Michael Meyer 2018-01-24 22:46:00
There is no building element more ubiquitous than lighting — there’s a light fixture roughly every 10 to 20 feet. Beyond being the most common element within a building, lighting has the unique aspect of being regularly arrayed into a grid. As we move to a more connected world, lighting provides a ready-made infrastructure for providing power for sensor technology to interface with plug loads, HVAC, and non-energy capabilities like asset tracking. New advances in lighting equipment and sensors allow for not only energy savings, but also non-energy features that can benefit and enhance facilities. OCCUPANT COMFORT With the increased penetration of LED lighting, the illuminance, which is the amount of light falling on a surface, has been re-evaluated. Although illuminance does not entirely represent the quality of the overall visual scene, it does provide a good indicator, and it is the easiest value for designers and engineers to calculate and measure. Thus, it is the metric that the industry often uses for lighting recommendations and evaluations within a space. As new LED lighting is installed, sites are re-evaluating their current lighting illuminance levels based on their situation and needs. Some spaces may have been over lighted in the past and a change in lighting technologies allows a fresh evaluation of existing conditions. Further, new lighting is more adjustable in output and different lighting levels can be more easily obtained. However, some LED fixtures lack proper optical controls or are poorly designed, which can result in glare or make the space feel too bright. To reduce the glare and brightness and to make the space more pleasant for occupants, the illuminance within the space is sometimes reduced from its previous levels. However, occupant comfort and industry guidelines should be consulted if the illuminance is significantly reduced. With fluorescent technology, the physics of the lamp allowed light in discrete amounts (for example, 2900 lumen lamps or 3100 lumen) and lamps of the same wattage from different manufacturers all basically produced the same amount of light. Options to vary the amount of light output of a lighting system were either limited to adding or removing tubes, or costly by installing dimming systems. However, the wide-scale introduction of LED lighting systems has changed the ability to vary light output, and this has led to additional discussions about light output. Most LED fixtures or retrofit kits leave the factory with a built-in dimming driver. Thus, with the proper control signal, these new LED fixtures can easily be dimmed. Product data sheets also list multiple light output options for virtually every LED product sold. WHITE-TUNABLE Beyond dimming LED systems, color-tunable technology is gaining ground. Certain light fixtures can adjust the color appearance of the light. This is known as CCT, or correlated color temperature. CCT is rated in terms of Kelvins (K), with low values appearing warmer, or white with a yellow or orange tint, and high values appear cooler, or white with a blue tint. A neutral CCT is 2700 K to 3500 K, where halogen is 3000 K and fluorescent is often 3500 K. CCT values greater than 4000 K are characterized as cool (white with a blue tint). Metal halide, some LED fixtures, and daylight often fall in the cool CCT category. Researchers from the University of Mississippi and University of Texas assessed the reading fluency of third-grade students under two conditions: high illuminance (≈100 fc) with high CCT (6500 K) lighting and typical elementary school lighting conditions (≈50 fc and 3500 K).1 The study found a 36 percent improvement of fluency performance under the 100 fc / 6500 K lighting condition, while there was a 17 percent fluency performance under 50 fc / 3500 K lighting conditions. The research did not examine the variables individually, so it is unknown if the change in CCT, change in illuminance, or the combination of the two could be behind the higher fluency. However, varying the visual scene can help direct focus. Moving from the classroom to a business, there is significant interest in the use of varying CCT in office and industrial spaces. The basic idea is humans evolved under daylight, which varies by time of day and year, so mimicking this change in electric lighting may have benefits to occupants in the space. These types of adjustments would have been laborious and costly to do with fluorescent lighting. However, this feature is enabled by some LED lighting. Although marketing departments of many lighting companies espouse the benefits of color tuning throughout the day, it must be kept in mind that the research on potential benefits is still ongoing and inconclusive. Varying the color appearance across the day could be used to draw or retain focus in class or break up the monotony of the office day, but monetizing increased focus or disruption of the monotony of the work day into tangible benefits, such as improved test scores or task productivity, is challenging for researchers. That being said, making a space more pleasant, and improving the mood of occupants, is always desirable. Most would agree that this can be done through delivering the correct amount of light and the desired lighting CCT for the task in a space, and reducing glare. PRODUCTIVITY AND EFFECTIVENESS Any claims of substantial changes in productivity (which is output compared to a unit of work) as a direct result of new lighting should be viewed with skepticism. Claims abound that using color-tunable light could increase productivity by 10 to 20 percent. First, many items can affect worker performance, including noise, temperature, lighting, bonuses, non-financial incentives, and social elements (for example, Cyber Monday, March Madness, etc.). Because many variables can affect worker performance, claims of double-digit increases in productivity must be carefully evaluated. Second, although the amount of light, shadows, color, glare and flicker can affect worker performance, the lighting in U.S. spaces exceeds (far exceeds in some cases) the bare minimum lighting needs affecting performance. Therefore, changes in lighting should not lead to significant (double-digit) enhancements, but maybe marginal improvements in worker productivity. In contrast, features of new connected lighting could make staff more effective via asset management, space utilization, or other features. NON-ENERGY BENEFITS Asset management is a non-energy benefit that could be offered via connected or smart lighting. Using physical tags — such as radio-frequency identification (RFIDs) or Bluetooth Low Energy (BLE) — on physical objects, sensors can be mounted on and powered by the light fixtures across the space to help track assets. Retail examples of this include tagging inventory. As the inventory leaves the distribution room within a store, it is tracked to the sales floor. Or tags can be placed on hangers for clothing, so that if the hanger and clothing are moved during the day by a customer, it is being counted. At the end of the day, the sales team has a better idea of the interest in particular items, counts of items, and where misplaced items may be located within the store. These tags have the potential to add value and free up staff time for other tasks. Similarly, hospitals are exploring asset tracking. Nurses spend an aggregate of 1 to 2 hours per day looking for equipment.2,3 As a result, anecdotally, hospitals often overbuy equipment to address this problem. Sensors mounted on the light fixtures could help track tagged equipment and inform the nursing staff where the equipment is located. In both the retail and healthcare scenarios, light-powered and mounted sensors help staff to be more efficient, although it is difficult to quantify exactly how much of a time savings staff would experience and thus still too early to directly monetize asset tracking. Beyond making staff members more effective, the use of physical spaces can also be made more efficient via connected lighting systems through space utilization. Some new occupancy sensors go beyond simply determining movement and can count the number of people in a room. Another way to count room occupants is via RFID or BLE tags placed in staff ID badges that can communicate with sensors connected to the lighting system. In either scenario, the connected lighting system can provide feedback to management about how effectively spaces are being utilized. The cost of the space easily dwarfs the cost of energy. For example, if two conference rooms are each used in a space, but only a portion of the day and with little conflict, one of the conference rooms could possibly be eliminated or repurposed. Again, because lighting systems are evenly spaced throughout the building, they can serve as an avenue to provide this information if the correct sensors are installed. Beyond making staff or spaces more effective, connected lighting can interface with the mechanical system and plug loads. If the new sensors can count bodies, they can interact with the HVAC system. The advantage to the mechanical system is that additional savings can be achieved from the sensor by changing the temperature or air flow to better account for the actual number of bodies in the room. Then when the room is empty, the sensors could dim or turn off the lights or direct a building management system to turn off certain plug loads or adjust HVAC system settings. New connected lighting is the key to delivering these benefits and additional functions to the building occupants as well as building systems. Remember, unlike virtually everything else in the building, light fixtures are abundant, distributed throughout the occupied space, and equipped with a power supply. These features make lighting an ideal platform to house and power sensors that allow for the capabilities previously mentioned. However, the key is in the selection of lighting technology that allows for these expanded capabilities. SIMPLE OR SMART LIGHTING The first consideration when choosing a lighting system is whether the equipment should be simple or smart. Simple lighting equipment provides lighting but no other secondary capabilities such as lighting controls, sensors, light color changing ability, or any feature beyond on/off of light output. Tubular LEDs (known as TLEDs) are probably the most common type of simple lighting. Many facilities are opting for this technology because of the low first cost, but very few TLEDs offer the smart capabilities that could add other benefits to the space. In contrast, retrofit kits and new luminaires are often available with some type of sensor embedded in the fixture. At a bare minimum, these sensors allow for basic occupancy sensing or daylight harvesting features to control the light output. However, many manufacturers also offer smart sensors and other features that allow for the lighting system to become connected to building management systems or to the larger inter-connected world. Significant energy savings can be achieved from connected lighting, and these savings can help off set the first costs of equipment and labor to install the new equipment. The industry is just starting to develop methods of monetizing certain non-energy benefits — for example, the value of asset tracking per square foot. The U.S. Department of Energy’s Better Building Alliance and Solid-State Lighting programs are conducting research and aiding in these areas. IFMA is a partner with the DOE in the Interior Lighting Campaign, or ILC. Participants in the ILC saved between 40 percent to 80 percent of the energy used by the original system through the installation of high-efficiency lighting systems. Energy savings are often the only metric used in lighting upgrade decisions. Savings this large should be used to leverage the installation of new lighting systems — ideally connected systems that offer additional benefits. KNOW YOUR LIGHTING ACRONYMS CCT Correlated color temperature, a measure of light color fc Foot-candle, a measurement of light intensity LED Light-emitting diodes, a lamp technology TLED Tubular LED, designed to replace fluorescent lamps Michael Myer is a senior researcher with Pacific Northwest National Laboratory (PNNL). PNNL is a U.S. Department of Energy national laboratory. Michael is the technical lead for the Interior Lighting Campaign and focuses on energy efficiency in lighting. He also supports DOE related to energy codes, appliance standards, and market transformation.
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