Facility executives can be forgiven for thinking that not much has changed in lighting over the past decade. After all, T8 lamps and electronic ballasts remain the workhorses of the industry. But significant gains have been made over the last 10 years. Even for facilities that underwent upgrades as recently as 10 years ago, evaluating how facility use has changed and how new energy efficient equipment reduces electric costs may make another upgrade attractive.
But facility executives who embark on a lighting project may find themselves floundering in a sea of technology options and sometimes obscure lingo. To take full advantage of the opportunities presented by current lighting choices, facility executives should have a solid grasp of energy-efficient lighting technologies and terminology, principles of effective upgrades and the impact of incentives. Whether an upgrade calls for the installation of controls, lamps, ballasts and other components, knowing how technologies work and how they can be applied to reduce costs is essential to a project’s success.
Lighting technologies convert electricity into light with varying efficiencies. About 90 percent of the power incandescent lamps consume turns into heat; the remainder becomes visible light. Like the gas light it replaced, incandescent technology is being supplanted by more efficient options. Fluorescent, HID and LED sources convert much more electricity into light than incandescent lamps, making them cheaper to operate.
Driven by tighter codes and rising energy costs, the efficiency of all sources is improving. T8 fluorescent lamps driven by electronic ballasts and housed in computer-designed fixtures have excelled in performance and light distribution, placing more light in the right places using the fewest watts. Other sources, such as compact fluorescent lamps, T5 fluorescents, and HID lamps may, however, be more appropriate and efficient, depending on application. LEDs are moving rapidly forward, breaking out of their niches for signage and decoration and into area lighting, though much work remains to better control and distribute their output.
While it’s important to choose light sources based on efficiency, it’s even more important to do so based on the needs of the tasks being illuminated. In many applications, fluorescent offers the best options for color rendering and efficiency. However, industrial and retail applications often use HID sources to light high bay areas.
The distribution of light from a fixture may also be crucial. A highly efficient fixture that creates glare on a computer monitor could cost far more in lost productivity than it saves on electric bills. This is where lighting design comes into play. Without the benefit of an experienced lighting practitioner, a well-meaning lighting product vendor or energy manager may create more problems than are solved.
On the other hand, a good lighting design can minimize or cure problems related to glare, flicker, inappropriate levels, and a lack of flexibility. Many new or renovated offices are now being designed, for example, using task/ambient lighting combinations in which a low level of general illumination is supplemented by portable fixtures that reside next to or on individual desks. Articulated LED and compact fluorescent desk lamps, such as goose neck lamps, may be relocated and angled to suit individual tastes, yielding a greater level of control that may enhance comfort and productivity, which are worth far more than energy savings.
Many financial incentives are available for reducing the cost of efficient lighting. A good lighting designer can find ways to maintain lighting quality while meeting codes and securing rebates and tax deductions. At no point, however, should such financial perks control the final choices in a design. A good lighting system needs to be maintained properly and economically, and minimizing the variety of lamps and ballasts will help ensure that the right components continue to be used. Such issues are best balanced within the lighting specifications, rather than making decisions after the upgrade project has started.
Various units describe the quantity and quality of light. A lamp’s output is measured in lumens or lux. A lux is about 1/10 of a lumen. A typical 4-foot T8 lamp produces about 2,900 lumens while consuming about 30 watts, yielding almost 100 lumens per watt. Many compact fluorescent lamps provide about 70 lumens per watt. Incandescent lamps are less efficient, producing roughly 20 lumens per watt. In general, the higher the lumens per watt, the lower the electric bill and the easier it is to meet energy codes that restrict watts per square foot for lighting.
When those lumens arrive at a surface, the result is measured as foot-candles. One foot-candle is simply one lumen spread across one square foot. Light coming straight from a fixture is called “direct” while light that first reflects from a surface, such as a ceiling, before striking a task is called “indirect.” Many pendant-mounted fixtures are designed to reflect a portion of their output off ceilings while sending the remainder down. Called “direct-indirect” fixtures, this style often provides a balanced distribution that eliminates shadows and the cave-like effect of some purely direct fixtures.
Except where desk lamps or other task lighting is used, most work surfaces receive a mixture of direct and reflected light. Room shape and surface reflectance, measured as a percentage relative to a bright white surface, affect how well a fixture can do its job. For best results, avoid black filing cabinets, dark ceiling tiles or walls with colors that absorb light.
The various shades of white light from most commercial lighting may be described by their Corrected Color Temperature, with higher temperatures being richer in blue and lower temperatures showing more orange. Lamps with lower Corrected Color Temperature appear to be warmer and closer to the type of light produced by incandescents. How naturally a lamp’s color renders objects is described by its Color Rendering Index (CRI). In general, room lighting should have a CRI of 70 or higher and Corrected Color Temperature between 2,700 K and 5,000 K. Studies have shown that using lamps at the high end of that range creates a perception of greater brightness even when measured foot-candle levels are lower.
To meet or exceed energy codes, many facilities are taking advantage of daylighting. Natural light use is being maximized in conjunction with electric lighting through light-sensitive controls. While best pursued as part of the design of a new building, various methods exist to improve how daylight enters and is distributed throughout a space. Sensors at various locations reduce the output and power consumed by lighting equipped with dimmable ballasts. Depending on ceiling and window height, light shelves may be added to reflect light further into a space while reducing excessive natural light at perimeter work stations. Various types of skylights, light pipes, light wells and automated window treatments also exist to control incoming natural light so as to minimize the need for electric lighting.
Even when no natural light is available, lighting controls may cut or dim lighting that is not immediately needed. Occupancy sensors have improved greatly for sensing when no one is in a space. State-of-the-art units use infrared, ultrasonic and audible sound to avoid false switching. Some also provide an audible warning signal just prior to shutting off lights, and most allow customization of delay periods, sensitivity and shutoff scenarios. Some will keep lights off even when a space is occupied, as may be required during a video presentation, or keep them on when little motion is occurring, such as when an exam is being administered. Some fixtures have built-in sensors to reduce light output in stairwells and odd-shaped spaces where individual fixture control is essential.
The advent of demand response programs, wherein customers get paid to reduce electric demand when called by the utility or grid operator, has produced several new opportunities for controls. A central building management system may be used to slightly lower fixture output and demand by a defined level as part of an overall building demand reduction. Selected bi-level light fixtures may have one lamp automatically shut down during such reductions. The system can also briefly shut off non-essential fixtures, such as atrium lighting, during reduction periods.
High-performance T8 lighting, using more efficient lamps and ballasts than previous generations of T8 lamps, cuts energy use by 7 to 17 percent while providing the same illumination. If the existing system is using T12 lamps and magnetic ballasts, savings approaching 40 percent may be possible. Where compact fluorescent lamps replace incandescents, savings of around 70 percent are possible. If occupancy, daylighting, or other levels of control are added, additional savings are attainable.
Where rates for peak demand charges have risen faster than those for consumption, a lighting upgrade may be an especially good way to cut the electric bill. Depending on the rate structure, kilowatt-hours for lighting may also be more costly than the facility’s average power price because most lighting is on during the building’s monthly peak demand period. Careful calculation may then show that the percentage dollar savings are higher than the percentage energy savings, making now a good time to upgrade.
Depending on the efficiency of existing lighting, it’s possible to reduce power consumption for illumination by 20 to more than 50 percent using off-the-shelf technology and techniques. Depending on electric rates and their structures, a comparable or even greater reduction in cost may be attainable. Where rates and incentives are high, such as in coastal and large urban areas, payback periods of two to four years are common, yielding exceptional rates-of-return while improving the quality of a workspace and cutting power plant emissions.
To get started, contact the local utility and state energy office to determine what financial options are available to cover the cost of an upgrade.
For commercial and government customers, the Energy Policy Act of 2005 offers tax breaks that can further buy down installation costs. Some state and utility programs cover part of the cost of lighting audits that count lamps and fixtures and produce recommendations for upgrades. Many energy service companies (ESCOs) will perform walk-through level audits at no cost to help a customer identify savings opportunities.
This is an ideal time to look — or look again — at how to take advantage of these opportunities.
LEXICON
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Lindsay Audin is president of EnergyWiz, an energy consulting firm based in Croton, N.Y. He is a contributing editor for Building Operating Management.
