Overview
Environmentally friendly options for replacing incandescent lighting are usually either Compact Fluorescent Lamps (CFL) or Light Emitting Diode (LED) bulbs.
Compact Fluorescent Lamps
CFLs operate similar to conventional fluorescent lamps where electricity is used to activate mercury vapor that resides in the glass tube. The current affects the mercury atoms to make ultraviolet (UV) light which is not visible to the eye. The photons from the ultraviolet light hit a phosphor layer inside the bulb housing to emit photons of visible light thereby creating light output from the tube. The ultraviolet light may cause fading in paintings or textiles. The mercury contained within the lamp means that the light bulbs need to be properly disposed of as compact fluorescent bulbs dumped in landfills burst, causing mercury to be released, draining into the ground, extremely contaminating the food chain. Some states, such as California, ban the disposal of mercury-containing bulbs in the trash. Some state laws require fluorescent bulbs to be collected as hazardous waste or properly recycled. Check with the EPA site to help you with proper disposal procedures according to your state, or you can find a recycling center near you at Earth911.
Unlike fluorescent tubes that do not contain circuitry, compact fluorescent typically integrate all of the necessary circuits in the bottom of the light allowing the single unit to be used in a standard incandescent light bulb socket. CFLs come in a variety of styles and shapes, but one will often see them in a tube or spiral option. Higher surface area allows for a higher light output in CFLs.
LED Lighting
Solid-state lighting, more commonly known as LED (light-emitting diode) lighting is a solid semiconductor light source that does not use a gas tube like that of the CFL. Light from an LED is made when electricity is applied through the semi-conductor doped with impurities to create one half which is a "p-side", and another half that forms the "n-side". The charge-carriers (electrons and holes) flow into the pn junction where these two halves meet, and releases energy in the form of a photon, theby creating light. The color of the light output depends on the materials forming the pn junction. There is no filament to burn out, and unlike CFLs, LED lights do not contain the toxic mercury, nor do they emit ultraviolet light.
To get a bright output, many older models of LED light bulbs had resorted to clustering many individual LEDs into a one housing, however many of the newer LED bulbs drive a single high powered LED element. These LED light bulbs are significantly smaller than their CFL counterparts, and are offered in form factors that produce a directional beam through the use of a glass or plastic lens, or encased behind a broken spreader to provide wider light coverage.
Summary of Benefits
Less Expensive Electricity Bil l:
Although the cost of the light bulbs are initially more expensive, both CFL and LED lamps save you money long run. Less electricity is used, and bulbs are being replaced much less frequently. LEDs use about half the amount of electricity that CFLs that output the same brightness use.
Long Lifespan:
Run-times of CFL bulbs typically range from 6,000 hours to 15,000 hours while the typical lifespan of an incandescent lamp is around 1,000 hours. A LED lamp can last 50,000 to 60,000 hours which equates to around 5 or 6 years (10 times longer than a CFL).
High quality light output:
Both CFL and LED bulbs can now provide a range of color temperatures. Consumers are no longer restricted to the blueish, "cool-white", of earlier bulbs, and can now buy warmer colored lamps. Lower quality CFL bulbs that use a magnetic ballast will flicker. Look for an electronic ballast when buying a CFL. LEDs are driven so that they do not flicker.
Versatility:
Indoor, outdoor, home, or commercial LED and CFL bulbs can be used in a many different types of applications where conventional bulbs were once used. LED bulbs and CFLs can be used in track lighting, table lamps, task lighting, recessed fixtures, and ceiling fixtures. Both types of bulbs are available in dimmable models for use with a standard dimmer switch.
Durability:
Since LED light bulbs do not use a filament like incandescent, they are shock resistant and can be used in high vibration applications.
Summary of Drawbacks and Limitations
CFLs:
No spot lights – Since CFLs do not project a focused beam like an LED bulb, they are best used for area lighting.
Temperature sensitivit y – CFLs are sensitive to heat, their lifetime will be reduced if the fixture does not properly dissipate heat. CFLs are also affected by cold. CFLs will take considerably longer to reach full brightness in cold weather. In extreme situations they may not properly warm up.
Warm-up time – LED lights turn on instantly, while CFLs take a few minutes to warm up and provide full brightness.
Hazardous waste – CFLs contain mercury and must be properly disposed of. The EPA website provides proper disposal options. LEDs do not contain mercury.
Frequent Cycling Lowers Lifespan – In high traffic areas, such as home bathrooms, where CFLs are turned on and off often, their lifespan will decrease quickly.
Ultraviolet Light – CFL bulbs can emit UV-light which may not be desirable for certain applications.
LEDs:
High initial cost – The LED bulbs themselves are costly, but the initial investment is quickly recuperated in lower electricity bills.
Heat generation – Certain high power (5w and up) LED light bulbs may produce significant heat. Heat-sinks are often built into the bulbs themselves, and may require LED specific fixtures to ensure proper air-flow.
LED light bulbs are becoming the choice for energy efficient lighting due to their varied bulb options, and the ease of which the light output can be layered and controlled when compared with CFL bulbs.
