Power Over Ethernet: A Smart Power Option for Smart Buildings

July 1, 2016 By Carl Weinschenk

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Image: Pixabay

Power over Ethernet (PoE) is an increasingly important tool for low-powered devices – those related to the Internet of Things (IoT) and others – as they push into every nook and cranny of a facility.

The idea is simple: Ethernet cables’ primary responsibility is telecommunications. However, they also are capable of carrying enough electricity to support less power-hungry devices. This opens up a world of possibilities for energy managers and facility managers because it allows IoT and other devices — including lighting — to be placed without worrying about their proximity to electric wiring. In essence, it doubles the chances of easily powering a device.

It seems like PoE’s capabilities are growing. LEDs Magazine last month posted a story about the use of PoE by Ricoh-subidiary mindSHIFT Technologies, a data center in the Long Island, NY, town of Commack. The 40,000 square-foot facility is using the approach to power 452 Cree LEDs that are being installed in partnership with Cisco. Conventionally powered LEDs already claim lower cost as an advantage over legacy lighting; the Cree/Cisco PoE-based installation at mindShift, the story says, will use use 70 percent less energy than it would have if powered conventionally.

It is a flexible approach. In May, Warren Miller offered details at DigiKey. He said that PoE is appropriate for “remote sensors, aggregators, wireless gateways, security cameras, and controllers within a smart connected building.” Indeed, it seems to be all upside, according to the story:

No additional wires need to be “pulled” to power these systems and the 13 W to 25 W available power is sufficient for most smart building remote devices. A PoE system is also lower cost because no additional wall adapter is required. A side benefit of this approach is that PoE-based devices can be easily powered on or off remotely, which supports smart-power management systems. Note that because the PoE system is separate from the main power system, it can be more easily utilized in power outage situations when a backup power source is provided to power the PoE sections of a smart building. This can be particularly helpful in emergency situations.

Nothing is without complexity and even risk, however. Lux, a U.K.-based organization that calls itself “an independent guide to lighting,” offered several things to keep in mind when considering a move to PoE lighting. An important point in the piece is the need to recognize that a PoE-driven device becomes “another part of the computer network.”

Thus, it is important to make sure that the computer network is up to the task. If the lights go down, they will have to be rebooted — just like a PC. Another issue of which to be aware is that a telecommunication network’s main purpose is communications. That’s a tautology, but one with a point: Electricity is the junior partner in the relationship. The priority will be on keeping  interference (“noise”) caused by the flowing electricity from limiting or disrupting the data flow, not keeping the LEDs or surveillance camera operating at the expense of the communications capabilities.

Power over Ethernet is not new. Indeed, it is regulated under standards that go all the way back to 2003 (IEEE 802.af-2003). It is gaining in importance, however, as the electrical needs of buildings grow denser. Indeed, PoE is a good fit. The per-sensor or per-controller power needs of IoT devices are not great and can readily be handled by well-designed PoE installations. Proponents say that it is a great option, since many of the devices are not near the electrical wiring. In addition – as the mindShift story indicates — the reduced power needs of LEDs makes PoE a viable power source.  The bottom line is that PoE is a valuable tool in planners’ tool chests.

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