Lighting accounts for about 25% of a building's electricity usage, which is why facility managers are trading in their old fluorescent fixtures for more efficient and longer lasting LEDs. While the cost of a lighting retrofit may take a few years to recoup, for new construction projects it's a clear decision to go with LEDs right off the bat. And with Power over Ethernet (PoE) gaining traction, it's easier than ever to integrate a building's energy management, lighting, and Internet into one set of cables. Cisco recently unveiled its Digital Ceiling, a backbone and communication protocol for PoE devices, and LED manufacturer Cree just jumped on board with SmartCast PoE, a new line of lighting fixtures and accessories designed to work with the Digital Ceiling. Let's see what they have to offer.

Lights

Cree is updating several models of its SmartCast lights, including both troffer and recessed downlight fixtures, all of which are dimmable and available in multiple color temperatures. The troffers include adjustable color temperatures - anywhere from 3000K (warm white) to 5000K (cool/daylight) in 100K increments - while the downlights come in a variety of fixed color temperatures. Varying color temperatures can adjust the lighting to match the body's natural circadian rhythms, which promotes alertness and productivity. With a minimum efficacy of 100 lumens per watt and a color rendering index (CRI) of 90, these LEDs provide highly efficient, quality lighting, as well as built-in intelligence.

Sensors and Controls

Each fixture includes a passive infrared motion sensor to detect room occupancy and an ambient light sensor to automatically adjust the brightness based on the natural light in the room. Sensor information is fed to the building automation system (BAS).

In addition to the manual wall switches and dimmers, the lights are designed to be integrated into the BAS. The SmartCast application programming interface provides information that allows the BAS to adjust lighting levels and color temperatures, HVAC, and security systems based on the time of the day, sensor information, and customized programs. Third party developers can write apps to control a variety of IoT devices on the network. The entire system is designed to integrate seamlessly into the Cisco Digital Ceiling. A dashboard allows the facility manager to monitor and adjust the system.

Upon initial setup, SmartCast uses a set of default strategies based on room occupancy and ambient lighting. From there, a building manager can tune the system according to specific needs. For example, a large laboratory may be occupied by one technician working at a lab bench. The system could detect the room status and dim most of the lights while maintaining bright task lighting over the technician's desk. In a meeting room, the lights can automatically dim when the projector turns on.

PoE

Power over Ethernet (PoE) allows low-voltage devices to be powered directly from the Ethernet cables, saving the expense of additional wiring. But the benefits don't stop after the installation; since LEDs are inherently DC-powered devices, PoE eliminates the need for an AC-to-DC converter on each light fixture. That circuit tends to be responsible for early failures of LED lamps, so PoE increases system reliability. The AC-DC converter is also a source of inefficiency since it takes power to drive the circuit.

On the other hand, low-voltage/high-current (PoE) traveling over long distances is less efficient than high-voltage/low-current (AC) over the same distance, due to the wire resistance power loss. Is it more efficient to run the lights on AC to reduce power loss over the lines or to run them on DC to reduce power loss in the AC-DC driver? I was about to do some calculations, but I found this article in LEDs Magazine that did the math for me. Follow the link if you want the details, but it turns out to be pretty much even - both methods are about 80-84% efficient, depending on wire length and the power used by each fixture.

Energy Savings

According to Cree, a lighting system based on SmartCast PoE could use 70% less electricity than standard LED lighting. Cree provides a downloadable savings worksheet to help facility managers perform their own financial analysis. As the saying goes, your mileage may vary.  

The Cree SmartCast PoE product line will be commercially available in the second quarter of 2016.

Images courtesy of Cree, Inc.

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