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