NATIONAL TECHNICAL UNIVERSITY OF ATHENS School of Electrical and Computer Engineering Lighting Controls Lambros T. Doulos Energy management Electric lighting consumes a significant amount of energy. About 25% to 35% 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's cooling load New legislation, codes, and standards (designed to establish minimum levels of energy efficiency) have been developed for responsible use of energy 1
Lighting system design for energy efficiency Key elements of lighting design for energy efficiency Space design & utilization Daylight Lighting Needs Light sources Luminaires Lighting controls Operation & maintenance Space design & utilization 2
Daylight Reflection & Redirection Diffusion Daylight 3
Light sources Lamp characteristics Luminous efficacy Color rendering Lamp life Light sources Color rendering Standard incandescent Tungsten halogen Compact Fluorescent Tubular Fluorescent Metal halide High pressure sodium 4
Luminaires The efficiency of the luminaire is affected by Lamps Ballasts Sockets Wiring Optical media (reflectors, louvers, lenses) Objectives of the lighting system Effective task illuminance Creation of a comfortable visual environment (temperature, color requirements, glare control) Accessibility Lighting controls 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 management programs for lighting of commercial, residential, industrial, and exterior areas. Studies of buildings that have implemented control strategies have shown that it is possible to reduce overall lighting energy consumption by as much as 80% in some localities. 5
Lighting controls LIGHTING CONTROL STRATEGIES LIGHTING CONTROL TECHNIQUES LIGHTING CONTROL EQUIPMENT IMPACT OF LIGHTING CONTROLS Lighting control strategies Energy Management Strategies Predictable and Unpredictable Scheduling Daylighting Brightness Balance Lumen Maintenance Task Tuning Aesthetic Control Strategies 6
Predictable scheduling Activities occur routinely during the day, and luminaires are operated on a fixed schedule Staff arrival and departure times Lunch periods Cleaning hours Weekends and holidays Prevision for overriding the schedule is provided (prevent to plunge occupants into darkness) Consumed Power Energy Savings reach 40% Unpredictable scheduling Unassigned areas such as restrooms, copy centers, filing areas, conference rooms, break rooms, and retail store dressing rooms are used sporadically and are not readily scheduled. Unpredictable scheduling strategies using occupancy/motion sensors have yielded energy savings of over 60% in some areas Consumed Power Energy Savings 7
Daylighting In the perimeter areas of buildings, part of the desired illumination can often be supplied by daylight. High levels of daylight must be present so that sufficient illumination for the task remains after the electric lighting has been lowered Illuminance (lux) Daylighting The energy savings realized from daylighting depends on many factors Climatic conditions Building form orientation and design Photosensor Control design and installation Activities within the building Size and shape of control zones Consumed Power Energy Savings Peak power demand hours 8
Daylighting The size and shape of control zones are usually constrained by the rapid falloff of horizontal illuminance from the window wall. The row of luminaires nearest the window should be controlled on a separate circuit from those in the interior area. Control zone depth Off 50% 100% Total lighting level Daylight level Artificial lighting level Brightness balance The 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 different brightness levels (like in tunnel lighting). 9
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 illuminance level. This requires the level of a new lighting system to exceed the design minimum by 20 to 35% to allow for lumen depreciation due to: Lamp lumen depreciation Luminaire dirt depreciation Room surface dirt depreciation Lumen maintenance Illuminance level without control Illuminance (lux) Wasted light Wasted light Clean luminaire and relamp Consumed Power Energy Savings Energy Savings Clean luminaire and relamp 1 st year 2 nd year 1 st year 2 nd year Target illuminance Illuminance level with control Illuminance level without control 1 st year 2 nd year 1 st year 2 nd year Consumed Power without control Consumed Power with control As lumen depreciation occurs, more power is applied to the lamps in order to maintain 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. 10
Task tuning The lighting system is adjusted or tuned in order to provide local illumination as needed instead of uniform illuminances throughout a space. 1 luminaire, 2X58W Total: 116 W 4 luminaires, 2X26W Total: 208 W Task tuning 380 Lux 280 Lux 11
Aesthetic control strategies Many spaces in commercial, institutional, and residential applications are used for more than one purpose. Different tasks require a variety of lighting conditions. Aesthetic controls provide the means to adjust the lighting to: Suit the purpose Maintain human visual performance Change the mood of the space Preset control systems allow for several lighting channels to be controlled simultaneously. All channels are programmed to provide multiple moods or scenes. Each of these scenes can be recalled with the touch of one button Aesthetic control strategies For opening tasks Recalled scenes For reading tasks During conference For slide presentation 12
Lighting Controls LIGHTING CONTROL STRATEGIES Photosensor (Daylight) Occupancy/motion Sensors (Unpredictable scheduling) Manual dimming with remote control (Task tuning) Lighting control with Η/Υ (Predictable scheduling) Lighting controls LIGHTING CONTROL STRATEGIES LIGHTING CONTROL TECHNIQUES LIGHTING CONTROL EQUIPMENT IMPACT OF LIGHTING CONTROLS 13
Lighting control techniques After the control strategies the selection of the major control techniques is particularly important in the specification process. The following three categories establish the major choices: Switching or Dimming control Local or central control Degree of control automation and zoning Choosing communication protocol 1-10V DMX DALI KNX LON 14
Switching Switching Via simple wall-box switches remotely via relays By a control system By occupancy sensors Suited to: Predicted Scheduling Unpredicted Scheduling (with occupancy sensors) Split-wired luminaires Always remember: inconvenient switches are never used Switching for split-wired luminaires Levels: 0%, 50% & 100% Levels: 0%, 33%, 66% & 100% 15
Dimming control Dimming The illuminance in each zone can be varied smoothly and continuously to dynamically match visual 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. 16
Local or central control All lighting control systems with local or central control are divided into independently controllable zones that contain three major components: Power controller This is the "business end" of a control system that electrically changes the output of the light source Logic circuit This is the intelligence that decides when to supply electric lighting, and how much. Sensing device The sensing device (such as a photosensor, an occupancy/motion sensor, or a timing device) sends information to the logic circuit. Two or more 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 Cheaper User friendly vs Highly automated Energy savings Override makes them friendlier Small zones vs Large zones Flexible More efficient to: Daylight Task tuning Cheaper (both in equipment and in installation costs) More efficient to: Scheduling Lumen maintenance 17
Lighting Controls LIGHTING CONTROL STRATEGIES LIGHTING CONTROL TECHNIQUES LIGHTING CONTROL EQUIPMENT IMPACT OF LIGHTING CONTROLS Control equipment by space use After the strategies and techniques are decided, it is necessary to select the specific lighting control equipment to be employed. 18
Control equipment based on expected lighting load profile Control equipment for different building applications 19
Manual Switching The design and the location of the manual control affects the energy consumption of the building. The convenience and flexibility of switching greatly affect the extent of any lighting energy savings. Manual Switching 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 20
Manual switching In three-lamp fluorescent luminaires, the middle lamps should be connected to a separate circuit from the outside lamps. In four-lamp fluorescent luminaires, the inside pair of lamps should be connected 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. Circuit A Circuit B Circuit C Off 50% 100% Total lighting level Daylight level Artificial lighting level 21
Timing and sensing devices Timing Devices The function of the timer is to control lighting in response to known or scheduled sequences of events, that is, to turn off the lighting that is not needed. Timers range from simple integral timers to microprocessors that can program a sequence of events for years at a time. As a general rule, some form of override must be provided to accommodate deviations from the preset schedule. Timing and sensing devices Photosensors Photosensors use electronic components that transform visible radiation (light) into an electrical signal, which is used to control another system or lamp. There are two modes of operation: The photosensor output activates a simple on-off switch 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. 22
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 23
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. Timing and sensing devices Occupancy/Motion Sensors The primary function of occupancy sensors is to automatically switch off luminaires when spaces are unoccupied, so as to reduce energy use. Frequently, this method offers the best savings and payback of all control options. The failure of an occupancy sensor installation is almost always a result of poor sensor placement or incorrect equipment selection. 24
Timing and sensing devices Occupancy/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 keep them 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 frustrate occupants in these situations. These nuisance actions can be minimized by suitable product selection and proper sensor location. Timing and sensing devices Occupancy/Motion Sensors The floor area covered by individual sensors can range from 15 m 2 in individual offices or workstations to 200 m 2 in large classroom or assembly spaces. Larger areas can be controlled by adding more sensors. Occupancy/motion sensors can be used in combination with manual switching (on or off), timers, daylighting sensors, dimmers, and central lighting controls. 25
Central processors 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 with a predetermined set of rules and a system change is initiated. Systems can also respond to manual switches. Central processors can respond to a number of complex lighting conditions in the space, collect power and energy-use data and supply summary reports for building management. Processors range in complexity from a microchip in a controller to a large computer. Central processors Sensing devices Processor (Logic circuit & Power controller) Rules Data Signal Existing protocols Various lighting groups Building Management System 26
Lighting controls LIGHTING CONTROL STRATEGIES LIGHTING CONTROL TECHNIQUES LIGHTING CONTROL EQUIPMENT IMPACT OF LIGHTING CONTROLS Impact of lighting controls Effects on the Whole Building Electrical Equipment Effects Power Quality Human Performance Effects 27
Effects on the whole building HVAC Effects 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. Electrical equipment effects Switching 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 unnecessary burning hours and dimming instead on and off. Interference Radio frequency interference (RFI) or electromagnetic interference (EMI) is inherent in all control systems that rapidly switch a portion of input power. There are two areas of concern with regard to radio noise: conducted emission and 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 emissions within the allowable limits. 28
Power quality The designer should be aware of potential harmonics, as they can overload the neutral conductor in three-phase electrical distribution systems, which can damage its insulation and overheat transformers. 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 working environment, provided that they add to the comfort and the aesthetics of 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 ensure that illuminance is not reduced below that required for visual tasks in the space. Audible noise, flicker, and source color changes caused by dimmer controls can also affect performance. Illuminance Control systems must be designed so that the lighting system can provide proper illuminance for various tasks such as reading, inspecting and assembling. 29
Human performance effects Audible Noise 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 Flicker is noticeable if the variation in light amplitude is sufficiently high. Even imperceptible flicker can cause eyestrain and fatigue at 50 Hz. Lamps should be selected that minimize flicker. Electronic fluorescent ballasts should be selected because they drive the lamps without flicker. Color Changes During lamp dimming, there can be a small shift in lamp color with fluorescent lamps (also in incandescent lamps ). This color shift is not usually considered significant, but it is noticeable. They should not be dimmed to levels that alter the aesthetics of the space, cause discomfort to the occupants, or affect tasks in which color rendition or discrimination are essential. On the other hand, the shift in incandescent lighting to a lower color temperature by dimming can actually be desirable in certain applications such as restaurants, where a warmer atmosphere can be inviting. 30