Energy Efficient Lighting

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Energy Efficient Lighting
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Energy for Lighting

• We spend about one-quarter of our electricity
  budget on lighting, or more than 37 billion
  annually
• Technologies developed during the past 10 years
  can help us cut lighting costs 30 to 60 while
  enhancing lighting quality and reducing
  environmental impacts.

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Objectives

• Lighting principles and definitions
• Types of lighting and how each works
• Energy-efficient lighting options, including
  daylighting, for new or retrofit applications.

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Lighting and Energy Savings

• Lighting principles and definitions
• Types of lighting and how each works
• Energy-efficient lighting options, including day
  lighting, for new or retrofit applications.

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How lighting is measured?

• The most common measure of light output (or
  luminous flux) is the lumen . All lamps are rated
  in lumens
• The distribution of light on a horizontal surface
  is called its illumination.
• Illumination is measured in footcandles. A
  footcandle of illumination is a lumen of light
  distributed over a 1-square-foot
  (0.09-square-meter) area

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How much light do we need?

• The task(s) being performed (contrast, size,
  etc.)
• Ambient
• Task
• Accent
• The ages of the occupants
• The importance of speed and accuracy

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Factors Affecting the Quantity of Lamps Required

• Fixture efficiency
• Lamp lumen output
• The reflectance of surrounding surfaces
• The effects of light losses from lamp lumen
  depreciation and dirt accumulation
• Room size and shape
• Availability of natural light (daylight)

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How Much Light?

• In the past, spaces were designed for as much as
  200 footcandles in places where 50 footcandles
  may not only be adequate, but superior.
• Not only does over lighting waste energy, but it
  can also reduce lighting quality
• 30 fc of ambient lighting for computer room
• 50 fc for reading and writing

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Color Rendition Index

• The ability to see colors properly is another
  aspect of lighting quality
• The color rendering index (CRI) scale is used to
  compare the effect of a light source on the color
  appearance of its surroundings. A scale of 0 to
  100 defines the CRI.
• A higher CRI means better color rendering, or
  less color shift

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Types of Lighting

• There are four basic types of lighting
• Incandescent,
• Fluorescent,
• High-intensity discharge, and
• Low-pressure sodium

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Incandescent Light

• Light is produced by a tiny coil of tungsten wire
  that glows when it is heated by an electrical
  current.
• shortest lives
• Inefficient

Filament
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Types of Incandescent Bulbs

• Standard incandescent
• Most common yet the most inefficient
• Larger wattage bulbs have a higher efficacy than
  smaller wattage bulbs
• Tungsten halogen
• It has a gas filling and an inner coating that
  reflect heat
• Better energy efficiency than the standard A-type
  bulb
• Reflector lamps
• Reflector lamps (Type R) are designed to spread
  light over specific areas
• floodlighting, spotlighting, and downlighting

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Fluorescent Bulbs

• filled with an argon or argon-krypton gas and a
  small amount of mercury
• coated on the inside with phosphors
• equipped with an electrode at both ends 3 to 4
  times as efficient as incandescent lighting
• Fluorescent lamps provide light by the following
  process
• An electric discharge (current) is maintained
  between the electrodes through the mercury vapor
  and inert gas.
• This current excites the mercury atoms, causing
  them to emit non-visible ultraviolet (UV)
  radiation.
• This UV radiation is converted into visible light
  by the phosphors lining the tube

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Fluorescent Bulbs

• Fluorescent lamps last about 10 times longer than
  incandescent bulbs
• Fluorescent lights need ballasts (i.e., devices
  that control the electricity used by the unit)
  for starting and circuit protection

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Types of Fluorescents
Compact fluorescent

• Tube fluorescent

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CFLs

• CFLs can replace incandescents that are roughly 3
  to 4 times their wattage
• They last 10 to 15 times as long.
• Cost from 10 to 20 times more than comparable
  incandescent bulbs
• One of the best energy efficiency investments
  available.

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High Intensity Discharge (HID) Lamp

• High-intensity discharge (HID) lamps provide the
  highest efficacy and longest service life of any
  lighting type
• mercury vapor
• metal halide, and high-pressure sodium

They also require ballasts, and they take a few
seconds to produce light when first turned on
because the ballast needs time to establish the
electric arc
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Efficacy

• This is the ratio of light output from a lamp to
  the electric power it consumes and is measured in
  lumens per watt (LPW).

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Improved Lighting Controls

• Snap Switches
• Photocells
• Timers
• Occupancy sensors
• Dimmers

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Resources

• http//www.eren.doe.gov/erec/factsheets/eelight.ht
  ml
• http//www.misty.com/don/dschlamp.html
• LIGHTING FUNDAMENTALS