earth’s changing environment lecture 17 lighting efficiency

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