national technical university of athens -...
TRANSCRIPT
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NATIONAL TECHNICAL UNIVERSITY OF ATHENSSchool of Electrical and Computer Engineering
Lambros T. Doulos
Lighting Controls
Energy management
Electric lighting consumes a significant amount of energy. About 25% to35% of all electricity used in buildings is used for lighting
Lighting also produces additional heat in buildings
The heat from lighting typically accounts for 15% to 20% of a building'scooling load
New legislation, codes, and standards (designed to establish minimumlevels of energy efficiency) have been developed for responsible use of energy
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Lighting system design for energy efficiency
Key elements of lighting design for energy efficiency
Lighting Needs
Space design & utilization
Daylight
Light sources
Luminaires
Lighting controls
Operation & maintenance
Space design & utilization
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Daylight
Reflection &Redirection
Diffusion
Daylight
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Light sources
Luminous efficacy Color renderingLamp life
Lamp characteristics
Light sourcesColor rendering
Standard incandescentTungsten halogenCompact FluorescentTubular FluorescentMetal halide
High pressure sodium
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Luminaires
The efficiency of the luminaire is affected by
LampsBallastsSockets Wiring Optical media (reflectors, louvers, lenses)
Objectives of the lighting system
Effective task illuminanceCreation of a comfortable visualenvironment (temperature, colorrequirements, glare control)Accessibility
In the past, controls were used primarily to turn lights on or off, or for special purposes such as stage, theater, and conference room lighting.
More recently the use of controls has become an essential element of good lighting design and an integral part of energy managementprograms for lighting of commercial, residential, industrial, and exteriorareas.
Studies of buildings that have implemented control strategies haveshown that it is possible to reduce overall lighting energy consumptionby as much as 80% in some localities.
Lighting controls
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• IMPACT OF LIGHTING CONTROLS
• LIGHTING CONTROL TECHNIQUES
Lighting controls
• LIGHTING CONTROL STRATEGIES
• LIGHTING CONTROL EQUIPMENT
Lighting control strategies
• Energy Management Strategies
Predictable and Unpredictable SchedulingDaylightingBrightness BalanceLumen MaintenanceTask Tuning
• Aesthetic Control Strategies
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Predictable scheduling
Staff arrival and departure timesLunch periodsCleaning hoursWeekends and holidays
Energy Savings
Con
sum
ed P
ower
reach 40%
Activities occur routinely during the day, and luminaires are operated on a fixed schedule
Prevision for overridingthe schedule is provided(prevent to plungeoccupants into darkness)
Unpredictable schedulingUnassigned areas such as restrooms, copy centers, filing areas, conference rooms, break rooms, and retail store dressing rooms areused sporadically and are not readily scheduled.
Energy Savings
Con
sum
ed P
ower
Unpredictable schedulingstrategies usingoccupancy/motionsensors have yieldedenergy savings of over60% in some areas
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Daylighting
In the perimeter areas of buildings, part of the desired illumination canoften be supplied by daylight.
Illum
inan
ce (
lux)
High levels of daylightmust be present so thatsufficient illuminationfor the task remainsafter the electriclighting has beenlowered
Con
sum
ed P
ower Energy
Savings
Climatic conditionsBuilding formorientation and designPhotosensorControl design and installationActivities within the buildingSize and shape of control zones
The energy savings realized from daylighting depends on many factors
Peak power demand hours
Daylighting
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The size and shape of control zones are usually constrained by the rapid falloffof horizontal illuminance from the window wall.
The row of luminaires nearest the window should be controlled on a separatecircuit from those in the interior area.
Daylight level Artificial lighting level
Total lighting levelOff 50% 100%
Control zone depth
Daylighting
Brightness balanceThe design goal is to balance different brightness levels in order to
• either reduce glare and shadows or
• provide a luminous transition between two spaces having very differentbrightness levels (like in tunnel lighting).
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Lumen maintenance
Lumen maintenance control strategy calls for reducing the initial illumination of a new system to the designed minimum level.
Lighting systems are usually designed for a minimum maintained illuminancelevel. This requires the level of a new lighting system to exceed the designminimum by 20 to 35% to allow for lumen depreciation due to:
Lamp lumen depreciationLuminaire dirt depreciationRoom surface dirt depreciation
Energy Savings
Con
sum
ed P
ower Energy
Savings
Clean luminaire and relamp
Consumed Power without controlConsumed Power with control
Clean luminaire and relampIll
umin
ance
(lu
x)
Target illuminanceIlluminance level with controlIlluminance level without control
Wasted light
Wasted light
Illuminance level without control
1st year 2nd year 1st year 2nd year 1st year 2nd year 1st year 2nd year
Lumen maintenance
As lumen depreciation occurs, more power is applied to the lamps in order tomaintain constant output. Thus, full power is applied only near the end of the lumen maintenance period, significantly reducing energy use over the life of the lamp.
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Task tuning
1 luminaire, 2X58W Total: 116 W
4 luminaires, 2X26WTotal: 208 W
The lighting system is adjusted or tuned in order to provide local illumination as needed instead of uniform illuminances throughout a space.
380 Lux 280 Lux
Task tuning
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Aesthetic control strategies
Many spaces in commercial, institutional, and residential applications are usedfor more than one purpose. Different tasks require a variety of lightingconditions.
Aesthetic controls provide the means to adjust the lighting to:
Suit the purposeMaintain human visual performanceChange the mood of the space
Preset control systems allow for several lighting channels to be controlledsimultaneously. All channels are programmed to provide multiple moods orscenes. Each of these scenes can be recalled with the touch of one button
For reading tasks
For slide presentation
Recalled scenes
During conference
For opening tasks
Aesthetic control strategies
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Lighting Controls
LIGHTING CONTROL STRATEGIES
Lighting control with
Η/Υ(Predictable scheduling)
Occupancy/motion Sensors
(Unpredictable scheduling)
Manual dimming with remote
control(Task tuning)
Photosensor(Daylight)
• IMPACT OF LIGHTING CONTROLS
• LIGHTING CONTROL TECHNIQUES
Lighting controls
• LIGHTING CONTROL STRATEGIES
• LIGHTING CONTROL EQUIPMENT
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Lighting control techniques
Switching or Dimming control
Local or central control
Degree of control automation and zoning
After the control strategies the selection of the major controltechniques is particularly important in the specificationprocess. The following three categories establish the majorchoices:
Choosing communication protocol
• 1-10V• DMX• DALI
• KNX• LON
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Switching
SwitchingVia simple wall-box switchesremotely via relays
Suited to:Predicted SchedulingUnpredicted Scheduling (with occupancy sensors)Split-wired luminaires
Always remember: inconvenient switches are never used
By a control systemBy occupancy sensors
Switching for split-wiredluminaires
Levels: 0%, 50% & 100% Levels: 0%, 33%, 66% & 100%
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Dimming control
DimmingThe illuminance in each zone can be variedsmoothly and continuously to dynamically matchvisual requirements.
Suited to:Daylighting applications
Local or central control
Lighting controls can be implemented in buildings using either a local approach, a central system or some combination of the two.
The two approaches are distinguished both by the size of the controlled areas and by how the control inputs are integrated into the system.
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Local or central controlAll lighting control systems with local or central control are divided intoindependently controllable zones that contain three major components:
Power controllerThis is the "business end" of a control system that electrically changesthe output of the light sourceLogic circuitThis is the intelligence that decides when to supply electric lighting, and how much.Sensing deviceThe sensing device (such as a photosensor, an occupancy/motionsensor, or a timing device) sends information to the logic circuit. Two ormore of these elements can be combined in a single system
The communication and wiring system must link these components
Degree of control automation and zoning
Manual Highly automated
Cheaper
User friendly
Energy savings
vs
Override makes them friendlier
Small zones vs Large zones
FlexibleCheaper
(both in equipment and in installation costs)
More efficient to:Daylight
Task tuning
More efficient to:Scheduling
Lumen maintenance
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• IMPACT OF LIGHTING CONTROLS
• LIGHTING CONTROL TECHNIQUES
Lighting Controls
• LIGHTING CONTROL STRATEGIES
• LIGHTING CONTROL EQUIPMENT
Control equipment by space useAfter the strategies and techniques are decided, it is necessary to selectthe specific lighting control equipment to be employed.
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Control equipment based on expected lighting load profile
Control equipment for different building applications
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Manual Switching
The design and the location of the manualcontrol affects the energy consumption of the building.
The convenience and flexibility of switching greatly affect the extent of anylighting energy savings.
•Each separate office should have its own control switch
•Similar work areas should be grouped together on one circuit
•Adjacent luminaires should be placed on alternate circuits
: Luminaires in circuit A
: Luminaires in circuit B
Manual Switching
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•In three-lamp fluorescent luminaires, the middle lamps should beconnected to a separate circuit from the outside lamps.
•In four-lamp fluorescent luminaires, the inside pair of lamps should beconnected to a circuit separate from the outside pair
Manual switching
•Task areas with high levels of lighting should be on separate switches.
•Luminaires along window walls should be wired on separate circuits and be controlled independently.
•Effective labels can cause occupants to use simple wall switches.
Daylight level Artificial lighting level
Total lighting levelOff 50% 100%
Circuit A Circuit B Circuit C
Manual switching
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Timing Devices
The function of the timer is to controllighting in response to known orscheduled sequences of events, thatis, to turn off the lighting that is notneeded.
Timers range from simple integraltimers to microprocessors that canprogram a sequence of events for years at a time.
As a general rule, some form of override must be provided toaccommodate deviations from the preset schedule.
Timing and sensing devices
Photosensors
Photosensors use electronic components thattransform visible radiation (light) into an electricalsignal, which is used to control another system orlamp. There are two modes of operation:
•The photosensor output activates a simple on-offswitch or relay.
•A variable output signal is established and sent to a controller that continuously adjusts the output of the electric lighting in proportion the daylight.
Timing and sensing devices
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Photosensors
The performance of the photosensor can be complex because it depends from a lot of variables, such as:
The distribution of daylight and artificial lighting in the space in which it is placed
The spectral composition of lighting
The adjustment settings for the calibration of the control
The ambient light level
The field of view, spectral response and control algorithm of the photosensor
Placement of photosensor
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Wide versus narrow spatial responses
In practice, the reflectance of the workplane is not constant, but changes depending on the activities going on in the room.
Examples include a dark desktop that is sometimes covered with white papers, the colors of peoples' clothing such as a white shirt versus a dark suit, and even rearrangement of the room's furniture.
Occupancy/Motion Sensors
The primary function of occupancy sensors is to automatically switch offluminaires when spaces are unoccupied, so as to reduce energy use. Frequently, this method offers the best savings and payback of all controloptions.
The failure of anoccupancy sensorinstallation isalmost always a result of poorsensor placementor incorrectequipmentselection.
Timing and sensing devices
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Timing and sensing devicesOccupancy/Motion Sensors
Occupancy is sensed by audio, ultrasonic, passive infrared, or optical means.
These devices are designed to switch lights on as an occupant enters and keepthem on while he or she remains in the space. Lights are switched off after a preset time following the departure of the occupant.
Quiet activities such as word processing, reading, or using the telephone, however, may not be detected, and lights being switched off can frustrateoccupants in these situations.
These nuisance actions can be minimized by suitable product selection and proper sensor location.
Timing and sensing devicesOccupancy/Motion Sensors
The floor area covered by individual sensors can range from 15 m2 in individual offices or workstations to 200 m2 in largeclassroom or assembly spaces. Larger areas can be controlled byadding more sensors.
Occupancy/motion sensors can be used in combination withmanual switching (on or off), timers, daylighting sensors, dimmers, and central lighting controls.
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Central processors
Central processors can respond to a numberof complex lighting conditions in the space, collect power and energy-use data and supply summary reports for buildingmanagement.
Processors range in complexity from a microchip in a controller to a large computer.
For centralized systems, the processor is the device that assimilates the data, determines the required change, and initiates action to effect the change.
Input is received from the sensors, data are analyzed in accordance witha predetermined set of rules and a system change is initiated. Systems can also respond to manual switches.
Central processors
Processor (Logic circuit & Power controller)
Various lighting groups
Signal
Sensing devices
Existing protocols
Building Management System
DataRules
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• IMPACT OF LIGHTING CONTROLS
• LIGHTING CONTROL TECHNIQUES
Lighting controls
• LIGHTING CONTROL STRATEGIES
• LIGHTING CONTROL EQUIPMENT
Impact of lighting controls
Effects on the Whole Building
Electrical Equipment Effects
Power Quality
Human Performance Effects
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Effects on the whole building
Lighting can be responsible for a major portion of a building's HVAC load. Lighting electrical loads affect the initial cost of the HVAC system as well as its annual energy consumption.
It is important that the HVAC system and controls be designed to respond to changes in the operation of the lighting system from lighting controls.
Daylighting can increase the initial cost and the annual energy consumption if the daylighting system is not carefully designed. Indeed, payback can be longer with daylighting controls. For example, a daylighting system can increase the necessary summertime cooling load of a building by letting more heat into the building.
Many modern occupancy sensors have dedicated control outputs for the simultaneous control of lighting and HVAC equipment.
HVAC Effects
Electrical equipment effects
Controls that switch lamps on and off excessively can reduce fluorescent lamp life. Increased cycling does not decrease ballast life or reliability. The actual service life of lamps can be extended by the elimination of unnecessaryburning hours and dimming instead on and off.
Switching
Interference
Radio frequency interference (RFI) or electromagnetic interference (EMI) isinherent in all control systems that rapidly switch a portion of input power.
There are two areas of concern with regard to radio noise: conducted emissionand radiated emission. Conducted emission is the noise fed directly into the power line by the device drawing power from that line. Radiated emission is the electrical noise radiated by the lamps in the luminaire.
Control systems use passive and active filters to keep the conducted emissionswithin the allowable limits.
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Power quality
The designer should be aware of potential harmonics, as they canoverload the neutral conductor in three-phase electrical distributionsystems, which can damage itsinsulation and overheattransformers.
In practice no problems have actually been attributed to the generation of harmonics by lighting control systems to date, but designers and engineers should become familiar with the issues when using these advanced lighting technologies.
Human performance effects
Lighting control systems can have a positive effect on the workingenvironment, provided that they add to the comfort and the aestheticsof a space. Controls can have further economic benefit if the productivity of the occupants is increased.
Care should be taken when attempting to reduce energy use to ensurethat illuminance is not reduced below that required for visual tasks in the space. Audible noise, flicker, and source color changes caused bydimmer controls can also affect performance.
Control systems must be designed so that the lighting system can provide proper illuminance for various tasks such as reading, inspecting and assembling .
Illuminance
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Audible Noise
Flicker
Color Changes
The manufacturer should be consulted to minimize the noise produced by the control system. Noise control strategies include careful lamp selection, enhanced dimmer filtering, and remote dimmer locations.
Flicker is noticeable if the variation in light amplitude is sufficiently high. Evenimperceptible flicker can cause eyestrain and fatigue at 50 Hz. Lamps should be selected that minimize flicker. Electronic fluorescent ballastsshould be selected because they drive the lamps without flicker.
During lamp dimming, there can be a small shift in lamp color with fluorescentlamps (also in incandescent lamps ). This color shift is not usually consideredsignificant, but it is noticeable.They should not be dimmed to levels that alter the aesthetics of the space, causediscomfort to the occupants, or affect tasks in which color rendition ordiscrimination are essential. On the other hand, the shift in incandescent lightingto a lower color temperature by dimming can actually be desirable in certainapplications such as restaurants, where a warmer atmosphere can be inviting.
Human performance effects