12.6 Lighting Systems 365
area. They are commonly used as floodlights or spotlights. The comparisons of performance of
incandescent lights are shown in Table 12.4.
The second most common type of lighting system is fluorescent lamps, which use 25% to 35%
of incandescent lamps and produce the same amount of illumination. The efficacy of fluorescent
lamps is somewhere between 30 to 110 lumens /watts. When compared to incandescent lamps, they
also have longer service life, in the range of 7,000 to 24,000 hours. In a fluorescent tube, electric
current is conducted through mercury and inert gases to produce light. The fluorescent lights used
to have poor color rendition, but because of improvements in technology, they now have high CRI
values. The 40 W, 4-foot (1.2-meter) lamps, and 75 W, 8-foot (2.4-meter) lamps are the two most
common fluorescent lamps. These lamps require special fixtures, but the new generation of com-
pact fluorescent lamps (CFLs) fit into the incandescent fixtures (Figure 12.16). Although CFLs areTABLE 12.4 Comparison of Incandescent Lights
Color
Incandescent Efficacy Life Rendition Color Temperature
Lighting Type (lumens/ W) (hours) Index (CRI) (K)Standard A 10 –17 750 – 2500 98 –100 2700 – 2800
(warm)Tungsten halogen 12 – 22 2000 – 4000 98 –100 2900 – 3200
(warm to neutral)Reflector 12 –19 2000 – 3000 98 –100 2800 (warm)
■Figure 12.16
Examples of compact fluorescent
lights that fit into screw-in-A-type.
Source:DOE’s Office of Energy
Efficiency and Renewable
Energy.Source:U.S. Department of Energy.
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