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Earth’s Changing Environment Lecture 17. Lighting Efficiency. Topics. Sunlight Incandescent Fluorescent Controls Using Daylight LED. Sunlight. Sunlight has peak in the middle of the visible spectrum with half the energy in the infrared. Some UV radiation. Incandescent Bulb.
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Earth’s Changing EnvironmentLecture 17 Lighting Efficiency
Topics • Sunlight • Incandescent • Fluorescent • Controls • Using Daylight • LED
Sunlight • Sunlight has peak in the middle of the visible spectrum with half the energy in the infrared. • Some UV radiation.
Incandescent Bulb • Bulbs are heated filaments at 2,500 K. • The Sun is 5,800 K. • Spectrum of hot filaments has more red.
Bulb Efficiency • Only 5% of energy input produces useful light. • Spectrum is different from sunlight.
Tube Fluorescent Lights • Efficient • Reflectors increase light level.
Compact Fluorescent Bulbs • Efficiency is 4X incandescent bulb. • 14 W bulb produces light level corresponding to 60 W bulb • Last 10X longer, 10,000 hours
Payback Period Calculation • Stop and work problems
Lighting Controls – Switch Off • Switch off campaigns are effective. • Fluorescent lights should be switched off if you’ll be gone more than 10 minutes.
Lighting Controls - Automatic • May irritate occupants. • Less efficient than switch-off
Bringing in Daylight • Has the right spectrum. • Uses no energy. • In some locations, need to avoid over-heating and UV effects.
LED Lighting • Very Efficient • Monochromatic • Expensive • No IR – No heat
White LED • Very Efficient • Monochromatic • Could be the lighting of the future