Spot Versus Group Relamping
There are a variety of reasons to practice group relamping, in which a set of lamps is replaced at a scheduled time, rather than spot relamping, in which lamps are only replaced when they burn out. Most of these reasons apply to fluorescent and high-intensity discharge (HID) lamps rather than incandescents, which have much shorter lifetimes.
Why Practice Group Relamping?
There are four main reasons to practice group relamping—it:
Requires less labor per lamp than spot relamping. A worker might take as long as a half hour to retrieve and install a single lamp. If all the materials wer…
Six Ways to Maintain Lighting Savings
Taking measures to reduce the energy used by lighting systems is only the first step to lower energy bills. The savvy user will also work to ensure that those savings continue throughout the life of the system. Following these six steps will help keep today’s savings available for tomorrow:
During system design, minimize the variety of lamps used.
Choose fixtures that use lamp-specific sockets.
Convert lighting upgrade specifications into purchasing specifications.
Regularly train lighting maintenance personnel.
Budget and train for group relamping.
Focus responsibility for lighting sy…
Light Output Declines with Time
Light output from a given fixture declines over time for two reasons: One is that the lamp output itself decreases—an effect known as lumen depreciation. The other is that dirt accumulates on lamps and fixtures.
Lumen depreciation. Data on lumen depreciation vary with the type of lamp, as shown in Figure 1. Data for a particular lamp can be found in the technical information that is available from each lamp's manufacturer. The output of incandescent lamps decreases as the filament is depleted and tungsten particles accumulate on the wall of the bulb. Fluorescent lamp output degrades bec…
Boosting Lighting Efficiency with Reflectors and Maintenance
Two relatively simple measures exist for improving the energy efficiency of existing fluorescent fixtures: the addition of reflectors and the cleaning of existing louvers and lenses.
Reflectors are specially shaped retrofittable metal sheets designed to improve the efficiency and light distribution of conventional white-painted, ceiling-mounted fluorescent downlight fixtures (Figure 1). With higher reflectivity and more directional control than the white paint on many existing fixtures, reflectors can significantly decrease the internal losses of fixtures and improve light distrib…
In a remote-source lighting (RSL) system, light from a single source is carried over a distance to one or more light outlets, or is emitted evenly along the way. Several benefits result from this type of light delivery system, including:
A reduction in the amount of infrared and ultraviolet energy introduced into a space.
Improved safety in wet or explosive environments.
Improved targeting of light.
Remote-source lighting also provides an aesthetic appeal that often can’t be achieved by other means.
Losses in the light distribution system generally make remote-source lighting less e…
Power reducers are a panel-mounted retrofit option for cutting energy costs in a fluorescent or high-intensity discharge (HID) lighting system. They control the voltage supplied to all the fixtures on a given lighting circuit. When voltage is reduced, both energy consumption and light levels are reduced as well. One of the devices' main attributes is that they are panel-mounted and therefore easier to implement than many other alternatives—one need only install a single device at the panel for each lighting circuit rather than, for example, install a new ballast at each fixture.
Personal Dimming Controls
Preferences for lighting levels vary widely in commercial buildings. Workers who use computer display terminals typically prefer relatively low lighting levels to minimize glare and reflections on their display screens. On the other hand, workers who read, write, and draw on paper typically prefer relatively high lighting levels so they can see small letters and fine details. Older workers, and others with weak vision, also need higher lighting levels. The ability to adjust lighting levels is especially important for workers seated near windows, who must adapt to varying levels of sunlight dur…
Lighting Occupancy Sensors
Occupancy sensors detect the presence or absence of people and turn lights on and off accordingly. Used properly, occupancy sensors can be a cost-effective tool for reducing the operating time and output of lighting systems, cutting energy consumption and—usually to a lesser extent—peak demand. They may reduce lighting energy consumption by 50 percent or more in some circumstances, but the savings could be much smaller, so it's important to carefully consider a wide variety of issues before installing an occupancy sensor in any specific location.
Occupancy sensors are used most ef…
Energy-Efficient Track Lights
Track lights provide directable beams of high-quality light for use in retail displays, galleries, museums, and residences. They are useful in locations where lights need to be aimed at different angles and where the position of the light may be changed frequently. Until recently, the only light sources that could provide the right kind of illumination for track lighting were inefficient halogen lamps. However, newer light sources now provide a wider array of options.
Low-wattage metal halide (MH) lamps introduced in the mid-1990s gave designers and specifiers the first energy-efficient alte…
Metal Halide Ballasts
Like other discharge light sources, high-intensity discharge (HID) metal halide lamps require a ballast to limit current to the electrodes. Ballasts also provide the correct voltage for starting and restarting, and they adjust current to maintain light color and intensity over time. All ballasts suffer internal losses—typically 5 to 30 percent of the lamp wattage—that should be included in any calculation of potential savings, especially when switching from nonballasted sources such as incandescent lamps. Two main types of ballasts are now available: the newer electronic ballasts a…
Light-emitting diode (LED) technology is rapidly improving and becoming more common in business settings. Although LEDs are not ready for all general lighting applications, they are a good choice for a growing variety of uses, including incandescent replacement lamps, parking-lot lighting, commercial signage, task lighting, refrigerated cases, recessed downlighting, ambient lighting in offices, and many high-bay applications. Despite the technological advances, successful application of LEDs still requires care in selecting products that will meet your illumination needs, match their manufactu…
Lighting controls help to make commercial buildings more comfortable, productive, and energy efficient. These controls can turn lights off when they are not needed or dim them so that no more light than necessary is produced. The two functions can be employed individually or, to provide even greater benefits, in tandem. The equipment used to achieve these functions ranges from simple timers to intricate electronic dimming circuits.
A well-designed control system will provide the right amount of light where and when it’s needed, and it will cut lighting energy use by 5 to 60 percent, depend…
Indirect lighting represents a significant segment of the overall lighting market in North America. This approach to space lighting typically features fixtures suspended from the ceiling that distribute the light mainly upward, and the indirect lighting is often combined with a certain portion of direct lighting, task lighting, or both. Indirect lighting minimizes glare on computer screens and creates a soft, inviting environment for concentrated work. The accompanying increases in productivity and occupant satisfaction are hard to quantify, but the benefits are significant. Indirect lighting …
High-Intensity Discharge Lamps
High-intensity discharge (HID) lighting offers very high efficiency, providing energy savings of 50 to 90 percent when replacing incandescent sources. Originally intended for outdoor and high-bay applications, the use of HID lamps has spread to some retail applications as the introduction of ceramic metal halide lamps has improved color-rendering characteristics and as smaller sizes have become available.
Mercury vapor lamps, metal halide lamps, and high-pressure sodium lamps all fall in the HID category. Mercury vapor lamps have become almost obsolete because the Energy Policy Act of 2005 (EP…
High-bay lighting—defined as indoor lighting in spaces with ceilings higher than 25 feet—is used in a variety of applications, including big-box stores, school gymnasiums, sports venues, warehouses, and manufacturing facilities. High-intensity discharge (HID) and fluorescent lighting still dominate the high-bay market, but light-emitting diodes (LEDs) are making inroads. LEDs can be cost-effective because long operating hours lead to higher energy and maintenance savings, and high-bay environments often provide opportunities to control light levels based on occupancy and daylight h…
Full-Size Fluorescent Lamps
Full-size fluorescent systems are among the most common and most efficient lamps in use. They are appropriate for general lighting in commercial, institutional, and industrial spaces with low to medium ceiling height. The introduction to the marketplace of high-intensity fluorescent lamps and fixtures also makes fluorescent systems a leading choice for areas with high ceilings (more than 15 feet)—the type of application that used to be the domain of high-intensity discharge (HID) light sources. (See the guide on Indirect Lighting.) How much energy a fluorescent lighting system uses depen…
Ballasts are electrical devices that convert line current into the proper voltage, amperage, and waveform to operate fluorescent lamps. Ballasts typically last from 40,000 to 100,000 hours and operate with an electrical efficiency of about 80 to 95 percent, consuming parasitic power of about one to a dozen watts.
The mix of ballasts in the market has been shifting steadily toward more efficient equipment over the past 10 years. High-efficiency electronic ballasts represent more than half of new ballast sales in the US, and that share will continue to grow rapidly as the 2005 efficiency standar…
Looking for a quick way to reduce energy and maintenance bills? Exit signs that must be lit 24 hours a day, 7 days a week can take a bite out of commercial and industrial budgets, but today’s more efficient exit signs can offer lifetime savings of up to $300 per sign in reduced energy, materials, and labor costs as compared with standard incandescent models.
The Energy Policy Act of 2005 requires that all exit signs manufactured after January 1, 2006, comply with version 2.0 of the Energy Star program requirements for exit signs. This version of the specification requires that exit signs…
Daylighting systems, which use natural lighting to supplement electric lighting, offer the potential to cut energy use, reduce peak demand, and create a more-desirable indoor environment. Some daylighting systems work well, cutting lighting energy use by 20 to 80 percent and providing an aesthetic work environment. But many systems fail to live up to expectations—often because of shortcomings with daylighting controls. The key to getting more systems to live up to their potential lies in combining good design of the control system with commissioning, effective coordination of the efforts…
Compact Fluorescent Lamps
Compact fluorescent lamps (CFLs) are a quick, easy replacement for typical screw-base incandescent lamps. CFLs use about one-third as much energy as incandescent bulbs to deliver the same amount of light, and they last about ten times as long. They also compete, as energy-efficient retrofits, with advanced halogen bulbs and LEDs. Higher-wattage CFLs can also replace linear fluorescent or metal halide lamps in some applications.
What Are the Options?
CFLs, advanced halogen bulbs, and LEDs can all meet the energy-efficiency requirements of the Energy Independence and Security Act of 2007 as r…