Not Dead Yet! Fluorescent Lighting - Part 2
As a continuation from yesterday's blog post, I'd like to also explain the opportunities we have in hybrid lighting. Modern fixtures present lighting designers with the opportunity to adapt the lighting to the needs of the space. Adjustable features such as open wings allow certain fixtures to throw more light onto a ceiling and flatten the light out evenly, providing even illumination that is ideal for low-ceilinged rooms.
Rubinstein argues that "until research drives the cost of LEDs down substantially, the greatest potential for improvements in lighting energy efficiency will come from combining advanced lighting controls with hybrid (fluorescent and LED) lighting systems, and designing the lighting to fit the space and occupant requirements in which they're used."
Figure 2 illustrates a hybrid lighting solution called task-ambient lighting, which some lighting designers are using more frequently. An overhead or undercabinet fluorescent fixture provides low ambient lighting to the pictured office, while an LED desk lamp provides task lighting to the office occupant at the desk and screen levels.
But Rubinstein believes that the real future of energy-efficient lighting is in hybrid systems with control devices. "As time goes on we're going to get smarter and smarter, and develop smart furniture with built-in occupancy and light sensors. The sensors, as part of a larger automated building energy control system will reduce the energy we waste from lighting we don't need."
Using a wireless lighting control system such as that pictured schematically in Figure 3, the lighting can respond automatically to increases or decreases in daylight coming through nearby windows if these are present; shut down and turn on automatically when office occupants leave and re-enter their office space; and even respond to the conditions on the electricity grid such as high prices or unusually high demand prefiguring grid failure (another technology known as automatic demand response).
An important component of this system will be personal controls. "Study after study has shown that lighting systems which give user personal control over the lighting in their work area results in saved energy," says Rubinstein. "They give users who don't want the full level of ambient lighting the option to set lighting at the level they're comfortable with."
A study by Rubinstein in a federal building showed that occupant-responsive lighting and personal controls resulted in 40% less lighting energy use than an energy code-compliant baseline system that had low power density but was manually switched. By giving occupants control over their environment, and the ability to adjust the overhead light level to their satisfaction, they make occupants feel happier with their surroundings--despite other shortcomings in their environment.
"Modern fluorescent lighting is the most efficient, cost-effective source for general lighting available today," he concludes. "Until LEDs become cost-competitive with modern fluorescents for general lighting, hybrid solutions are still the most energy-efficient lighting systems in the marketplace. And whatever lighting technology is used, the key to maximum energy savings and comfort is an intelligent control system that combines automatic with manual controls."
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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