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7/28/2019 CHAPTER 6 Illumination.pdf
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06/12/2012
1
By Dr. KokBoon Ching
2012@J EK/FKEE1
OutlinesOutlines
y Introduction
y Important Definitions in
Lighting
y Laws of Illumination
y
Types of lamps and theircharacteristics
y Electrical Lighting Design
Lighting
2
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IntroductionIntroductiony Light is just one portion of the various
electromagnetic waves flying through space
which have both frequency and length.
3
IntroductionIntroduction
4
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IntroductionIntroductiony Light is emitted through:
a) Incandescence: Solids and liquids emit visible
temperatures about 1000K.
b) Electric Discharge: When an electric currentis passed through a gas, the atoms andmolecules emit radiation whose spectrum ischaracteristic of the elements present.
c) Electro luminescence: Light is generated
w en e ectric current is passe t roug certainsolids such as semiconductor or phosphormaterials.
d) Photoluminescence: Radiation at onewavelength is absorbed, usually by a solid, andre-emitted at a different wavelength.
5
IntroductionIntroduction
y Energy consumption via lighting systems is
si nificant.
y The global electricity consumption for lighting
in 2005 is estimated at 3418 TWh
(terawatthours), i.e. 19% of total global
electricity consumption.
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IntroductionIntroductiony Today the global light
production (in lumen) can
e v e as o ows on t e
different sectors:
◦ 44 % for lighting of
commercial and public
building,
◦ 29 % for industrial lighting,
◦
or res ent a g t ng,◦ 12 % outdoor lighting
(streets, security, road signs
and car parks).
7
IntroductionIntroductionEnergy consumption in different sectors:
8
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Important Definitions in LightingImportant Definitions in Lighting
2 objectives of lighting designer:
1. to provide the right quantity of light.
2. to provide the right quality of light.
9
Important Definitions in LightingImportant Definitions in Lighting
y Luminous flux, F (lumen, lm)¾Total amount of visible li ht ower emitted b a li ht
source.
¾1 lumen = the photometric equivalent of the watt.
¾1 lumen = luminous flux per m2 of a sphere with 1 mradius and a 1 candela isotropic light source at the
centre
wa umens a nm wave eng
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Important Definitions in LightingImportant Definitions in Lightingy Illuminance, I (Lux, lx)¾The amount of li ht arrivin on a workin lane.
¾1lux = 1lm/m2. This value is used in light calculations
and design plans.
¾Or unit in foot-candles (1 Lux = 0.0929 fc) – USA.
11
Important Definitions in LightingImportant Definitions in Lighting
For example, 1000
,
into an area of one square
meter, lights up that
square meter with anilluminance of 1000 lux.
The same 1000 lumens,
square meters, produce a
dimmer illuminance of
only 100 lux.
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Important Definitions in LightingImportant Definitions in Lightingy Luminous intensity, P
candela cd = lm/sr
Measure of the luminous flux emitted by a light source
in a particular direction, measured in lumens per
steradian.
13
Important Definitions in LightingImportant Definitions in Lighting
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Important Definitions in LightingImportant Definitions in Lightingy Luminance (cd/m2)
of luminous intensity in
a given direction. It
describes the amount
of light that passes
t roug or s em ttefrom a particular area,
and falls within a given
solid angle.15
Important Definitions in LightingImportant Definitions in Lighting
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Important Definitions in LightingImportant Definitions in Lighting
y Uniformity
spreads over an area. Non-uniform illuminance creates bright
and dark spots, which can distract and discomfort some
occupants.
17
Important Definitions in LightingImportant Definitions in Lighting
y Glare
are s a sensat on cause y re at ve y r g t o ects n an
occupant’s field of view. The key word is relative, because
glare is most probable when bright objects are located in
front of dark environments.
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Important Definitions in LightingImportant Definitions in Lightingy Colour Rendering
The colour rendering of a light source is an indicator for its
ability of realistically reproducing the colour of an object.
Colour rendering is given as an index between 0 and 100,
where lower values indicate poor colour rendering and
higher ones good colour rendering. Other index used is 1A
(extremely good), 1B (Very good), 2 (Moderate), 3 (Low),
and 4 (Little or almost none).
19
Important Definitions in LightingImportant Definitions in Lighting
y ColourTemperature (K)¾Color a earance of a lam and the li ht it
produces.
¾It’s expressed in degrees Kelvin (K).
¾Below 3300K, the source is considered as “warmlight”. Above 5300K, the source is considered as
“cold light”.
“ ”ncan escen amps: rue va ue co or empera ure.
¾Fluorescent and high intensity discharge (HID)
lamps: correlated color temperature.
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ColourColour Temperature in Temperature in
Degrees KelvinDegrees Kelvin
21
Laws of IlluminationLaws of Illumination
y Inverse Square Law
illuminance from a point source and
distance.y Lambert’s Cosine Law
States that the illuminance fallin on an
surface varies as the cosine of the
incident angle, θ.
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Laws of Illumination –
Inverse Square Law
y The illuminance from a point source can be put
n t e orm
2)(d
P I =
23
Laws of Illumination –
Inverse Square Law
Example 1:
22 =
22
2
1
2
2
1
21
2211
/40/105.0
1mlmmlm
m
m I
I d
d I
=×⎟ ⎠
⎞⎜⎝
⎛ =
×⎟⎟ ⎠
⎞⎜⎜⎝
⎛ =
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Laws of Illumination –
Lambert’s Cosine Law
y The illuminance or the intensity of
illumination is written as:
NormalLuminous 2
1 D
F I =
D1
uxθ cos'
2
2 D
F I =
25
D2
Laws of Illumination –
Lambert’s Cosine Law
y Example:
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Example 2:
Two lamps with 3000 lumens and 5000 lumens are placed at
Laws of Illumination –
Lambert’s Cosine Law
A and B, respectively. The arrangement is shown as follows:
Normal
10 m 7 m
A
B
θ1
θ2
C is the midway between the lamps. Calculate the
illumination on the floor at positions C .27
CD
15 m
2.5 m
Solution:
Illumination at C,
Laws of Illumination –
Lambert’s Cosine Law
LuxCOS BC
COS AC
77.4741.3236.1550003000
2212=+=×+×= θ θ
m AC 5.125.710 22 =+=
m BC 26.105.77 22 =+=
28
5.12cos 1 =θ
26.10
7cos 2 =θ
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Types of Types of lampslamps• Incandescent lamps
• ungsten a ogen amps
• Fluorescent lamps
• High pressure sodium lamps
• Low pressure sodium lampsHID lamps
• Mercury vapour
• Metal halide
• Blended lamps
• LED lamps 29
Incandescent LampsIncandescent Lamps
• Efficiency: 70 – 90 % of
energy converted into heat.
• Bulb contains vacuum or
gas filling
• Efficacy: 12 lumen / Watt
• Color renderin index: 1A
• Color temperature: 2500 –
2700 K
• Lamp life <2000 hrs
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Tungsten Tungsten--Halogen LampsHalogen Lamps•Tungsten filament and a halogen gas filled bulb
•
and move to cooler wall of bulb
•Efficacy: 18 lumens/Watt
•Color rendering index: 1A
•Color temperature: warm
Advantag es:
• More compact
• Longer life
•Lamp l ife < 4000 hrs • More and whiter light
Disadvantages:
• Cost more
• Increased IR and UV
• Handling problems
31
Fluorescent LampsFluorescent Lamps
STEP 2 The impact diverts the electron of the
mercury atom out of its orbit. When it snaps back
into lace ultra-violet radiations are roduced.PHOSPHOR
VISIBLE
LIGHT
ELECTRODE
32
STEP 1 Electron emitted by
electrode at one end of fluorescent lamp
travels at high speed through the tube
until it collides with one of the electrons
of the mercury atom.
STEP 3 When the ultra-violet
radiations reach the phosphor crystal, the
impulse travels to one of the active centers in
the crystal and here an action similar to that
described in Step 2 takes place. This time,
however, visible light is produced.
ATOM OF VAPORISED MERCURY
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Compact Fluorescent LampsCompact Fluorescent Lamps•Different types (T12,
T10, T8 and T5 differin
Features:
Halo-phosphate
• Efficacy – 80 lumens/Watt (HF
in diameter and
efficiency
•Most efficient at ambient
temperature of 20-30 oC,
gear increases this by 10%)
• Color Rendering Index –2-3
• Color Temperature – Any
• Lamp Life – 7-15,000 hours
Tri-phosphor
• Efficacy – 90 lumens/Watt
• Color Rendering Index –1A-1B
• Color Temperature – Any
• Lamp Life – 7-15,000 hours
•Compact fluorescentlamps (CFL) have much
smaller luminaries
Compact fluorescent lamp (CFL)33
High Pressure Sodium (HPS) LampsHigh Pressure Sodium (HPS) Lamps
•Used in outdoor and indust rial applications
• - ,
starter, ceramic arc tube, xenon gas fil ling,
sodium, mercury
•No starting electrodes
•High efficacy: 60 – 80 lumen/Watt
• -
•Color temperature: warm
•Lamp l ife < 24,000 hrs
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Low Pressure Sodium (LPS) LampsLow Pressure Sodium (LPS) Lamps
• Commonly included in the HID family
• g es e cacy: - umen a
• Poorest quality light: colors appear
black, white or grey shades
• Limited to outdoor applications
• Color rendering index: 3
• Color temperature: yellow
• Lamp l ife < 16,000 hours
35
Mercury Vapor LampsMercury Vapor Lamps
• Oldest HID lamp
•
gas and quartz envelope, third electrode, outer
phosphor coated bulb, outer glass envelope
• Long life and low in itial costs
• Very poor efficacy: 30 – 65 lumens/Watt
•
• Color temperature: intermediate
• Lamp li fe: 16000 – 24000 hours
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Metal Halide LampsMetal Halide Lamps• Works similar to tungsten halogen lamps
• Lar est choice of color, size and ratin
• Better efficacy than other HID lamps: 80 lumen/Watt
• Require high vo ltage ignition pulse but some have
third electrode for starting
• Color rendering index: 1A – 2
•
3000 – 6000 K
• Lamp life:
6000 – 20,000 hours
37
Blended LampsBlended Lamps
•“Two-in-one” : 2 light sources in 1 gas filled bulb
• Quartz mercur dischar e tube
• Tungsten f ilament
• Suitable for f lame proof areas
• Fit into incandescent lamps fixtures
• Efficacy: 20 – 30 lumen/Watt
• Lamp li fe < 8000 hours
• High power factor : 0.95
• Typical rating: 160 W
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LED LampsLED Lamps• Newest type of energy efficient lamp
• Two t es:
• red-blue-green array
• phosphor-coated blue lamp
• Emit visible light in a very narrow
spectrum and can produce “white
light”
• Used in exit signs, traffic signals, andthe technology is rapidly progressing
• Significant energy savings: 82 – 93%
• Longest lamp li fe: 40,000 – 100,000
hours39
ReflectorsReflectors
• Impact how much light reaches
area and dist ribut ion pattern
• Diffuse reflectors:
•70-80% reflectance but declining in t ime
•Painted or powder coated white finish
• Specular reflectors:
• -
•Polished or mirror-like
•Not suitable for industrial open-type strip fixtures
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GearGear Ballast
• Current limitin device
• Helps voltage build-up in fluorescent lights
Igniters
• Start metal halide and sodium vapor lamps
41
Comparing LampsComparing Lamps
Lumens /
Watt Color Life
Index
(Hours)
Range Avg.
Incandescent 8-18 14 Excellent Homes, restaurants, general
lighting, emergency lighting
1000
Fluorescent Lamps 46-60 50 Good w.r.t.
coating
Of fi ces , s ho ps , h os pi tal s, h om es 5000
Compact fluorescent lamps (CFL) 40-70 60 Very good Hotels, shops, homes, offices 8000-10000
High pressure mercury (HPMV) 44-57 50 Fair General lighting in factories, 5000
garages, car par ng, oo
lighting
Halogen lamp s 18-24 20 Excellen t Display, flood lig hting, stadium
exhibition grounds, construction
areas
2000-4000
High pressur e sodium (HPSV)
SON
67-121 90 Fair General lighting in factories, ware
houses, street lighting
6000-12000
Low pressure sodium (LPSV)
SOX
101-
175
150 Poor Roadways, tunnels, canals, street
lighting
6000-12000
42
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Electrical Lighting DesignElectrical Lighting Design
Better lightingincreased
productivity
Two main• Choose correct
lighting level
ques ons or designer:• Choose quality of light (color
rendering)
43
Recommended Light LevelsRecommended Light Levels
Illuminance
level (lux)Examples of Area of Activity
Gener al L i ht in fo r 20 Minimum servi ce il luminance in ex te rior c ir cu lat ing areas,
rooms and areas
used either
infrequently
and/or casual or
simple visual tasks
outdoor stor es , stockyards
50 Exterior walkways & platforms.
70 Boiler house.
100 Tr an sf or mer yar ds , f ur nac e r oo ms et c.150 Ci rculat ion areas in indust ry, s to res and stock rooms.
200 Mi ni mu m s er vi ce i ll um in an ce o n t he tas k
300 Medium bench & machine work , general process in
chemical and food industri es, casual reading and filing
General lighting for
interiors
.
450 Hangers, inspec tion , draw ing of fi ces , f ine bench and
machine assembly, colour work, critical drawing tasks.
1500 Very f ine bench and machine work, inst rument & smal l
precision mechanism assembly; electronic components,
gauging & inspection of small intricate parts (may be
partly provided by local task lighting)
Add it ional local ized
lighting for visually
exacting tasks
3000 Minutely detai led and prec ise work, e.g. Very small par ts
of instruments, watch making, engraving.
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SolutionSolution Power required for total fluorescent load
= 190 x 55 W = 10.45 kW
Annual Energy Savings
= (20 – 10.45) x 4000 = 38,200 kWh
Annual cost savings
= 38,200 x RM 0.22 = RM 8404.00
Replacement cost
= 190 x RM13.5/unit = RM2565.00
Simple payback period
= (RM 2565.00/ RM 8404.00) X 12 = 4 months
47
Methods of LightingMethods of Lighting
Watts Per Square
Meter MethodRough calculations andnormally for checkinguse only. According to
the watts/m2 of area to
Lumen or LightFlux Method
Most commonly usedmethod in lighting
scheme design.
Point to PointMethod
Applicable toilluminate a point due
to one or moresources of light is
required. Normally for.
calculation.
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planeworkingon thereceived Lumens
Lumen MethodLumen Method
N = number of lamps
W = wattage of each lamp
MFUFW NOR DF
UF W N ××××=×××= η η
η = e icacy o eac amp umens wattUF = utilisation factor
DF = depreciation factor
MF = maintenance factor49
Utilisation FactorUtilisation Factor
planeworkingthereachingLumens UF =
0.25 – 0.35
0.35 – 0.45
Semi-IndirectLighting
Indirect
0.5 – 0.55
Lighting
DirectLighting
50
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Depreciation FactorDepreciation Factor
conditionsworkingnormalunder onIlluminati
conditionscleanideallyunder onIlluminati DF =
lamp
reflector
Dust absorb some light
Typical value:ranging from
1.2 to 1.4.
51
Maintenance FactorMaintenance Factor
The ratio of illumination on a given area after a period
of time to the initial illumination on the same area.
Lighting efficiency is seriously impaired by blackened
lamps, by lamp life, and by dirt on the lamp reflecting
surfaces of the luminaire. The losses are due to the physical changes on lamps,
reflecting and transmitting surfaces, ceiling and walls.
yp ca va ue s a out . .
52
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Example 4Example 4A lecture hall with dimension of 12 m
and the illuminance required is 350 Lux.
Assuming a depreciation factor of 1.2 and
utilisation factor of 0.6 for the lighting
scheme design. If 36 W fluorescent lamps
umens watt were to e use ,calculate the number of fluorescent lamps
required.
53
SolutionSolution
Area = 12 m x 10 m = 120 m2.
= 350 lux x 120 m2 = 42,000 lumens.
1 x 36 W Fluorescent lamp
= 75 lumens/W x 36 W = 2700 lumens.
= 42,000 x (1.2/0.6) = 84,000 lumens.
Nos of lamps = 84,000/2700 ≈ 32 lamps.
54