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Illumination.
1. AR 307: Building Services-II
ILLUMINATION
Lecture 1
Illumination: Introduction
Light: Basics
Definitions of terms
Laws of Illumination
Light flux method
Types of Lamps, Luminaires.
Residential, Commercial,
Industry, flood and Street
lighting.
2. Illumination – objective of study for architects…..
.
• to understand importance of proper illumination from
human factors point of view eg. Ergonomics, anthropometry,
Psychology etc.
• to know about proper ambient lighting for areas where
people work. eg. to provide safety and prevent accidents.
• Lighting energy consumption contribute to 20 to 45% in
commercial buildings and about 3 to 10% in industrial plants.
Hence, to increase awareness of energy savings in lighting
systems realized with a minimal investment of capital and
“common sense”.
• it may be necessary to consider modifications of the lighting
design in order to achieve the desired energy savings.
• to make effort to produce light sources with higher
luminous efficacies, better color rendering properties and
longer life expectancies.
• knowledge of purchase cost and maintenance cost are also
quite essential for the proper choice.
3. .
Hence, Three primary considerations to ensure energy
efficiency in lighting systems are:
1. Selection of the most efficient light source possible in
order to minimize power costs and energy consumption.
2. Matching the proper lamp type,
to the intended work task or aesthetic application,
consistent with color, brightness control and other
requirements.
3. Establishing adequate light levels to maintain
productivity
improve security and
increase safety.
4. Illumination – history…........
.
• Luminous efficacies were increased enormously through the centuries
from 0.01 lm/W candle to above 100 lm/W for modern “white” light
sources.
• Torch was probably the first lighting source and fixture as well around
400000 years BC.
• simple lamps made of shell and fat around 13000 BC.
• pottery lamps (with refined design) around 600 BC.
• Candle appeared around 400 AD and was the first light source that
could be used either in interior or exterior with or without a
transparent protective case.
• Around 1800 the carbon arc lamps were introduced
• gas lamps in 1814.
• incandescent lamp has appeared during 1879 by Thomas Edison with
luminous efficacy ~1.4 lm/W.
• High Intensity Discharge lamps introduced in 1901.
• low pressure sodium in 1932,
• fluorescent in 1932.
• quartz and metal halide in 1960.
• then Sulfur lamp- exciting sulfur and quartz with microwaves.
5. Illumination – history contd...
.
• In recent years LED use have become widespread. There are two
possible approaches to produce white light. The first is to use a blue
LED coated with a white phosphor (1996).
• The second method of producing white light is to use additive mixing of
the three primary colours red, green and blue.
6. Light – basics..
.
Light
Electromagnetic radiation that the unaided human eye can
perceive, having a wavelength in the range from about 370 to
800 nanometres (nm) and propagating at the speed of
299,792.5 km/sec.
Light is just one portion of the various electromagnetic waves
flying through space. These waves have both a frequency and a
length, the values of which distinguish light from other
forms of energy on the electromagnetic spectrum.
7. Light – basics..
.
Light is emitted from a body due to any of the following
phenomenon.
• Incandescence: Solids and liquids emit visible radiation
when
they are heated to temperatures about 1000K. The intensity
increases and the appearance become whiter as the
temperature increases.
• Electric Discharge: When an electric current is passed
through a gas the atoms and molecules emit radiation
whose spectrum is characteristic of the elements present.
• Electro luminescence: Light is generated when electric
current
is passed through certain solids such as semiconductor or
phosphor materials.
8. Light – basics….. Contd.
.
Photoluminescence: Radiation at one wavelength is absorbed,
usually by a solid, and re-emitted at a different wavelength.
When the re-emitted radiation is visible the phenomenon
may be termed either fluorescence or phosphorescence.
16. Light – basics..
.
Figure 1.Illustration of the distribution of light from a light source following the inverse-square law
(Sanders & McCormick, figure 16-4, pp517)
23. Light – basics..
.
Incidence
The striking of a ray of light or sound on a surface.
Reflection
The return of light, sound or radiant heat after striking a
surface.
Refraction
The process by which the direction of light changes as it
passes obliquely from one medium to another in which
its speed is different.
25. Light – definitions..
.
Figure 1.Illustration of the distribution of light from a light source following the
inverse-square law (Sanders & McCormick, figure 16-4, pp517)
26. Light – definitions..
.
‘luminous flux’ (F) is the flow rate of light energy and the unit is
‘lumen (lm)’
‘luminous intensity’(I) is the flow rate of light energy per solid
angle. The unit is lm/solid- angle or 1 candela (cd).
(A solid angle is measured in steradians (sr) and there are
4 π sr in a sphere).
Let’s consider a point source whose luminous intensity is
strong enough to distribute 1 lm / solid-angle (i.e., 1cd).
Because in one sphere, there are 4π solid-angles, the total
luminous flux require to maintain 1cd luminous intensity will
be 4π lm.
Therefore, we say 1cd emits a total of 4π lm flux.
Thus the luminous flux emitted by an isotropic light source of
intensity I is given by:
Luminous flux (lm) = 4π × luminous intensity (Cd)
27. Light – definitions..
.
‘illuminance’ (E)- density of light shining onto a surface.
lux (lx)- The SI unit of illuminance equal to one lumen per
square meter.
‘illuminance’ is measured as:
1 lm/m2 = 1 lux (lx) [SI unit]
1 lm/ft2 = 1 foot-candle (fc) [US unit]
Lumen- The quantity of luminous flux emitted within a unit
solid angle (one steradian) by a point source with one
candella intensity in all directions.
28. Light – definitions..
.
The difference between the lux and the lumen is that the lux
takes into account the area over which the luminous flux is
spread.
1000 lumens, concentrated into an area of one square meter,
lights up that square meter with an Illuminance of 1000 lux.
The same 1000 lumens, spread out over ten square meters,
produce a dimmer Illuminance of only 100 lux.
29. Light – definitions..
.
Luminance - The luminous intensity of a surface in a given
direction per unit area of that surface as viewed from that
direction; often incorrectly referred to as "brightness.“
Candela (cd)- The SI unit of luminous intensity (formerly called
the candle). One candela equals one lumen per steradian - the
luminous intensity, in a give direction, of a source that emits
monochromatic radiation at a frequency of 540x10¹² hertz and
of which the radiant intensity in that direction is 1/683 watts
per steradian.
30. Light – Laws of illumination..
Where E = Illuminance, I = Luminous intensity and d = distance
An alternate form of this equation which is sometimes more convenient is:
Distance is measured from the test point to the first luminating surface -
the filament of a clear bulb, or the glass envelope of a frosted bulb.
.
The Inverse Square Law
The inverse square law defines the relationship between the
illuminance from a point source and distance.
It states that the intensity of light per unit area is inversely
proportional to the square of the distance from the source
(essentially the radius).
32. Light – Laws of illumination..
.
Lambert’s cosine law- the illumination produced on a surface
by a point source is proportional to the cosine of the angle of
incidence
33. Light – Laws of illumination..
.
Lambert’s cosine law- the illumination produced on a surface
by a point source is proportional to the cosine of the angle of
incidence
34. http://lumenistics.com/energy-efficient-lighting-basics/
CRI is an internationally accepted
measure of how well a light source
renders colors, compared to
incandescent and daylight sources.
The CRI scale of 0 and 100, with 100
representing perfect color rendering
based on illumination by a 100-watt
incandescent light bulb.
Color appearance and CRI values for
energy-efficient lighting
technologies:
•Incandescent bulbs: 2,700 K,
100 CRI
•Cool white fluorescent tube:
4,100 K, 62 to 80 CRI
•Noon sunlight: 4,500 K to
5,400K, 100 CRI
Measuring Lighting Quality
37. There are several lumen traps that you must know about. Six of the most important lumen
traps are
1) Luminaries/ System efficiency
2) Ballast and Driver efficiency
3) Scotopic superiority
4) Lumen Maintenance
5) Uniformity of light distribution and light hotspots under traditional lights
6) Colour reproduction
•Scotopic sensitivities peak about 50 nm lower in the
blue-green region of the spectrum at 507 nm, where the
rods are most receptive.
Scotopic vision is the vision of the eye under
low light conditions or Night Vision
The sensitivity of eye is known as the Photopic response
and refers to colour vision and the perception of fine detail.
Photopic sensitivities are at a maximum in green light at
about 555 nm which is the wavelength at which the cones in
our retina are most receptive.
In normal light (luminance level 1 to 106 cd/m²), the vision
of cone cells dominates and is photopic vision. There is
good visual acuity (VA) and color discrimination.
http://www.venturelighting.com/techcenter/LowLightLevels.html
38. Lumen Maintenance
Lumen maintenance is another area that decision makers need to consider. The human eye can
adapt well to up to 30% reduction in light levels. When light levels fall below the 30 % threshold
reduction in light levels become evident and vision is compromised. Thus, lights need to be
designed based on average lumens over the useful life of a light.
A comparison of the lumen maintenance data of
different types of lights is shown in the graph above.
A summary of the abbreviations, common name, and
life till 70% of peak light output levels is given below.
PSMH – Pulse Start metal halide – 12000 hours
CMH – Ceramic Metal Halide – 16000 hours
HPS – High Power Sodium – 24000 hours
LED – Light Emitting Diode – 50000 hours and more.
The figure demonstrates why “Luminance” is
important. Differences in installation height, air
quality, electricity quality, reflectance of the surface
mean that most lamps are rated for their Luminous
flux or light output.
39. http://www.myledlightingguide.com/Article.aspx?ArticleID=38
Human eye responds better to shorter wavelengths of 510 and 550 nm.
These are conspicuous by their absence in HPS lights. Each LED
photopic Lumen is equivalent to 2.4 Scotopic lumens (For a detailed analysis of
the relationship between photopic and scotopic Lumens please refer to ou r article on Pupil Lumens and
The complete guide to LED street lights – part I). When it comes to Scotopic equivalent
lumens HPS lamps are no match for LED lights with richer light
spectrum.
Several advantages of LED lighting systems are immediately visible.
LED lights have significantly less glare, more uniform Light distribution,
fewer shadows, and improved visibility. The best part is that this
improvement is obtained with fewer lumens and 40 % or more savings
in electricity and maintenance costs.
•An HPS lamp has a larger profile, a
single source of light and a considerable
amount of light trapped in the reflector.
•An LED light has a small profile, several
sources of light ensuring better light
distribution.
•All the light is produced and directed
downwards. There are no problems of
reflector efficiency, aging of reflector
coating and consequent loss in light
output.
LED VERSUS TRADITIONAL LAMPS
40. •The picture shows the
advantage of uniform lumen
distribution achieved by LED
outdoor lights.
•The upward directed light in a
traditional luminaries is
reflected straight down.
•This causes a ‘hotspot’ to
form right below the luminaries
while areas further away from
the bulb have poor light
intensity.
•These hotspots can be clearly
seen in the picture of the bridge.
•In this case, the improvement
in lighting was accompanied
with a 13 % savings in energy
consumption, long maintenance
free life span and the possibility
of pairing the LED fixture with
smart energy saving
technologies in the future.
41. Light –types of illumination schemes..
.
Exercise-TYPES OF OUTDOOR LIGHTS
Designing and Installing Outdoor Lighting -
http://www.sustland.umn.edu/implement/outdoor_lighting.html
http://www.docstoc.com/docs/64891791/LIGHTING-DESIGN-
BASICS
44. Styles of Luminare
Down lights
Troffers
Commercial Florescent Fixtures
Industrial Luminaries
Linear Lighting Systems
Architectural Lighting Fixtures
•Wall washers
•Wall Grazing Fixtures
•Accent Fixtures
•Cove Lights
•Task Lights
•Decorative lighting – Trochee, Lantern,
Chandeliers, Adjustable Down lights,
Ceiling drums, wall scones, Pendants
Lights, Vanity Lights, etc
45. Types of Direct Lights
•These include most surface-mounted fixtures on walls and ceilings,
often with a diffusing globe or lens to reduce glare.
•In general, these are very efficient sources of light, but may also
produce a lot of glare.
•Common types include surface-mounted ceiling fixtures, pendants,
chandeliers, and sconces.
Surface-mounted ceiling lights. Either
incandescent or fluorescent fixtures mounted
directly on the ceiling are a very efficient source
for ambient lighting. Some, such as fluorescent
“clouds,” use rounded diffusers that cast light on
the ceiling as well as downward.
Chandeliers.
Sconces. Wall sconces provide soft lighting in
living and dining areas and hallways. Most provide
some direct lighting as well as an indirect “wash”
of light upward onto walls and ceilings. Often
placed in pairs, they are typically located about 66
inches from the floor to the centre.
Pendant ceiling lights. Pendant fixtures are often
used to provide task lighting above kitchen tables
or eating counters and may also project light
sideways and upward to the ceiling.
46. When lighting a picture or single object, use a directional spot lamp in a shielded fixture.
These are often track-mounted or adjustable recessed fixtures, such as “eyeballs.”
Accent Light
47. Recessed Lighting
•Typically used with a
narrow spot to provide
bright focused light on a
small area.
•Slotted wall wash trim is
used to splash diffused
light on broad areas of wall
or bookcases.
•Nondirectional A-lamps or
compact fluorescents work
well in this application.
48. Light –types of lamps…
.
There are three main types of household lamps or lights to
choose from:
• Incandescent – inexpensive to buy, but running costs are
high compared to other lamps. Bulbs only last up to 1000
hours. Recommended for infrequently used rooms.
• Halogen – twice as energy efficient as incandescent
globes. They are more expensive to buy, and last up to
2000 hours. Ideal for highlighting features, such as a
painting on a wall. Halogen lamps are low voltage lights and
require a transformer, which uses more energy. Because
halogen globes emit a beam of light, many more fittings are
required in a room than for conventional lighting.
• Fluorescent – these are the most energy efficient form of
lighting. Bulbs are cheap to run and last up to 8000-16000
hours. There are two main types of fluorescent lamps::
49. Light –types of lamps…
.
Fluorescent lamps
• Fluorescent lamps contain mercury vapour with extremely
low pressure.
• Electrodes are located on both ends of the fluorescent
lamp.
• The electrons hit mercury atoms on their path through the
discharge tube.
• Upon collision, the mercury atoms are shortly excited.
• The absorbed shock energy is immediately released in the
form of invisible UV radiation.
• While passing through the fluorescent layer on the inner side
of the discharge tube, the shortwave UV radiation is partially
transformed into visible light.
51. Light –types of lamps contd…
.
1. Compact fluorescent lamps (CFL) - fit into conventional
light sockets. They use around one fifth of the power of
incandescent globes to provide the same amount of light.
These are ideal for rooms where lighting is required for long
periods of time, such as in the living room and kitchen.
Frequently switching fluorescent lights on and off can
reduce their life so they are not recommended for pantries
and toilets.
2. Tubular fluorescent lamps - also known as tube lights, are
available as straight or circular tubes. Tube lights are ideal
for kitchens, bathrooms, rumpus rooms, garages and
workshops.
55. Light –types of lamps contd…
.
The term high-intensity discharge applies to arc-discharge
sources with a high power density. With most HID lamps, the
arc tube is enclosed in an outer glass bulb.
1. High intensity discharge lamps (HID)
HID lamps used for illumination in buildings belong to three
principal families:
1) mercury-vapour lamps
2) high-pressure sodium lamps
3) low pressure sodium lamps
4) metal-halide lamps
56. Light –types of lamps contd…
.
1) Mercury-vapour lamps
With mercury vapour lamps, light is produced by an
electric discharge through mercury vapour, resulting in
poor quality of a greenish hue.
2) High-pressure sodium lamps
- High-pressure sodium lamps are manufactured with
tube-shaped ellipsoidal bulbs with wattage of between 50 W
and 1000 W.
- High-pressure sodium lamps achieve a extremely high
luminous efficacy up to 130 lm/W,
- These lamps are only used in warehouses and similar
locations when used in interiors; their main application is
outdoors for the illumination of streets and car parks.
57. .
3) Low-pressure sodium lamps
- These lamps have high efficiency (up to 180 lm/W),
quite long life (up to 16000 hours) and reduced running
costs.
- As their name implies sodium in the lamp causes the light
to be a yellow color.
- LPS is commonly used for road lighting, parking areas etc..
- A short warm-up period is needed for the lamp to reach
full brightness.
58. .
4) Metal-halide lamps
- are a further development of high-pressure mercury-
vapour lamps.
- the luminous efficacy is about 95 lm/W.
- colour rendering is improved considerably.
- The lamps are available with an ellipsoidal bulb with
wattages ranging from 250W to 1000W; their wattage
increases to 3500 W when shaped like a tube.
- Single and double-ended lamps with a lower wattage are
also available with wattages beginning from 35 W that are
particularly suitable for the energy-efficient lighting of
offices, salesrooms and window-shops.
59. .
4) LED-technology for lighting
- Light emitting diodes (LED) are light sources based on
electro luminescence and are very similar to conventional
semiconductor diodes.
- enormous life time and a very high efficiency.
- The size of the active light emitting area is typical smaller
than 1 mm² and acts quasi as a point source.
60. .
Hence, energy savings can be realized with,
• Replacing mercury vapor or incandescent sources with
metal halide.
• high pressure sodium results in reduced energy
costs and increased visibility.
• Installing and maintaining photo-controls, time clocks, and
energy management systems can also achieve extraordinary
savings.
61. .
Light –types of luminaries…
A luminaire is a complete lighting unit consisting of one or
more lamps (light sources) together with
optical and
mechanical components.
It is designed
to operate the lamps, that means
to position and protect the lamps and
to connect them to the power supply.
62. .
Light –types of luminaries…
The most important element in a light fitting, apart from the
lamp(s), is the reflector.
They impact on how much of the lamp’s light reaches the
area to be lit as well as the lighting distribution pattern.
Reflectors are generally either diffuse (painted or powder
coated white finish) or specular (polished or mirror-like).
The degree of reflectance of the reflector material
and the reflector’s shape directly influence
the effectiveness and
efficiency of the fitting.
