntary commitment to cap the amount of mercury used in CFLs. Due to health and environmental concerns about mercury, it is unlawful to dispose of fluorescent bulbs as universal waste in the states of California, Minnesota, Ohio, Illinois, Indiana, Michigan, and Wisconsin.
According to the European Commission Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR) in 2008, the only property of compact fluorescent lamps that could pose an added health risk is the ultraviolet and blue light emitted by such devices. The worst that can happen is that this radiation could aggravate symptoms in people who already suffer rare skin conditions that make them exceptionally sensitive to light. They also stated that more research is needed to establish whether compact fluorescent lamps constitute any higher risk than incandescent lamps.
If individuals are exposed to the light produced by some single-envelope compact fluorescent lamps for long periods of time at distances of less than 20 cm, it could lead to ultraviolet exposures approaching the current workplace limit set to protect workers from skin and retinal damage.
The UV received from CFLs is too small to contribute to skin cancer and the use of double-envelope CFL lamps "largely or entirely" mitigates any other risks.
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