esd m2.ppt Lighting schemes and calculations
- 1. EET 402 :ELECTRICAL SYSTEM DESIGN MODULE 2 LIGTHING SCHEMES AND CALCULATIONS Prepared by SAJINA M K ASSISTANT PROFESSOR EEE DEPARTMENT MESCE
- 2. Syllabus Lighting Schemes and calculations (6 hours): Lighting design calculations - Definitions of luminous flux, Lumen, Luminous intensity/illuminance (Lux), Illumination calculations, factors affecting Coefficients of Utilisation (CoU) - and Light Loss Factor (LLF). Benefits of LED lamps over the yesteryear luminaires – Efficacy of present- day LED lamps Design of illumination systems – Average lumen method - Space to mounting height ratio Design of lighting systems for a medium area seminar hall using LED luminaires Exterior lighting design- point to point method - road lighting and public area lighting- Space to mounting height ratio - selection of luminaires- Metal Halide- High & Low pressure Sodium– LED lamps.
- 3. BASIC DEFINITIONS • Light : That part of radiant energy from a hot body which produce visual sensation on human eye • Luminous intensity (I) :Luminous Intensity is a measure of the wavelength- weighted power radiated by a light source in a particular direction per unit solid angle and is measured in Candela. • Luminous Flux (L) : From the light source, energy is radiated in the form of light waves. This flow of light from the source is known as Luminous Flux (L) and unit is lumen • Lumen : One lumen is the luminous flux emitted per unit solid angle from a point source of one candle power
- 4. BASIC DEFINITIONS • Illuminance (E) : Illuminance is the total luminous flux incident on a surface, per unit area and is measured in lux. • 1lux=lumen/area= 1lumen/m2 • Luminaire ( light fitting ): It is the apparatus which distributes, filters or transforms the light given by a lamp. It includes all the items necessary for fixing and protecting the lamps and for connecting them to the supply circuit. • Candle power: Number of lumens given out by a source per unit solid angle in a given direction is called candle power Solid angle =4π steradians in a full sphere • Total luminous flux= CP*4π lumens • CP is the unit of luminous intensity
- 5. LAWS OF ILLUMINATION INVERSE SQURAE LAW: States that the illumination (E) of a surface is directly proportional to the luminous intensity and inversely proportional the square of the distance between the source and the illuminated surface, as long as the source remains the same. E = I/r2 I= luminous intensity E- illumination of the surface r- distance between the source and surface to be illuminated This is true only when the surface to be illuminated is placed normal to the direction of the light beam.
- 7. COSINE LAW • When the plane to be illuminated may not be normal to the direction of luminous flux, and is inclined by an angle θ, where θ is the angle between the line of flux and the normal to the illuminated plane. • The law states that the illumination on a surface is proportional to the cosine of the angle between the normal to the surface and the line of flux and also to power of the source. E is inversely proportional to r2. • E = I cos θ/r2 • These laws are applicable only to point sources( no reflecting surfaces)
- 8. COSINE LAW • Consider a point 'P' on a plane surface and the distance between the source of light (S) and the point 'P' is 'r' meters. The source (S) is located at height of 'h' meters from the surface and its luminous intensity is 'I' candle power as shown in Figure • E = I Cos θ/r2 • r= h/Cos θ
- 9. DESIGN CONSIDERATIONS FOR A GOOD LIGHTING SCHEME • Intensity of illumination Intensity of illumination required for different types of work differ from place to place. • Selection of lamps or selection of luminares The choice of lamps for different types of application differs Fluorescent lamps and tungsten filament lamps are used when lighting is needed in small areas In large areas, the lighting can be provided by high intensity lamps such as mercury or discharge lamps Depending upon the type of illumination required, the type of luminare is decided
- 10. DESIGN CONSIDERATIONS FOR A GOOD LIGHTING SCHEME • Size of the room The lumen output of the source or lamp is not fully utilized at the work place. A part of the light is lost in the fittings and some part is directed to the walls and ceilings where a part will be absorbed and a part will be reflected . This is taken into account by a factor known as Coefficient of Utilization (CU). The ratio of lumens reaching the working plane to the total lumens given out by the lamps is known as CU or Utilization factor. Factors affecting Coefficient of Utilization (CU). Lumen output of the fitting Shape of the room Reflection factors of walls and ceilings Height of the ceiling Arrangement of the fittings etc
- 11. DESIGN CONSIDERATIONS FOR A GOOD LIGHTING SCHEME • Mounting height and spacing of fitting Governed by the type of the building and the type of lighting scheme employed. The distance of the light source from the wall should be equal to half of the distance between the two adjacent light sources. Also distance between lighting fitting should not exceed 1.5 times the mounting height Or spacing to mounting height ratio can be upto 1.5 • Condition of use For different types of buildings, the condition of use of light varies. Dust and dirt particles of the surroundings get deposited on the light fitting and hence deteriorate the lamp efficiency. If regular periodic cleaning is adopted and assuming good atmospheric condition, the maintenance factor (MF) is taken as 0.8 , but for dirty and dusty atmosphere, the MF is taken as 0.4. Depreciation factor (DF) =1/Maintenance Factor Maintenance factor is also called Light Loss Factor(LLF) Provide light of suitable colour. Avoid glare and hard shadows as far as possible.
- 12. LIGHT LOSS FACTOR (LLF) • Periodic schedule and appropriate maintenance is very essential in maintaining the initial lighting level. • An LLF would not be required if light output remains constant throughout the useful life. • Inherent light loss characteristics of the luminaire and unfavorable ambient conditions will force the net output to deteriorate with time • An LLF is introduced in lighting calculations to make up for expected loss of light in the lighting system. The various factors that contribute to light loss are of two types. – Recoverable – Non-recoverable.
- 13. The recoverable factors include: – Luminaire dirt depreciation (LDD) – Room surface dirt depreciation (RSDD) – Lamp lumen depreciation (LLD) and – Lamp burn out (LBO) Luminaire dirt depreciation (LDD) • The greatest loss of light output is due to the dirt accumulation on lamps and luminaire reflecting surface • Proper selection of maintenance is essential – Air-conditioned spaces - Once in two years – Non A/C offices, School, etc - Once in a year – Industrial areas- 3-6 times a year – Food preparation area - every week Room surface dirt depreciation (RSDD) • This factor takes into account the dirt or dust accumulation on surfaces • A proper schedule for cleaning the reflecting surface must be followed to maintain the reflectance
- 14. Lamp lumen depreciation and lamp burn out (LLD and LBO) • Lamp lumen depreciation is an inherent characteristic of all lamps. • Two types – Spot re-lamping – Group re-lamping. • Spot re-lamping refers to changing of lamps as and when a lamp burns out • Group re-lamping is the process of replacing all the lamps in an installation after the useful life period of the lamps irrespective of the fact whether the lamps are in working condition or not
- 15. Non-Recoverable factors • These factors present those conditions of a lighting system that reduce the light output, where nothing in terms of periodic maintenance can recover the losses These include: – Luminaire ambient temperature (LAT) – Voltage variation (VV) – Ballast factor (BF) – Luminaire surface depreciation (LSD) Luminaire ambient temperature (LAT) • A variation in the ambient temperature does not have much effect on the incandescent and HID lamps • Fluorescents are affected by a change in ambient temperature • Fluorescent produces a peak output at about 25 °C Voltage variation factor (VV) • For incandescent lamps a variation of 1% voltage may cause as much as 3% variation in light output • For HID and fluorescents also variation in voltage affects their output
- 16. Ballast Factor (BF) • Ratio of light output by a commercial ballast to that by reference ballast . Luminaire surface depreciation factor (LSD) • Changes in the various components used in the manufacture of luminaires can cause reduction in the light output . • Due to aging, polished surface will have reduced reflectance. All four non-recoverable factors will depreciate the output permanently and nothing can be done to recover them.
- 17. Benefits of LED lamps over yesteryear luminares 1. LEDs use less power (watts) per unit of light generated (lumens) 2. LED lighting achieves energy savings of 30% to 90%. 3. LED lamps work at a much lower temperature, reducing the risk of burns if touched. 4. Maintenance-free and easy to install. 5. Delivering better lighting quality and visibility. 6. Tremendous design flexibility. 7. Smart connectivity features. 8. Lasting for many years (even decades). 9. LEDs have less impact on the environment and human health. 10. LEDs are more robust. 11. LEDs offer greater cost savings.
- 18. Efficacy • Efficacy is a measure of how much light a light source produces for the energy put in to it. This is normally expressed in Ln/W (lumens per watt) • The luminous efficancy of LEDs can be as high as 300 ln/W, which is over 18 times more than traditional light bulbs . • Although LEDs are a more expensive light source, they are worth choosing due to their high energy efficiency and long life.
- 19. LIGHTING CALCULATIONS Average lumen method • Simplified way of calculating an average uniform illuminance level on a plane in interiors • Takes into account the effects of surface reflectance • Simplified and accurate method of quantity evaluation for interiors • This method is developed from the basic definition of lux, which states that one lux is the illuminance on a surface of one square meter having a light flux of one lumen • Illuminance E= L/A where L = lumens produced by all the luminaries in room and A= area in sq.m. • In reality, all the luminous flux generated by the lamps will not fall on the work plane • Factors like luminaire candle power distribution, efficiency, room size and shape and luminaire height, will affect the total number of lumens reaching the work plane • The formula is multiplied by a coefficient of utilization (CU) to take into consideration all above factors. Therefore, E=(L*CU)/A
- 20. LIGHTING CALCULATIONS • The luminaire, lamp and even the surface will accumulate dust over a period of time and the lamp lumen output will depreciate with time • To obtain the maintained illuminance level, the formula now must be multiplied by a light loss factor(LLF) to account for the depreciation in light output E=(L*CU*LLF)/A • The formula can be modified as E=(Ln*N*CU*LLF)/A where Ln, = Initial lumen output per luminare and N= total number of luminares or lamps Number of luminares or lamps N=(A*E)/(Ln*Cu*LLF) • From the above, it is obvious that for a given level of illuminance and area, the only means or reducing the number of luminaires is by using the highest values of Ln, CU and LLF • The lower the number of luminaires, the less the power consumption. • Area per lamp luminare (fixture)=Room area/ No.of lamps or fixtures • Spacing between fixtures or lamps=√Area per fixture
- 21. Solution Working area A= 15m X 9m Required illumination ,E=200 Lux Lumen out put of one lamp, L= 3000 Lumens CU= .75 Maintenance factor(MF)= Light loss factor( LLF)=.8 Number of lamps required, N=E x A/(Lx CU x LLF) =200 X 15 X 9 /(3000 X .75 X .8) =15
- 22. Determine the power of Lamp in Candela also. Solution Working area A= 30m X 15m Required illumination ,E=200 Lux Lumen out put of one lamp, L= 2700 Lumens CU= .6 Depreciation factor DF=1.25 Maintenance factor(MF)= Light loss factor( LLF)=1/DF=1/1.25=.8 Number of lamps required, N=E x A/(Lx CU x LLF) =200 X 30X 15 /(2700 X .6 X .8) =70 Power of lamp in Candela(I) =Lumen/4π=2700/4π=215Cd
- 27. Qn. An office room of size 9X15m is to be illuminated by 2x18W LED luminaire. The lamps are being mounted at a height of 3m from the work plane. The average illumination required is 240 lux. Calculate the number of lamps required to be fitted, assuming a CU of 0.75 and a LLF of 0.8. Assume the ceiling height of the room as 5m. Draw the layout of the luminaire arrangement. The lumen output of 2x18W LED may be taken as 4000 lumens.
- 28. EXTERIOR LIGHTING Lighting design for exterior application will have to consider the following aspects:- • Functional lighting-Road lighting, yard lighting (area lighting), flood lighting • Decorative lighting- Monumental lighting, façade lighting and special lighting for festivals General consideration • Primary aim of exterior lighting :- Safety and Security • Luminaires used for exterior lighting can be classified into :- – Static luminaries-Luminaries fixed on top of a pole, to produce light in a predetermined manner. – Adjustable luminaries - Luminaries mounted with adjustable brackets are referred to as adjustable luminaries. Mostly used for flood lighting and area lighting
- 29. ROAD LIGHTING Requirements of street lighting i. Luminance Level. • Main requirement is to provide driver of a moving vehicle the exact information continuously and accurately from the road • Objects should be present with clear contrasts with their surroundings • Dangerous objects shall be seen and recognized in time ii. Luminance Uniformity. iii. Degree of Glare limitation. iv. Lamp Spectra v. Effectiveness of visual guidance. • The scene should have adequate brightness, at the same time it should not appear to be so bright to cause discomfort or disability vii . The patterns created by the road lights shall not be confusing to the driver
- 30. Classification of roads • Classified based on the volume of traffic, speed and composition of the traffic • For roads with width ranging from 6-9m, lamp posts are arranged on side of the roads • For roads with width 9-12m, zig zag spacing is recommended • For roads with width 12-20m, face to face spacing of lamp posts on both sides of the road becomes necessary • For multi-lane roads, spacing of lamp posts on the median or on the median plus the curbs on both sides may have to be chosen depending upon the number of the lanes of traffic, planned on the road
- 32. Design considerations • Initial lumen Ln = (E*A)/(LLF*CU) • Area of the road = Width* Spacing between lamp poles • LLF= LLD* LDD – LLD- lamp lumen depreciation – LDD- lamp dirt depreciation • Spacing = (Ln*LLF*CU)/(E*W) • It is necessary that the illuminance directly under the luminaire be the same as the midway between the poles • For the purpose of Energy saving, economy and uniformity of illumination the ratio of spacing to mounting height should not be less than 3 or larger than 5. • The ratio of average to minimum illuminance should not be greater than 3 • Distance between two light points should not be more than 35m • For residential areas the ratio can be as high as 6 • Three popular models of the pole placement along the roadway are: – Spaced continuously on the road side with a spacing of S meter (least expensive and less wiring) – Staggered spacing on both sides of the road with spacing of S meters between consecutive poles – Spacing on opposite sides of the road with a spacing of 2S meter between two consecutive poles on the same side
- 33. LAMPS USED FOR EXTERIOR LIGTHING STREET/AREA LIGHTING • Metal Halide Street Lights. • Light Emitting Diode (LED) Street Lights. • High Pressure Sodium (HPS) Street Lights. • Low Pressure Sodium (LPS) Street Light.
- 34. Metal Halide lamps Merits • Metal halide lights are 3-5 times as efficient as incandescent bulbs and produce a much higher quality light. • In many cases, and depending on the particular mix of metal halides, they have a very high color temperature (up to 5500K) Demerits • light pollution • UV emission if their outer glass breaks • use of mercury and other heavy metals
- 35. High Pressure Sodium (HPS) Street Lights. Merits • Most efficient member of the HID light family, 7 times as efficient as incandescent and over 2 times as efficient as mercury vapor. • Warm-up period is 3-4 minutes, which is somewhat less than that of a mercury vapor or metal halide lamp. • Long lamp life -- 24,000 hours. • Excellent lumen maintenance • Cheaper price • Higher lumen efficiency than older street light types. Demerits • Does not accurately reflect the true color of objects. • Needs a transformer/ballast for voltage and current regulation to assist start up and operation. • Requires a few minutes (5 to 10 minutes) before reaching full light brightness. • Needs one minute to cool down. • Produces reddish color at the end of its life • Burns at the end of its life. • Broken bulbs emit some poisonous mercury as a gas
- 37. Light Emitting Diode (LED) Street Lights Merits • LED bulbs are more efficient • less costly in the long run • better for the environment , LED does not contain harmful metal mercury, and will not cause harm to the environment when it is scrapped • they use far less energy than the alternatives. • An LED bulb's lifespan is around 50,000 hours, or about 10 years, which means it lasts 10 times longer than an incandescent bulb • Less energy use reduces the demand from power plants and decreases greenhouse gas emissions. • luminous efficiency of LED street lights is stronger than that of high- pressure sodium lamps. • The light decay of LED light is small, it is less than 3% in a year while the high-pressure sodium lamp has a large decay about 30% in a year. • LED street lights have faster switching time, no need a period of warm up or cool down
- 39. SOLVED PROBLEMS ON ROAD /STREET LIGHTING-1
- 41. SOLVED PROBLEMS ON ROAD /STREET LIGHTING-2
- 42. SOLUTION
- 43. AREA LIGHTING • Illumination of large area with average level of lighting • Examples are airport parking space, railway yards, vehicle parking space etc • All luminaires used for road lighting can be used for area lighting • Limiting factors for area lighting are – Mounting height – Colour rendering property of light source – Spacing limitations • Spacing between poles shall not be more than 4.5 times the height of the poles • Spacing between the edges of the area and the nearest pole shall not be greater than 2.25 times the mounting height • A minimum of two lights per pole shall be employed for even distribution of lighting
- 44. SOLVED PROBLEMS ON AREA LIGHTING-1
- 46. SOLVED PROBLEMS ON AREA LIGHTING-2
- 47. SOLUTION
- 48. Selection of light sources Exterior lighting installations normally use High Intensity Discharge Lamps (HID) • Used to designate 3 distinct type of lamp- mercury vapour, metal halide and high pressure sodium • Produce light by establishing an arc between two electrodes, the electrodes being few centimetres apart enclosed in a transparent arc tube • Arc tube is then enclosed in an outer bulb that is filled with nitrogen and an inert gas Mercury vapour lamps (MV) • Outer tube is filled with nitrogen and inner tube contains mercury and argon gas • Consists of starting electrode and main electrode • When voltage is applied to starting electrode, an argon arc is produced by main electrodes adjacent to it which heats up and vaporises mercury • These ionised mercury atoms decrease the resistance between the main electrodes and produces arc to strike • Available from 40-1000W Metal Halide lamps (MH) • Contains metallic additives in addition to argon and mercury in the arc tube which produces different colour rendering in the overall light output • Higher efficacy (66-100 lumens/watt) than metal vapour lamps • Better colour rendering •
- 49. High pressure sodium vapour lamps (HPS) • Produce energy in all wavelengths • Light produced is golden white colour • Has highest efficacy of all lamps (60-127 lumens/watt) • Available in 35-1000W size • Life is 24000 hours • Best energy savers in HID lamps Low pressure sodium vapour lamps • 183 lumens/watt • Monochromatic light output (yellow) • Life of 18000 hours • Used in street lighting and outdoor area & security lighting LED Lamps LEDs are the best choice for outdoor lighting for many reasons. Outdoor LED lighting benefits include: • Brighter light: LEDs are a brighter white than traditional halide street lamps, helping better illuminate streets, sidewalks and parking lots. • Longer life: LEDs, depending on their usage, can last up to 50,000 hours.