Savvy? Choose Power over Ethernet for Lighting

Savvy? Choose Power over Ethernet for Lighting

This piece was originally published in the February 2018 issue of electroindustry.

Robert Hick, Vice President, R&D Engineering, Leviton Lighting & Energy Solutions

Power over Ethernet (PoE) provides both power and data to devices such as Voice over IP (VoIP) telephones. Light-emitting diode (LED) luminaires are another device that may benefit by connection to a PoE network.

Recent advances have reduced the power needed to operate LED luminaires to the point where network data switches that are compliant with PoE standards (such as IEEE 802.3at) can also supply the power needed to operate them. Ethernet communications also direct the luminaires to dim, brighten, and report status such as lamp failure, sensor information, and energy consumption.

The widespread acceptance of lighting fixtures based on high-efficacy LED light sources, along with advancements in networked lighting controls, has changed the landscape of the entire lighting industry. The demand for connected lighting solutions continues to increase, as it becomes an essential requirement for high performance buildings.

Unlike many other past light sources, LEDs use direct current (DC) to produce light. Using DC can be much more efficient than the customary practice of using an alternating current line voltage converted to DC for LED power. A power system that provides DC at a voltage close to the low voltage (30-60 VDC) that most commercial LED light sources use, therefore, can also provide higher efficiency.

Ethernet uses twisted pair low-voltage communications cable (also known as category cable), which has been a core infrastructure for commercial buildings for many years. It connects computers, phones, printers, and other equipment to business information servers and the internet. It is more reliable and carries data faster than most common wireless technologies.

In 2003, a method for sending DC power over this same cable (i.e., PoE) was born. Initially, only about 15 watts of power was available. It was enough to power digital telephones, leading to the surge of VoIP phones that most businesses use today. The DC power capability was increased to 30 watts in 2009 and recent breakthroughs increased it to 60 watts. A new standard, IEEE 802.3bt, should boost capability to more than 90 watts of DC power in 2018.

Since LED power requirements are decreasing while PoE power capabilities are increasing, PoE has become a viable alternative for powering modern luminaires. Furthermore, energy efficiency is maximized by following the new ANSI C137.3 Minimum Requirements for Installation of Energy Efficient PoE Lighting Systems. Without the need for line voltage, a single low-voltage category cable can connect to one or more luminaires to provide both power and robust data for lighting, sensing, and control while facilitating additional advanced benefits such as light communications (Li-Fi), positioning, and other digital technologies.

There are three architecture types for PoE lighting products that use a category cable for power and data use:

  • integrated into the luminaire, where the PoE electronics are part of the luminaire design;
  • independent PoE LED drivers that can daisy chain with category cable to other drivers and work with a variety of luminaires; and
  • remote drivers that provide direct LED drive current for several luminaires from one device.

Building owners should consider the advantages of this infrastructure for their high performance buildings, and savvy installers should consider seizing the opportunity to expand their business potential.

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