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UM Guide to Energy-Efficient Lighting
Green Lighting: What a Bright Idea!
Lighting consumes a greater share of U-M's energy budget than any other function except heating. Each year over $4 million is spent on electricity to operate the lights in the buildings on U-M's Central and North campuses in Ann Arbor. Much of this energy is needed, but a significant portion is consumed unnecessarily in areas that use inefficient or excessive lighting systems.

Inefficient lighting also has a negative impact on the environment, by requiring the combustion of greater quantities of fossil fuels in electric power plants. The burning of coal, oil, or natural gas results in atmospheric pollutants shown to cause acid rain, smog, and global warming.
Many organizations have come to think of lighting as a prime opportunity for cost saving. Not only can the right lighting system lower electricity bills, but it can often make a work environment more comfortable.

The U-M Plant Department has recently undertaken an ambitious program to upgrade many lighting systems so that they operate more efficiently.

This booklet is an attempt to provide some information about lighting systems and the ways they can be made more efficient. Hopefully, with everyone's cooperation, we can transform the U-M campus into an example of efficient and environmentally friendly lighting.



Fluorescent Lighting
As a general rule, U-M uses fluorescent light fixtures to provide illumination in most of its buildings. Fluorescent lighting has been shown to be the most efficient and cost-effective lighting to provide the high quality of illumination suitable for most classrooms, offices, and laboratories.

Because they are so prevalent in U-M buildings, it is worthwhile to understand a little bit about how fluorescent lights work, and the way in which the lamps are rated.

Ballasts:
Fluorescent fixtures produce illumination by passing a low intensity electric current through a special gas. The "ballast" is a device mounted inside a fluorescent fixture which develops the proper voltage needed to start the flow of electricity through the gas, and then regulates the flow in order to stabilize light output once the lamp has been turned on.

In the past, the most common type of ballast was an electromagnetic design which operated at 60 Hertz. Electromagnetic ballasts were cheap and reliable, however they had several drawbacks including noise, light flicker, heat generation, and PCB contamination.

High-Efficiency Electronic Ballasts:
Within the last ten years or so, lamp manufacturers have developed a ballast of electronic design which is rapidly replacing the older, electromagnetic types in most buildings in the U.S. These electronic ballasts operate at frequencies much higher than 60 Hertz; in fact the typical electronic ballast operates at about 20,000 - 25,000 Hertz. Because they control a much higher frequency current, less electric energy is needed to produce the same level of illumination. In addition the high frequency operation eliminates the annoying problems of light flicker and noise which have traditionally been the bane of fluorescent fixtures.

Electromagnetic vs. Electronic Ballasts

Electromagnetic Ballast
Electronic Ballast

Heat
Generates about 30 deg. C more heat than electronic.
Internal losses are less than 8 watts.

Light Flicker
60 Hz frequency causes light flicker levels of 30% or higher.
20,000-25,000Hz frequency produces virtually no detectable flicker.

Noise
Vibrations induced by electromagnetic field causes humming noise.
No audible noise.

Weight
Heavy components coated in heavy protective material.
Weighs about half as much as electro-magnetic type.


Ballast Retrofits:
Because of their obvious advantages, the University of Michigan has made a commitment to replacing worn out electromagnetic ballasts with the newer electronic types. For several years, Plant electricians have followed the practice of installing an electronic ballast whenever an electromagnetic ballast fails. As a result, there are today several thousand electronic ballasts already installed on the U-M campus.

The clear advantage of electronic ballasts has led to the decision in some buildings to make a complete changeover all at once, even though the existing electromagnetic ballasts may still be functioning. The energy cost savings from such a change are is often large enough to justify this approach. In addition, the quality of lighting is usually improved.

Fluorescent Lamps
Fluorescent lamps come in many different ratings. There is a great deal of confusion about what the ratings mean, and which rating is best for a given application. Hopefully, the following discussion will clear up most of the confusion:

Lamp Dimensions:
The older, less-efficient fluorescent lamps were designated as "T-12" lamps, meaning simply that the diameter of the bulb was 1.5 inches. Under Federal regulations adopted in 1992 as part of the "Federal Energy Act of 1992," no T-12 lamps were to be manufactured after October 1995.

T-8 lamps, having a tube diameter of 1.0 inch, are more efficient and are used in place of the old T-12s. T-8 lamps are rated at 32 watts compared to the 40 watt rating of T-12 lamps, and yet they provide the same amount of illumination.
Coloration:
Many people are concerned about whether the "color" produced by the newer fluorescent lamps is as good as what they have become used to. The ability of lamps to render colors is rated by illumination engineers by a Color Rendering Index (CRI). Under the CRI, a light source with a rating of 100 has the same color rendering qualities as sunlight.

The old T-12 fluorescent lamps had a CRI rating of about 62; the light that they produced, while intense, did not have the characteristics of sunlight. That is why you often heard people complaining about the "artificial," or "unnatural" feeling of a room illuminated by the old fluorescent lamps.

The T-8 lamp which the University has adopted as its new standard has a CRI of 75, which is a 21 per cent improvement over the old T-12s. This means that colors should appear truer to sunlight under the T-8 lamps.

Note: Fluorescent lamps are available which have CRI ratings as high as 90, however, the lumen efficiency may be less. In addition, the higher the CRI rating, the more expensive the lamp. In rare applications which require excellent color rendering it may be necessary to install a lamp having a CRI of 85 or higher.


Chromaticity:
The chromaticity of a fluorescent lamp is another parameter used to gauge light quality. Chromaticity refers to the pattern of visible wavelengths emitted by a bulb. Chromaticity is measured in units of degrees Kelvin (K).

Most lamps fall in the range of 2200 to 7500 K. The lower a lamp's Kelvin rating the more it will create a visually "warm" atmosphere, with a slightly pinkish coloration. Many people prefer to use these "warm white" lamps in their homes, because they create coloration which is psychologically warm and restful.

The higher a lamp is rated on the Kelvin scale the "cooler" it will appear, creating bluish tones that some people find harsh or uncomplimentary.

The T-8 lamp which the University has adopted as its standard has a chromaticity of 3500 K. These lamps are considered to be visually "neutral," being neither warm nor cool, and result in improved color rendering for most general office work.


"Full Spectrum" Lamps:
"Full spectrum" lamps are defined as fluorescent lamps having a CRI of 90 or better and a color temperature of 5000 K. They are designed to provide a completely balanced pattern of visible wavelengths for applications where highly accurate color rendering is required. In a sense, full spectrum lamps produce the most accurate colors, however they are not "natural" in the sense that they do not replicate natural sunlight, or the normal conditions in which people view things. Full spectrum lamps are much more costly than regular lamps, and they require more electricity for a given level of light output.


In summary:
The T-8, 3500 K fluorescent lamp was designated as the U-M "standard" in 1993 based upon its improved performance and energy efficiency. The T-8 lamp provides a high quality of light which is suitable for the vast majority of functions carried out in U-M buildings. In most cases, the new T-8 lamp will provide a higher quality of illumination than the T-12 lamps which they replace, in the sense that colors will be truer and closer to natural daylight.

In a few rare instances, certain areas which carry out special functions may require a lamp having different characteristics than the standard T-8. Please contact your Facilities Manager or the lighting engineers in the Utilities Department to discuss these situations and the options which are available.
Ultra-Violet Radiation
With the increased publicity about potential health hazards from ultraviolet radiation, there has been a growth in the public's interest about whether the amount of ultraviolet (UV) radiation emitted by general lighting fixtures is a health risk.

Virtually all light fixtures emit some amount of ultraviolet radiation. The amount, however, is far below the levels which are found in natural daylight. In fact, they are even lower than the levels produced by daylight filtered through a normal glass window pane. The next table gives "permissible exposure times" for a variety of different lighting fixtures.

A recent U.S. Food and Drug Administration study found that exposure to eight hours of fluorescent lamp light (in a typical office environment) resulted in the same UV radiation as standing in summer sunshine for 72 seconds in Washington, D.C. (1)

(Note: If you have further questions concerning UV exposure from your lighting system, feel free to request more information from OSEH or the Utilities Department.)

Permissible Exposure Time (PET) Table
The American National Standards Institute (ANSI) has proposed a new standard entitled "Photobiological Safety for Lamps - Risk Group Classification and Labeling," which establishes a Permissible Exposure Time (PET) for existing lamps. Lamps with a PET rating of greater than 8 hours are not considered by ANSI to be a cause for concern.

Light Source Type PET: (hours)
Sun, at 30¡ from zenith (near noon at 40 N latitude): 0.2
Sun, at 60¡ from zenith (~5:00 p.m. in summer): 0.6
Sun, at 80¡ from zenith (10¡ above horizon): 0.8

Incandescent & HalogenIncandescent Lamps
MR 16 50W halogen lamp, without cover glass: 18
MR 16 50W halogen lamp, with cover glass: 600
120 Volt/500W linear quartz halogen: 4.6
120 Volt/350W linear quartz halogen-IRª: 540
PAR38 120W incandescent: 250
PAR38 90W glass halogen: 720
PAR 38 60W quartz halogen-IR: 5,000

Fluorescent Lamps
F40 T12 cool white fluorescent: 16
F32 T8 SP41 (made in US): 30
F32 T8 SP41 (made in UK): 108

High Intensity Discharge (HID) Lamps
400W mercury vapor: 72
400W metal halide: 260
400W high pressure sodium (HPS): 6,800


Other Lighting Systems
Fluorescent lighting is not the only type of lighting found on the U-M campus. Other types of lighting fixtures which are appropriate for certain applications are described below:

Compact Fluorescent Lamps:
If an office or work area is equipped with small incandescent lamps, it may be worthwhile to replace these fixtures with a relatively new device called a "compact fluorescent lamp." A compact fluorescent lamp provides the benefits of fluorescent illumination in a device which can be installed into the screw-in sockets used by incandescent lamps. They are, however, incompatible with circuits which dim lights.

Compact fluorescent lamps can be as much as 80% more efficient and can last more than ten times longer than filament lamps. For instance, a 26 watt compact fluorescent lamp can replace a 100 watt incandescent lamp for a savings of 75%. Compact fluorescent lamps have an average CRI of 82 and come in a wide range of color temperatures. (3)

Halogen Lamps:
When compared to conventional incandescent lamps, tungsten halogen lamps have a longer life, higher efficiency, and compact size. They are, however, more expensive than conventional lamps. Because of these characteristics, they are used in applications such as floodlighting, display and accent lighting, and automobile headlighting.

Even more efficient than regular halogen lamps are Halogen-IR (HIR) lamps. These lamps trap wasted invisible infrared emissions and redirect them to produce more visible light. This results in a more than 40% efficiency gain over standard halogens, while providing the same amount of light output, beam control and compactness as the standard halogen, HIR lamps usually have a chromaticity of 2700-3000K while providing a CRI greater than 96.

Unlike the compact fluorescent lamps, halogens can be used in dimming circuits. At some point in time, halogen lamps may experience bulb blackening due to frequent dimming. This problem can be easily remedied by leaving the lamp on at full brightness for about 8 hours.

High Intensity Discharge (HID) Lighting:
These discharge lamps use ballasts to produce light by passing an electric current through a vapor or gas like the fluorescent lamps, rather than through a tungsten wire.

HID lamps are some of the most efficient and long-lived lamps available. They have a long lamp life (approximately 10,000-25,000 hours), high light output and can cover large areas. This makes them a good choice for industrial, commercial, and floodlighting applications.

HID lamps include groups of lamps known as mercury vapor, metal halide (MH), and high pressure sodium (HPS). All three of the lamps can be used for street or parking lot floodlighting and industrial and commercial applications such as gymnasiums and rooms with high ceilings as well as retail merchandise displays. Also, as stated above, some models can also be used in office or classroom applications.

The metal halide and the sodium lamps are more efficient and can have better color rendition4 than the mercury lamps. These two types of lamps can produce over 60% more lumens than a mercury vapor lamp of the same wattage. Also, at the end of the average rated life, a mercury vapor lamp will have dropped down to less than 45% of its initial lumens while the metal halide and sodium lamps will only have dropped to 65% and 80%, respectively10. Due to these drawbacks, U-M no longer uses mercury vapor lamps.

Seasonal Affective Disorder (SAD)

Seasonal Affective Disorder (or SAD) is a recently identified illness characterized by a vague sense of depression during the winter months. It is estimated that SAD affects ten million Americans to some degree or another, 83 per cent of whom are women. (2)

Experiments have shown that SAD is directly related to the amount of light that enters the eyes, which is why it usually worsens when the days shorten in the fall and then subsides in the spring. For some people, light entering the eye is believed to modify hormone levels in the brain, causing feelings of mild depression.

SAD patients are often treated with light therapy which involves periodic exposure to very intense light levels. Upon hearing of this treatment, many people conclude that SAD can be avoided by installing special lights in their home or office. Unfortunately, this is not the case.

The light levels which are used in therapy for SAD patients are extremely intense: somewhere between 5 to 20 times greater (2400-10,000 lux) than normal indoor lighting levels. Therefore, the lighting in an indoor space cannot reasonably be modified to provide the extremely high levels of light needed to be an effective source of therapy. Keep in mind that the hormone levels are usually triggered by sunlight which can have a brightness level of 10,000 lux.

It has also been found by doctors that the "therapeutic light" for SAD does not need to have any special wavelength characteristics; it is the intensity of the light which is important, not the color quality. All types of fluorescent lights are equally effective, so changing the lamps in a room to some special type will not produce a benefit to persons suffering from the SAD syndrome.

Lighting Controls
Another way to save energy on lighting is by insuring that lights are only used when they are needed, or only to the extent they are needed. There are various types of automatic control devices which are sometimes used for this purpose:

Occupancy Sensors:
An occupancy sensor is a device that detects the presence of people in a room and turns off the lights when the room has been unoccupied for a set period of time. When a sensor detects someone entering the room it will turn on the lights again.

There are several different types of sensors; some operate by detecting the heat emitted by a person's body, and some by sensing movement using ultrasonic Doppler technology. It is possible to adjust the time delay to the specific needs of the area being surveyed.

Listed below are a few examples of sensor applications and the typical amount of energy that can be saved in each:
Application Typical Energy Savings

Offices 15-70%
Restrooms 30-75%
Corridors 30-60%
Classrooms 20-75%
Dimming Controls:
If it is not practical to turn off all of the lights in a room, it may be worthwhile to install lighting systems that have dimming capabilities. These allow the reduction of the lighting intensity in a room during periods of non-occupancy. In addition, they are sometimes used to adjust lighting in response to changes in the amount of natural daylight.

It is important to remember that not all lamps work with dimming circuits (compact fluorescent for example). To get this capability, it may be necessary to replace both the lighting fixtures and the lamps.

What You Can Do
Many of the things which are done to improve lighting efficiency at U-M involve the overall design and layout of the lighting system. Once a lighting system is in place, however, there are a number of things that building occupants can do to reduce the energy used for lighting:

Turn off the lights in classrooms, offices or restrooms when the rooms are not occupied. The energy saved by doing so will far outweigh the slight reduction in lamp life.

Consider using desk lamps (so-called "task-lighting") and reducing the overall brightness in the room. In addition to saving energy, this change often creates a more comfortable work environment.



Use natural daylight when possible.
If you spend a lot of time working on a computer, consider reducing the overall brightness level in your room to enhance CRT screen visibility.
Report any lighting problems to your Zone Maintenance office. This might include a burned-out lamp, defective occupancy sensor, or a flickering bulb.
If your building has areas where occupancy sensors are being used, please cooperate with their use.
If a lighting upgrade is being planned in your building, be aware that slight differences in brightness or coloration may be noticeable for a short period. However, in most cases at U-M, light system retrofits actually improve the overall lighting environment.
Conclusion
We hope this booklet has been helpful in answering some of the questions that are most often asked about lighting systems and lighting system retrofits at the University of Michigan. Trying to reduce energy costs should be a concern to all members of the U-M community.

Footnotes
GE Lighting Answer Center. 1-800-933-5489. 1996
Mental Health Association of Colorado, Inc., Denver Colorado 80224. (303) 377-3040.
Spectrum 9200 Catalog, General Electric Company, 1993.
A Mercury lamp CRI = 15-50, sodium lamp = 22-70, metal halide = 65-85. Information taken from the Spectrum 9200 Catalog, General Electric Company, 1993.
For more information about lighting system retrofits or to discuss an energy conservation idea, contact the U-M Utilities Department at 764-2492.

Questions or comments about this document can be directed to Yoshiko Hill (get address) (72.157.177.137).

Content modified: August, 2004

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Energy Efficient Lighting
< live >
Benefits of the Compact Fluorescent Bulbs
Choosing a CFL Bulb
Limitations, Disposal of CFLs
LED Lights, Benefits, Uses
Online Sources for Energy-efficient lighting

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• Visit Eartheasy's online store
Electric lighting burns up to 25% of the average home energy budget.
The electricity used over the lifetime of a single incandescent bulb costs 5 to 10 times the original purchase price of the bulb itself.

Compact Fluorescent Lights (CFL) and Light Emitting Diode (LED) bulbs have revolutionized energy-efficient lighting.

CFLs are simply miniature versions of full-sized fluorescents. They screw into standard lamp sockets, and give off light that looks just like the common incandescent bulbs - not like the fluorescent lighting we associate with factories and schools.

LEDs are small, solid light bulbs which are extremely energy-efficient. New LED bulbs are grouped in clusters with diffuser lenses which have broadened the applications for LED use in the home.

Benefits
Efficient: CFLs are four times more efficient and last up to 10 times longer than incandescents. A 22 watt CFL has about the same light output as a 100 watt incandescent. CFLs use 50 - 80% less energy than incandescents.
Less Expensive: Although initially more expensive, you save money in the long run because CFLs use 1/3 the electricity and last up to 10 times as long as incandescents. A single 18 watt CFL used in place of a 75 watt incandescent will save about 570 kWh over its lifetime. At 8 cents per kWh, that equates to a $45 savings.
Reduces Air and Water Pollution: Replacing a single incandescent bulb with a CFL will keep a half-ton of CO2 out of the atmosphere over the life of the bulb. If everyone in the U.S. used energy-efficient lighting, we could retire 90 average size power plants. Saving electricity reduces CO2 emissions, sulfur oxide and high-level nuclear waste.
High-Quality Light: Newer CFLs give a warm, inviting light instead of the "cool white" light of older fluorescents. They use rare earth phosphors for excellent color and warmth. New electronically ballasted CFLs don't flicker or hum.
Versatile: CFLs can be applied nearly anywhere that incandescent lights are used. Energy-efficient CFLs can be used in recessed fixtures, table lamps, track lighting, ceiling fixtures and porchlights. 3-way CFLs are also now available for lamps with 3-way settings. Dimmable CFLs are also available for lights using a dimmer switch.
Choosing a CFL
CFLs come in many shapes and sizes. When purchasing CFLs, consult the seller for recommendations and consider the following:
• Choose the color temperature, if listed, that’s right for you; for example:
Approx. 2700K = Warm White (looks just like incandescent)
Approx. 5000K = Cool White (white/blue, often higher CRI)

• Choose the shape. CFLs are available in a variety of shapes to fit a range of lamps and lighting fixtures. See below on this page for the most popular CFL shapes.

• Match lumens to the incandescent being replaced. Lumens indicate the amount of light being generated. (Watts is a measure of energy use, not light strength.) To compare lumens and watts see chart below:

..................Incandescent Watts...... . ..CFL Watt range... . . ... .. Lumen Range
40
60
.75
100
150
8 - 10
13 - 18
18 - 22
23 - 28
34 - 42
450
890
1210
1750
2780


Models

CFLs are available in a variety of styles or shapes. Some have two, four, or six tubes. Older models, and specialty models, have separate tubes and ballasts. Some CFLs have the tubes and ballast permanently connected. This allows you to change the tubes without changing the ballast. Others have circular or spiral-shaped tubes. In general, the size or total surface area of the tube determines how much light the bulb produces.

The following CFL bulb models come with standard sockets for easy installation in most common household applications.

Spiral Lamps
These bulbs are designed as a continuous tube in a spiral shape which has similar outside shape and light casting qualities to a standard incandescent bulb. Spiral CFL bulbs are made in several sizes to fit most common fixtures. more info

Triple Tube Lamps
These CFLs have more tubing in a smaller area, which generates even more light in a shorter bulb. They pack high light output into a very small space and can be used in fixtures designed for incandescent bulbs, such as table lamps, reading lamps, open hanging lamps, and bare bulb applications. more info

Standard Lamps
These are spiral lamps with a dome cover. They are designed to give the appearance of the traditional light bulb for consumers looking for the more familiar light bulb appearance. The glass diffuser provides a quality of light similar to the 'soft-white' type of incandescent bulbs. more info

Globe Lamps
This shape is commonly used in bathroom vanity mirrors or open hanging lamps, and bare bulb applications. Bathroom vanities usually require multiple bulbs, which generate radiant heat. The CFL globe will reduce this heat buildup while saving energy. The glass diffuser provides a soft-white light. more info

Flood Lamps
These lamps are designed to be ideal for recessed and track lighting fixtures, indoors and outdoors. They provide diffused, soft, white light, and generate less heat than will an incandescent flood or a halogen bulb. more info

Candelabra
The screw-in torpedo-shape and the small-base of this bulb is designed for smaller light fixtures throughout the house, from chandeliers to sconces. To use a smaller candelabra-based bulb in a regular socket, you can use a socket reducer, available at many hardware stores and home improvement centers.







Limitations
Although CFLs are an excellent source of energy-efficient lighting, they are not always the best choice for all lighting applications. Here are a few limitations to consider:
On/Off cycling: CFLs are sensitive to frequent on/off cycling. Their rated lifetimes of 10,000 hours are reduced in applications where the light is switched on and off very often. Closets and other places where lights are needed for brief illumination should use incandescant bulbs.
Dimmers/Timers: not all CFLs can be used on dimmer switches. Most CFLs can be used with a timer or a three-way fixture. Be sure to check the bulb package, which will indicate if the lamp is not intended for use with electronic timers or photocells. However, use of a timer will shorten the life of a CFL bulb. Note: some manufacturers, such as Philips, have recently introduced "dimmable" CFL bulbs to the market, so this limitation is being addressed.
Outdoors: CFLs can be used outdoors, but should be covered or shaded from the elements. Low temperatures may reduce light levels - check the package label to see if the bulb is suited for outdoor use.
Retail lighting: CFLs are not spot lights. Retail store display lighting usually requires narrow focus beams for stronger spot lighting. CFLs are better for area lighting.
Mercury content: CFLs contain small amounts of mercury which is a toxic metal. This metal may be released if the bulb is broken, or during disposal. New 'Alto' CFL bulbs are now available with low-mercury content. These low-mercury CFLs are available at our online store. For more information about mercury and CFLs, see below.

Mercury and CFLs

Mercury is a toxic metal associated with contamination of water, fish, and food supplies, and can lead to adverse health affects. A CFL bulb generally contains an average of 5 mg of mercury (about one-fifth of that found in the average watch battery, and less than 1/100th of the mercury found in an amalgam dental filling). A power plant will emit 10mg of mercury to produce the electricity to run an incandescent bulb compared to only 2.4mg of mercury to run a CFL for the same time. The net benefit of using the more energy efficient lamp is positive, and this is especially true if the mercury in the fluorescent lamp is kept out of the waste stream when the lamp expires.

All fluorescent lamps do not contain the same amount of mercury. Philips lamps with Alto Lamp Technology, for instance, contain less mercury than conventional fluorescent lamps. Philips claims the bulbs have the lowest amount of mercury of any bulb on the market at less than 3.8 mg per bulb. To achieve this, Philips uses a specially developed mercury capsule which ensures the exact amount of mercury is placed in a tiny glass capsule which is attached to the lamp cathode. To purchase the new 'Alto' CFLs, click here.

Important Note: Handling and Disposal of CFLs

The mercury in compact fluorescent bulbs poses no threat while in the bulb, but if you break one:
- open a window and leave the room for 15 minutes or more
- immediately use a wet rag to clean it up and put all of the pieces, and the rag, into a plastic bag
- place all materials in a second sealed plastic bag
- call your local recycling center to see if they accept this material, otherwise put it in your local trash. Wash your hands afterward.
- if bulb breaks on a carpet, pick up pieces using sticky tape. If any debris remains, use the vacuum and dispose of vacuum bag by sealing it in plastic bags (as above), before disposal.

Although household CFL bulbs may legally be disposed of with regular trash (in most US states), they are categorized as household hazardous waste. As long as the waste is sent to a modern municipal landfill, the hazard to the environment is limited. However, CFLs should not be sent to an incinerator, which would disperse the mercury into the atmosphere.

The best solution is to save spent CFLs for a community household hazardous waste collection, which would then send the bulbs to facilities capable of treating, recovering or recycling them. For more information on CFL disposal or recycling, you can contact your local municipality.


--------------------------------------------------------------------------------

LED Lighting
LEDs (Light Emitting Diodes) are small, solid light bulbs which are extremely energy-efficient.

Until recently, LEDs were limited to single-bulb use in applications such as instrument panels, electronics, pen lights and, more recently, strings of outdoor Christmas lights.
Recent improvements in manufacture have lowered the cost of LEDs, which has expanded their application. The bulbs are now available in clusters, from 2 to 36 bulbs, and are popular especially for battery powered items such as flashlights and headlamps. LEDs are also available in arrays which fit standard AC and DC receptacles, lamps, recessed and track lights.
Benefits:
Long-lasting - LED bulbs last 10 times as long as compact fluorescents, and 133 times longer than typical incandescents.
Durable - Since LEDs do not have a filament, they are not damaged under circumstances when a regular incandescent bulb would be broken. Because they are solid, LED bulbs hold up well to jarring and bumping.
Cool - these bulbs do not cause heat build-up; LEDs produce 3.4 btu's/hour, compared to 85 for incandescent bulbs.
Energy-saving - LEDs use a fraction of the wattage of incandescent bulbs. Batteries will last 10 to 15 times longer than with incandescent bulbs. Also, because these bulbs last for years, energy is saved in maintenance and replacement costs. Many cities in the US are replacing their incandescent traffic lights with LED arrays because the electricity costs can be reduced by 80% or more.
Light for remote areas - because of the low power requirement for LEDs, using solar panels becomes more practical and less expensive than running an electric line or using a generator for lighting.

Limitations:
Cost - although the cost keeps going down, LEDs are still expensive. A single AC bulb (30 LED), replacing a 25 watt incandescent, may cost about $40.
Light Field - LEDs are focused lights, and therefore are best as task specific lighting such as reading lights, desk lamps, night lights, spotlights, security lights, signage lighting, etc. They do not radiate light in 360 degrees as an incandescent does. The light will be bright where you point it towards.

New designs in LED bulbs are addressing this problem of directional focus. Diffuser lenses with clustered bulbs are becoming more common on the market which is broadening the applications for LED use in the home.

LED Colors:
Red - red is the traditional color for maintaining night vision.
Green - green is now the preferred color for pilots and the military. The green color is also great for retaining night vision, and it doesn’t erase the red markings on maps and charts.
Blue - many people like the blue because it is very easy on the eyes. Blue appears to be a good reading light for elderly eyes. Elderly folks report that they can read under the blue light for hours without eyestrain, compared to severe eyestrain in less than 30 minutes with incandescent lighting.
White - the most popular of the LED colors. It produces a soft white light, without harsh reflection, glare or shadows.
Amber - LED amber bulbs do not attract flying insects, as do ordinary white bulbs. Amber LEDs are used outdoors in areas such as patios and decks where insects flying around lights are a nuisance.

Although LEDs are expensive, the cost is recouped over time and in battery savings. For the AC bulbs and large cluster arrays, the best value comes from commercial use where maintenance and replacement costs are expensive. Traffic lights, for example, are being switched over to LEDs in many cities.

Smaller arrays, such as those in flashlights, headlamps and small task lights are great for specialty and outdoor use. New clustered arrays with various lenses are now available for more residential applications.



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Energy-Efficient Lighting: Online Sources

Compact fluorescent light bulbs are available at your local lighting store, many hardware and home supply stores. Online sources often have greater selection.

CFLs and LEDs are also available online at Eartheasy's online store.



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