Better Light, Lower Cost
When facility executives evaluate ways to go green, often the lighting system is perceived as low-hanging fruit. The rising costs of electricity and the potential to improve lighting quality make the benefits from a lighting system upgrade significant and immediate in terms of cost-savings and indoor environmental quality.
The breadth and variety of choices continually grows with non-stop innovations in illumination science. A review of new devices, ones that will soon be available or have appeared in the last two or three years, shows that there is a bountiful crop of options ripe for the picking.
While high-performance T8 (HPT8) fluorescent lighting has been around for several years, the number and variety of options continues to expand. In essence, HPT8 covers linear fluorescent lamps with initial lumen output of 3,100 for a 4-foot lamp (compared to a typical 2,900), lumen maintenance of 94 percent or better, color rendering index greater than 81, and a rated lifetime of 24,000 hours or longer. When combined with electronic ballasts that can drive such lamps to greater (or lower) output without harming them, energy savings of 7 to 20 percent, relative to standard T8 systems, are attainable.
HPT8 electronic ballasts are now available across a relatively wide range of ballast efficacy factors (BEF). BEF indicates the amount of light output relative to a standard for a given wattage input. A standard two-lamp ballast may, for example, output 88 percent of the light of a ballast standard, yielding a ballast factor of .88. Its BEF, if pulling 62 watts, would then be 1.42 (= .88 x 100 / 62). For two-lamp fixtures, HPT8 ballasts are available with BEF ranging from 1.48 to over 1.60. Some call them low- or high-power ballasts. That means light levels or wattages may be tailored across a range of roughly 20 percent, merely by ballast selection.
Quality and Performance
To be listed as HPT8 ballasts, units must also attain quality standards: a frequency of 20 to 33 kHz or more than 40 kHz, a .9 or better power factor, and total harmonic distortion of 20 percent or less. They must also meet or exceed BEF levels based on the number of lamps and the ballast starting method. (See “Keeping Up With the Lumens” on page 30.) When a low BEF ballast is paired with a high lumen output T8, light output may be maintained using fewer watts or fixtures.
On the flip side, low-wattage T8 lamps (25 and 28 watts) are being promoted as an easy way to cut light output and wattage simply through routine group relamping. Some care is necessary when using them: Among other issues, they may work properly only with certain types of ballasts and only at 60 degrees F (or above) room temperatures.Because the 25-watt lamps run much cooler than 32-watt units, one test in a three-lamp open troffer found that light levels dropped only 5.7 percent while wattage dropped more than 16 percent. Fluorescent lamps lose output if they get much warmer or cooler than a defined temperature, and the 25-watt lamps were closer to that ideal point than the standard 32-watt units.
Recent independent tests have quantified how perceived brightness varies with corrected color temperature (CCT). Long known anecdotally by professionals who conduct lighting upgrades, light from lamps with high color rendering index (CRI) and color temperatures of approximately 3,500K and above appeared brighter than that of old style T12 lamps, many of which had CRI of around 70, even though light meter readings were the same for both lighting systems. In one test, light from 5,000 K lamps with 80 CRI appeared to many as about 20 percent brighter than that from lower CCT lamps. Can light output and wattage really be cut by 20 percent using such lamps without impacting occupants? That may be a stretch, but savings of more than 10 percent are easily attainable merely by using such higher CCT lamps.
Careful Maintenance Needed
Customizing light levels based on lamp and ballast choices may create a problem unless maintenance is carefully controlled. Four-foot T8 lamps look about the same while in the relamper’s cart and in the supply room where they are stocked. Extra care is therefore needed to ensure that the right lamps end up in the right fixtures. Otherwise, varying light outputs may be mixed together in the same fixture or room, just as different shades of white are often mixed in the same fixture in buildings where maintenance becomes sloppy.
The same may be true when replacing ballasts: Customizing light output by using high- or low-power ballasts requires that good records be kept of the proper ballast for each fixture/room. Otherwise, facility executives may lose savings or occupants may complain if the wrong replacement ballasts are installed. Ballast choices may also affect lamp lifetime. Programmed start (also called “soft start”) ballasts are easier on lamp cathodes than instant start ballasts. Where used in conjunction with occupancy sensors that may significantly increase lamp cycling, replacement of a burned out programmed start unit with a typically cheaper instant start ballast could cause lamp life to drop noticeably, resulting in more spot relamping or outage complaints.
Other Fluorescent Goodies
While linear T5 lamps are not new, ballast choices have expanded, and some dimming ballasts, such as for T5HO, have become more efficient when at full output. Many new T5 fixtures are now available, offering wider choice for new construction or major remodeling. While still a bit pricey, T5 options allow smaller fixtures or fewer lamps per fixture.
Compact fluorescent lamps (CFLs) have also expanded in wattage and variety. Giant screw-in units (for example, 85 watts) are now available that may replace high-wattage incandescents (which may be more than 300 watts) in the same socket. New dimmable units, in some cases below 10 percent output and available in the shape of PAR lamps, use either existing dimmers or proprietary systems that work with existing wiring. Various other shapes and sizes of bi-pin lamps are available that allow for smaller or uniquely shaped fixtures.
Lower mercury versions of both linear and compact fluorescents are also available. One manufacturer recently announced a T8 lamp that is 50 percent lower in mercury than its previous low-mercury T8s.
One new offering in high-intensity discharge (HID) lighting is a 175-watt HID backup ballast. During a brief (several minutes or less) power outage, this unit keeps HID lamps running, thus avoiding the long re-strike times typical after power interruptions. Versions for higher wattage fixtures are now in the works.
More options for better color and CRI, among other things, are also now available in the CMH (ceramic metal halide) and CDM (ceramic discharge metal halide) families, as are electronic ballasts for low-wattage metal halides, down to a 20-watt unit for CMH spot and track lights.
One company offers an electronic ballast dimmable down to 50 percent for 250- to 400-watt metal halides. It is 13 percent more efficient than magnetic pulse-start units, while offering major savings when warehouse spaces are either unoccupied or during demand response events, especially when coupled with new bi-level occupancy-sensing controls.
LEDs stood out at a recent tradeshow, with one lamp wowing showgoers with continuous white light output at 70 lumens per watt (even higher for brief periods), rivaling compact fluorescent efficiency. A variety of devices have already appeared that try to take advantage of high efficacy LEDs. Some of them, like the $50 T8 tube containing approximately 300 LEDs, are a bit odd, but well-known fixture manufacturers are offering applications, such as step lights and bollards, that are appropriate to the size, durability, and longevity of this source.
LEDs are also appearing in task lights, downlights, and undercabinet fixtures, and as direct replacements for some incandescent sockets. Some outdoor area lighting poles, such as for walkways, are using LEDs powered by photovoltaic panels and batteries. As with many new technologies, measuring standards have not kept pace, so end users are cautioned to try out samples of such new devices before committing to large purchases, regardless of vendor claims.
It should be noted that the extreme longevity of LED sources (50,000 hours or more) is based on when the units lose 30 percent of light output. That lifetime is, however, closely linked with lamp temperature and rated amperage: When too hot or too amped, lifetime drops very rapidly, with some charts showing lifetimes of only 10,000 hours. Warranties on many LED lamps and fixtures do not yet reflect the claimed lifetime of their light sources.
Controlling Energy Needs
Daylighting, seen by many as the Holy Grail of lighting efficiency options, has moved forward via improvements in software for analysis and for renderings of natural light distribution. Hybrid lighting systems, which incorporate dimmable electric light sources into skylights and light pipes, may avoid daylight glare without requiring the architectural alterations common to some daylighting methods.
Lighting controls manufacturers have introduced numerous ways to alter lighting patterns, schedules and outputs. Wireless and touchless switches, occupancy and light level sensors, bi-level switching that allows for a 50 percent demand response in selected fixtures, and “smart” occupancy/vacancy sensors are all now available. Not only may sensor sensitivity and time delay be customized by users, but options now exist for timed “on” periods when no motion occurs (such as during a school test), timed “off” periods when motion is detected (as during a slide show), customizable warning tones before lights go off, and other features.
A recent research finding now employed by those participating in demand response programs is that a gradual drop over a minute or two in light levels of 15 to 20 percent is not noticed by occupants performing paper and computer tasks. Even greater reductions may be possible in other cases. Using dimmable ballasts and an automated control system, such gradual reductions could be activated when requested by the utility or grid operator, yielding incentive payments and lower overall electric rates.
As with any device that may involve programming, adjustment, and maintenance, facility executives are cautioned not to install anything much “smarter” than the people using or maintaining it, and to allow time and resources for proper commissioning.
Each time energy prices rise, some old ideas are re-invented. One resurrected idea involves altering the AC power wave form to cut energy use. One such device clips part of the AC wave near the zero crossover point, ostensibly reducing power usage without reducing light output. Two identical electronically-ballasted fixtures were running at a demonstration, one on regular AC and the other served by the wave chopper. Electric meters showed lower wattage for the wave-chopped fixture, which appeared obviously dimmer. The manufacturer had no light meter to back up its claim that the two fixtures were equally bright.
Consultations with manufacturers of electronic ballasts verified that, depending on their circuitry, many would simply compensate for a temporary reduction in voltage by pulling more amperage, and thus the same wattage. Others would simply dim the lights proportionately. Of major concern was the fact that ballast warranties would be voided for ballasts fed by such devices.
A few final caveats. Some items mentioned above have not yet appeared on the market. In a few cases, lighting devices are more advanced than the standards needed to judge them. Early adopters are cautioned to “test before you invest” to avoid disappointment — and the urge to sue suppliers — if outcomes are not as claimed. If it’s something really novel, don’t buy more than a sample without first seeing independent test results or reviews backing up vendor claims. Remember: If it sounds too good to be true, it probably is.
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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.