Energy Efficient Artificial Lighting

8/11/2019 Energy Efficient Artificial Lighting

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Energy Efficient ArtificialLighting

Name : S.P.M. SudasingheIndex No : 100523GField : Electrical Engineering

EE 3202

Individual Project


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CONTENTS

Page

1. Introduction 1

2. Light

Measurements of Light 3

3. Lighting Technologies

Incandescent Lamp

Tungsten Halogen Lamp

Fluorescent Tubes

CFL

High Intensity Discharge Lamps

LED Lamps

Improving Technologies

4

5

6

7

8

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9

4. Strategies for energy efficient lighting

Define light requirements

Choose efficient light source

Select best light fitting

Lighting Maintenance

Maximum use of day light

Lighting Control

Other methods to improve efficiency

9

10

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12

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5. Conclusions 14

6. References 15


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1. INTRODUCTION

Providing light by means other than the sun is called Artificial Lighting. In early days people use artificial

lighting to get the sight when there is no sun light, but today it is used not only for get the sight but also for

Aesthetic purposes. From around 70000 BC people use fire to get light. Romans produce the first candle with

wick and gas lighting was common in 19thcentury. As time passes the era of electric lighting began. The first

electric lamp was the arc lamp in which an electric current was made to jump across two carbon electrodes.

After that Sir Joseph Swannof England and Thomas Edisonboth invented the first electric incandescent lamps

during the 1870s. After that various electric lighting technologies were introduced to the world. People concernvery much on the efficient lighting technologies in the past few decades.

Estimates indicate that energy consumption by lighting

is about 15 - 30% of a commercial buildings total

energy consumption and about 3 - 10% in an industrial

plants total energy consumption.

According to the Reports of CEB,

street lighting contributes to about

2% of the electricity consumption

of Sri-Lanka. Considerable

percentage of Domestic andreligious electricity consumptions

are also for artificial lighting. In

Sri Lanka the peak demand is in

between 6:30-8:30 PM. This is

mainly due to electric consumption

of domestic consumers and street

lighting. Lighting load is greater at

night and this contributed very

much to the peak demand on that

period. Power plants with high

operating costs such as coal and

diesel plants have to be used to

provide this high demand at the

peak and it affects not only to the economy of the consumers but also for the economy of the country.

Due to the high demand for the energy in the present world cost of energy increases rapidly as well as the

electricity bill. So it is essential to use energy efficiently for the day to day work, for the interest of both

consumers and the country. Efficiency in lighting usage plays a major role in the energy saving due to the above

reasons. We have to find the ways of efficiency without sacrificing the quality of the lighting output.

The main objective of this project is to find the ways of energy efficiency and reduce the energy wastage from

electric lighting. Study of energy efficiency depends on the purpose of lighting such as Domestic, Commercial,

Industrial, Street lighting, Hotels, Public places etc. But in our country majority of the energy wastage is done

by the domestic consumers. Hence the study is limited to the energy efficiency of domestic lighting.

Figure 1: Energy consumption of a typical building

Source:SLEMA

Figure 2: Daily load curve of Sri-Lanka and contribution of different loads to

the demand

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Objectives:

Use energy efficiently for lighting purposes in Domestic sector

Reduce energy wastage from electric lighting in domestic consumers

Save on electricity bill and save on demand

Methodology:

In the very beginning of the project, the scientific literature relevant to the project such as the basics of

Illumination Engineering and photometry are studied. After that the study is about the lighting technologies in

the word, and about their advantages, disadvantages and suitability for the domestic lighting purposes.

Incandescent, Fluorescent and LEDs are the common lighting technologies used in the domestic usage. Typical

data about these technologies such as cost, efficacy and life time are collected from trusted sources and from the

local market. Then a comparison of these technologies is carried out to select an efficient one through them

based on the cost effectiveness.

Selecting an efficient light source is not enough to increase the efficiency of a lighting system. It is essential to

minimize the energy wastage and use the energy with maximum efficiency as possible. So the ways of energy

wastage in the domestic lighting system is find out and also the solutions to minimize them.

Some of these solutions can be applied at the designing and construction process of the building such as the

ways to maximize the use of natural day light. There are many architectural solutions to maximize the use of

natural day light without increasing the load on the air conditioning system and without sacrificing the comfort

of the residents. And then the study is about the methods of improving the efficiency of the building after the

construction process such as maintenance of a lighting system and adding automatic controllers.

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2. LIGHT

Visible Light is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of

sight. Visible light has a wave length in the range of about 380 740 nm between the invisible infrared, with

longer wave lengths and the invisible ultraviolet with shorter wave length

Measurements of Light

Light has an intensity that is determined by the amplitude of the radiation and determines the perception of the

brightness of the light. It also has a wave length or frequency that determines the colour. Light may include a

range of different frequencies or colour.

The sensitivity of the human visual system is not the same at all wavelengths in the range 380 nm to 780 nm.

This makes it impossible to adopt the radiometric quantities conventionally used to measure the characteristics

of the electromagnetic spectrum for quantifying light. Hence another two systems have introduced to measure

light.

a) Photometry System

In this system light quantities are measured with wave length weighted with respect to a standardized

model of human brightness perception.The Commission Internationale de lEclairage (CIE) has introducedtwo major standard observers to represent the sensitivity of the human visual system to light at different

wavelengths, in different conditions. They are Photopic Observer and Scotopic Observer.

These functions are used to measure the light quantities and thephotopic observer is widely used.

Luminous Flux (Lumen): The quantity of radiant flux which

express its capacity to produce visual sensation.

Luminous flux =

Where = Radiant flux in a small wave length

V= Relative luminous efficiency functionKm= Constant (683Lm/W for photopic observer)

Luminous Intensity( Candela): Luminous flux emitted per unit solid angle

Illuminance( lm/m2or Lux) : Luminous flux falling on unit area of a surface

Luminance(Candela/m2) : The luminance of a surface is the luminous intensity emitted per unit

projected area of the surface in a given direction.

Luminous Efficacy(lm/W) : The efficiency with which a light source converts electrical energy in to

Light

b) Colourimetry System

Photometry does not take into account the wavelength combination of the light. Thus it is possible for twosurfaces to have the same luminance but the reflected light to be made up of totally different combinations ofwavelengths. Hence colourimetry is used to quantify and describe physically the human colour perception.

Colour Temperature (K) : It is the temperature of an ideal black body radiator that radiates light of comparablehue to that of the light source.For incandescent lamps, the color temperature is a "true" value; for fluorescentand high-intensity discharge (HID) lamps, the value is approximate and is therefore called Correlated ColorTemperature.

CRT Light Description

27003000 Warm White

30005000 Neutral White

4100 Cool White50006500 Daylight

> 6500 Cool Daylight

Figure 3: Photopic and Scotopic Functions

Table 1: CRT Ranges

(Source: Sri Lanka Sustainable Energy Authority)

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Color Rendering Index : The ability of a light source to render colors of surfaces accurately can be conveniently

quantified by the color-rendering index.If CRI is close to 100 then the source renders true colours well.

As important as the quantity or brightness of light is the quantity. The three main problems that compromise thequality of light are

i. Glare :- The presence of a luminance much above the average fore the visual field will producediscomfort and is called glare.

ii. Veiling Reflections :- Veiling reflections are caused by bright light sources reflected from a tasksurface, such as a book.

iii. Excessive Brightness Ratio :- It occurs when there are surfaces within the same space with largedifferences in brightness

3. LIGHTING TECHNOLOGIES

3.1 Incandescent Lamp

In incandescent lamp, which is also called General Lighting Service Lamp (GLS), light is produced

with a Tungsten filament (melting point 3695K) heated to a high temperature by an electric current

through it.The bulb is filled with an inert gas such as argon (93%) and nitrogen (7%) to reduce evaporation ofthe filament and prevent its oxidation at a pressure of about 70 kPa (0.7 atm). The filament is coiled to reduceheat convection to the filling gas.The bulbis generally made of a soft soda glass and its size is set so that it doesnot get too hot and the tungsten that evaporates from the filament during the life of the lamp does not blackenthe bulb too much.An electric current heats the filament to typically 2,000 to 3,300 K. These lamps can operateboth from DC or Ac current. Incandescent bulbs have a continuous spectrum radiating more energy at longwave lengths (Red), and excellent colour rendering index about 100. Only 10% of the electrical energy input is

converted to visible light and other 90% of energy emits as heat.Due to the poor efficiency of incandescent

bulbsmany governments have introduced measures to ban their use. Incandescent bulbs are manufactured in awide range of sizes, light output, and voltage ratings, from 1.5 volts to about 300 volts. They require no external

regulating equipment and have low manufacturing costs. As a result, the incandescent lamp were widely usedin household and commercial lighting, for portable lighting such as table lamps, car headlamps, and flashlights,

and for decorative and advertising lighting.In buildings where air conditioning is used, incandescent lamps' heatoutput increases load on the air conditioning system.

Typical Properties of Incandescent bulbs:

Efficacy - 5-15 lm/W (12 lm/W)

Life - 1000 hours

CRI - 100

CCT - 2500K-2700K(Warm)

Dimming - easily dimmable

Lighting

Technologies

Incandescence

IncandescentTungsten

Halogen

Gas Discharge

Fluorescent HID

Solid State

LED OLED

Figure 4: Spectral distribution of the output of Incandescent bulb

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Advantages

Inexpensive

Easy to use, small and does not need auxiliaryequipment

Easy to dim by changing the voltage

Excellent color rendering properties

Directly work at power supplies with fixed voltage

Free of toxic components

Instant switching

Disadvantages

Short lamp life (1000 h)

Low luminous efficacy

Heat generation is high

Lamp life and other characteristics arestrongly dependent on the supply voltage

The total costs are high due to high operationcosts.

3.2Tungsten Halogen Lamp

Tungsten halogen lamps are derived from incandescent lamps. Inside the bulb, halogen gas in high pressurelimits the evaporation of the filament, and redeposits the evaporated tungsten back to the filament through the so

called halogen cycle

Halogen Cycle:

The Halogen combining with the Tungsten vapor on the wall of the lamp at about 2500C

The Tungsten Halide vapor reach close to the filament in extremely high temperature

It splits into Tungsten and Halogen again and Tungsten deposited on filament

Compared to incandescent lamp the operating temperature is higher, and consequently the color

temperature is also higher, which means that the light is whiter. Color rendering index is close to 100

as with incandescent lamps. Due to the higher temperature bulb must be made from quartz or high

melting point glass.These bulbs are more expensive as it is hard to make the quartz outer bulb and it is harderto introduce the gas fill into the lamp due to the high filling pressure.Halogen lamps have continuous spectrum that emits UV, visible light (12%) and infrared radiation andbulbs are

doped or coated to filter out the UV radiation.The latest progress in halogen lamps has been reached by

introducing selective-IR-mirror-coatings in the bulb. The infrared coating redirects infrared radiations

back to the filament. This increases the luminous efficacy by 4060% compared to other designs and

lamp life is up to 4000 hours.

There are halogen lamps available for mains voltages or low voltages (6-24V). The small size of halogenlamps permits their use in compact optical systems for projectors. Also they are used for light source ofAutomobile head lights and some manufacturers produce them for household fittings to replace standardincandescent bulbs. Special precautions are required to avoid from firing and burning hazards due to hightemperature.

Typical features:

Efficacy - 15-35Lm/W (18 lm/W)

Life - 2000 - 4000 hours

CRI - 100

CCT - 2800K - 3200K (Warm) Dimming - easy

Advantages

Small size

Directional light with some models (narrow

beams)

Low-voltage alternatives

Easy to dim

Instant switching and full light output

excellent color rendering properties

Disadvantages

High surface temperature

Lamp life and other characteristics are

strongly dependent on the supply voltage

Expensive than incandescent

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3.3Fluorescent Tube

Fluorescent lamps are the most commonly used form of discharge lamp. They come in a variety of shapes and

sizes and are available in a wide range of colours. The original form of the lamp was a long straight tube.

Fluorescent lamps work by generating ultraviolet radiation in a discharge in low pressure mercury vapor. This is

then converted into visible light by a phosphor coating on the inside of the tube. The electric current supplied to

the discharge has to be limited by control gear to maintain stable operation of the lamp because theydisplay

negative voltage-current characteristics. Traditionally this is done with magnetic ballast but most circuits

now use high frequency electronic control gear.

The tube is made from a glass with high iron content to absorb

the UV radiation. Phosphor coating is applied inside the bulb.

There is wide variety of phosphors available each produces

different spectrum of light. Tube is filled with noble gas.

Linear lamps come in variety of diameters and lengths. In diameter

T12 (12*1/8 inch), T8 (8* 1/8 inch) and T5 (5* 1/8 inch).T5 lamps

perform best at the ambient temperature of 35C, and T8 lamps

at 25C. The T5 has a very good luminous efficacy (100 lm/W),

the same lamp surface luminance for different lamp powers

(some lamps), and optimal operating point at higher ambienttemperature. T5 lamps are shorter than the correspondent T8

lamps, and they need electronic ballasts.

Correlated color temperatures (CCT) vary from 2700 K (warm white) and 6500 K (daylight) up to

17 000 K and color rendering indices (CRI) from 50 to 95 are available. Because they contain

mercury, many fluorescent lamps are classified as hazardous waste. The United States Environmental Protection

Agency recommends that fluorescent lamps be segregated from general waste for recycling or safe disposal

Typical Features

Luminous Efficacy : 50-100 lm/W

CCT : 27006500K CRI : 5095

Lamp Life : 10000-16000 hours

Ballast

Ballast is acurrent limiting device, to counter negative resistance characteristics of any discharge lamps. Incase of fluorescent lamps, it aids the initial voltage build-up, required for starting. There are two types of

ballasts called Magnetic ballast (choke) and Electronic ballasts.

Magnetic ballast is basically an inductor. It limits the current (slow down the increasing of current) and

the voltage spike is produced when current through the inductor is rapidly interrupted (is used in some circuits

to first strike the arc in the lamp). For large lamps, line voltage may not be sufficient to start the lamp, soan autotransformer winding is included in the ballast to step up the voltage. For magnetic ballasts, capacitormust be connected in parallel for power factor correction. They operate at the 50 or 60Hz frequency of the AC

voltage. This means that each lamp switches on and off 100 or 120 times per second, resulting in a possiblyperceptible flicker and a noticeable hum.

Advantages

Inexpensive ( than CFL and LED)

Good luminous efficacy

Long lamp life, 10 00016 000 h

Large variety of CCT and CRI

Disadvantages

Ambient temperature affects the switch-on

and light output

Need of auxiliary ballast and starter orelectronic ballast

Light output depreciates with age Contain mercury

Short burning cycles shorten lamp life

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Electronic ballastalters AC voltage frequency (50 Hz) into high-frequency AC (25- 50 kHz) while alsoregulating the current flow in the lamp. Some still use an inductance to limit the current, but the higherfrequency allows a much smaller inductance to be used. High frequency operation reduces the ballast losses andalso makes the discharge itself more effective. Other advantages of the electronic ballasts are that the light is

flicker-free and there is the opportunity of using dimming devices.

Fluorescent lamp ballasts differ from the starting method of the lamp. They are

Preheat starting (switch start): - It is an old method used to start the fluorescent tubes using a

starter switch and ballast (choke coil). Starter passes the current through it at starting and filaments

heat up in that period. After some time starter interrupt the connection through it and hence voltage

pulse generated by the choke coil.

Rapid Start: - the lamp's ballast constantly channels current through both electrodes. This

current flow is configured so that there is a charge difference between the two electrodes,

establishing a voltage across the tube.Less voltage is required for starting than with instant

start lamps, thus using smaller, more efficient ballasts

Instant Start: - simply use a high enough voltage to break down the gas and mercury column

and thereby start arc conduction.

3.4 Compact Fluorescent Lamp (CFL)

The CFL is a compact variant of the fluorescent lamp. The overall length is shortened and the tubular discharge

tube is often folded into two to six fingersor a spiral. For a direct replacement of tungsten filament lamps,

such compact lamps are equipped with internal ballasts and screw or bayonet caps (Integrated CFL).

There are also pin base CFLs, which need an external ballast and starter for operation (Non-Integrated CFL).

In general compact fluorescent lamps are less efficient than linear lamps. Integrated CFLs are easy to install and

the advantage of pin base lamps (Non-integrated) is that it is possible to replace the burnt lamp while keeping

the ballast in place. CFLs turn on within a second, but many still take time to achieve full brightness.CFLs, like

all fluorescent lamps, contain mercury as vapor inside the glass tubing. Most CFLs contain 35 mg per bulb,

with the bulbs labeled "eco-friendly" containing as little as 1 mg. Health and environmental concerns about

mercury have prompted many jurisdictions to require spent lamps to be properly disposed of or recycled, rather

than being included in the general waste stream sent to landfills. Safe disposal requires storing the bulbs

unbroken until they can be processed.

Typical features

Luminous Efficacy - 50-70 lm/W

Life - 5000h - 15000h

CRI - >80

CCT - 2700K6500K

Dimming - possible for some types only

Run up time - about 60s ( for full brightness)

Advantages

Good luminous efficacy

Long lamp life (6000-12 000 h)

The reduced cooling loads when

replacing incandescent lamps

Easy to install

Disadvantages

Expensive

Not dimmable (apart from special models)

Light output depreciates with age

Short burning cycles shorten lamp life

Contain mercury

When tube burns out whole lamp is useless

3.4High Intensity Discharge Lamps

The family of architectural light sources with the highest light output levels is called high intensity discharge orHID lamps. High-intensity discharge lamps(HID lamps) are a type of electrical gas-discharge lamp which

produces light by means of an electric arc between tungsten electrodes housed inside a translucent ortransparent fused quartz or fused alumina arc tube. This tube is filled with both gas and metal salts. The gasfacilitates the arc's initial strike. Once the arc is started, it heats and evaporates the metal salts forming a plasma,which greatly increases the intensity of light produced by the arc and reduces its power consumption. High-intensity discharge lamps make more visible light per unit of electric power consumed

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than fluorescent and incandescent lamps since a greater proportion of their radiation is visible light in contrast to

heat. Like fluorescent lamps, HID lamps require a ballast to start and maintain their arcs. Unlike thermal solidsources with continuous spectral emission, radiation from the gas discharge occurs predominantly in form ofsingle spectral lines. These lines may be used directly or after spectral conversion by phosphors for emission oflight. Discharge lamps generate light of different color quality, according to how the spectral lines aredistributed in the visible range.HID lamps are typically used when high levels of light over large areas are required, and when energy

efficiency and/or light intensity are desired. These areas include gymnasiums, large public areas, warehouses,

movie theaters, football stadiums, outdoor activity areas, roadways, parking lots, and pathways

Factors of wear come mostly from on/off cycles versus the total on time. The highest wear occurs when the HID

burner is ignited while still hot and before the metallic salts have recrystallized. Restrik time of HID lamp is

about 15 minutes.

Varieties of HID lamps include

Mercury Vapour Lamp

Metal Halide Lamp

Sodium Vapour Lamp

3.5 LED Lamp

LED lamps are the newest addition to the list of energy efficient light sources. LEDs emit light in a very small

band of wavelengths. But general-purpose lighting needs white light. To emit white light from LEDs requires

either mixing light from red, green, and blue LEDs, or using a phosphor to convert some of the light to other

colors.

RGB white LEDs uses multiple LED chips, each emitting a different wavelength, in close proximity to generate

the broad spectrum of white light. The advantage of this method is that the intensity of each LED can be

adjusted to "tune" the character of the light emitted. But colour rendering of these lights are poor and has high

production cost.

Phosphor converted LEDs uses one short-wavelength LED (usually blue, sometimes ultraviolet) in combination

with a phosphor which absorbs a portion of the blue light and emits a broader spectrum of white light. The

major advantage is the low production cost. The color rendering index can range from less than 70 to over 90,and color temperatures in the range of 2700 K up to 7000 K are available. This is the most widely used LED.

Efficiency of LED devices continues to improve, with some chips able to emit more than 100 lumens per watt.

LEDs do not emit light in all directions, and their directional characteristics affect the design of lamps. Thus

illuminating a flat defined area requires less Lumen compared to light sources which would need reflectors or

lenses to do the same. For illuminating an 360 orbit, the benefits of LED are much smaller.

LEDs are degraded or damaged by operating at high temperatures, so LED lamps typically include heat

dissipation elements such as heat sinks and cooling fins. A single LED is a low-voltage solid-state device and

cannot be directly operated on standard high-voltage AC power without circuitry to control the current flow

through the lamp.

Assemblies of high power light-emitting diodes can be used to replace incandescent or fluorescent lamps. Some

LED lamps are made with identical bases so that they are directly interchangeable with incandescent bulbs.

Compared to Incandescent or CFL bulbs, LED bulbs are more efficient and offer lifespan of 30,000 or more

hours, reduced if operated at a higher temperature than specified.Several companies offer LED lamps for

general lighting purposes. The technology is improving rapidly and new energy-efficient consumer LED lamps

are available. LED lamps are more environmental friendly as they didnt contain mercury and energ y efficient.

Also they didnt generate much heat as other lights such as HID and incandescent.

Typical Features

Luminous Efficacy - 30-100 lm/W

Life - 15000h-60000h

Available power range - 1-5 W

CCT -2685K-6500K

CRI - 40-85

Dimming - Easy

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Advantages

Small size (heat sink can be large)

Physically robust

Long lifetime expectancy (with proper thermalmanagement)

Switching has no effect on life, very short rise

time

Contains no mercury

Excellent low ambient temperature operation

High luminous efficacy (Developing fast)

New luminaire design possibilities

Possibility to change colors No optical heat on radiation

Disadvantages

High price

Low luminous flux / package

CRI can be low

Risk of glare due to high output with smalllamp size

Need for thermal management

Lack of standardization

3.6Improving Technologies

OLED (Organic LED) : - Organic semiconductor materials are used instead of inorganic semiconductors. They

are very thin lights and used for digital displays and television screens. Still it is developing technology. They

have luminous efficacy about 10-30 lm/W which is higher than incandescent. Life time is about 5000h and has a

good colour rendering index about 75.

Induction Lamps: - Induction lamps are essentially gas discharge lamps that do not have electrodes. Instead the

electric field in the lamp is induced by an induction coil that is operating at high frequency. The only types of

induction lamps that are currently in production are based on fluorescent lamp technology. They are, however,

slightly less efficient. The big advantage with this type of lamp is long life about 60000h.

4. STRATEGIES FOR ENERGY EFFICIENT LIGHTING

The challenge in lighting design is to provide sufficient light where it is required at the times when it is required,

without providing excess light. If this is done using the most appropriate light sources and fittings, andcombined with an effective control system, then substantial energy savings can be achieved.

4.1 Define light requirements

For energy efficient lighting, it is best to define the light requirements of the lighting location at different timesto avoid lighting levels that are higher than actually needed which causes energy wastage.

Table 2: recommended illuminance levels (source:SLEMA)

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4.2Choose efficient light sources, best suitable for the purpose

Designing lighting in a low carbon building requires specifying the right light source for the job, which includesnot only energy efficiency but a number of other considerations. An efficient but inappropriate (e.g.photometrically or start-up time) lamp cannot be considered to be sustainable. Important parameters that shouldbe considered prior to select a light source are

Cost (operating & capital cost)

Luminous Efficacy

Colour Rendering Index

Colour Temperature

Lamp life

Run up time

Dimming possibility

Environment effects

For domestic purposes main competitors are Incandescent, CFL and LED lamps. LEDs are still

developing technology and new lamps with new features are coming to the market.

Cost Effectiveness

To compare the cost effectiveness of these three light sources, widely available characteristics of the

lamps in the market are considered. Total monthly cost of a bulb in a typical house, works 5 hours per

day is compared among these three technologies.

To calculate the operating cost, unit electricity cost is taken as Rs10.50 (according to the domestic

tariff rates if the units consumed are lee than 90).

Incandescent CFL LED

Lumen output (lm) 650 650 650

Power (W) 60 11 9

Efficacy (lm/W) 11 60 70

Life time (h) 1000 8000 50000

Cost of one lamp (Rs.) 45 350 1500

Monthly Capital cost (Rs.)(for 5h/day)

6.75 6.50 4.50

kWh consumed(for 5h/day)

9.0 1.65 1.35

Monthly Operating cost (Rs.)(for 5h/day)

94.50 17.33 14.18

Monthly Total cost (Rs.)(for 5h/day)

101.25 23.83 18.68

Net Saving over Incandescent 76% 81%

Hence both CFL and LEDs are cost effective light sources. Many governments have introduced measures to ban

the use of Incandescent bulbs due to their poor efficiency.

Lamp life of LEDs is much higher than CFLs. Number of Switching cycles affect the lamp life of CFLs very

much. Most CFL lights operate for 30000 switching cycles according to the manufacturers data sheets. Life

time of the compact discharge tube of CFL lights have less life time than the electronic circuitry of the lamp.

But it is not possible to replace it in integrated CFL lights. LED lights are much durable than CFL and havegood lumen maintenance.

Also CFL bulbs properly work under the temperatures within 10450C only. But the operation of LED lights

is not temperature dependant.

Table 3: Cost comparison of light sources

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CFL bulbs contain about 1g of mercury and it is hazardous to the environment and humans. Hence disposing

requires special concern. CFL generates UV radiation but didnt allow them to radiate outside. But there is some

risk associated with it. LEDs are much environmental friendly than CFL as they are mercury free.

But still CFL lights are the most popular energy saving lamp because LEDs are still developing.

Energy Labeling

Energy labeling makes the consumer aware of the energy consumption levels and energy efficiency rating of

energy appliances in their purchasing; shortly it enables the consumer to identify whether that product saves

energy or is an energy guzzler. SLSEA is the authoritative agency and SLSEA in collaboration with the SLSI

implement the energy standards and labeling program. The first Energy Label introduced in Sri Lanka was for

Compact Fluorescent Lamps (CFLs) in the year 2000. CFL was selected as the first item for energy labeling

program since it required heavy promotion.

Upon the value for the performance grading Star Ratings are assigned. The higher the number of stars, the more

the energy efficiency of the CFL. Efficacy of the lamp contributes 90% for the performance grading.

4.3 Select Best Light fitting, suitable for the purpose

It is important to use suitable light fittings to direct light from the source to the working area. Luminaire

includes reflectors, refractors, diffusers and filters to direct the light to the task surface with maximum

efficiency without resulting in direct glare, veiling reflections or excessive brightness ratios. It is essential to use

luminaire for fluorescent tubes.

Different lamp technologies and different lighting environments require different luminaire

construction principles and features. Most HID lamps and LED lamps require thermal control

mechanism to control the internal temperature of the luminaire for proper working of the lamp.

Source : SLSEA

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Although some amount of energy is lost and reduces the efficiency of lamp due to the optic

controlling, luminaire helps to provide good quality light output for required purpose. Some times

luminaires are used only for the decorative purposes without considering about other factors. This

cause in vain energy lost.

4.4 Lighting Maintenance

Maintenance is vital to lighting efficiency. Light levels decrease over time because of aging lamps and

dirt on fixtures, lamps and room surfaces. Together, these factors can reduce total illumination by 50

percent or more, while lights continue drawing full power. The following basic maintenance suggestions

can help prevent this.

Clean fixtures, lamps and lenses every 6 to 24 months by wiping off the dust.

Replace lenses if they appear yellow.

Clean or repaint small rooms every year and larger rooms every 2 to 3 years. Dirt collects on

surfaces, which reduces the amount of light they reflect.

Consider group re-lamping. Common lamps, especially incandescent and fluorescent lamps, lose 20

per cent to 30 per cent of their light output over their service life. Many lighting experts recommend

replacing all the lamps in a lighting system at once. This saves labor, keeps illumination high and

avoids stressing any ballasts with dying lamps.

4.5 Maximum use of day light

Physically, daylight is just another source of electromagnetic radiation in the visible range. Physiologically,

daylight is an effective stimulant to the human visual system and the human circadian system. Psychologically,

daylight and a view out are much desired and, in consequence, may have benefits for human well-being.

As a tropical country Sri Lanka get daylight more than 10 hours per day without seasonal variation. Day light is

a natural and free light source and lighting for day time can be achieved from daylight which reduces the cost of

lighting. But solar radiation contains heat energy and it causes thermal discomfort or increasing the load oncooling system. Glare occurs when a bright light source such as the sun is in the field of view of users. It can

also occur when reflections of the sun are in the field of view.

Figure 5: Different types of luminaires

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And some times the occupants of the buildings forgot to switch off the light when they leave the building. This

wastage can be reduced by using controllers sensitive to the occupancy. IR based occupancy sensors can be used

to detect the occupancy of the room.

Timers can also be used to control the lights.

In modern control systems available in the market all two features are available. They control the light output

depending on the occupancy and the day light intensity inside the room.

4.7 Other methods to improve the efficiency of the lighting system

Decorate rooms with light colours. Light coloured walls, ceilings, tiled floors reflect light than dark

colours.

Use task lighting where ever as possible. Directing the light output to the working surface increases

the efficiency

Use Electronic ballasts instead of electromagnetic ballasts

5.

CONCLUSIONS

Efficient lighting system should contain

Efficient light source best suitable for the purpose

Luminaire best suitable for the purpose

Light control system

LED and CFL bulbs are more efficient and cost effective than Incandescent lamps and Incandescent

lamps should replace with CFL or LED lights

LED lamps are more environment friendly than the CFL lights, because they didnt contain mercury Fluorescent tubes or non integrated CFL lights are more cost effective than integrated CFL lights

because their ability to replace the discharge tube.

Fluorescent tubes are more suitable for the commercial and industrial buildings

Efficiency of the lighting system can be improved by

Proper maintenance of lighting system

Maximum use of day light as much as possible with the architectural concern at the design of

the building

Controlling the electrical lighting output with respect to the day light

Hybrid use of day light and electric lighting

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17/17

REFERENCES

1. Lighting Handbook, 2009 by Society of Light & Lighting

2. Guide book energy efficient electric lighting for buildings by ECBCS

3. Lighting Reference Guide by Natural Resources Canada

4. Code of practice for energy efficient buildings in Sri Lanka 2008 by SLSEA

5. The lighting handbook for utilities from RCL (Regional Center for Lighting)

6. Lighting Fundamentals Handbook from RCL

7. Light and the Environment by Osram

8. Lighting Handbook by Illuminating Engineering society of North America

9. OLED technology by Osram

10.http://www.rclsa.net

11.http://www.energy.gov.lk(Sri Lanka Sustainable Energy Authority)

12.http://www.slema.org.lk(Sri Lanka Energy Managers Association)

13.http://www.wikipedia.org

ACKNOWLEDGMENTS

The author gratefully acknowledges the contributions of Dr. Udayange Hemapala, Department of Electrical

Engineering, for his advices on this project. And also for Mr.Janaka Aluthge, Product Development Engineer

of Kevilton Electrical Products (PVT) LTD and Mr Lalith Dissanayaka and Miss Paboda from Orel MFG (PVT)

LTD for their support providing the data relevant to the project.

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http://www.rclsa.net/http://www.rclsa.net/http://www.rclsa.net/http://www.energy.gov.lk/sub_pgs/energy_managment_regulatory_energyLabelling_CFL.htmlhttp://www.energy.gov.lk/sub_pgs/energy_managment_regulatory_energyLabelling_CFL.htmlhttp://www.energy.gov.lk/sub_pgs/energy_managment_regulatory_energyLabelling_CFL.htmlhttp://www.slema.org.lk/http://www.slema.org.lk/http://www.slema.org.lk/http://www.wikipedia.org/http://www.wikipedia.org/http://www.wikipedia.org/http://www.wikipedia.org/http://www.slema.org.lk/http://www.energy.gov.lk/sub_pgs/energy_managment_regulatory_energyLabelling_CFL.htmlhttp://www.rclsa.net/

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Energy Efficient Artificial Lighting

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