Md. Mizanur Rahman, PhD School of Mechanical Engineering Universiti Teknologi Malaysia UTM Cell phone: 0176480491 E-mail: mizanur@mail.fkm.utm.my

Energy Efficiency: Lighting

Energy management: Lighting

• Globally, around 20% of the total electricity is consumed by the lighting sector.

• Around 48% of the global lighting electricity is consumed by the service sector.

• The rest is residential sector (28%)

• Industrial sector (16%)

• Street and other lighting (8%)

2

Different Light Sources

• The different light sources have different characteristics – Incandescent lamps

• Very low efficacy • Cheap • Dimmable • General use

– Fluorescent lamps (CFL) • High efficacy, especially with electronic

ballasts • Highly suitable for lighting rooms

evenly • Widely used

– Low Pressure Sodium lamps • Very high efficacy • Monochromatic light • Used for outside lighting where colour

rendering is unimportant

– High Pressure Sodium lamps • High efficacy and long life • Low to moderate colour rendering • Used for street lighting, industrial lighting

and floodlighting

– Metal Halide lamps • Start up time a few minutes • High light output per lamp • Favourable efficacy • Good colour rendering • Highly suitable as spot lights; used for

street lighting, industrial lighting and floodlighting

3

4

Bulbs are rated based on light output, which is closely related to power consumption. When selecting a bulb, consider these standard ratings: • Watts – Bulb manufacturers have traditionally used watts to represent light output, but wattage is actually a measure of power consumption, not brightness. CFL, for example, will have a much lower wattage than an incandescent bulb that produces same light. • Lumens – The standard unit of light output for bulbs is the lumen. A higher lumen number indicates a brighter bulb, and a lower lumen number indicates a dimmer bulb. A CFL and an incandescent bulb with the same lumen rating will produce the same amount of light

Light output VS power consumption

5

• Equivalent Wattage – To make it easier to compare, manufacturers generally provide an equivalent wattage rating along with the lumens rating. The equivalent wattage tells you what type of incandescent bulb has the same light output as the CFL. For example, a CFL with an wattage of 12 produces the same amount of light as a 60-watt incandescent bulb.

• Lumens per watt – The standard measure of efficiency is the ratio of light output to power usage, represented as lumens per watt, or LPW. A higher LPW rating indicates greater energy efficiency and increased savings

• Efficacy- All electric lamps are specified by their electrical input, not their light output. The efficiency of an electric lamp (i.e. efficacy) is the ratio of light output (in lumens) to electrical input (in watts)

Luminous flux - the light emitted by a light source or luminaire or received by a surface irrespective of the directions in which it is distributed. The unit is the lumen (lm) or klm.

Illuminance -the luminous flux incident on a surface per unit area. The unit is the lux (lx), 1 lux = 1 lm/m²

Bulb Life: Bulb manufacturers typically provide an estimated bulb life for CFLs, generally listed in total hours. Quality CFLs have a bulb life rating of 10,000 hours or more.

Light meters can be used to measure illuminance

What is the illuminance in this room?

6

7

8

9

Type of bulb Watts Typical hourly running cost

Incandescent 60W $ 0.02

Main voltage halogen

45W $ 0.01

Compact fluorescent light (CFL)

13W $ 0.004

Linear fluorescent

9W $ 0.003

LED downlight 12W $ 0.004

Cost of bulbs to deliver the same output as a 60W incandescent bulb

Improving of efficiency of lighting

• Means include:

• Installing more energy-efficient lighting such as T5 fluorescents (CFL) with high frequency (HF) operation, high-pressure sodium lamps, light-emitting diodes (LED), etc.

• Reducing the wattage of lights

• Sectioning off the lighting system to enable more effective occupancy control

• Using sensors

Improved hardware-luminaires (the fixtures within which the lamps are placed)

Improved use of that hardware better or smarter controls

combining with daylight

11

12

Incandescent CFL LED

Capital cost per

bulb

$ 2

$ 6 $ 10

Average lifespan 1,200 hours 8,000 hours 24,000 hours

Watts used for

same lighting

60W 14W 10W

Lighting required

per year

2400 h/yr

Discount rate 5%

Electricity cost $0.12 per kWh

Which option is economically superior for the whole life time of 20 years?