PoE Lighting, The Foundation for Smart Buildings
What is PoE Lighting? Well, PoE refers to Power over Ethernet, which is a widely used technology that most of us are accustomed to. Typically, the applications that use power over ethernet are VOIP phones, IP cameras, and wireless access points. The general definition of power over ethernet lighting is lighting systems that are “smart”. While that sounds cool, saying that my lights have the potential to be smart doesn’t really explain anything. A “smart building” is a simple way of saying that the building applications are all connected through an IOT software (Internet of Things), and PoE is a type of hardware that fits into an IOT infrastructure. What does this mean and how does this make buildings “smart”? Well, let’s jump down the rabbit hole of PoE Lighting and learn about it.
AC vs DC
To begin, a brief history of AC/DC is necessary. AC stands for alternating current, while DC stands for direct current. DC was the type of power that was used by Edison. It is current that runs in one direction, the way power moves in a battery, and doesn’t convert easily into higher or lower voltages. AC, on the other hand, was used by Tesla and reverses in direction multiple times per second and is easily converted to higher or lower voltages.
During the late 1800s, a rivalry between Tesla and Edison took place. Edison had acquired a patent on DC power and began to discredit the AC technology that Tesla was working on as too dangerous to use. He most likely knew that AC was a more efficient way to transport energy but was stuck with his DC patent. In 1893, the Chicago World’s Fair sent out a bid to determine who would get to power the fair. The power company General Electric, using Edison’s DC, bid that they could power the fair for $554,000. George Westinghouse, using Tesla’s AC, bid that he could do it for $399,000 and ultimately got the contract. The attention from the fair led to Westinghouse, who had licensed Tesla’s AC patent, creating a contract with the Niagara Falls Power Company to generate power for the city of Buffalo in 1896.
What follows is the use of alternating current to power household appliances like refrigerators, ovens, and dishwashers. Though DC is more stable and is generally safer to transport over long distances, typically our power grids operate in AC. Even though it may seem like AC has the upper hand, much of our new technology uses DC power: electric vehicles, computers, and LED lights to name a few. But since power grids handle energy in AC form, converters are needed to transform the AC from the grid into usable DC that powers our machines. Because of this need of conversion, DC tends to require more infrastructure within a building. Most rectifiers/converters are 90-95% efficient, but that means there is a loss of power during the conversion process.
To transport this energy, we have electrical grids that are made up of power lines that can be high or low voltage lines depending on location and intended use. The same is true for power distribution in buildings but at a much smaller scale (I like to think of this a micro electrical grid). Common methods of distributing power in a building are raceway and conductors, busways, or cable assemblies. However, in the past decade a new method has emerged using ethernet cables and has been coined Power over Ethernet or PoE.
Ethernet came about when Robert Metcalfe was asked to create a local network that would allow a personal workstation to connect with the first laser printer. The solution needed to be able to connect hundreds of computers and run fast enough to keep up with the printer. Metcalfe ended up using a coaxial cable and termed it the ethernet cable for its lightning-fast transmission. It was coined after the archaic physics term “luminiferous ether” which described the medium light traveled through.
In the beginning, ethernet was used within closed local network as a way to carry packets of information from computer to computer at 3 megabits per second. This one of several examples of early information technology devices and connecting them via a network by which using packets of data lead to the standardization of information technology languages. After many iterations, wire types, and a patent, ethernet became popular commercially and eventually the standard for data transfer. In 2000, ethernet advanced even more when Cisco developed a version of ethernet that was able to deliver not only data, but power, to phone handsets. It mimicked the way a traditional landline operated and could support 48 volts of DC power, thus allowing one line for a broader range of devices and including a mechanism that protected devices that were not supported by PoE. Overall, PoE had the superior ability to transfer power, the bonus of improved safety, and reduced the number of cables needed which cuts down on installation cost. As the commercial markets and industry came to depend on networks of ITDs to efficiently run their operations security concerns began to rise. PoE offered the market a method to power devices and deliver data, thereby, allowing for the option to create a closed network for increased security. Developments to increase the amount of power that could be carried using PoE facilitated the transition of building security infrastructure, such as, cameras and door locks, to utilize PoE. Today, ethernet cables can carry 100 megabits of data per second and can support up to 90 watts.
You may be asking, “How does PoE actually work?” Basically, a piece of equipment called power sourcing equipment (PSE) supplies DC voltage over ethernet cables to another connected device that’s called a powered device (PD). This connection allows for devices to be powered without a local power source or a separate cable for power.
Lighting and PoE
Now we ask the question: what if a light fixture could be treated like an information technology device? With the ability to deliver power and information over the same wire, would it be possible to connect and power a light fixture through a network? Before we answer that question, let’s review how we have traditionally powered lights and where they are today.
Contrary to popular belief, Thomas Edison did not invent the first light bulb. In fact, many scientists were experimenting with electric light over 70 years before Edison joined the stage. In 1802 Humphry Davy created light while experimenting with carbon and an electric battery. Now, this was not anything like the modern bulb and didn’t produce light for very long. Other inventors dabbled in glowing wires over the next few decades, but the next step in lighting technology was in 1840 when Warren de la Rue used a vacuum tube to pass electric current through a platinum wire. While this lasted longer than any previous glowing wire and was effective, the platinum was expensive, and his design couldn’t be mass produced.
Then, in the 1870s a working light bulb as we recognize it was developed by Joseph Swan, a physicist. This model used carbonized paper filaments and an evacuated bulb but had issues with the vacuum seal and had a short lifetime. In 1874, Henry Woodward and Matthew Evans patented a model that used a similar design as Swan. Woodward and Evans’ model had nitrogen filled glass cylinders and different sizes of carbon rods between the electrodes. The two tried to commercialize their patent but failed, which brings us to the illustrious Edison. The Woodward and Evans patent was then sold to Edison in 1879. And this is where our aforementioned discussion of AC versus DC and Edison versus Tesla comes into play. Since the battle of currents, we have developed a few types of light bulbs including fluorescent, incandescent, mercury vapor, HID, neon, and most recently LED.
LEDs are unique in that they are not technically light bulbs as we know from history. They are actually semiconductors that emit visible light. LEDs, or a light emitting diode, is a diode that contains an anode that passes electricity to a cathode, this transfer of current produces visible light. LEDs behave more like a battery than a traditional light bulb. When considering the voltage of light bulbs, a typical light bulb requires about 110 volts to operate. Some fluorescent bulbs are made to be low voltage, only requiring 12-24 volts. LEDs on the other hand, only take between 1.8 and 3.3 volts, depending on the color and type. Since PoE typically refers to power transfer in watts, let’s convert bulb voltage to wattage: normal bulbs are anywhere from 40-100 watts, low voltage fluorescent bulbs are about 15 watts, and LEDs are typically only 2-10 watts.
Since they require an extremely low voltage and wattage, LEDs are an ideal candidate for use in a PoE system, allowing then to be classified as an information technology device for its applications. We have already established that PoE can support up to 90W of power, meaning that PoE would be able to power a system of LEDs. We have already touched on how AC and DC differ, and which type of electronics use which type of power. For normal lighting situations, multiple wires, transformers, and hardware are needed to convert power from the grid to power that is used in lighting. When installing or modifying lighting, an electrician is needed because of the intensity of the wiring. This makes it expensive and time consuming to change lighting design.
PoE infrastructure moves the power conversion and control system upstream to a single unit which makes it safer to change or redesign without an electrician. This also means that each lighting fixture would generate less heat, since no conversion is taking place at the fixture itself, which would allow for a heat sink with a smaller volume. In addition, new materials would be able to be tested as a heat sink which may have not been suitable for lighting before. Lastly, PoE infrastructure uses less wiring which results in a cheaper installation, but also has the potential to make installation easier for electricians which further reduces the cost of installation. The manufacturing of LEDs has the potential to be more efficient and cost effective, since less materials are needed for PoE lighting. New features could also be added if LEDs used PoE.
The Future of Lighting Controls
One important hardware component of PoE lighting is LLLC, or Luminaire-Level Lighting Controls. An LLLC is the ability to have embedded sensors during manufacturing, such as, occupancy and ambient light sensors, incorporated into each light fixture. The sensors allow for flexible lighting controls that respond to changing conditions under each fixture. Depending on how many people are inside a room or how much daylight enters the building, the lighting levels will conform accordingly. Pairing with the LLLC allows us to extend the network hardware as well as connect that hardware to our network software for management. More commonly, networks are connected wirelessly using a hub or gateway which allow the input of data from users to be transmitted to the hardware for the desired output or the lighting system responding to users’ commands. Having lighting systems connected with PoE and wireless gateways allows for the utilization of the security and dependability of a closed network while simultaneously giving users the potential to expand or contract our network.
Ultimately, if a building’s lighting system is connected to PoE, the lights are deployed in a grid (or microgrid), for commercial applications, throughout the building and each fixture becomes capable of sending and receiving data. This is beneficial since lights are unique in that they are in every building regardless of its age, use, or location. Using commercial lighting as a grid for a central network for buildings would allow for a PoE system that could act as a data highway or backbone for network infrastructure for all the control systems in the building. If this backbone were put in place, it would create a network throughout the entire building, which would mean that other control systems could utilize or be controlled with it. This is what would be called a “smart” environment monitoring system which is where the term “smart building” comes from.
There are a couple types of systems that are used to monitor a building’s network. The two main categories of systems are passive and active environment monitoring systems. A passive system looks at the performance of the network as a whole and pulls data from the history of network use. An active system analyzes the network in real time and generates data that determines the current performance.
Some notable buildings that currently use PoE lighting are DPR Construction in San Francisco, The Edge in Amsterdam, and the Burj Khalifa in Dubai. DPR Construction is the first certified Net Zero Building in San Francisco and includes PoE lighting as one of its green features. The Edge has been called the most intelligent building in the world and is ranked one of the greenest buildings as well. Almost all systems in the building are connected to the grid and it utilizes ethernet as much as possible. The LED lighting systems in this building are one of the highlights that allow it to use as little energy as possible and in the most efficient way. And finally, the Burj Khalifa’s entire façade is lined with LED lights that are programed and controlled by PoE systems. This building uses ethernet in a way that not only shows off current lighting technology to the people inside the building, but to the entire city as well.
As we have seen, power over ethernet lighting is utilized in high performing and efficient buildings. But where will we see this technology used first in the US? Most likely we will see it in street grids and traffic lights. The grid networking and lighting used along streets is well suited for a transition to PoE. Some other suitable situations would be school campuses, warehouses, box retails centers, grocery stores, commercial offices, or manufacturing plants. These building types would save lots of energy and would be easily programmable since they all operate on rigid time schedules. Introducing a cohesive PoE lighting system would also provide a network that would act as a backbone for any future system updates. Power over ethernet lighting could be used as an introduction for buildings to transition to a more efficient and effective way to use energy.
Isabelle is currently pursuing a master's degree in Architecture at University of Idaho Boise campus and is set to graduate in the Fall of 2025. Afterwards, she plans to continue living in her home town to pursue high performance building design and conservation. Isabelle has developed a love for the built environment and how it interacts with nature and hopes to learn more about urban design and building science in her studies. When she is not in class or the office, she enjoys reading, traveling, and talking with plants.