The introduction of solid-state lighting (SSL) to environmental lighting applications has been the most disruptive break-through within the lighting segment since the invention of the light bulb. LEDs enable intelligent and flexible illumination while being a lot more energy efficient than conventional light sources (learn more in the article “Artificial Light Can Do A “LoT” More Than You Might Know” here).
Control & Powering Of LED Applications
In order to access new possibilities like human centric or horticultural lighting intelligent control of the applications is required. Within the age of the IoT this means in addition to power modern light fixtures will need to be able to exchange data with the internet. As LEDs consume less energy than other lighting solutions power over ethernet (PoE) can be a feasible alternative to conventional power lines in order to connect lighting applications to the internet as well as to distribute the required electricity.
Current PoE Standards & Basics
Let’s take a look at some basics of this technology. PoE has first been standardised in 2003 by the IEEE P802.3af DTE Power via MDI Task Force. The basic standard can be used only in combination with 10BASE-T and 100BASE-TX which use only two of the four available pairs in the network cable for data transmission. The maximum power delivered by the power sourcing equipment (PSE) is 15.4 W. Due to losses the standard considers that at the end of a 100 meter long cable approx. 12.95 W are available to the powered device (PD).
This standard which uses the free cable pairs 4/5 and 7/8 for electricity transmission (“mode B”) is well suited for VoIP phones, print-servers, webcams and WLAN-access-points.
In 2009 PoE received an update with the IEEE 802.3at standard (PoE+). PoE+ enables the use of PoE in conjunction with 1000BASE-T (gigabit Ethernet). In addition the power is increased by nearly a factor two up to 25.5 W. The max. current within 802.3at is 600mA (802.3af allows only 350mA) thus the use of a cat5e or cat6 cable with lower resistance is recommended. The PD receives approx. 21.9 W of power within this standard.
There are two different power modes, A and B, available. The PSE determines which one is used. In mode A power is delivered over the data pairs (phantom technique) of 100BASE-TX or 10BASE-T whereas mode B uses the spare pairs. Within 1000BASE-T there are no free cable pairs, thus the power transmission has to be achieved using the phantom technique. In this case the current is limited to 175mA per pair in the cable; however by using all four pairs for power and data transmission 25.4 W can be achieved.
Regarding PSE there are two different types. Endspan devices are Ethernet switches which include the PoE transmission circuitry. Midspan devices are power injectors which are inserted between Ethernet switch and PD.
It is worth mentioning that the IEEE P802.3bt DTE Power via MDI over 4-Pair Task Force works on further enhancements of PoE (referred to a PoE++ or 4PPoE) which will allow power of up to 100 W.
PoE Adds Great Value To Lighting Applications
With PoE+ and PoE++ (as well as with non-standardised custom solutions) enough power can be delivered to drive LED lighting applications. As mentioned above this enables advanced control of lighting. Instead of only switching lights on or off the colour, intensity, temperature and more can be adjusted. This feature is important in order to realise e.g. human centric and therapeutic lighting solutions. In addition remote control e.g. via smartphone is easy to implement.
Through the addition of sensors to lighting applications new use cases are created. In combination with air quality sensors the lights can function as warning system and change their colour if the measurements reach a critical value.
Another example for sensor enhanced lighting is the recognition of individuals entering a room or building to adjust the lighting automatically.
In addition sensors in light fixtures are able to collect valuable information for energy efficient building management.
In traffic lights and street lighting PoE and sensors can transform light sources into powerful, intelligent nodes (e.g. surveilling traffic, smog levels) and thus lighting applications could play a central role within the realisation of smart cities.
Internet connection via PoE can also be used to distribute data to consumers and IoT devices. In such a model the data can be embedded in lightwaves using sophisticated technologies like Li-Fi (similar to Wi-Fi in which data is transmitted via RF) in order to connect devices in close proximity to the internet.
Costs & Prerequisites
The high costs for the sophisticated light fixtures and LED technology can be justified with the value of the new applications. In addition smart LED lighting helps to significantly reduce the energy expenses especially in larger buildings. As Ethernet cabling eliminates the need for conventional higher-voltage wiring and the connected costs for certified electricians there is additional potential to equalise the costs compared to conventional lighting solutions.
Another cornerstone of the success of PoE powered and sensor-enabled lighting applications is the new expertise required for the development of lighting applications as well as the installation and management of the new devices and infrastructure.
Instead of electricians those solutions require skilled experts within the field of semiconductor/LED technology, IT as well as software/service platforms. It’s predictable that we might see some new players as well as uncommon cooperations in this field in the future.
A good example for the shift in the industry is the pilot project of Cisco usually known for IT products which has equipped a school in the US with new indoor illumination.
To put it in a nutshell PoE in lighting is still in the early stages and there are a lot of challenges to overcome until such systems will work perfectly. However it can be rewarding to adopt the new technology as early as possible in order to upgrade the lighting and power supply infrastructure within buildings to be prepared for future enhancements and new possibilities.
As semiconductor manufacturers offer solutions which support the development and introduction of PoE enabled lighting EBV is able to support projects with hardware and engineering expertise.
Feel free to contact EBV here in order to get full support with your lighting and PoE projects and questions.