BY STAN LYNCH, director of technical sales support,
Echelon Corporation,
www.echelon.com
Smart lighting is taking hold in a big way. Cities and municipalities, auto dealerships, airports, university and corporate campuses—all are embracing LED outdoor lighting for their energy and cost savings. Adding wireless control networks to their LED lighting further enhances the benefits, and many organizations are finding they can go even further beyond the expected enhancements through technologies such as distributed intelligence, point-to-multipoint communications and zero-cross switching.
These advanced capabilities can lead to lighting systems that have expanded wireless radio frequency (RF) ranges, lower equipment costs by requiring fewer gateways, longer lifespans, easier and less-expensive maintenance, and more reliable operations.
Networks, sensors, LEDs
In the past, lighting control typically meant per-luminaire photocells that would turn lights on when it was dark outside. Such basic control functionality was a step in the right direction, but there’s no doubt it left significant energy savings untapped.
The increased adoption of LED lighting — digital technologies that enable dimming of lights as well as the possibility of sensor integration and sophisticated networked control — means that it’s now possible to deploy outdoor lighting that adapts to changes in the sensed environment; delivers recommended light levels in response to real-world activities in the vicinity; and dims to conserve energy when full light levels are not necessary.
Fig. 1: Lighting controls, such as Echelon's Lumewave TOP900 wireless grid-smart module, bring a new level of savings and control to outdoor lighting.
These advanced control systems incorporate RF communications and metering capabilities into the traditional photocell, enabling individual luminaires to act as part of a larger, programmable network. The result is further optimized energy savings, the ability to meter the energy use of each lighting fixture in the system, and lighting that better serves the needs of all its users.
The control factor
Adding an advanced control system to networked LED lighting increases savings in energy use, maintenance costs, and extended fixture life an estimated 30% to 40% above and beyond a simple upgrade to LED technology.
Such an advanced lighting control system might include:
• An RF network
• Dimmable outdoor LED luminaires connected in groups or zones
• Motion-detector sensors
• Videocameras
• Alarms
• Actuators (e.g., able to open or close a gate or door)
• Photocells
• Graphical user interface for visualizing and controlling networked lights individually or in groups
Lighting control software should be simple and intuitive to use, and it should enable simple set up, scheduling, commissioning and programming of the outdoor lighting system. Ideally, it should also provide revenue-grade metering of energy and fixture health that’s reported regularly, such as daily, as well as performance history. The performance history is useful for predictive maintenance and for tuning the system to optimize efficiency, reliable operations and cost reductions.
Because the LED luminaires are connected to one another through the wireless network, they can be used on roadways or paths to anticipate direction and rate of travel of motor vehicles or pedestrians, brightening the route ahead when and where higher light levels are needed.
More advanced control technologies include:
• In a distributed intelligence system, all the information about what particular LED luminaires are supposed to do resides at each individual luminaire, so they don’t have to communicate with a centralized controller for every action. As a result, the control system minimizes the volume of communication being broadcast, and a single control system can talk to a greater number of luminaires than in a system where the intelligence is centralized. The advantage is greater efficiency and the need for far fewer gateways—which significantly reduces system costs while boosting reliability.
• In point-to-multipoint communication, control messages are broadcast to a group or zone of luminaires. All the other groups or zones included in the network can ‘hear’ the message, but only the ones addressed to respond will take action. This approach is more efficient than having to address each instruction to only the intended recipients each time.
• Whenever lighting is switched on, there’s a huge inrush of power, which can cause lighting relay contacts to weld together and stick. Once welded, the lights are unable to turn off again, and stay on until the relays or controls are replaced. In zero-cross switching, a circuit in the control system times the opening and closing of the relay to avoid inrush and arcing, eliminating the problem. As a result, zero-cross switching extends the life of the relays and prevents the need to deal with relays that have been welded shut by a power inrush.
A real-world example
Many cities and municipalities worldwide are making the move to LED outdoor lighting for reasons of energy savings and greater sustainability.
A New England city of more than 100,000 people recently replaced all of its nearly 5,000 streetlights with new LED luminaires. As a result, the city has slashed its outdoor lighting energy consumption to about one-fourth of the previous system’s levels—saving an estimated $350,000 to $500,000 a year in electricity costs.
Fig. 2: Parking lots, public arenas, large campuses, and auto dealerships are rapidly adopting new outdoor lighting systems, not only to be better neighbors but to gain more control over energy consumption, aesthetics and safety.
Additionally, the LED lights’ more uniform lighting improves the quality of outdoor light throughout the city, which not only enhances aesthetics—making historic buildings look better at night, for instance—but also makes it safer for pedestrians and vehicles to make their way through city streets.
In conjunction with the LED lighting upgrade, the city also installed a wireless lighting control system that enables adaptive lighting—changing lighting levels in response to what’s actually needed at any given time—which includes dimming of streetlights. Streetlights can be dimmed according to time of night; amount of daylight, using the photocell function; or actual usage, based on motion detectors installed in the LED luminaires.
Soon after installing its new LED lighting and control system, the City discovered an unexpected and quite welcome benefit of its decision. Some residents complained that the new lights were too bright—a common complaint with LED lighting—and were interfering with their sleep. The City simply used its lighting control system to set the lights so their maximum output was 70% of full brightness.
Problem solved. Residents were satisfied with the reduced light levels, the City was able to practice responsive governance, and the city found it could save even more in energy costs than originally projected. That’s a lot of good to come from a new LED-plus-controls outdoor lighting system.
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