Part 2: energy Conservation In Lighting systems

Outline Introduction Lighting Fundamentals & Terminology Lighting System Components Lighting Controls Conservation Strategies & Opportunities Maintaining System Performance

Introduction Electricity used to operate lighting systems represents a significant percentage of electricity consumed in most countries. Lighting usually accounts for 30-70% of the total energy cost in commercial and residential sectors, and 5-25% in industrial facilities. The lighting system provides many opportunities for cost-effective energy savings with little or no inconvenience.

Introduction Since all buildings have lights, lighting retrofits are very common and generally offer an attractive return on investment. Lighting improvements are often easier to make than many other process upgrades. In many cases, in addition to energy and cost savings, the lighting quality can be improved.

Introduction In all cases, the minimum lighting level standards (for example, the Illuminating Engineering Society) should be followed. Lighting is usually used as a starting place for any energy management program. It can attract immediate employee attention and participation. Lighting is also used as an indicator of the attitude of the top managers towards energy management.

Lighting Fundamentals & Terminology Any efficient lighting system should: Provide the right quantity of light. Provide the right quality of light. Lighting quantity is the amount of light provided to a room. Lighting quality can be represented by four main considerations: Uniformity, glare, color rendering index, and coordinated color temperature.

Lighting Quantity Lighting quantity is primarily expressed in three different types of units: Watts Lumens Lux or Foot-candles

Lighting Quantity: Watt Watt (W) is the unit for measuring electrical power. It defines the rate of energy consumption by the lamp when it is in operation. Therefore, the amount of Watts consumed represent the electrical input to the lighting system.

Lighting Quantity: Lumens The output of a lamp is measured in a lumens. The amount of lumens can also be used to describe the output of an entire fixture (consisting of several lamps) For example, one standard four-foot fluorescent lamp would provide 2,900 lumens in a standard office system. Therefore, the number of lumens describes how much light is being produced by the lighting system.

Lighting Quantity: Lux The number of Lux or Foot-candles shows how much light is actually reaching the workplace (or task). Lux = Lumens/m2 Foot-candles = Lumens/ft2 This can be measured using a light meter. It is the most important measurement since it expresses the end result, not the effort of the lighting system.

Lighting Quantity: Lux Standards specify lighting requirements in terms of lux or foot-candles, not lumens or watts: Parking lot 20 Lux Hallways 100 Lux Factory floor 300 Lux Offices 500 Lux Inspection 1000 Lux Operating room 10000 Lux

Lighting Quantity Optimum lighting designs should avoid over- illuminating of a space. Most existing buildings are over illuminated in comparison with optimum lighting standards. It is important to remember that standard light levels correspond to particular visual tasks.

Lighting Quantity For example: in an office there are different types of tasks: walking around the office, viewing computer screens, reading and writing. Each task requires a different light level. Optimum lighting system design can provide minimum lighting level for ambient lighting and additional task lighting to achieve the required levels for reading/writing tasks.

Lighting Quantity: Efficacy The amount of lumens produced per Watt from a lighting source. By definition, it is similar to efficiency (output/input). A common misconception is that lamps with higher wattage provide more light. High efficacy light sources can provide more light with the same amount of power (Watts) in comparison with low efficacy light sources.

Lighting Quality Lighting quality can have a dramatic influence on the attitude and performance of occupants. In fact, different “moods” can be created by a lighting system. Consider the behavior of people when they eat in different restaurants. If the restaurant is a fast-food restaurant, the space is usually illuminated by bright white lights, with a significant amount of glare from shiny tables. Occupants rarely spend much time there partly because the space creates an uncomfortable mood and the atmosphere is “fast” (eat and leave).

Lighting Quality In contrast, consider an elegant restaurant with a candle-lit tables and a “warm” atmosphere. Occupants tend to relax and take more time to eat. Although occupant behavior is also linked to interior design and other factors, lighting quality represents a significant influence. Occupants perceive and react to a space’s light color. It is important that the lighting designer be able to recognize and create the subtle aspects of an environment that define the theme of the space.

Lighting Quality For example, drug and grocery stores use white lights to create a “cool” and “clean” environment. Imagine if these spaces were illuminated by the same color lights as in an elegant restaurant. How would the perception of the store change? The goal of the lighting designer is to provide the appropriate quality of light for a particular task to create the right “mood” for the space.

Lighting Quality Employee comfort and performance are worth more than energy savings. Although the cost of energy for lighting is substantial, it is relatively small compared to the cost of labor. Improvements in lighting quality can yield high dividends for businesses because gains in worker productivity are common when lighting quality is improved. Conversely, if a lighting retrofit reduces lighting quality, occupant performance may decrease, quickly off- setting any savings in energy costs.

Lighting Quality: Uniformity Uniformity describes how evenly light spreads over an area. Creating uniform illumination requires proper fixture spacing. Non-uniform illuminance can create bright and dark spots which can cause discomfort for occupants. Traditionally, light designers tried to achieve uniform illumination throughout the target space. However, when this is applied to large spaces, it can cause tremendous waste of energy and money. For task lighting, uniform illumination should be applied.

Lighting Quality: Glare Glare is caused by relatively bright objects in an occupant’s field of view. Although most visual tasks generally become easier with increased contrast, too much brightness can cause glare and result in visual discomfort. Visual Comfort Probability (VCP): VCP is a rating given to a fixture that indicates the percentage of people who are comfortable with the glare.

Lighting Quality: Glare A fixture with a VCP=80 means that 80%of occupants are comfortable with the amount of glare from the fixture. Usually, a VCP of 70 is recommended for general spaces. VCPs exceeding 80 are recommended for computers areas, and high-profile environments.

Lighting Quality: Glare Glare can be reduced by: Replacing fixtures with high VCP fixtures, or relocating fixtures. Using indirect lighting. Reducing ambient light levels. In rooms where many Visual Display Terminals (VDTs) are used, glare can be a significant problem. The use of movable task lights and fixtures with high VCP is recommended for such environments.

Lighting Quality: Color Light sources are specified based on two color- related parameters: Color rendering index (CRI) Coordinated color temperature (CCT) CRI indicates the effect of a given light source on the color appearance of objects. CCT describes the color of the light source.

Lighting Quality: Color - CRI Values of CRI range from 0 to 100. The higher the number, the easier it is to distinguish colors. Light sources with CRI>75 provide excellent color rendition. Light sources with CRI<55 provide poor color rendition. High CRIs are required in galleries and show rooms where it is important to distinguish colors. On the other hand, outdoor security lighting does not need high CRIs.

Lighting Quality: Color - CCT CCT is measured in (Kelvins) and represents the color that an object would radiate at a certain temperature: Red: CCT = 2000K White: CCT = 5000K Blue: CCT = 8000K Hospitals, laboratories, and grocery stores usually use (blue-white) sources. In contrast, an expensive restaurant would use a (yellow- red) source.

Lighting System Components: Lamps The lamp is the first component to consider in the lighting design process. The lamp choice determines the light quantity, CRI, CCT, relamping time interval and operational costs of the lighting system.

Lamps: Incandescent The oldest electric lighting technology is the incandescent lamp. Incandescent lamps are also the least efficacious (have the lowest lumens per watt) and have the shortest life.

Lamps: Incandescent They produce light by passing a current through a tungsten filament, causing it to become hot and glow. As the tungsten emits light, it gradually evaporates, eventually causing the filament to break. When this happens, the lamps is said to be “burned- out.” Although incandescent sources are the least efficacious, they are still sold in great quantities because of economies of scale and market barriers.

Lamps: Incandescent Consumers still purchase incandescent bulbs because they have low initial costs. However, if life-cycle cost analyses are used, incandescent lamps are usually more expensive than other lighting systems with higher efficacies.

Lamps: Compact Fluorescent Lamps (CFLs) Compact Fluorescent Lamps (CFLs) are energy efficient, long lasting replacements for some incandescent lamps. CFLs are available in many styles and sizes.

Lamps: Compact Fluorescent Lamps (CFLs) CFLs (like all fluorescent lamps) are composed of two parts, the lamp and the ballast. The short tubular lamps can last longer than 8,000 hours. The ballasts (plastic component at the base of tube) usually last longer than 60,000 hours. Some CFLs can be purchased as self-ballasted units, which “screw in” to an existing incandescent socket.

Lamps: Compact Fluorescent Lamps (CFLs) In most applications, CFLs are excellent replacements for incandescent lamps. CFLs provide similar light quantity and quality while only requiring about 20-30% of the energy of comparable incandescent lamps. In addition, CFLs last 7 to 10 times longer than their incandescent counterparts. In many cases, it is cost-effective to replace an entire incandescent fixture with a fixture specially designed for CFLs.

Lamps: Fluorescent Lamps Fluorescent lamps are the most common light source for commercial interiors in the world. They are repeatedly specified because they are relatively efficient, have long lamp lives and are available in a wide variety of styles.

Lamps: Fluorescent Lamps For many years, the conventional fluorescent lamp used in offices has been the four-foot F40T12 lamp, which is usually used with a magnetic ballast. However, these lamps are being rapidly replaced by T8 or T5 lamps with electronic ballasts.

Lamps: Fluorescent Lamps The labeling system used by manufacturers may appear complex, however it is actually quite simple. For example, with an F34T8 lamp, the “F” stands for fluorescent, the “34” means 34 watts, and the “T8” refers to the tube thickness. Since tube thickness (diameter) is measured in 1/8 inch increments, a T12 is 12/8 or 1.5 inches in diameter. A T8 lamp is 1 inch in diameter.

Lamps: High Intensity Discharge (HID) High-Intensity Discharge (HID) lamps are similar to fluorescent lamps because they produce light by discharging an electric arc through a tube filled with gases. HID lamps generate much more light, heat and pressure within the arc tube than fluorescent lamps, hence the title “high intensity” discharge.

Lamps: High Intensity Discharge (HID) Like incandescent lamps, HIDs are physically small light sources, (point sources) which means that reflectors, refractors and light pipes can be effectively used to direct the light. Although originally developed for outdoor and industrial applications, HIDs are also used in office, retail and other indoor applications. With a few exceptions, HIDs require time to warm up and should not be turned ON and OFF for short intervals.

Lamps: High Intensity Discharge (HID) Most HIDs have relatively high efficacies and long lamp lives, (5,000 to 24,000+ hours) reducing maintenance re-lamping costs. In addition to reducing maintenance requirements, HIDs have many unique benefits. There are four popular types of HID sources (listed in order of increasing efficacy): Mercury Vapor, Metal Halide, High Pressure Sodium, and Low Pressure Sodium.

HID: Mercury Vapor Mercury Vapor systems were the “first generation” HIDs. Today they are relatively inefficient, provide poor CRI and have the most rapid lumen depreciation rate of all HIDs.

HID: Mercury Vapor Mercury Vapor lamps provide a white-colored light which turns slightly green over time. Because of these characteristics, other more cost- effective HID sources have replaced mercury vapor lamps in nearly all applications. A popular lighting upgrade is to replace Mercury Vapor systems with Metal Halide or High Pressure Sodium systems.

HID: Metal Halide Metal Halide lamps are similar to mercury vapor lamps, but contain slightly different metals in the arc tube, providing more lumens per watt with improved color rendition and improved lumen maintenance.

HID: Metal Halide With nearly twice the efficacy of Mercury Vapor lamps, Metal Halide lamps provide a white light and are commonly used in industrial facilities, sports arenas and other spaces where good color rendition is required. They are the current best choice for lighting large areas that need good color rendition.

HID: High Pressure Sodium (HPS) With a higher efficacy than Metal Halide lamps, HPS systems are an economical choice for most outdoor and some industrial applications where good color rendition is not required.

HID: High Pressure Sodium (HPS) HPS is common in parking lots and produces a light golden color that allows some color rendition. Although HPS lamps do not provide the best color rendition, (or attractiveness) as “white light” sources, they are adequate for indoor applications at some industrial facilities. The key is to apply HPS in an area where there are no other light source types available for comparison.

HID: High Pressure Sodium (HPS) Because occupants usually prefer “white light,” HPS installations can result with some occupant complaints. However, when HPS is installed at a great distance from metal halide lamps or fluorescent systems, the occupant will have no reference “white light” and he/she will accept the HPS as “normal.”

HID: Low Pressure Sodium (LPS) Although LPS systems have the highest efficacy of any commercially available HID, this monochromic light source produces the poorest color rendition of all lamp types. With a low CCT, the lamp appears to be orange, and all objects illuminated by its light appear black and white or shades of gray. Applications are limited to security or street lighting.

HID: Low Pressure Sodium (LPS)

HID: Low Pressure Sodium (LPS) LPS has become popular because of its extremely high efficacy. With up to 60% greater efficacy than HPS, LPS is economically attractive. Although there are many successful applications, LPS installations must be carefully considered. Often lighting quality can be improved by supplementing the LPS system with other light sources (with a greater CRI).

LED Lamps An LED lamp is a light-emitting diode (LED) product which is assembled into a lamp (or light bulb) for use in lighting fixtures. LED lamps have a lifespan and electrical efficiency which are several times longer than incandescent lamps, and significantly more efficient than most fluorescent lamps. Some LED lamps are made to be a directly compatible drop-in replacement for incandescent or fluorescent lamps.  LED chips need controlled direct current (DC) electrical power; an appropriate circuit is required to convert alternating current from the supply to the regulated low voltage direct current used by the LEDs. LEDs are adversely affected by high temperature, so LED lamps typically include heat dissipation elements such as heat sinks and cooling fins.

LED Lamps

Lighting System Components: Ballast With the exception of incandescent systems, nearly all lighting systems (fluorescent and HID) require a ballast. A ballast controls the voltage and current that is supplied to lamps. Because ballasts are an integral component of the lighting system, they have a direct impact on light output. The ballast factor is the ratio of a lamp’s light output to a reference ballast.

Ballast: Fluorescent Specifying the proper ballast for fluorescent lighting systems has become more complicated than it was 25 years ago, when magnetic ballasts were practically the only option. Electronic ballasts for fluorescent lamps have been available since the early 1980s, and their introduction has resulted in a variety of options. Two types will be described of fluorescent ballasts: magnetic and electronic.

Electronic Ballast: Fluorescent During the infancy of electronic ballast technology, reliability and harmonic distortion problems hampered their success. However, most electronic ballasts available today have a failure rate of less than one percent, and many distort harmonic current less than their magnetic counterparts.

Electronic Ballast: Fluorescent Electronic ballasts are superior to magnetic ballasts because they are typically 30% more energy efficient, they produce less lamp flicker, ballast noise, and waste heat. In nearly every fluorescent lighting application, electronic ballasts can be used in place of conventional magnetic core and coil ballasts.

Electronic Ballast: Fluorescent Electronic ballasts improve fluorescent system efficacy by converting the standard 50 Hz input frequency to a higher frequency, usually 25,000 to 40,000 Hz. Lamps operating on these frequencies produce about the same amount of light, while consuming less power than a standard magnetic ballast. Other advantages of electronic ballasts include less audible noise, less weight, virtually no lamp flicker and dimming capabilities.

Electronic Ballast: Fluorescent T12 and T8 ballasts are the most popular types of electronic ballasts. T12 electronic ballasts are designed for use with conventional (T12) fluorescent lighting systems. T8 ballasts offer some distinct advantages over other types of electronic ballasts. They are generally more efficient, have less lumen depreciation, and are available with more options.

Electronic Ballast: Fluorescent T8 ballasts can operate one, two, three or four lamps. Most T12 ballasts can only operate one, two or three lamps. Therefore, one T8 ballast can replace two T12 ballasts in a 4 lamp fixture. Some electronic ballasts are parallel-wired, so that when one lamp burns out, the remaining lamps in the fixture will continue to operate. In a typical magnetic, (series-wired system) when one component fails, all lamps in the fixture shut OFF.

Electronic Ballast: Fluorescent Before maintenance personnel can re-lamp, they must first diagnose which lamp failed. Thus the electronically ballasted system will reduce time to diagnose problems, because maintenance personnel can immediately see which lamp failed. Parallel-wired ballasts also offer the option of reducing lamps per fixture (after the retrofit) if an area is over-illuminated.

Lighting System Components: fixture A fixture is a unit consisting of the lamps, ballasts, reflectors, lenses or louvers and housing. The main function is to focus or spread light emanating from the lamp(s). Without fixtures, lighting systems would appear very bright and cause glare. Fixtures block or reflect some of the light exiting the lamp.

Fixture Efficiency The efficiency of a fixture is the percentage of lamp lumens produced that actually exit the fixture in the intended direction. Efficiency varies greatly among different fixture and lamp configurations. For example, using four T8 lamps in a fixture will be more efficient than using four T12 lamps because the T8 lamps are thinner, allowing more light to “escape” between the lamps and out of the fixture.

Reflectors Installing reflectors in most fixtures can improve its efficiency because light leaving the lamp is more likely to “reflect” off interior walls and exit the fixture. Because lamps block some of the light reflecting off the fixture interior, reflectors perform better when there are less lamps (or smaller lamps) in the fixture. Due to this fact, a common fixture upgrade is to install reflectors and remove some of the lamps in a fixture.

Reflectors A variety of reflector materials are available: highly reflective white paint, silver film laminate, and anodized aluminum. In addition to installing reflectors within fixtures, light levels can be increased by improving the reflectivity of the room’s walls, floors and ceilings. For example, by covering a brown wall with white paint, more light will be reflected back into the workspace, and the Coefficient of Utilization is increased.

Light Distribution/Mounting Height Fixture mounting height and light distribution are presented together since they are interactive. HID systems are preferred for high mounting heights since the lamps are physically small, and reflectors can direct light downward with a high degree of control. Fluorescent lamps are physically long and diffuse sources, with less ability to control light at high mounting heights. Thus fluorescent systems are better for low mounting heights and/or areas that require diffuse light with minimal shadows.

Lighting Controls Lighting controls offer the ability for systems to be turned ON and OFF either manually or automatically. There are several control technology upgrades for lighting systems, ranging from simple (installing manual switches in proper locations) to sophisticated (installing occupancy sensors).

Lighting Controls: Switches The standard manual, single-pole switch was the first energy conservation device. It is also the simplest device and provides the least options. One negative aspect about manual switches is that people often forget to turn them OFF. If switches are far from room exits or are difficult to find, occupants are more likely to leave lights ON when exiting a room.

Lighting Controls: Switches However, if switches are located in the right locations, with multiple points of control for a single circuit, occupants find it easier to turn systems OFF. Once occupants get in the habit of turning lights OFF upon exit, more complex systems may not be necessary. The point is: switches can be great energy conservation devices as long as they are convenient to use them.

Lighting Controls: Switches Another opportunity for upgrading controls exists when lighting systems are designed such that all circuits in an area are controlled from one switch, yet not all circuits need to be activated. For example, a football stadium’s lighting system is designed to provide enough light for TV applications. However, this intense amount of light is not needed for regular practice nights or other non-TV events. Because the lights are all controlled from one switch, every time the facility is used all the lights are turned ON.

Lighting Controls: Switches By dividing the circuits and installing one more switch to allow the football stadium to use only 70% of its lights during practice nights, significant energy savings are possible. Generally, if it is not too difficult to re-circuit a poorly designed lighting system, additional switches can be added to optimize the lighting controls.

Lighting Controls: Time Clocks Time clocks can be used to control lights when their operation is based on a fixed operating schedule. Time clocks are available in electronic or mechanical styles. However, regular check-ups are needed to ensure that the time clock is controlling the system properly. After a power loss, electronic timers without battery backups can get off schedule—cycling ON and OFF at the wrong times.

Lighting Controls: Photocells For most outdoor lighting applications, photocells (which turn lights ON when it gets dark, and off when sufficient daylight is available) offer a low- maintenance alternative to time clocks. Unlike time clocks, photocells are seasonally self- adjusting and automatically switch ON when light levels are low, such as during rainy days. A photocell is inexpensive and can be installed on each fixture, or can be installed to control numerous fixtures on one circuit.

Lighting Controls: Photocells Photocells can also be effectively used indoors, if daylight is available through skylights. Photocells should also be cleaned when fixtures are re-lamped. Otherwise, dust will accumulate on the photodiode aperture, causing the controls to always perceive it is a cloudy day, and the lights will stay ON.

Daylight Harvesting Daylight harvesting is a control strategy that can be applied where diffuse daylight can be used effectively to light interior spaces. Daylight harvesting employs strategically located photo-sensors and electronic dimming ballasts. To effectively apply this strategy requires more knowledge than just plugging a sensor into a dimming ballast.

Daylight Harvesting Photosensors and dimming ballasts form a control system that controls the light level according to the daylight level. The fluorescent lighting is dimmed to maintain a band of light level when there is sufficient daylight present in the space. The output is changed gradually by a fade control so occupants are not disturbed by rapid changes in light level.

Lighting Controls: Occupancy Sensors Occupancy sensors save energy by turning off lights in spaces that are unoccupied. When the sensor detects motion, it activates a control device that turns ON a lighting system. If no motion is detected within a specified period, the lights are turned OFF until motion is sensed again. With most sensors, sensitivity (the ability to detect motion) and the time delay (difference in time between when sensor detects no motion and lights go OFF) are adjustable.

Lighting Controls: Occupancy Sensors Occupancy sensors are produced in two primary types: Ultrasonic (US) and Passive Infrared (PIR). Dual-Technology (DT) sensors, that have both ultrasonic and passive infrared detectors, are also available. The Table in next slide shows the estimated percent energy savings from occupancy sensor installation for various locations.

Lighting Controls: Occupancy Sensors ————————————————————————— Application Energy Savings ———————————————————————— Offices (Private) 25-50% Offices (Open Spaces) 20-25% Rest Rooms 30-75% Corridors 30-40% Storage Areas 45-65% Meeting Rooms 45-65% Conference Rooms 45-65% Warehouses 50-75%

Occupancy Sensors: Ultrasonic Sensors Ultrasonic sensors transmit and receive high-frequency sound waves above the range of human hearing. The sound waves bounce around the room and return to the sensor. Any motion within the room distorts the sound waves. The sensor detects this distortion and signals the lights to turn ON. When no motion has been detected over a user- specified time, the sensor sends a signal to turn the lights OFF.

Occupancy Sensors: Passive Infrared Sensors (PIR) Passive Infrared sensors detect differences in infrared energy emanating in the room. When a person moves, the sensor “sees” a heat source move from one zone to the next. PIR sensors require an unobstructed view, and as distance from the sensor increases, larger motions are necessary to trigger the sensor. Applications include open plan offices (without partitions), classrooms and other areas that allow a clear line of sight from the sensor.

Occupancy Sensors: Dual-Technology Sensors (DT) Dual-Technology (DT) sensors combine both US and PIR sensing technologies. DT sensors can improve sensor reliability and minimize false switching.

Process to Improve Lighting Efficiency The three basic steps to improving the efficiency of lighting systems: Identify necessary light quantity and quality to perform a visual task. Increase light source efficiency if occupancy is frequent. Optimize lighting controls if occupancy is infrequent.

A- Identify Necessary Light Quantities & Qualities Identifying the necessary light quantities for a task is the first step of a lighting retrofit. Often this step is overlooked because most energy managers try to mimic the illumination of an existing system, even if it is over-illuminated and contains many sources of glare. For many years, lighting systems were designed with the belief that no space can be over- illuminated.

A- Identify Necessary Light Quantities & Qualities Although the number of workplane lux is important, the occupant needs to have a contrast so that he can perform a task. For example, during the daytime your car headlights don’t create enough contrast to be noticeable. However, at night, your headlights provide enough contrast for the task. The same amount of light is provided by the headlights during both periods, but daylight “washes out” the contrast of the headlights.

A- Identify Necessary Light Quantities & Qualities The same principle applies to offices, and other illuminated spaces. For a task to appear relatively bright, objects surrounding that task must be relatively dark. For example, if ambient light is excessive (1500 lux) the occupant’s eyes will adjust to it and perceive it as the “norm.” However when the occupant wants to focus on something he/she may require an additional light to accent the task (at 2000 lux).

A- Identify Necessary Light Quantities & Qualities This excessively illuminated space results in unnecessary energy consumption. The occupant would see better if ambient light was reduced to 300-400 lux and the task light was used to accent the task at 500 lux. Excessive illumination is not only wasteful, but it can reduce the comfort of the visual environment and decrease worker productivity. After identifying the proper quantity of light, the proper quality must be chosen. The CRI, CCT and VCP must be specified to suit the space.

B- Increase Source Efficacy Increasing the source efficacy of a lighting system means replacing or modifying the lamps, ballasts and/or fixtures to become more efficient. In the past, the term “source” has been used to imply only the lamp of a system. However, due to the inter-relationships between components of modern lighting systems, we also consider ballast and fixture retrofits as “source upgrades.”

B- Increase Source Efficacy Thus increasing the efficacy simply means getting more lumens per watt out of lighting system. For example, to increase the source efficacy of a T12 system with a magnetic ballast, the ballast and lamps could be replaced with T8 lamps and an electronic ballast, which is a more efficacious (efficient) system. Another retrofit that would increase source efficacy would be to improve the fixture efficiency by installing reflectors and more efficient lenses.

B- Increase Source Efficacy

Task lighting As a subset of Increasing Source Efficacy, “Task lighting” or “Task/Ambient” lighting techniques involve improving the efficiency of lighting in an entire workplace, by replacing and relocating lighting systems. Task lighting means retrofitting lighting systems to provide appropriate illumination for each task. Usually, this results in a reduction of ambient light levels, while maintaining or increasing the light levels on a particular task.

Task lighting For example, in an office the light level needed on a desk could be 500 lux. The light needed in aisles is only 200 lux. Traditional uniform lighting design would create a workplace where ambient lighting provides 500 lux throughout the entire workspace. Task lighting would create an environment where each desk is illuminated to 500 lux, and the aisles only to 200 lux. The Figure in next slide, shows a typical application of Task/Ambient lighting.

Task lighting

Task lighting Identifying task lighting opportunities may require some creativity, but the potential dollar savings can be enormous. Task lighting techniques are also applicable in industrial facilities—for example, high intensity task lights can be installed on fork trucks (to supplement headlights) for use in rarely occupied warehouses. With this system, the entire warehouse’s lighting can be reduced, saving a large amount of energy.

C- Optimize Lighting Controls The third step of lighting energy management is to investigate optimizing lighting controls. As shown earlier, improving the efficiency of a lighting system can save a percentage of the energy consumed while the system is operating. However, sophisticated controls can turn systems OFF when they are not needed, allowing energy savings to accumulate quickly.

C- Optimize Lighting Controls The Electric Power Research Institute (EPRI) reports that spaces in an average office building may only be occupied 60-75% of the time, although the lights may be ON for the entire 10 hour day. Lighting controls include switches, time clocks, occupancy sensors and other devices that regulate a lighting system.

HVAC Effects Nearly all energy consumed by lighting systems is converted to light, heat and noise, which dissipate into the building. Therefore, if the amount of energy consumed by a lighting system is reduced, the amount of heat energy going into the building will also be reduced, and less air conditioning will be needed. Consequently, the amount of winter-time heating may be increased to compensate for a lighting system that dissipates less heat.

HVAC Effects Because most offices use air-conditioning for more months per year than heating, a more efficient lighting system can significantly reduce air- conditioning costs. In addition, air conditioning (usually electric) is much more expensive that heating (usually gas). Therefore, the savings on air-conditioning electricity are usually worth more dollars than the additional gas cost.