Efficient lighting and daylighting

Lighting levels required depends on the property type

The illuminance is the total amount of light (flux) falling on a surface and is measured in lux (SI uni). Lamp output is measured in lumens. Lux = lumens per square metre. Determining lighting levels depends on the design of the building

  • Daylighting (Advantages: Energy savings, positive psychological impact, increased productivity. Disadvantages: Increase heat load, costly to integrate with artificial light, glare and internal shadows)
  • Daylighting + Artificial lighting
  • Artificial lighting alone

    Table of Lighting Levels (AS 1680)

    Table of Lighting Levels (AS 1680)

Ways to maximise daylight

  • Light shelves: High reflectance upper surface, reduces glare, improves light distribution, better in temperate climates. However, can reduce overall daylight in some conditions
  • Laser cut panels:  Acrylic panel mounted internally or externally with laminate, low glare, high level of light deflection, general increases in light distribution achieved. However, some distortion of outside view and relatively expensive
  • Reflective blinds/ louvres: Placed externally, internally or between panes, manual or automatic control, can increase daylight penetration into space in sunny conditions. However, it can obstruct view and cleaning maybe difficult

This slideshow requires JavaScript.

Types of  artificial lamp are available

Types of Artificial Lamps

Types of Artificial Lamps

The most efficient are

  1. High-pressure sodium lamps 183-200 lm/W
  2. High intensity discharge lamp 150 lm/W
  3. Conventional Fluorescents
  4. Compact Fluorescents
  5. LED 131 lm/W

Lamp efficacy (LPW) = L (lumens)/ W (Watts)

where L = Light emitted; W = Power required

Lamps have varying efficacy

Lamps have varying efficacy

 

How do we calculate the energy consumption of a lighting system?

Energy (Wh) = Sum of Number of lamps (N)*Wattage of lamp (W)*Operating Hours (H)

 

Considerations for artificial lamps

  • cost
  • size
  • life time and reliability
  • colour properties
  • dimmability
  • simplicity and convenience in use
  • disposal
  • environmental effects
  • lumen maintenance

 

Strategies to reduce lighting energy use

Low cost techniques

  • remove lamps
  • replace lamps to more efficient ones
  • improve user behaviour
  • improve lamp maintenance

Retrofit or redesign

  • Introduce task oriented lighting
  • change colour of walls, floors and ceiling
  • Increase use of daylighting
  • Install automatic control system (motion sensors or time of day)
Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s