Lighting Efficiency: Making It Happen — Part 1

First, determine what light level you have, and then set the level you're seeking. Next, choose between a lighting upgrade and relighting your facility. Lighting system upgrades are booming! To save energy and improve company profitability and worker productivity, owners and end-users are upgrading their facility's lighting systems. Although this activity is on the rise, it's just beginning to impact

First, determine what light level you have, and then set the level you're seeking. Next, choose between a lighting upgrade and relighting your facility.

Lighting system upgrades are booming! To save energy and improve company profitability and worker productivity, owners and end-users are upgrading their facility's lighting systems. Although this activity is on the rise, it's just beginning to impact the U.S. commercial building sector. Consider these statistics from the Energy Efficient Lighting Association: 90% of the 4.8 million commercial U.S. buildings are more than 10 years old. Yet, with most of the new lighting efficiency products developed during the past 10 years, owners and end-users have upgraded only about 10% of the 70 billion sq ft of commercial floor space. Clearly, many opportunities exist to upgrade lighting systems for the benefit of the owner, operator, and user.

Upgrading options. There are two major upgrade approaches. The simplest is usually a packaged or generic retrofit that considers only one option, such as converting fixtures with older T12 lamps and magnetic ballasts to T8 lamps and electronic ballasts. However, many disadvantages (including improper light levels and lower lighting quality) can outweigh the advantage of such simplicity.

Another approach is to carry out a comprehensive lighting analysis that considers multiple retrofit options. This approach usually results in higher-quality lighting. However, it's more complex and sometimes results in longer payback periods.

Upgrade or relight? The decision to upgrade existing fixtures or relight with new fixtures involves several considerations. Sure, an upgrade may seem simple, but if only one improvement is put into place, then there's a lost opportunity to add more. By calculating the cost effectiveness of both alternatives, you'll get the economic information need to arrive at the right decision.

Special circumstances may tip your decision one way or the other. For example, suppose your fixtures are old, and the lamps don't seat well in their sockets. If you don't change the sockets and install new lamps and electronic ballasts, you'll have lighting failures haunting the project with callbacks and lost profits.

Ways to upgrade existing fixtures. Okay, the physical condition of your existing fixtures is good enough for use in retrofitting. What options do you have to improve their efficiency? You could install new lamps and ballasts, clean all reflecting surfaces, install specular reflectors, or even replace lenses or diffusers.

  • Lamp and ballast upgrade.

    Some call this simple upgrade a "no-brainer." You simply install new T8 lamps (they fit in the same sockets used for the older T12 lamps) and new electronic ballasts (wired to the sockets, as shown on the ballast label). However, many lamp and ballast upgrades suffer from one or more shortcomings. The most important is inappropriate light levels. This usually happens when the old lighting system was last upgraded or installed, and the illumination level was not changed to accommodate the current tasks. When light levels are too high, you waste energy and degrade lighting quality. Light levels that are too low can put occupants at risk.

  • Cleaning reflecting surfaces.

    Many overlook the simplest upgrade: cleaning. Cleaning a fixture's reflective surfaces improves optical efficiency, which allows the fixture to emit more light. Considering the installation as a complete system, you'll find you need fewer fixtures if you maintain the system.

    You can account for light loss (as dirt accumulates on reflecting surfaces) by increasing the initial light level with more fixtures. Studies at Penn State University show you can offset additional costs of cleaning and annual relamping with the savings in initial equipment and annual energy costs.

  • Installing specular reflectors.

    Installing specular reflectors can improve thermal and optical efficiency of a fixture by about 17%. This may allow you to use fewer lamps or ballasts with a lower ballast factor (BF). This type of retrofit requires special care.

  • Installing new lenses or louvers.

    The function of a fixture lens is to break up the direction of light rays and disperse them randomly. A lens also hides the lamp image. You've seen plastic diffusers on older discolored fixtures. These are made of polystyrene. Ultraviolet radiation from the lamps causes them to turn brown or yellow. Installing a new lens or louver improves optical efficiency and gives fixtures a new look. An acrylic diffuser lens won't discolor like polystyrene diffusers.

    Some manufacturers provide retrofit louver kits, allowing you to modify fixtures. You simply remove the lens and replace it with a louver. While increasing lighting quality, this improvement may cost as much as a new fixture. Some kits mount between the fixture and a T-bar ceiling, requiring enough of a gap between the fixture and the ceiling for this additional space.

  • Relighting with new fixtures.

    The option to install new, more efficient fixtures gives you the chance to change the original parameters of the system, including the number of lamps per fixture and total number of fixtures. Using a computer program to perform zonal-cavity lighting calculations, you can determine the required number of fixtures and lamps. Many installers now replace older four-lamp fixtures with three-lamp T8 units with little or no loss of effectiveness.

  • Don't forget exit lights.

    Installers have upgraded less than 15% of the estimated 100 million exit lights in buildings in the United States. A common condition is burned-out incandescent lamps, which compromise the safety and security of facilities. However, this is an opportunity to improve the reliability and to upgrade well-maintained exit lights to energy and maintenance-saving units. Because exit lights are lit constantly, investments in new units are usually paid back in two to three years.

    When considering exit light replacements, you must meet public safety codes and equipment standards, including the NEC, Life Safety Code (NFPA 101), and OSHA.

    The light-emitting diode (LED) exit light is the most popular type, and manufacturers now supply a new generation of these. However, sales of retrofit kits are declining. These small solid-state electronic devices light up when a small current energizes them. Compared to incandescent exits, there are no filaments to burn out. They generate little heat, and the expected long life of LEDs makes them attractive for the low-maintenance and high-reliability requirements for this life-safety application.

    Incandescent lamps for exit light applications commonly rate for 3000-hr average rated life, but some special retrofit lamps have ratings up to 100,000 hrs. LEDs can theoretically last up to 80 years with no maintenance, depending on which ones you use and how you power them.

    The key to long life exit signs is the LED drive-circuit design. Power supply designs using simple series capacitors to reduce the AC voltage to the LED array can exceed the peak inverse voltage (PIV) rating and overpower the LEDs. This operation affects lumen maintenance and LED life. Some designs using DC power circuits and traditional power supplies do not exceed PIV ratings. The better designs incorporate transient protection to protect the units from overvoltage conditions.

    Red LEDs have a higher efficiency (nearly 25 LPW) than the less-efficient green LEDs (2 LPW to 6 LPW). Significant developments have reduced the cost and improved the performance of the newest generation signs. These low-energy, cavity-lighted units are aesthetically pleasing for any building application. The new LEDs in the new exit lights are 30 times brighter than first generation devices, and you can easily hide backups inside the units.

Use HID upgrades for more efficient lighting. The trend in HID lighting is toward white light, metal-halide (M-H) systems for interior and exterior applications. This trend provides you the opportunity to change high-pressure sodium (HPS) systems to M-H systems by changing fixtures. You can even upgrade recently installed standard M-H systems by installing a pulse-start (PS) system. You'll be able to save the fixtures, but you'll need new lamps, ballasts, and starters; all of the PS type.

There are significant performance improvements when upgrading to PS systems. The system components include a new family of lamps (called formed-body arc tubes), magnetic (or electronic) ballast with a reduced crest-factor, and separate PS ignitor. The formed-body arc tubes feature a uniform geometry. There's no need for a starter electrode, as found in standard, pinched arc tubes. These changes result in higher lamp efficiency (up to 110 LPW), improved lumen maintenance (up to 80%), consistent lamp-to-lamp color, and 50% faster warm up and restrike.

Three new HID ballast types include the standard (super) CWA for all voltages, the linear reactor for 277V systems only, and the premium, regulated-lag ballast for most voltages. Some of the linear reactor designs have the ignitor built in. It supplies the high-voltage pulse to start the lamp and is usually a separate component.

Examples of HID retrofits. You can see a retrofit example, using 350W PS systems with linear reactor ballasts in Table 1, above. In addition to the annual energy savings of $13,800, there's about a 9% higher light level with the PS system over the standard M-H system.

When you have new construction of a lighting system, the annual savings are even greater. The illumination level increases slightly, the number of fixturesdecreases, and the annual savings is now $19,100.

For both tables, the higher mean lumens of the 350W PS lamp (31,500 lumens) outperforms the lower mean lumens of the 400W standard lamp (28,800 lumens). By using the total lumens to get the same light using 350W PS MH lamp/ballast system as the 400 fixtures with the 400W standard MH lamp/ballast system, you can better understand the calculation for the 366 fixtures. By using 366 fixtures for this new construction scenario, there is a definite advantage in a lower first cost.

How controls improve efficiency. Controls can reduce the hours of lighting system use and/or reduce the amount of power serving lighting loads. Timers, central controls, and occupancy sensors are excellent ways to control lighting. But, use the correct technology of occupancy sensors for applications.

Passive infrared sensors must "see" an area to control it. Partitions, toilet stalls, and bookshelves block detection and can put people in the dark. You should set the delay time, as a test, to about 20 min, to avoid shortening lamp life.

Demand controls, daylight harvesting, and lumen depreciation compensation are good strategies to control lighting power. New dimming electronic ballasts can lower lighting levels from 100% down to 5% or 10%. Some dimming ballasts employ connections to sensors using telephone cable, providing a convenient plug-and-play installation.

Suggested Reading:

Electric Power Research Institute (EPRI) Related Publications:
EPRI Publication No.TR-107230 (1996) "Lighting Control: Patterns for Designs." For ordering information on EPRI publications, call (800) 313-3774, press 2, or (423) 974-8288.

EC&M books:
EC&M's Step-by-Step Guide to Lighting, Order No. 6956. For ordering information, call (800) 543-7771.

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