Module about Basics of illumination engineering.pdf

Some topics covered on illumination engineering

1. EE3044D
Electrical System Design for Buildings
Module 2
Illumination Engineering

2. Illumination schemes –types of light sources and
lighting arrangements –energy efficiency in lamps
and illumination –design of lighting for various
purposes.

3. Physical Processes Employed in Artificial Sources
1.Incandescence
•Thermoluminescenceisbydefinitionradiationathightemperature(hotbody
radiation)
•ThesourcesemployingthisprocessareIncandescentlamp,Gaslamp
•Theyleadtoacontinuousspectrumofradiation.
2.Luminescence
•Luminescence is emission of light that does not produce heat (cold body
radiation)
•It can be caused bychemical reactions,electrical energy or subatomic motions.
•Chemiluminescence, Bioluminescence, Electroluminescenceare different
types of Luminescence.
•Here color of radiation depends on the material employed.
•Usually this process leads to line or band spectrum.

4. Physical Processes Employed in Artificial Sources
3.Fluorescence
•Fluorescenceisaprocessinwhichradiationisabsorbedatonewavelength
andradiatedatanotherwavelength.
•Inmostcases,theemittedlighthasalongerwavelengththantheabsorbed
radiation.
•Fluorescentlamp
4.Phosphorescence
•Phosphorescenceisdefinedasemissionoflightfromasubstanceexposedto
radiationandpersistingasanafterglowaftertheexcitingradiationhasbeen
removed.
•ExamplesofthisprocessareLuminouspaintsthatcontaincalciumsulfidethat
leadtoPhosphorescence.
•Theyproducelightradiationafterexposuretolight.

5. Physical Processes Employed in Artificial Sources
•GoodefficientlightingisobtainedbycombiningLuminescenceand
Fluorescence.
•Intensitydependsongasorvaporinvolvedandphosphormaterial.
•Thetemperatureofthematerialalsoplayaroleinradiation.

6. Terms used in Illumination
1.Light
2.Luminousflux
3.Lumen
4.Planeangle
5.Solidangle
6.Steradian
7.Candlepower
8.Luminousintensityreductionfactor
9.Glare
10.Lampefficiency

7. Terms used in Illumination
Light
•That part of radiant energy from a hot/cold body which produces visual sensation
on human eye is called light.
Luminous Flux
•The total quantity of radiant energy per second responsible for visual sensation
from a luminous body is called Luminous Flux.
•It is represented as F or Φ
•Measured in lumens.

8. Terms used in Illumination
Lumen
•Onelumenisdefinedastheluminousfluxemittedperunitsolidangle froma
pointsourceofonecandlepower.
SolidAngle
•The angle subtended by the partial surface area of a sphere at its centreis
calledassolidangle.
•Itismeasuredinsteradians
•It is equaltotheratio ofareaofthesurfacetothesquareofradiusofsphere
•ω=areaofsurface/squareofradius
=A/r
2
steradians

9. Terms used in Illumination
Steradian
•Theunitofsolid angle.
•One steradianisdefinedasthe solidangle thatis subtendedatthe centre
ofasphere byitssurfacehaving areaequalto radiussquare.

10. Terms used in Illumination
Candle Power
•The light radiating capacity of a source is called its candle power
•The number of lumens given out by a source per unit solid angle in a given
directionis called its candle power.
•It is denoted by C.P
•Total flux emitted = C.P * solid angle

11. Terms used in Illumination
Luminous Intensity
•Luminous intensity in any particular direction is the luminous flux emitted by
the source per unit solid anglein that direction.
•It is denoted by I
•Its unit is candela
•Luminous intensity of source in a particular direction, I = φ / ω

12. Terms used in Illumination
Reduction Factor
•Reduction factor of a source of light is the ratio of its mean spherical candle
power to its mean horizontal candle power.
•Reduction factor = MSCP/ MHCP
MEAN SPHERICAL CANDLE -POWER
•A unit of measure that represents the average output of a light source measured
in all directions (360°)
•MSCP= F/4π
MEAN HORIZONTAL CANDLE -POWER
•The average value of the candle-power of a light source in all directions in a
horizontal plane through the source

13. Terms used in Illumination
Illumination(Illuminance)
•Whenlightfallsonasurface,itbecomesvisible,thephenomenoniscalledas
illumination.
•Itisdefinedasluminousfluxfallingonasurfaceperunitarea.
•ItisdenotedbyE
•Measuredinlux(lumenpersquaremeter)
•E=Ф/A

14. Terms used in Illumination
Lux
•Onemetercandleorluxisdefinedastheilluminationproducedbya uniform
source of one CP on the inner surface of a sphere of radius onemeter.

15. Terms used in Illumination
Luminance
•It is a parameter related to the source.
•It is the intensity of light emitted from a surface per unit areain a given
direction
•Measured in cd/m
2
•It can be interpreted as analogous to Brightness (B).
•L = I / A

16. Terms used in Illumination
Glare
•Inthehumaneye,theopeningofpupiliscontrolledbytheintensityoflight
receivedbytheeye.
•Iftheeyeisexposedtoaverybrightsourceoflight,thepupiloftheeye
contractsautomaticallyinordertoreducetheamountoflightadmittedand
preventdamagetotheretina.Thiseffectiscalledglare.
•Glareisdefinedasthebrightnesswithinthefieldofvisionsoastocause
discomfortandinterferenceinvision.

17. Terms used in Illumination
Lamp Efficiency
•It is defined as the visible radiations emitted by it in lumens per watt.
Depreciation factor
•Defined as the ratio of illumination when everything is clean to illumination
under normal working conditions.
•Due to accumulation of dust on lamp they emit less light
•Depreciation factor should always be greater than 1.
Utilization factor or coefficient of utilization
•Defined as the ratio of total lumens reaching the working plane to total lumens
given out by the lamp.

18. Law of Illumination
•Theilluminationonasurfacedependsupon
•Luminousintensity
•Distancebetweenthesourceandsurface
•Directionofraysoflight
•It isgovernedbyfollowinglaws:
1.Inversesquarelaw
2.Lambert’scosinelaw

19. Inverse Square Law
•Itstatesthattheilluminationofasurface isinverselyproportionaltothesquareof
the distanceofthesurfacefromthesource.
•E
�
??????
�
•E=
??????
??????
�
Where
I -Luminous intensity of source
d –distance of point from the source

20. Lambert’s cosine Law
•This law states that the illumination on any surface is proportional to thecosineof
anglebetweenthedirectionoftheincidentfluxand perpendiculartothearea.
•Ecosθ
•E =
??????
??????
�
cosθ
Where,
I -Luminous intensity of source
d –distance of point from the source

21. Illumination at point ‘P’ is given by
Substituting for r,
Now we get
Where,I/h
2
is the illumination at any point located directly below the source of light.

22. Lumen Method

23. Design consideration of a good lighting scheme
•The required illumination level
•Selection of required lamp and fitting
•The size of the room
•The condition under which the illumination is used

24. Lighting Design
•Shorthandmethod
•Longhandmethod
•Simplifiedmethod

25. Short hand method
•It is assumed that average maintained quantity of lumens arriving on the work
plane is the half the quantity of new lamp lumens.
•This method assumes normal sized rooms.
•Normal sized room is the one in which mounting height is less than half the
smallest room dimension.
•It is also assumed that conventional room fixtures are used.
•Spacing should not be more than mounting height for high bay fixtures and 1.5
times the mounting height for low bay fixtures.

26. Short hand method
Total number of fixtures (luminaries) to be used is then calculated as:

27. Long hand method
•Moreaccurateandeffectivemethodofestimatingthenumberoflight
fixturesandtheirspacing
•Thecoreideaofthismethodisthedeterminationofcoefficientof
utilizationontheconceptthattheareatobelightedhasthreecavities
orspacesthathaveeffectivereflectancewithrespecttoeachotherand
workplane.

28. Long hand method

29. Long hand method

30. Long hand method

31. Long hand method

32. Long hand method

33. Simplified method

34. Simplified method

35. Simplified method