Lighting controls have always been an essential component of a lighting system, as they enable basic functionality: turning lights on and off, and dimming. But today, these functions are being automated in order to reduce energy consumption—a trend driven by sustainable design and commercial-building energy codes, which have made automatic controls a staple in new construction. According to a new study—"A Meta-Analysis of Energy Savings from Lighting Controls in Commercial Buildings," prepared by Lawrence Berkeley National Laboratory (LBNL) in Sept. 2011, in which 88 papers and case studies were analyzed—popular lighting control strategies yield an average of 24 to 38 percent lighting-energy savings in commercial buildings.
As lighting designers, clients, and building owners require greater functionality for lighting controls, more sophisticated lighting-control solutions are being specified. Traditionally, these lighting controls were built as systems separate from the luminaire. But a growing number of luminaire manufacturers are beginning to integrate lighting controls as product components, enhancing visual aesthetics while simplifying design and installation.
Lighting controls are input–output devices. The input can be manual, such as changing the slider on a dimmer (intended to support a visual change, but with energy savings as a byproduct). Or the input can be automatic, such as with an occupancy sensor (intended to manage energy use). The output is the power that the controller allows through to the lighting load, using either switching or dimming, depending on how much flexibility is desired. If the controller is intelligent, it can make decisions based on a programmed optimal output.
Specific lighting-control options include the aforementioned occupancy controls, which reduce lighting based on occupancy (indoors) or motion (outdoors), and daylight-based controls, which reduce lighting based on daylight availability. In both, input is automatic and output may be switched, step-switched, step-dimmed, or continuous-dimmed.
Additionally, personal tuning provides individual-user control of light levels to support visual needs; the input is manual and the output may be the same as for automatic controls. And institutional tuning serves groups using ballast-factor reduction, high-end trim, and manual group controls.
Over the past 10 years, energy codes have encouraged the growth of these options by requiring space controls and automatic shutoff; the LEED system has also helped by promoting daylight harvesting. In addition, the decentralization of commercial-building controller function and system intelligence has encouraged the use of luminaire-integrated control systems for code-compliant lighting designs.
There are a number of different approaches to configuring a lighting control system. One option, a simple occupancy-sensing or daylight-harvesting system, includes a sensor element and a controller that controls power to the lighting load, which may include a fixed-output or dimmable ballast. A digital dimmable ballast also could serve as the controller.
Lighting-control outputs are highly compatible with solid-state lighting. LED luminaires are instant-on, and frequent switching does not decrease diode life, making them suitable for use with occupancy sensors. Dimming not only saves energy in a linear relationship between light output and power across most of the dimming range, but it can also extend the lives of these products.
Any of these elements may be specified as part of a luminaire. Integrating the sensor into the luminaire can achieve several benefits:
- Aesthetics can be improved, as the sensor is removed from the ceiling plane.
- When suspended luminaires are used, the sensor gains an unobstructed view of its coverage area, and is closer to the task, resulting in greater alignment between the light level falling on the sensor and that falling on the task.
- Control design and installation are simplified, as the sensor and controller are pre-installed in the luminaire, with no additional low-voltage wiring required.
A growing number of lighting manufacturers are offering integrated control options for their general lighting products, but they're taking different approaches. In general, they are either offering a product that contains an individual sensor supplied by a control manufacturer, or partnering with that control manufacturer for a broader solution.
Finelite, for example, offers luminaires with either an integral switching or continuous-dimming light sensor from WattStopper; a continuous-dimming light sensor from Philips; or a continuous-dimming light sensor from Lutron, which is compatible with EcoSystem ballasts and controls. This means that when you specify fixtures with integral control options, you need to familiarize yourself with the control manufacturer and its products—because, essentially, in cases such as that one, there are two manufacturers being specified.