The energy and life-cycle benefits of LED lighting have been well documented but less attention has been paid to the opportunity they offer for utilising Power over Ethernet. Andrew Pease of Mackwell discusses these additional benefits
Readers of Electrical Review will be very familiar with the significant energy savings that LED light sources can deliver, compared to more traditional incandescent and discharge lighting. The potential life-cycle cost savings resulting from longer lamp life and reduced maintenance requirements are also well understood and play a key role in return on investment calculations.
In addition to these benefits, the ongoing development and improvement of LED lighting technology now also makes it possible to make use of Power over Ethernet (PoE). At the risk of stating the obvious, this is where electrical power is carried over the network cables rather than there being a separate power supply to a particular piece of equipment.
In the case of lighting, this opportunity to make use of PoE arises because an LED lighting installation is effectively a low voltage, low power environment – compared to traditional lighting.
Whereas traditional light sources such as fluorescent and high intensity discharge (HID) light sources required hundreds of volts and a significant power supply, LED light sources, by their nature need far fewer volts to drive them. For instance, a single LED may only require a voltage of 3V, so an array that uses 10 LEDs will only require 30V.
As a result of this greatly reduced voltage requirement, the Ethernet cables that are already present in the majority of commercial and industrial buildings can also be used to carry the power supply to the luminaires, as well as carrying the data that is required for monitoring and control. Clearly this then obviates the need for separate power cabling to the luminaires.
This is the case even in situations where the majority of networking is carried out over a Wi-Fi network, as is now the case in many commercial environments, rather than hard-wired ethernet connections to devices. Despite the heavy reliance on Wi-Fi there will still be ethernet cables present to connect Wi-Fi repeaters throughout the various spaces.
From an installation perspective, the use of low voltage Ethernet cable means that the cabling work can be done more efficiently. There is no need to terminate individual wires and the strain relief is integrated into the termination method. However, if this opportunity is to be fully exploited it is essential to ensure that all of the lighting – including the emergency lighting – is using a low voltage supply. If the emergency lighting still requires line voltage in the ceiling/luminaires then costly isolation, as well as additional terminations, are required.
It is immediately apparent that using PoE in this way offers significant savings in material costs and installation time as less cable is used and connections can be made for more quickly. There will also be additional benefits in terms of the reduced maintenance requirements for the cabling infrastructure.
In addition, by using ethernet cabling, rather than the more traditional twisted pair control cable, larger volumes of data can be transported more quickly between the points on the network.
Aesthetic benefits
Use of PoE can also deliver aesthetic benefits and greater design flexibility as there are fewer constraints on the design of the LED luminaires that are used. In a traditional situation where the luminaire has a separate line voltage power supply there will also need to be an LED driver installed within the luminaire. Clearly this occupies space and therefore the design of the luminaire needs to accommodate that.
When PoE is used, LED drivers are still required but these can be installed in a central location away from the luminaires themselves or even built into the LED PCB, with just a low voltage supply to the LED engines in the luminaires. This removes one of the constraints on the luminaire design and potentially enables luminaire manufacturers to be more innovative with their products.
Smart lighting
Over and above the potential cost savings, the PoE approach creates an opportunity to exploit what is becoming known as ‘smart lighting’. This refers to a scenario where the lighting infrastructure is used to perform a wider range of functions than simply lighting the spaces.
For instance, the majority of modern lighting systems will make use of occupancy sensors (presence or absence) to switch the lighting on or off, or dim it, in response to people entering or leaving a space. This clearly plays a valuable role in preventing wastage and reducing energy consumption but this data can also be used to provide key metrics for the facilities manager.
A good example of this is space utilisation, where facilities managers devote considerable time and effort to gain an understanding of how space is being used within their portfolio. Traditionally this has involved people walking around the building trying to evaluate how workstations and meeting rooms are being used. Apart from being highly resource-intensive, this procedure is very prone to errors because the modern workplace is dynamic and continually changing.
In making use of occupancy sensors that are already present in the lighting system, and therefore monitoring movements of people through different spaces, this whole procedure can be greatly streamlined while also providing more accurate and meaningful data.
The same principle could also be applied to monitoring footfall through different areas of a retail space at different times of day, helping retailers to understand the flow of customers more accurately and configure their merchandising accordingly.
In terms of meeting rooms, this principle can be taken a step further. As well as providing data about the usage of such spaces the lighting network can also interface to a room booking system. So as well as controlling lighting as people enter the room it can also be configured to flag-up non-attendance if not activated within a given period after the time meeting starts, so that the room can then be made available on the system for other users.
Li-Fi rather than Wi-Fi
A somewhat more futuristic vision for PoE and smart lighting is the concept of ‘Li-Fi’. The thinking behind this is that LEDs can be modulated on and off at a frequency that is undetectable by the human eye but could be used to transmit data – essentially it works in a similar way to Wi-Fi but using light instead of radio frequencies.
Project management
For designers and specifiers of such systems the potential use of PoE clearly has implications in terms of the management of projects. Particularly important is the potential involvement of the client organisation’s IT department – something that is inevitable given the level of integration required between the lighting and the rest of the building’s network.
For this engagement to be fully productive it is essential that the electrical designer, potentially with the support of a lighting control company, is sufficiently knowledgeable about IT infrastructure to ensure a meaningful discussion.
On this subject it is also important to bear in mind that people previously engaged in Ethernet network design and installation are unlikely to have the required knowledge to design a lighting system, calculate lighting levels and ensure compliance with appropriate legislation. It therefore makes sense to work with supply chain partners that are well grounded in lighting technology and its application, as well as having wider knowledge of more general IT infrastructure.
As LEDs become the light source of choice for the majority of commercial (and increasingly industrial) projects we can expect to see considerable growth in the use of PoE. In fact, given the benefits it offers, it would be negligent not take advantage of this technology.
All of which highlights the importance of teamwork in such projects, with the various professionals sharing their specialist knowledge and experience through productive alliances that will ensure the delivery of smart lighting systems and the many benefits they offer.
