Stricter energy efficiency requirements that have been sought for the past several years are cited as absolutely necessary for the bloc to meets its goal of cutting emissions 20 percent from 1990 levels by 2020. Complimentary to these efforts European countries are required to establish a certification system to measure buildings' energy efficiency. These certificates will be required for any new construction or buildings that are sold or rented to new tenants. Existing buildings will also have to, during any major renovation, improve their efficiency if at all feasible.
With these mandates, is there a way to make the light “intelligent” such that, in essence, it becomes similar to the human eye and adjusts according to the many light sources – and people – in a room? There is; and the unique approach is to focus on the light not on the power supply. The coming wave of Cognitive Lighting will demand independent smart sensors that are 'environmentally aware' in order to provide not simply data on the surrounding environment, but answers to how best to respond, both to save energy and enhance lighting quality.
Intelligent Lighting and Daylight
Sustainability mandates and financial incentives have driven many companies to set aside the capital budgets needed to upgrade to more efficient lighting systems. Quite often, the light sources in use, such as T8 fluorescents, are both highly efficient and long-lived, which suggests to many facility operators the need to wait until more efficient light sources, such as LED lighting, mature to the point they show a clear operating advantage before making upgrades. In fact, there are ample incentives to move now, by taking advantage of “daylight harvesting”. Ambient light sensors combining photopic, human-like sensitivity with wide dynamic range are enabling a new generation of lighting controls that may be built directly into replacement lamps and luminaires to shift more of the interior lighting burden onto the available daylight.
In a facility with skylights, windows or sidelights there is available daylight, which varies according to time of day, weather conditions and more. Areas that get light from those sources don't necessarily need much artificial light – at least not during the day – but areas farther from those sources do. In a smaller facility, companies often simply turn out the lights on sunny days. The challenge typically arises in a larger sites with thousands of square meters of space where managing each fixture's light output to compensate for the changing amounts of ambient light during the day is an enormous challenge and is impossible to do manually.
To date, facility managers trying to take advantage of daylight have looked to external daylight harvesting sensors that attach to groups of lights. These after-market offerings can provide incremental energy reductions, but still leave substantial savings on the table and have a number of performance issues that result in over- or under-lit areas and jarring jumps or drops in light levels.
Image 2: Photopic response, mimicking the spectral response of human vision, senses a narrower range of wavelengths than a silicon photodiode.But a sensor built into the luminaire that automatically responds to its environment – whether it's occupancy, available daylight, time of day or other variables – and delivers just the right amount of light when and where it is needed -- is the perfect solution for reducing energy consumption and costs. Rather than applying controls as an afterthought the built-in approach maximizes energy efficiency.
Added intelligence within the sensor systems also greatly enhances the control ability of the facility operator. Remote control systems allow the setting of target light levels without a facility manager needing to get up on a lift and adjust dipswitches on sensors controlling 100+ fixtures. By supplementing the working space with only the amount of light needed to maintain a uniformly lit environment, tremendous energy savings can be realized when compared to existing installations which do not respond to changes in ambient light.
Image 3: Sensor driven lighting adjustments maintain constant illumination (70 foot candles on desks) while reducing output based on available daylight.
Now system-on-chip light sensor solutions provide a complete light sensing subsystem, including conversion of analog readings to a digital I2C output signal. This includes correction for any errors caused by the fixture's own imperceptible flicker, on an integrated circuit as small as 2mm square, and costs about the same, or even less, than a simple photosensitive component alone. Additionally, sophisticated filters automatically reject the 50-60Hz ripple typically produced by a building's fluorescent lighting systems, enabling the sensed light levels to more accurately measure the daylight that is entering the building.
Being fully aware of the lit environment also allows optimization that extends beyond energy savings. In integrated building management and control systems, the combination of proximity/motion and light sensing provides an abundance of data concerning the interior environment. Additionally, daylight sensing/harvesting combined with precise control mechanisms enable the lighting system to deliver not just the needed amount of light, but also offers the ability to tune the type of light to suit the activity and users in a particular space.
Intelligent Lighting and Existing Light Sources
Fluorescent luminaires are already in widespread use so it makes sense to integrate a system that can improve efficiency of these fixtures up to 50 percent through smarter lighting controls that match lighting to the demands of the business and environment. What is critical is a sensor system that connects to today's existing building management structure.
Although modern fluorescent lamps are highly efficient, adding the components to support dimming can be costly, and the nature of the ballast systems does not lend them to the faster on/off cycle times that would be considered ideal for motion sensor or proximity control scenarios. However, through the use of intelligent sensors, the technology senses a rise in ambient illumination and dims the luminaire in response; as the daylight increases, fluorescent light will decrease.
Environmentally aware, decision-directed, multi-sensor networks and optimized light will enhance not only the productivity of the built space, but also worker and group productivity, as well as increasing the health and well-being of individuals.
Autonomous Light Controls
Although previous smart lighting controls were always centralized, today's technology enables lights that think for themselves. With ambient light sensors built into each lighting instrument, you get on-the-spot decision-making regarding how much ambient light is present. With low-cost and low-power wireless networking (such as ZigBee), or wired networks, group intelligence (semi-autonomous controls aware of what each other are doing, and able to self-organize the most efficient lighting plan for each moment) and centralized control systems can be readily implemented.
Image 4: An ALS lighting control system using both wired and wireless communications.
A smart-sensor driven lighting system that is aware of the immediate environment and broader operating concerns, and is able to intelligently adapt to user and facility requirements with autonomous local- or centralized- control is critical to meet government mandates to reduce energy consumption and lessen greenhouse gas emissions. This next wave of Cognitive Lighting systems will finally make use of the abundance of data available in the light and autonomously adjust the built environment to enhance comfort, productivity, safety and efficiency at the same time.
The demand for power around the world continues to increase. It's essential, therefore, to have fixtures that reduce this consumption. Currently, all sensors and daylight harvesting systems are driven by controls and power rather than using light as the starting point. However, by looking at light differently and understanding that the future of lighting must be fully adaptive is the only way to truly lower energy consumption and costs.
About the author: Sajol Ghoshal is the Director of the Sensor Driven Lighting business at austriamicrosystems and may be reached at firstname.lastname@example.org.
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