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8. LIGHTING SYSTEM

8.1       Introduction

Lighting is an essential service in all the industries. The power consumption by the industrial lighting variesbetween 2 to 10% of the total power depending on the type of industry. Innovation and continuous improvement in the field of lighting, has given rise to tremendous energy saving opportunities in this area.

Lighting is an area, which provides a major scope to achieve energy efficiency at the design stage, byincorporation of modern energy efficient lamps, luminaires and gears, apart from good operational practices.

8.2       Basic Terms in Lighting System and Features

Lamps

Lamp is equipment, which produces light. The most commonly used lamps are described briefly as follows:

•            Incandescent lamps:

Incandescent lamps produce light by means of a filament heated to incandescence by the flow of electriccurrent through it. The principal parts of an incandescent lamp, also known as GLS (General LightingService) lamp include the filament, the bulb, the fill gas and the cap.

•            Reflector lamps:

Reflector lamps are basically incandescent, provided with a high quality internal mirror, which follows exactly the parabolic shape of the lamp. The reflector is resistant to corrosion, thus making the lamp maintenance free andoutput efficient.

•            Gas discharge lamps:

The light from a gas discharge lamp is produced by the excitation of gas contained in either a tubular or ellipticalouter bulb.

The most commonly used discharge lamps are as follows:

• Fluorescent tube lamps (FTL)
• Compact Fluorescent Lamps (CFL)
• Mercury Vapour Lamps
• Sodium Vapour Lamps
• Metal Halide Lamps

Luminaire

Luminaire is a device that distributes, filters or transforms the light emitted from one or more lamps. Theluminaire includes, all the parts necessary for fixing and protecting the lamps, except the lamps themselves. In some cases, luminaires also include the necessary circuit auxiliaries, together with the means for connecting themto the electric supply. The basic physical principles used in optical luminaire are reflection, absorption,transmission and refraction.

Control Gear

The gears used in the lighting equipment are as follows:

•            Ballast:

A current limiting device, to counter negative resistance characteristics of any discharge lamps. In case of fluorescentlamps, it aids the initial voltage build-up, required for starting.

•            Ignitors:

These are used for starting high intensity Metal Halide and Sodium vapour lamps.

Illuminance

This is the quotient of the illuminous flux incident on an element of the surface at a point of surface containing thepoint, by the area of that element.

The lighting level produced by a lighting installation is usually qualified by the illuminance produced on aspecified plane. In most cases, this plane is the major plane of the tasks in the interior and is commonly calledthe working plane. The illuminance provided by an installation affects both the performance of the tasks andthe appearance of the space.

Lux (lx)

This is the illuminance produced by a luminous flux of one lumen, uniformly distributed over a surface area of onesquare metre. One lux is equal to one lumen per square meter.

Luminous Efficacy (lm/W)

This is the ratio of luminous flux emitted by a lamp to the power consumed by the lamp. It is a reflection of efficiencyof energy conversion from electricity to light form.

Colour Rendering Index (RI)

Is a measure of the degree to which the colours of surfaces illuminated by a given light source confirm to those of the same surfaces under a reference illuminent; suitable allowance having been made for the state of Chromaticadaptation.

8.3       Lamp Types and their Features

The Table 8.1 shows the various types of lamp available along with their features.

8.4       Recommended Illuminance Levels for Various Tasks /Activities / Locations

Recommendations on Illuminance

Scale of Illuminance: The minimum illuminance for all non-working interiors, has been mentioned as 20 Lux (asper IS 3646). A factor of approximately 1.5 represents the smallest significant difference in subjective effect of illuminance. Therefore, the following scale of illuminances isrecommended.

20–30–50–75–100–150–200–300–500–750–1000–1500–2000, … Lux

Illuminance ranges:         Because circumstances may be significantly different for different interiors used for thesame application or for different conditions for the same kind of activity, a range ofilluminances is recommended for each type of interior or activity intended of a singlevalue of illuminance. Each range consists of three successive steps of therecommended scale of illuminances. For working interiors the

middle value (R) of each range represents the recommended service illuminance that would be used unless one or more of the factors mentioned below apply.

The higher value (H) of the range should be used at exceptional cases where low reflectances or contrasts are present in the task, errors are costly to rectify, visual work is criti- cal, accuracy or higher productivity is of great importance and the visual capacity of the work- er makes it necessary.

Similarly, lower value (L) of the range may be used when reflectances or contrasts are unusually high, speed & accuracy is not important and the task is executed only occasionally.

Recommended Illumination

The following Table gives the recommended illuminance range for different tasks and activities for chemical sector. The values are related to the visual requirements of the task, to user's sat- isfaction, to practical experience and to the need for cost effective use of energy.(Source IS 3646 (Part I) : 1992).

For recommended illumination in other sectors, reader may refer Illuminating Engineers SocietyRecommendations Handbook/

Chemicals

Petroleum, Chemical and Petrochemical works

Exterior walkways, platforms, stairs and ladders                              30–50–100

Exterior pump and valve areas                                                         50–100–150

Pump and compressor houses                                                        100–150–200 Process plant withremote control                                                                                                                       30–50–100 Process plant requiring occasional manualintervention                                                                                      50–100–150 Permanentlyoccupied work stations in process plant                                                                                                150–200–300 Control rooms for process plant  200–300–500

Pharmaceuticals Manufacturer and Fine chemicals manufacturer

Pharmaceutical manufacturer

Grinding, granulating, mixing, drying, tableting, s                       300–500–750 terilising, washing,preparation of solutions, filling,

capping, wrapping, hardening

Fine chemical manufacturers

Exterior walkways, platforms, stairs and ladders                              30–50–100

Process plant                                                                                    50–100–150

Fine chemical finishing                                                                  300–500–750

Inspection                                                                                       300–500–750

Soap manufacture

General area                                                                                   200–300–500

Automatic processes                                                                      100–200–300

Control panels                                                                                200–300–500

Machines                                                                                        200–300–500

Paint works

General                                                                                                         200–300–500

Automatic processes                                                                                     150–200–300

Control panels                                                                                              200–300–500

Special batch mixing                                                                                  500–750–1000

Colour matching                                                                                         750–100–1500

8.5       Methodology of Lighting System Energy Efficiency Study

A step-by-step approach for assessing energy efficiency of lighting system is given below:

Step–1: Inventorise the Lighting System elements, & transformers in the facility as per following typicalformat (Table – 8.2 and 8.3).

In case of distribution boards (instead of transformers) being available, fuse ratings may be inventorised alongthe above pattern in place of transformer kVA.

Step–2: With the aid of a lux meter, measure and document the lux levels at various plant locations at working level, as daytime lux and night time lux values alongside the number of lamps "ON" during measurement.

Step–3: With the aid of portable load analyzer, measure and document the voltage, current, power factor and power consumption at various input points, namely the distribution boards or the lighting voltage transformers at thesame as that of the lighting level audit.

Step–4: Compare the measured lux values with standard values as reference and identify locations as under litand over lit areas.

Step–5: Collect and Analyse the failure rates of lamps, ballasts and the actual life expectan- cy levels from thepast data.

Step–6: Based on careful assessment and evaluation, bring out improvement options, which could include :

i)         Maximise sunlight use through use of transparent roof sheets, north light roof, etc.

ii)         Examine scope for replacements of lamps by more energy efficient lamps, with due consideration to luminiare, color rendering index, lux level as well as expected life comparison.

iii)         Replace conventional magnetic ballasts by more energy efficient ballasts, with due consideration to life andpower factor apart from watt loss.

iv)         Select interior colours for light reflection.

v)         Modify layout for optimum lighting.

vi)         Providing individual / group controls for lighting for energy efficiency such as:

1. On / off type voltage regulation type (for illuminance control)
2. Group control switches / units
3. Occupancy sensors
4. Photocell controls
5. Timer operated controls
6. Pager operated controls
7. Computerized lighting control programs

vii)         Install input voltage regulators / controllers for energy efficiency as well as longer life expectancy for lampswhere higher voltages, fluctuations are expected.

viii)         Replace energy efficient displays like LED's in place of lamp type displays in control panels /instrumentation areas, etc.

8.6       Case Examples

Energy Efficient Replacement Options

The lamp efficacy is the ratio of light output in lumens to power input to lamps in watts. Over the yearsdevelopment in lamp technology has led to improvements in efficacy of lamps. However, the low efficacylamps, such as incandescent bulbs, still constitute a major share of the lighting load. High efficacy gasdischarge lamps suitable for differ- ent types of applications offer appreciable scope for energy conservation. Typical energy efficient replacement options, along with the per cent energy saving, are given in Table- 8.4.

* Wattages of CFL includes energy consumption in ballasts.

Energy Saving Potential in Street Lighting

The energy saving potential, in typical cases of replacement of inefficient lamps with efficient lamps in streetlighting is given in the Table 8.5

8.7       Some Good Practices in Lighting

Installation of energy efficient fluorescent lamps in place of "Conventional" fluorescent lamps.

Energy efficient lamps are based on the highly sophisticated tri-phosphor fluorescent powder technology. They offer excellent colour rendering properties in addition to the very high lumi- nous efficacy.

Installation of Compact Fluorescent Lamps (CFL's) in place of incandescent lamps.

Compact fluorescent lamps are generally considered best for replacement of lower wattage incandescent lamps. These lamps have efficacy ranging from 55 to 65 lumens/Watt. The aver- age rated lamp life is 10,000 hours, whichis 10 times longer than that of a normal incandescent

lamps. CFL's are highly suitable for places such as Living rooms, Hotel lounges, Bars, Restaurants, Pathways,Building entrances, Corridors, etc.

Installation of metal halide lamps in place of mercury / sodium vapour lamps.

Metal halide lamps provide high color rendering index when compared with mercury & sodium vapourlamps. These lamps offer efficient white light. Hence, metal halide is the choice for colour critical applications where, higher illumination levels are required. These lamps are highly suitable for applications such as assembly line, inspection areas, painting shops, etc. It is recommended to install metal halide lamps where colour rendering is more critical.

Installation of High Pressure Sodium Vapour (HPSV) lamps for applications where colour rendering is notcritical.

High pressure sodium vapour (HPSV) lamps offer more efficacy. But the colour rendering prop- erty of HPSV is very low. Hence, it is recommended to install HPSV lamps for applications such street lighting, yard lighting, etc.

Installation of LED panel indicator lamps in place of filament lamps.

Panel indicator lamps are used widely in industries for monitoring, fault indication, signaling, etc. Conventionally filament lamps are used for the purpose, which has got the following dis- advantages:

• High energy consumption (15 W/lamp)
• Failure of lamps is high (Operating life less than 1,000 hours)
• Very sensitive to the voltage fluctuations Recently, the conventional filament lamps are being replaced withLight Emitting Diodes (LEDs).

The LEDs have the following merits over the filament lamps.

• Lesser power consumption (Less than 1 W/lamp)
• Withstand high voltage fluctuation in the power supply.
• Longer operating life (more than 1,00,000 hours)

It is recommended to install LEDs for panel indicator lamps at the design stage.

Light distribution

Energy efficiency cannot be obtained by mere selection of more efficient lamps alone. Efficient luminaires along with the lamp of high efficacy achieve the optimum efficiency. Mirror-optic luminaires with a high output ratio andbat-wing light distribution can save energy.

For achieving better efficiency, luminaires that are having light distribution characteristics appropriate for the task interior should be selected. The luminaires fitted with a lamp should ensure that discomfort glare and veilingreflections are minimised. Installation of suitable lumi- naires, depends upon the height - Low, Medium & High Bay.Luminaires for high intensity dis- charge lamp are classified as follows:

• Low bay, for heights less than 5 metres.
• Medium bay, for heights between 5 – 7 metres.
• High bay, for heights greater than 7 metres.

System layout and fixing of the luminaires play a major role in achieving energy efficien- cy. This also varies from application to application. Hence, fixing the luminaires at optimum height and usage of mirror opticluminaries leads to energy efficiency.

Light Control

The simplest and the most widely used form of controlling a lighting installation is "On-Off" switch. The initialinvestment for this set up is extremely low, but the resulting operational costs may be high. This does not provide the flexibility to control the lighting, where it is not required.

Hence, a flexible lighting system has to be provided, which will offer switch-off or reduc- tion in lighting level, when not needed. The following light control systems can be adopted at design stage:

•            Grouping of lighting system, to provide greater flexibility in lighting control

Grouping of lighting system, which can be controlled manually or by timer control.

•            Installation of microprocessor based controllers

Another modern method is usage of microprocessor / infrared controlled dimming or switching circuits. The lighting control can be obtained by using logic units located in the ceiling, which can take pre-programme commands and activate specified lighting circuits. Advanced lighting control system uses movement detectors or lighting sensors,to feed signals to the controllers.

•            Optimum usage of daylighting

Whenever the orientation of a building permits, day lighting can be used in combination with electric lighting. This should not introduce glare or a severe imbalance of brightness in visual environment. Usage of day lighting (in offices/air conditioned halls) will have to be very limit- ed, because the air conditioning load will increase on account of the increased solar heat dissi- pation into the area. In many cases, a switching method, to enable reduction of electric light in the window zones during certain hours, has to be designed.

•            Installation of "exclusive" transformer for lighting

In most of the industries, lighting load varies between 2 to 10%. Most of the problems faced by the lighting equipment and the "gears" is due to the "voltage" fluctuations. Hence, the lighting equipment has to be isolated from the power feeders. This provides a better voltage regulation for the lighting. This will reduce the voltage related problems, which in turn increases the effi- ciency of the lighting system.

•            Installation of servo stabilizer for lighting feeder

Wherever, installation of exclusive transformer for lighting is not economically attractive, servo stabilizer can be installed for the lighting feeders. This will provide stabilized voltage for the lighting equipment. The performance of "gears" such as chokes, ballasts, will also improved due to the stabilized voltage.

This set up also provides, the option to optimise the voltage level fed to the lighting feeder. In many plants, during the non-peaking hours, the voltage levels are on the higher side. During this period, voltage can be optimised,without any significant drop in the illumination level.

• Installation of high frequency (HF) electronic ballasts in place of conventional ballasts New high frequency (28–32 kHz) electronic ballasts have the following advantages over the traditional magnetic ballasts:

Energy savings up to 35%

Less heat dissipation, which reduces the air conditioning load

• Lights instantly
• Improved power factor
• Operates in low voltage load
• Less in weight
• Increases the life of lamp

The advantage of HF electronic ballasts, out weigh the initial investment (higher costs when compared with conventional ballast). In the past the failure rate of electronic ballast in Indian Industries was high. Recently, many manufacturers have improved the design of the ballast leading to drastic improvement in their reliability. The life ofthe electronic ballast is high espe- cially when, used in a lighting circuit fitted with a automatic voltage stabiliser.

The Table 8.6 gives the type of luminaire, gear and controls used in different areas of industry.