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 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 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.

Skylights

Skylight Tubes

LED Lighting Very Efficient Monochromatic Expensive No IR – No heat

White LED

Very Efficient Monochromatic Could be the lighting of the future