Intelligent lighting control and energy performance
- Understand the codes and standards that dictate lighting design.
- Learn the steps to design and implement a smart lighting system.
- Realize the importance of control system commissioning.
Lighting is typically one of the largest energy loads in any building, and historically it has been the hardest to control. People turn lights on and forget to turn them off. But technology has become more effective at combating this human weakness.
The first revision of the simple on-off switch on the wall was the replacement of the switch with a dial or slider incandescent dimming switch, which saved electricity by allowing the user to select intermediate levels of illumination. Then, in the thick of the energy crisis of the late 1970s, the first occupancy sensors hit the market. No longer were humans the sole determinant of whether the lights were on or off—now the machines also had a say. Stand-alone occupancy sensors and timer switches were connected to lighting fixtures, acting as a “big brother” and turning the lights off if no occupancy was sensed for a certain length of time, or when the time on the timer switch ran out. This innovation represented a tremendous improvement over the manual switch, bringing massive reductions in lighting loads.
Next came network-based lighting controls, which controlled lighting zones by layering a time schedule over stand-alone controls and manual switches, turning off all the lights in the building at a certain time, overriding the switches and the stand-alone controls.
The latest iteration, the advanced lighting control system, leverages the power of digitization and granularity. When properly implemented, these systems are user-friendly and easy to maintain, they provide the ability to effectively manage all of a building’s lighting from a single centralized location, and they streamline physical maintenance and operation. Software-based lighting control also allows sharing of data not only between components of the lighting control system, but also with mechanical, fire safety, and security systems. This integration of smart systems enables effective management of all the building’s energy consumers to realize energy reduction and cost savings.
Despite the benefits, many engineers don’t really understand advanced lighting control systems. This may be because the comprehensive nature of the system can seem complex and overwhelming, and engineers often just haven’t taken the time to learn about it. The term “advanced lighting control system” may sound complicated, but what it really means is that you are merely layering communication interfaces over common hardware that engineers have traditionally used and are already quite familiar with—ballasts, lamps, occupancy sensors, and other control devices—or you are using a special type of this equipment. Often designers don’t realize that familiarizing themselves with advanced lighting control systems can save them time and energy in the long run. The hardware is pretty much the same as it has been; the real change and advancement is the software systems.
Updates to codes and standards
Energy codes such as ASHRAE Standard 90.1, International Energy Conservation Code (IECC), and California Title 24 are becoming more stringent, and advanced lighting controls simply make it much easier to comply. With each new version, energy codes are trending toward the ultimate goal of net-zero energy consumption. Each of the codes is updated every 3 years, and the biggest changes are that the thresholds for triggering compliance are revised to encompass more projects.
As an example, let’s look at ASHRAE 90.1-2007 versus ASHRAE 90.1-2010 for some specific highlights:
- Threshold for compliance
- 2007: Any new or retrofit projects encompassing 50% or greater alteration of the connected lighting load
- 2010: Any new or retrofit projects encompassing 10% or greater alteration of the connected lighting load
- Automatic shutoff of lighting
- 2007: Required in buildings greater than 5,000 sq ft
- 2010: Required in all spaces
- Light level reduction
- 2007: Not a requirement
- 2010: Lighting must be wired to allow for a power reduction of 30% to 70%, in addition to turning off the lighting by either dimming or switching
- Daylight zones
- 2007: Not a requirement
- 2010: Daylighting control must be automatic based on natural light contribution, and must be installed in spaces with windows and skylights
- Exterior lighting
- 2007: Lighting must be off during the day
- 2010: Lighting must be off during the day, and lighting must be off or at a reduced level at night
- Plug load control
- 2007: Not a requirement
- 2010: 50% of receptacles in private offices, open offices, and computer classrooms must be automatically shut off.
Instead of looking at lighting control from a building level, many engineers still try to address each energy code requirement individually, installing multiple types of systems (e.g., relay control, architectural dimming systems, wall box dimming) in a single building without any central control. While this approach may satisfy the project’s basic functional and energy code requirements, trying to fit a set of piecemeal systems together is really the harder way to go about things.
Energy code requirements, rising energy costs, the importance of historical and up-to-the-minute building data collection and analysis, research on the effectiveness of controls, emerging technologies like easy-to-control LEDs, and demand for “green” buildings have driven manufacturers to develop systems that engineers can implement to meet these requirements. The thinking now is to make lighting controls as seamless as HVAC control—provide the user comfort, but only use what you absolutely need. With the addition of the plug load control requirement, lighting control systems are quickly moving into the realm of energy management.
There are essentially two types of advanced lighting control system implementation methods. The first is the use of digital addressable lighting interface (DALI) equipment. The address required for the system programming control is embedded in the ballast and control devices. The second is the use of addressable input/output modules that are “layered” over standard ballast and control devices. DALI-based systems seem to be proprietary in nature because you are restricted to specific equipment. Some DALI-based system manufacturers require their devices be implemented for proper operation. On the other hand, layered systems allow any device combination..
But what really sets these systems apart is the software interface. Several manufacturers now use a graphical user interface (GUI) that allows the user to point and click to make programming changes to the system. Software also provides unprecedented energy management power, by enabling centralized management (with remote access); easy integration and data sharing with other building systems such as building automation systems (BAS), security systems, or fire alarm systems; and automatically generated maintenance alerts, device and system commissioning reports, and device usage reports. Armed with all of this data and computing power, building operators are empowered as never before to optimize energy consumption in their facilities.
Advantages of advanced lighting control systems
Advanced lighting control systems offer significant cost savings over conventional lighting controls. They provide additional granularity of control to ensure that all spaces, and even all luminaires, can be optimized around energy savings and visual performance. The control, and the finely detailed control and optimized energy savings, can be achieved by implementing six basic lighting control strategies:
- Time/astronomical scheduling: Lighting in a defined area turns on or off, or dims, based on a predetermined, customizable schedule.
- Occupancy/vacancy control: Lighting is turned on or off based on detected occupancy. With vacancy control, users must manually turn lights on, but lights are automatically turned off when a space is vacant.
- Daylight harvesting: Electric light levels are automatically adjusted to account for the amount of natural sunlight in a space. Appropriate light levels are maintained for functional purposes, and total illumination is evenly maintained throughout the space.
- Task tuning: Maximum light levels are set for a particular use or task in a specific room to prevent overlighting.
- Personal control: Individuals can tailor the lighting in their workspace to their personal preferences, via a GUI on their computer.
- Load shedding (or demand response): Lighting control can contribute to a building-wide effort to reduce demand. Lighting is turned off or dimmed in predetermined areas at times of peak demand.
Advanced lighting control systems allow you to employ all six of these strategies simultaneously. Without an advanced lighting control system, you are limited to the use of time scheduling, occupancy/vacancy control, and daylight harvesting. It is also important to note that you can’t harness the full potential of daylight harvesting with conventional controls. Conventional controls require one daylight sensor to control a group of lights, typically on one circuit or switch leg, which means that large groups of luminaires are controlled in the same manner. Centralized software control is required to implement task tuning, personal control, and load shedding (demand response).
In addition to maximizing lighting efficiency, these systems increase occupant satisfaction and possibly even productivity. When occupants have control over their space, they tend to be happier and more productive. Easy-to-use control system software helps make required adjustments to keep up with dynamic changes.
Best practices for design implementation
Energy codes (ASHRAE 90.1, IECC, Title 24) basically define guidelines of best practices for the design implementation of an advanced lighting control system within the requirements. For example, for automatic daylighting control, ASHRAE 90.1 states that electric lighting shall be reduced with at least one control step that is between 50% and 70% of design lighting power and another control step that is no greater than 35% of power design.
The following examples spell out best practices for implementing current energy code requirements.
- Start with a simple user-triggered lighting strategy. In each area of the building, occupants turn lights on via a low-voltage switch, and off by the same low-voltage switch. Electricity savings are maximized if users turn the lights on manually when they enter and remember to turn them off when they exit. If the user forgets to turn the lights off, automatic sensor coverage picks up the slack, signaling the central lighting control system to switch the lighting off in an area that is unoccupied or vacant, per energy code requirements. Vacancy sensors are generally considered more efficient than, and therefore preferable to, occupancy sensors, because they only turn lighting off, not on—users have to turn lights on manually. In a private office with large windows letting in ample daylight, for example, the vacancy sensor ensures that the lights will only be turned on when occupants truly want or need them.
- In addition to this simple lighting switching strategy, the advanced lighting control system automatically dims the lighting in areas that have adequate daylight penetration. As daylight levels change, the dimming levels of individual luminaires are adjusted so that the total illumination is evenly maintained throughout the space at the required level.
- The advanced lighting control system controls emergency egress lighting. In the past, lighting on emergency circuits was often “on” 24/7 as a safety measure, burning through the night long after occupants of a building had left. Advances in control devices now allow emergency lighting circuits to be controlled by time schedules or by automatic sensors, and by equipping these devices with a UL 924 emergency transfer device that can override the digital lighting control system if normal power is lost, the system is able to turn on all lights connected to the emergency circuit and maintain egress levels for occupant safety without wasting energy when no one is around.
- The advanced lighting control system is digitally connected to the BAS to use the detection signal of occupancy sensors at all hours to adjust mechanical setpoints. If multiple lighting control zones are provided in a single mechanical system zone, the lighting control system can accumulate the occupancy zones within the mechanical zone to help refine the efficiency of the HVAC system.
Specific space requirements:
- Interior private offices or rooms: Occupants turn lights on and off by pressing a low-voltage wall switch. A ceiling-mounted occupancy sensor operating in vacancy mode turns the room lighting off if occupants forget to turn it off when they leave. Personal control of these luminaires is made available on occupants’ computers.
- Perimeter offices or rooms with adequate daylight: Occupants turn lights on and off by pressing a low-voltage wall switch. This switch turns the lights on to a level allowed by a photosensor that monitors the amount of daylight hitting the exterior of the window glass. A ceiling-mounted occupancy sensor operating in vacancy mode turns off the room lighting if occupants forget to turn it off when they leave. Personal control of these luminaires is made available on occupants’ computers.
- Corridors and lobby: These are the only building areas with two modes of operation: “during business hours” and “after business hours.” In the corridors, an array of occupancy sensors turn lighting on and off according to occupancy and the current response mode, dictated by the advanced lighting control system’s time clock. Perimeter areas are also equipped with photosensors to adjust the amount of electric light based on the amount of daylight in the space. Luminaires in these areas are adjusted to lower level output when a load shed signal is sent.
- During business hours: Upon detecting occupancy in a corridor, the advanced lighting control system turns lights on and keeps them on until the system enters “after business hours” mode, after which point it only turns lights on when the building has occupancy, preventing the corridors from lighting up on holidays, snow days, and other low-occupancy days. Lighting remains on in the corridor throughout the business day once triggered, preventing short on-off cycling of corridor lighting as occupants move from space to space. At the end of “during business hours,” the system transfers to the “after business hours” lighting control mode.
- After business hours: Occupancy sensors control corridor lighting via auto-on and auto-off functions. After 15 minutes of nondetection, lighting automatically turns off. Minimum cycling of lighting is expected during these low-occupancy hours. Maximum light levels are set during this time period, as it is anticipated that the full light level will not be needed.
- Restrooms and stair towers: Lighting in these rooms is determined 24/7 by occupancy sensors. After 15 minutes of nondetection, the lighting automatically turns off. Luminaires in these areas are adjusted to lower level output when a load shed signal is sent.
- Utility and storage rooms: Occupants turn lights on and off by pressing a low-voltage switch on the wall. A 2-hour timeout sequence starts when the switch is activated. A blink warn occurs when five minutes remain in the 2-hour countdown. If the user wants to remain in the room, the switch can be activated again, and another 2-hour timeout sequence commences. Luminaires in these areas are adjusted to lower level output when a load shed signal is sent. It is worth noting that NFPA 70: National Electrical Code (NEC) Article 100.26 (D), requires a manual switch/override for electrical rooms.
- Conference rooms: Occupants turn the lights on and off by either pressing a low-voltage wall switch or utilizing a preset scene dimming control station. Ceiling-mounted occupancy sensors operating in vacancy mode turn the lighting off if occupants leave without turning off the lights. Maximum light levels are set for this space for certain tasks.
Commissioning lighting controls
Both ASHRAE 90.1 and IECC require commissioning of all control hardware and software to ensure that these elements perform as intended. The commissioning agent ascertains that the controls’ locations, adjustment, aiming, calibration, and programming all align with construction documents, field conditions, and manufacturer instructions.
Commissioning of advanced lighting controls generally needs to be done outside of a space’s normal work hours. The commissioning agent performs a number of procedures to test automatic sensors, photosensor and daylighting controls, time switches, and programmable schedule controls. Sensors are inspected to ensure that they are correctly placed and that their sensitivity and time-out adjustments deliver performance. Programmable schedule controls and time switches are checked to make sure they are set to turn the lights off as intended. Photosensor controls are inspected to ensure that their placement and sensitivity adjustments achieve the desired reduction in electric lighting based on available daylight. Commissioning of a daylight harvesting system often is required to occur at night so the true output of the electric system can be factored into the photosensor programming without any daylight contributions.
The advanced lighting control system itself is also commissioned. The manufacturer of the system builds in testing procedures for individual components such as onboard fixture controllers to allow them to be checked when they are being installed. The system also takes stock of all components that are connected to it, allowing the commissioning agent to detect any unconnected or “orphaned” components. The commissioning agent also checks zoning, or the grouping of lights, and the system’s programming, including control profiles, schedules, and load shedding sequences.
Engineers and designers can aid the commissioning process by requesting the following items in the design specifications as part of the system submittal: programming intent narrative, a detailed bill of material, contractor checklist, and start-up request form.
One concern often voiced about advanced lighting control systems is that they are expensive. To operate an advanced lighting control system at the extreme of optimization, each light fixture would be able to be individually controlled, and therefore equipped with a dimming ballast, or driver. Such a system would indeed be very expensive.
But a few things have helped that type of system become competitive. First, LED technology is increasingly affordable, and it is being used more frequently. One advantage of LED lighting is that it is inherently dimmable: If you pair the LED’s dimmable driver with a compatible control, additional components are not required to tune the light. The 20% to 30% adder for a controllable fluorescent ballast has disappeared, opening up the possibilities of light modularity as the norm instead of a novelty.
Second, as engineers have learned how to leverage advanced lighting controls to manage energy usage, they have realized that significant savings in the system first cost could be achieved by thoughtfully grouping control of light fixtures into zoned areas, and not relying on individual light fixture control, which is rarely really necessary in typical building designs. Third, most advanced control systems use distributed low-voltage components instead of more traditional “pipe and wire” control strategies, so costs associated with a less rigorous installation method can often be reduced if a savvy contractor is brought on to implement the design.
Another common concern is that advanced lighting control systems are difficult to manage. But this is generally a matter of perception. When you are dealing with a building that has more than 1,000 light fixtures, the thought of individually controlling each of them can seem overwhelming. But, as noted above, individual control isn’t necessary, and careful planning can create a system that goes a long way to help facilities managers truly understand more about how their buildings really operate. Management of the entire building is done through web-based software. Anyone comfortable with using software on a PC will find this kind of system very straightforward to manage properly.
Rising energy costs and more regulation through energy codes are making energy management a top priority for building owners and managers. The points noted above give designers and engineers additional tools to both meet and exceed the expectations of current and future energy code regulations.
Robert J. Garra Jr. is vice president at CannonDesign. An engineering leader who understands clients and their goals, Garra applies his project leadership and industry knowledge across the firm’s market segments, while providing strategic direction to the engineering group. He effectively manages integrated projects by encouraging multidisciplinary, high-performance design teams among CannonDesign, contractors, and clients. He is a Consulting-Specifying Engineer 2013 40 Under 40 award winner.