Illumination.

AR 307: Building Services-II

ILLUMINATION

Lecture 1

Illumination: IntroductionLight: BasicsDefinitions of termsLaws of IlluminationLight flux methodTypes of Lamps, Luminaires.Residential, Commercial, Industry, flood and Street lighting.

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.

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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.

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.

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.

Light – basics...

LightElectromagnetic 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 otherforms of energy on the electromagnetic spectrum.

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.

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.

Light – basics...

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)

Light – basics...

Light – basics...

IncidenceThe striking of a ray of light or sound on a surface.

ReflectionThe return of light, sound or radiant heat after striking a surface.

RefractionThe process by which the direction of light changes as it passes obliquely from one medium to another in which its speed is different.

Light – basics...

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)


‘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 solidangle. The unit is lm/solidangle 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)


‘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.


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.


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.

Light – Laws of illumination..

Where E = Illuminance, I = Luminous intensity and d = distanceAn 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.

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The Inverse Square LawThe 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 inverselyproportional to the square of the distance from the source (essentially the radius).

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

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

Lighting Type Summary

There are several lumen traps that you must know about. Six of the most important lumen traps are

1) Luminaries/ System efficiency2) Ballast and Driver efficiency3) Scotopic superiority4) Lumen Maintenance5) Uniformity of light distribution and light hotspots under traditional lights6) 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

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 hoursCMH – Ceramic Metal Halide – 16000 hoursHPS – High Power Sodium – 24000 hoursLED – 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.

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

•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.

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

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Light –types of illumination schemes..

Light –types of illumination schemes...

Styles of LuminareDown lightsTroffersCommercial Florescent FixturesIndustrial LuminariesLinear Lighting SystemsArchitectural 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

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.

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

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.

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::


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.

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.


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 lamps2) high-pressure sodium lamps3) low pressure sodium lamps4) metal-halide lamps


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.

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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.

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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.

. 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.

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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.

. 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.


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 materialand the reflector’s shape directly influence

the effectiveness and efficiency of the fitting.

. Light–lumen method of calculation of no. of lamps…

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Illumination.

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Transcript of Illumination.