Earth

1
Earths Changing EnvironmentLecture 17

• Lighting Efficiency

2
Topics

• Sunlight
• Incandescent
• Fluorescent
• Controls
• Using Daylight
• LED

3
Sunlight

• Sunlight has peak in the middle of the visible
  spectrum with half the energy in the infrared.
• Some UV radiation.

4
Incandescent Bulb

• Bulbs are heated filaments at 2,500 K.
• The Sun is 5,800 K.
• Spectrum of hot filaments has more red.

5
Bulb Efficiency

• Only 5 of energy input produces useful light.
• Spectrum is different from sunlight.

6
Fluorescent Bulb
7
Tube Fluorescent Lights

• Efficient
• Reflectors increase light level.

8
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

9
Payback Period Calculation

• Stop and work problems

10
Lighting Controls Switch Off

• Switch off campaigns are effective.
• Fluorescent lights should be switched off if
  youll be gone more than 10 minutes.

11
Lighting Controls - Automatic

• May irritate occupants.
• Less efficient than switch-off

12
Bringing in Daylight

• Has the right spectrum.
• Uses no energy.
• In some locations, need to avoid over-heating and
  UV effects.

13
Skylights
14
Skylight Tubes
15
LED Lighting

• Very Efficient
• Monochromatic
• Expensive
• No IR No heat

16
White LED
17
White LED

• Very Efficient
• Monochromatic
• Could be the lighting of the future