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.
Fluorescent Bulb
Tube Fluorescent Lights
EfficientReflectors increase light level.
Compact Fluorescent Bulbs
Efficiency is 4X incandescent bulb.14 W bulb produces light level corresponding to 60 W bulbLast 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.
Skylights
Skylight Tubes
LED Lighting
Very EfficientMonochromaticExpensiveNo IR – No heat
White LED
White LED
Very EfficientMonochromaticCould be the lighting of the future