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Automatic Lighting Control for Energy Savings ncontrolled lighting wastes energy. By installing an automatic lighting control system, your lights will be on only when necessay, or will be dimmed for certain times of the day and types of activities. The system can help yeduce energy costs and increase lamp life. In this Technology Update, you will leam more about various automatic lighting control systems and the benefits they provide. U Backgrou nd Automatic lighting control systems are now available that will economically provide light when and where it is needed (Figure 1). Electronic sensors and microprocessor-based energy controllers will contribute to cost savings by regulating light output according to available daylight and lamp aging. Energy savings of 50 percent to 65 percent can be obtained using this equipment. The total initial electrical installation cost for new office buildings with automatic fluorescent dimming systems will be 10 to 12 percent higher than with conventional line voltage switching systems. The additional expense will be recovered in approximately 5 years through energy and operating cost savings. Figure 1. Typical energy savings with automatic lighting control nergy use with circuit breaker switching I Energy use with automatic lighting control -Vi I I I I I I I I I I I I I I I I I midnight 6 am. noon 6 p.m. I midnight Time Energy saved by using people presence sensors Toll-free Hotline 1-800-872-3568 Bonneville POW E R A D MI N ISTRATI 0 N m Energy saved by takhg advantage of dMbt FAX 1-800-872-3882 Energy saved by matctug C@Mg to task Electronic Bulletin Board 1-800-762-3319 Figure 2. Ceiling mounted electronic sensor H The area or zone where the activity is carried out H The time of day Lampaging People For many lighting installations there is no need to activate artificial lighting unless people are in the area. An electronic sensor (Figure 2) may be used to detect human presence and switch lighting through an automatic control system. The sensor will ensure that lights are automatically turned off in unoccupied areas. lnstallina Automatic Lighting3ontrol Automatic lighting control systems are available that will adjust artificial lighting according to these variables: The presence of people The activity or "task" being performed The contribution available from daylight Task Lighting needs vary according to the activity being performed. What people are doing in an area will affect illumination level requirements. A level of 70 footcandles may be required for continuous office work (Figure 3), but after normal working hours the cleaning staff may need only 28 footcandles to perform its work. Combining human presence sensors with dimming controllers that have time-of-day capabilities will provide this control alternative. For office areas, fluorescent and incandescent dimming equipment will provide lighting control according to task. For industrial areas and recreational facilities, the high intensity discharge (mercury vapor, metal halide, high pressure sodium) automatic energy control system shown in Figure 4 may be used to vary lighting levels. For example: An automatic energy control system can vary the lighting levels in an ice arena according to the use of the ice. Low levels of light may be used for figure skating, public skating, and ice cleaning, while a higher level would be used for recreational hockey, and the full design level would be used for competitive hockey. The light- Figure 3. Lighting level controlled by work performed, time of day, and human presence I 28 footcandles for cleaning tasks 70 footcandles for off ice tasks 2 ing controls would provide a Figure 4. Automatic energy control system for use in recreational facilities pre-set proper level of dimming and industrial areas for the activity scheduled for that time of day, combining dimming and a time clock. System input from lighting transformer Facility operators may use a wall-mounted control station to adjust lighting levels according to area use. Additional savings can be obtained by supplementing the system with timing controls to dim lighting during lunch and break periods, and for janitorial and security work after hours. Day1ig ht A fluorescent energy management lighting controller automatically adjusts lights in response to changes in daylight while maintaining constant illumination on the work surface. required ligl,til,g level may be set manually or changed by automatic timers or programs. Figure 5. Monitor/co nt rol station -i'here are many periods when perimeter areas in an office building are adequately illuminated by daylight. Automatic fluorescent dimming systems controlled by photocells (Figure 5 ) can take advantage of this "free" lighting. Fluorescent energy management lighting controller I ti 3 The area shown as Zone 1 in Figure 6 is approximately onethird of the total floor area and receives, on a yearly average, enough daylight to supply as much as 30 percent of the required lighting. A 10 percent overall saving can be achieved using a fluorescent dimming system that takes advantage of daylight. For an office building this represents a minimum saving of a proximately 0.62 kWh/ft /yr. At 5c/kWh the minimum annual cost saving will be $30.79 for each 1,000 ft2 of office space. Y Zone using the dimming systems just described each lighting zone in an officebuilding can be maintained at the recommended light level for the type of work being performed. Savings may be maximized by reducing light levels for 'Ones needing Only low levels of illumination. Using the zoning pattern shown in Figure 7, an automatic lighting control system can provide low levels of illumination for hallway and service areas and higher levels for accounting, typing, and drafting areas. Time Programmable time controllers are available to independently switch several lighting circuits on a 7-day, time-of-day, on-off schedule. A calculator-type keyboard (Figure 8) is used to program the controller for a normal daily schedule and a holiday schedule 7 days in advance. Similar controllers are available that can transmit power line carrier signals on the standard electrical wiring circuits. These devices do not require col,trol wiring for light switching. Lamp Aging An automatic dimming system controlled by a photocell will correct for lamp aging and depreciation. Figure 6. Plan view of off ice floor showing zone 1, which will benefit from daylighting l~ Standard lighting design practices are based on maintaining the required illumination levels throughout the life of a lamp. To compensate for aging and depreciation, a higher initial illumination must be accepted for a standard fluorescent lighting system. For a lighting task requiring 70 footcandles, Figure 9 shows that 102 footcandles will be provided in the first year of fluorescent lamp life. The lighting level in the second year will be approximately 84 footcandles. Only in the third year of lamp life will the lighting level drop to the specified 70 footcandles. Energy has been wasted in maintaining excessive lighting levels in the first 2 years of lamp life. An automatic fluorescent dimming system will ensure that the required 70 footcandles is maintained throughout the life of the lamps. The graph on the left in Figure 10 shows a Figure 7. Office floor layout Zone 1I perimeter daylighting I 1 buildinm envelope 4 I I I zone4 I Figure 8. Calculator type keyboard for programming schedules Using the zone control switch , on-off switching or multilevel switching can be provided for lighting zones using a low voltage remote switching system. Programmable Lighting ControlIers lighting level with a standard system varying from 102 footcandle to 70 footcandles. The energy use is 100 percent for the 3-year period. The graph on the right shows 70 footcandles maintained over 3 years with a dimming system that will reduce relative energy use to 70 percent at the beginning of the period and will gradually increase use to 100 percent in the third year. The central controller (Figure 12), containing a microprocessor and logic circuitry, can be programmed to provide discretionary control and to override functions by keyboard entry. Programs can also be entered on data cards to take account of seasonal factors, vacation shutdown, and other variables. The controller can also be equipped with an optional CRT display or printer to provide status readout. Advantages of Automatic Lighting Control Systems Using an automatic lighting control system to increase levels when required and reduce levels or switch lights when a higher level is not needed produces lighting that is more effective and energy efficient. The following major advantages may be obtained from automatic lighting control. Energy Cost Savings Total savings of 50 to 65 percent are obtainable. Dollar figures shown in Table 1 are based on an energy cost of 5 cents/kWh. Figure 9. Lamp aging pattern using a standard fluorescent switching system Low Voltage Remote Switching Systems Lighting may be controlled to various light levels by wiring fluorescent luminaires as shown in Figure 11. Low voltage remote switching relays are used to control levels. Three-lamp lighting fixtures can be controlled to three levels. Two or four lamp fixtures can be controlled to two levels. 5 Figure 10. Variation in lighting level and power consumption I -9 v) w >-a c 70 footcandles required liahtinq level z g 120_(=- ." J , g 00 I Years 100% - , Years I 1 Standard system I I I 2 3 Years 1 Years 1 I I 2 I 3 Dimming system loo%-. 3 1 2 Standard system Reduction of Energy Used for Air Conditioning Energy savings from daylight and air conditioning are complementary. Daylight is at a maxiOne watt of air conditioning load is required to remove every mum on sunny days when the potential for air conditioning two or three watts of heat load produced by lighting. Reducing savings highest. lighting energy use through Although lighting makes a conautomatic COntrOlS Will reduce tribution to the heating of a air conditioning energy use. building, the annual energy reduction from air conditioning Figure 11. Multiple level fixtures using low voltage relays, ballasts not hown A .. B A+B . None 6 33% SSYO 100% _. 0% 2 Dimming system savings is generally greater than energy contributed by lighting during the heating season. Increased Lamp and Ballast Life Reducing the operating hours of lamps and ballasts will increase their productive life. Decreasing the total hours of lamp operation from 5,000 to 4,000 hours per year will increase the life of fluorescent lamps (rated at 20,000 hours lamp life) from 4 years to 5 years. Compatible with Energy Management and Building Control Systems Automatic dimming systems and low voltage remote switching relays may be integrated with microprocessor-based small-user energy management systems that incorporate peak demand control and time-ofday control of heating and ventilation systems. __ - ~- Figure 12. Programmable lighting control schematic I Photocontrol 7 Automatic lighting control may also be integrated with computerized building control systems that have energy management functions in addition to fire and security system functions. Elec- cording to zone and light level tronic sensors used to detect human presence for lighting con- requirements using computerized building control systems. trol may be used as inputs for central computerized security systems. Security lighting may also be centrally controlled acTable 1. Energy Cost Savings Type of Control Action Energy Saving** Annual Cost Saving *** (kWh/ft2/year) ($/I,OOO ft2/year) Reduction* (%) Detecting presence of people 25 1.5 75 Dimming to reduce effect of compensating for lamp aging, lens depreciation, and dirt depreciation 15 0.9 45 Dimming to take advantage of daylight 10 0.6 30 Matching lighting to task and person 15 0.9 45 Totals 65 3.9 $195 . - . *Theestimates listed are the savings in lighting energy use. **Energysavings are based on 5,000 hr/year operation. ***Airconditioning savings will accrue in proportion to the reduction in lighting energy use. When office lighting energy use is reduced by 50 to 65 percent, annual air conditioning operating cost reductions in the order of $75 to $85 per 1,000 ft2 will generally be achieved. 7 - v The Electric Ideas Clearinghouse is a comprehensive infomation source for commercial and industrial energy users. It is operated by the Washington State Energy Offzce and is part of the Electric Ideas technology transfer program sponsored by participating utilities and the Bonneville Power Administration. Electric Ideas Clearinghouse P.O. Box 43171 Olympia, WA 98504-3171 v Technology Update CH-32 Toll-free Hotline: 1-800-872-3568 Fax: 1-800-872-3882 Electronic Bulletin Board: 1-800-762-3319 Adapted from B.C. Hydro. Automatic Lighting Control for Energy Savings. Guides to Energy Management. GEM No. L108. January 1990. With permission from B.C. Hydro, Vancouver, British Columbia DOE/BP-3 983 3 -2 3 March 1993 15C a