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Why Fluorescent Lighting Isn't Dead - Part 1

Posted by Allan Chen on July 06, 2011
The future of energy-efficient lighting, many experts will tell you, is the solid-state LED (light-emitting diode). You have already begun to see these tiny, bead-like lights in special applications such as traffic signals, exit signs, automotive headlights, and lightweight flashlights. Maybe you have begun to see them in high-end ambient room lighting applications, such as energy-efficient desk lamps and kitchen underlights.

"The common view," says Francis Rubinstein, a scientist and energy-efficient lighting expert at Lawrence Berkeley National Laboratory's Environmental Energy Technologies Division, "is that LED lighting is replacing fluorescent lighting with the same inevitability that mammals replaced dinosaurs as the dominant large life forms on Earth."

Ongoing research at national laboratories and in the lighting industry is focusing on improving the light output, lifetime, and durability of LEDs, as well as driving their costs down. Many lighting experts expect that LEDs will eventually be used widely in general lighting applications, replacing inefficient incandescent bulbs, as well as energy-efficient fluorescent lamps (both the linear and compact varieties). LEDs have the potential to be more energy-efficient than fluorescent lights.

But wait, says Rubinstein, who has been delivering a talk to lighting industry audiences titled "Why Fluorescent Lighting Isn't Dead." He believes that modern fluorescent lighting will continue to dominate the general lighting market and that solid-state LED lighting will coexist in the marketplace with fluorescent lighting for some time to come. Rubinstein sees a near-term future in which LED and fluorescent lighting coexist in hybrid systems that will be more adaptable to the lighting needs of a wide variety of residential, commercial, and industrial building types and space configurations.

Rubinstein has been studying lighting systems in buildings for some thirty years. He has participated in energy efficiency improvement projects at the White House, congressional office buildings, the San Francisco and Oakland federal buildings, public and private buildings, and military bases. In his current research, much of which takes place in real buildings such as federal offices and large commercial facilities, he's been studying lighting systems combined with advanced wireless control systems, personal and workstation controls, and daylighting, to manage the lighting needs of work spaces energy efficiently.

In some recent studies, Rubinstein and his research team have installed an advanced lighting and wireless control system in a testbed on one or more floors of a building, monitored the energy use, and surveyed the user satisfaction with the new system. Such systems now on the market, or in prototype, use lighting industry standards such as BacNet and DALI, and leverage wireless protocols such as ZigBee and Wi-Fi.

"Modern fluorescent lighting is the most energy-efficient, cost-effective source for general lighting available today," says Rubinstein. "Although solid-state LED technology has advanced, fluorescent lighting technology is also improving in energy efficiency and new features."

Where Edison's Fixture Still Rules

Residential lighting is dominated by the Edison fixture, into which occupants screw incandescent bulbs or compact fluorescent lamps. There are about 4.5 billion of these in the U.S. In commercial buildings, there are about one billion linear fixtures and anywhere from two to three billion lampholder pair fixtures.

"LEDs already have two strikes against them in this market," says Rubinstein, "They have to fit into an electrical infrastructure that isn't designed for LED replacements, and incandescent sockets work best with point sources such as the CFL or incandescent, while the fluorescent works best with line sources such as the linear fixtures everyone knows from office buildings."

Although researchers are working to improve the performance of LEDs and drive down their cost, fluorescent lamp and fixture technology is not standing still either. The lighting industry, Rubinstein points out, has improved ballast technology in fluorescent lighting substantially.

1990s Parabolic Louvered Fixture Efficiency 62% Modern Recessed Direct/Indirect Fixture Efficiency (90% T-5, 85% T-8)

Figure 1. Improved ballasts and innovative fixture design have brought offices better efficiency and lighting distribution.

Ballasts are the electronics that regulate the power flowing into the fluorescent lamp. Back in the 1970s, most fluorescent lamps used magnetic ballasts. At that time, EETD researchers began developing electronic ballasts, which are 20 percent or more energy efficient than magnetic ballasts, and they worked with the lighting industry to field-test and commercialize the technology.

Today, the lighting industry has run with it. Manufacturers have introduced and improved the energy efficiency of instant-start ballasts, and they have introduced and increased the performance and efficiency of ballasts designed for dimming fluorescent lamps.

The industry has also improved the light distribution efficiency of its fixtures (see Figure 1). Rubinstein has measured the fixture efficiency of 1990s-vintage parabolic louvered fixtures at around 60 percent. Current-technology recessed direct/indirect fixtures distribute 90 percent of the light coming from the fluorescent lamp into the space (see illustration).

"My key point," says Rubinstein, "is that if you use LEDs to replace fluorescents, then you are on a battleground where cost is king, and the performance of fluorescents has slowly, but continually improved over the years." LEDs have not yet caught up to fluorescent lighting in cost per lumens of light delivered—they are sometimes ten times more expensive per lumen than fluorescent lighting, and in the lighting market, decisions about which technology to install are cost-driven.

"We are so blasé about how good and cheap modern fluorescent lighting has become, that we forget what a well-evolved technical tour de force it really is," says Rubinstein.

Allan Chen is the leader of the Communications Office in the Environmental Energy Technologies Division at Lawrence Berkeley National Laboratory in Berkeley, California.

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