After incandescents, fluorescent lamps are the second most common light source. They are the most common source used in commercial buildings, producing about two-thirds of our nation's illumination.
Fluorescents are easily distinguished by their tubular design. They come in circular, straight or bent in a "U" shapes.
In operation, an electric arc is drawn along the length of the tube. The ultraviolet light produced by the arc activates a phosphor coating on the inside wall of the tube, causing light to be produced. Unlike the incandescent lamp, the fluorescent lamp requires a ballast to strike the electric arc in the tube initially and to maintain the proper voltage and current to the lamp to maintain that arc. Proper ballast selection is important to optimum light output and lamp life.
Lamp sizes range from four watts to 215 watts. The efficiency (lumens per watt) of a lamp increases with lamp length (from four feet to eight feet). The reduced-wattage fluorescent lamps introduced in the last few years use from 10 percent to 20 percent less wattage than conventional fluorescent lamps, depending on size. For most applications, the cool white and warm white lamps provide very acceptable color and energy efficiency ratings.
Like the incandescent lamp, the fluorescent lamp can be dimmed, but not as easily. Dimming fluorescents is done with special ballasts and controls for dimming from 100% to 0% of output, or by multi-level ballasts that step down light output to specific levels (e.g., 75%, 50%, etc.).
Fluorescent lamp life is rated according to the number of operating hours per start, for example, 20,000 hours at three hours operation per start. The greater the number of hours operated per start, the greater the lamp life. Because fluorescent lamp life ratings have increased, however, the number of times you turn a lamp on or off has become less important. As a general rule, if a space is to be unoccupied for more than a few minutes, you should turn the lamps off.
Fluorescents are a good retrofit for incandescent lamps that operate a significant number of hours. Circular fluorescent lamps can be used where exposed socket incandescent bulbs are currently used. Compact or PL fluorescent lamps (available in 5-40 watts) can be substituted for many incandescent bulbs and will fit in many types of fixtures.
Facilities already using fluorescent lamps should consider high efficiency fluorescent lamp designs. They produce about the same amount of light, while saving about 10 to 15% of the energy usage.
4 to 5 times more efficient than incandescent, and an exceptionally long life (10 to 20 times greater than incandescent).
Easy to maintain.
Lamp life is greatly affected by the average number of hours the lamp is cycled on and off.
The lamps are also low cost and available in a wide range of sizes and colors.
Relatively low surface brightness and heat generation, and are relatively insensitive to small changes in building voltage. This can be very important where brownouts are common.
Most lamps are relatively large and require a relatively expensive fixture.
The ballasts in fluorescent fixtures can have an objectionable hum (some louder than others).
Ballasts are now given a noise rating. Quiet ballasts are recommended for office areas, louder and less expensive ballasts can be used in industrial facilities.
Fluorescent lamps are temperature sensitive and may have difficulty starting at low temperatures. Also, lumen output drops at low and high temperatures. Special ballasts are available for low and high temperature applications.
While dimming of fluorescents is possible, it requires special, relatively expensive ballasts
Incandescent lamps are the most familiar source of light and are widely used in residential and other low-annual-hours-use applications. The popularity of the incandescent lamp is due to the simplicity with which it can be used and the low price of both the lamp and the fixture. Also, the lamp requires no special equipment, like a ballast, to modify the characteristics of its power supply. Incandescents are often used in commercial and industrial applications where the intended hours of use are low (less than 500 hours per year), where needed for aesthetic purposes, or where initial cost is an overriding criterion.
The most common types are: the "A" or arbitrary bulb-shaped lamp; the "PS" or pear-shaped lamp; the "R" or reflector lamp; the "PAR" or sealed-beam lamp, and the tungsten-halogen lamp.
The tungsten-halogen lamp, like the other incandescent lamps, uses a tungsten filament as the light source. Unlike others, however, the lamp's fill-gas is composed of a "family of elements" known as halogens. The halogens prevent lamp walls from darkening as quickly as those of other incandescent lamps, so more light is available to the task or work surface. In other words, the light output of tungsten-halogen lamps does not drop off as rapidly as the light output of other incandescent lamps.
Although incandescents are the least efficient light sources, their advantages assure them a place in most homes and businesses for the foreseeable future. Therefore, we should at least use the wisely and recognize ways to save money using them. For instance, knowing that the efficiency of incandescent lamps increases as lamp wattage increases can allow you to save energy. This makes it possible to save on both energy and fixture costs whenever you can use one higher wattage lamp instead of two lower wattage lamps. For example, one 100-watt lamp produces more light, 1740 lumens, than two 60-watt lamps (860 lumens each) for a total of 1,720 lumens. Whenever you can substitute one 100 watt lamp for two 60s, you save 20 watts. Beware though, read the fixture ratings. Some are rated for 60 watt or lower lamps.
The specific type of incandescent lamp used and the kind of fixture involved also make a difference. For example, a 75-watt ellipsoidal reflector lamp delivers more light in a stack-baffled downlight than a 150-watt R lamp. This is because much of the R lamp's light is trapped in the fixture and converted to heat. The 75-watt ER lamp's shape and reflective interior focuses light down, outside of the fixture, thereby producing more light on the surface.
Low initial cost
Excellent color rendition
Inexpensive dimming capability
Skin-flattering warm color
Small size, which allows it to be used in point fixtures, such as spot lamps
Wide variety of shapes, sizes, colors and wattages are available
Output unaffected by high or low ambient temperatures
Simple to operate and install
Requires no ballast
High brightness light source
Available in many colors
Variety of filament design possibilities offer optical control, accurate distribution patterns and critical service operation
Relatively short useful life with poor over-voltage tolerance. At 10% over voltage, life is reduced about 75%!
Very inefficient source of light. On average, less than 10% of the wattage goes to produce light; the remainder becomes heat.
High heat component can create hidden energy costs due to increased cooling needs.
High Pressure Sodium
High pressure sodium (HPS) lamps are the most efficient member of the HID family where some degree of color rendition is important. Standard HPS lamps produce a golden white light when they reach full brightness. Many recognize them as the familiar golden light from street lights, one of their principal applications. There are versions of the HPS lamp designed for indoor use with improved color over standard HPS lamps, but the improvements come at the cost of shorter lamp life and lower efficacy. These lamps are now a readily accepted light source in industrial plants and also are being used in many commercial and institutional applications.
HPS lamp sizes range from 35 to 1,000 watts. Ballasts designed specifically for high pressure sodium lamps must be used. The figure shown here shows the lamp shape for both a metal halide lamp and a high pressure sodium lamp.
Most efficient member of the HID light family, 7 times as efficient as incandescent and over 2 times as efficient as mercury vapor.
Warm-up period is 3-4 minutes, which is somewhat less than that of a mercury vapor or metal halide lamp.
Long lamp life -- 24,000 hours.
Excellent lumen maintenance.
Wide range of lamp types with wattages ranging from 35 to 1000 watts.
Most HPS lamps can operate in any position.
The light produced is a golden white color, which may not be appropriate for certain applications.
Requires a ballast.
Once started can take from five to ten minutes to reach full light output. They also require at least a one minute cool-down to re-strike.
End of life is characterized by on-off-on cycling, and continued operation can damage the lamp ballast if not replaced quickly
Light Emitting Diode
Light Emitting Diode (LED) Lamps represent new technology with expanding applications, particularly in color and specialty applications. If you still think LEDs are only for little red indicator lights on electronic gizmos, check out LEDs. LED replacements for incandescent bulbs are available for numerous applications in many sizes, shapes, colors and packages.
The lighting efficiency of LED lamps typically varies with the color produced. As this is a developing technology, manufacturers are constantly researching for improved efficiencies. These are some typical values as of February 2004.
Red LEDs - 22-42 lumens/watt
Orange LEDs - 18-22 lumens/watt
Yellow and "amber" LEDs - 14-35 lumens/watt
Green LEDs - 20-32+ lumens/watt
Blue-Green LEDs - 25-28 lumens/watt
Blue LEDs - 8 to10 lumens/watt
White LEDs -The better usual modern white LEDs (as of January 2004) produce about 17-25 lumens of light per watt of electricity delivered to the LEDs. Compare to 14-17.5 lumens per watt for standard 120 volt 60 to 100 watt incandescent lamps, and typically 16 to 21 for most halogen lamps rated to last 2,000 hours or more.
Light Emitting Diode (LED)
Light Emitting Diode (LED) Lamps represent new technology with expanding applications, particularly in color and specialty applications.
Festival Lighting LED lights can be direct replacements for colored lamps. The Festival lights can replace a typical 60-watt painted incandescent bulb with only 2.5 watts of power. Imagine using 1000 lamps in an installation.
Cove and Marquee Lighting LED lamps can be for both cove light and marquee lighting applications. For cove applications, the even light distribution and low heat generation make them ideal for placement in those hard to get to places.
Festoon Lighting such as to highlight the outline of a building or bridge. A typical installation would use hundreds to thousands of 25-60 Watt lamps. Festival LED lamps are direct replacements.
Important Advantages include:
- Power Savings - A 1000 bulb installation with 25-60 watt lamps would require 25-60 kW of power over large cables. With Festoon LED lamps, the power requirements lower to only 2.5 kW.and much smaller wiring.
- Better visual effects - Festoon lamps are for decoration and are point source devices meant to be viewed. With painted incandescent lamps, light escapes from the back of the globe as well as the front. This lowers the contrast, making it harder to see. Also, incandescent painted lamps have a tendency to light up the inside of people's offices, a source of complaints from the building occupants. As LED lamps are point sources and do not "paint" the rear surface with light and greatly increases the contrast and overcomes the problem of lighting up the occupant's space.
- Visibility during the day - Painted lamps must be on during the day to see the colors because the lamps look black when turned off. Festoon LED colored globes glow in its original color, activated by the sun's Ultra Violet rays. Operators may choose to power down the lamps during the day and yet still see the colors, adding more energy cost savings.
- Low heat generation - LED lamps produce very little heat, thus reducing the air conditioning load and associated electric bills. This also reduces the fire hazards involved with flammable material touching the surfaces of the lamps.