By Matthias Kassner, Product Marketing Director, EnOcean
LED lighting is revolutionising the lighting industry and creating completely new market conditions. However, unlocking its full potential has been hampered by a lack of simple and easy to install industry standard solutions enabling personal control, energy conservation and compliance with increasingly stringent building standards. To fulfil all of these requirements, LED control based on standardised wireless technology is the way forward.
With LEDs replacing old lighting technologies, new control capabilities enable building owners to achieve higher energy efficiency rates and increased comfort. Fulfilling this potential requires selecting a suitable control solution. As the lighting market is still evolving, different standards and architectures exist for lighting control to cover the comprehensive requirements of changing colours, dimming, occupancy-based on/off, demand response or sophisticated daylight harvesting.
Regulations, such as the EU Directive for the Energy Performance of Buildings, became a vital part of building regulations in a drive for greener buildings. It aims to make energy use in buildings transparent by issuing Energy Performance Certificates (EPC) as well as identifying and developing new opportunities for a reduced carbon footprint. Besides this, green building certification programmes such as LEED or BREEAM call for integrated control of building areas for the achievement of the maximum number of points.
The limits of wires
One option for installing LED lighting control is a wired system. This is mainly suitable for simple use cases where all lights are connected to the same bus and set to the same light intensity. But wiring complexity grows significantly once the system is required to control a set of lights together. Furthermore, an upgrade from a simple scenario to an advanced control system cannot be implemented without costly changes to the existing wiring and the controller. In addition, it is almost impossible to include sensors, for occupancy detection or daylight harvesting for example. For retrofit projects in particular, the installation of wired controls can be complex, costly and time-consuming.
An alternative to a wired system is wireless control. It has increased in popularity in the last decade due to advances in radio technology and the emergence of standards which enable seamless communication between different devices. The key advantages of wireless control are the ease of upgrading existing buildings and expanding a system at any time. No new control wiring is required for existing lights; they simply have to be upgraded with wireless control units.
Several standards already exist for wireless communication in a building automation system. The energy harvesting wireless or so-called EnOcean standard is one of the most established. It is defined by the EnOcean Alliance, a consortium of international companies of the building automation industry. The wireless communication uses the 868 MHz frequency, which delivers a distance of up to 30 metres in buildings and has no interference impacts from local Wi-Fi or Bluetooth devices. RF reliability is assured as wireless signals are less than one millisecond in duration and are transmitted multiple times for redundancy. These characteristics make the standard well suited for wireless lighting control in larger buildings with a few hundred wireless sensor nodes up to several thousands.
Elimination of batteries
The standard is optimised for ultra-low power communication, which allows the use of battery-less sensors and switches. For lighting control purposes, the two main energy sources for battery-less, wireless devices are motion and light. Self-powered switches use kinetic energy to generate a wireless signal for controlling and dimming. The second energy source is provided by miniaturised solar cells which harvest ambient light and convert it to electrical energy. This approach is particularly suitable for light level or occupancy sensors. Based on standardised application profiles, energy harvesting wireless devices from different vendors can seamlessly communicate with each other.
The energy harvesting wireless standard enables a complete wireless LED control system for retrofit projects. Solutions based on this standard include LED controllers, solar-powered occupancy and light level sensors, kinetic-powered light switches and a remote commissioning software tool. The controller wirelessly communicates using the energy harvesting radio standard at 868 MHz. Via this protocol, it receives wireless telegrams from all linked self-powered wireless switches and sensors and adjusts its outputs accordingly. It provides a switched output for the supply of connected loads as well as a control output to dim connected loads. Multiple fixtures can be daisy-chained, e.g. 20 each 30W fixtures or 10 each 60W fixtures.
The wireless controller supports several usage scenarios. In a very simple configuration only wireless light switches will be connected for manual control of the lights. If desired, it is possible to configure an auto-off timer which turns the lights off after a certain amount of time. Another basic installation can be implemented by connecting occupancy sensors, which sense motion in a room and send wireless signals to the controller, which controls LED lighting according to occupancy. Both the standard on/off configuration as well as switching between two dimming levels is possible. The latter case is important in applications where a minimum light level must always be maintained. Instead of an on/off configuration, the occupancy sensors’ signals can also be used to set different dimming levels in the range between 100% and 0%.
The combination of occupancy sensors and rocker switches enables the user to manually turn on the light, whereas the occupancy sensors automatically switch off the light after a pre-configured period of time when the room is unoccupied. Light can be automatically turned back on if occupancy is detected.
The addition of a light level sensor allows the implementation of daylight harvesting based on open loop control. This means that the light sensor, positioned facing a skylight or window, measures the amount of available natural light and regulates the output light level accordingly. The lighting controller will then only add as much artificial light as needed.
Configuration over the air
More advanced settings, such as thresholds, dimming levels, ramp speeds, or timers can be changed wirelessly via a remote commissioning interface. By employing a Windows-based laptop computer equipped with a remote commissioning tool, an installer can locate wireless devices throughout the facility, logically connect the controller to switches and sensors, and configure settings in the controller over the air, all completely without physical access. It is also possible to link the LED controller via a central unit or a gateway to a supervisory building automation system like BACnet or KNX.
Low installation effort
Thanks to wireless technology, all of these scenarios can be set up quite easily at low installation costs and only require a minimum of maintenance. Therefore, building operators can fulfil regulatory requirements and achieve immediate energy savings and increased comfort with low investments and a fast return on investment (ROI). The wireless sensors and switches can be flexibly and optimally positioned without requiring repair to walls or ceilings. Due to the self-powered operation they even eliminate the need for changing batteries.
Wireless standards offer valuable benefits to LED control by following an integrated approach consisting of accessories, software and easy-to-use commissioning tools. At the same time, they combine control functionalities and networking abilities with a consequently standardised communication. The wireless technology allows users to easily install, retrofit, move and commission LED lighting control even in complex systems achieving large scale economies.