Replacing the incandescent bulb with a more efficient light source is only the first step in developing an energy-efficient lighting system. Improved fixtures can raise the system's efficiency even further. At LBL's Energy-Efficient Fixtures Laboratory, researchers in the Lighting Systems Group study the optical and thermal efficiency of luminaires, and work closely with fixture manufacturers to develop more efficient products. "Fifty to seventy percent efficiencies are now typical of fixtures," says senior research associate Chin Zhang, "and we're trying to improve them to eighty to ninety percent."
Oliver Morse adjusts a centralized light guide system consisting of a 250-watt metal halide lamp, a high-efficiency beam splitter and four hollow light guides. This results in a lighting load of only 60 watts per work station with light levels even higher than those provided by typical fluorescent systems and superior light quality.
A visitor to the Lab will see test devices that mimic the ceiling plenum space, found in most commercial buildings, into which the lighting fixtures are recessed. These chambers are designed for studying the thermal characteristics and performance of different types of fixtures such as CFL recessed downlights, T12 recessed, and pendant-mounted fixtures. The simulated plenum chambers are ideal for measuring light, input power, and temperatures of these fixtures and light distribution systems. For example, researchers can use these chambers to study the performance of a typical T12 fixture with or without "spot coolers," a thermally conductive device developed at LBL to optimize light output of the fixture. The long, narrow T12 fluorescent fixture has been a traditional staple of office lighting systems.
The air-handling test facility, a specialized version of the plenum chamber, simulates the flow of air through open luminaires, measuring the performance of air-handling and static fixtures. As air flows from below into the plenum, a photocell measures the relative light output as a function of lamp wall temperature and air flow rate. Venting cools fixtures and has been found to increase performance by up to 20 percent (CBS News, Winter 1993, p. 4).
The Lab's dirt depreciation chamber provides a dust-filled facility to study the effect of dirt deposits on the light output and temperature of vented versus unvented CFL fixtures. The chambers air injection and heating system produces simulated convection currents that propel fine dust into the fixtures as photocells measure their behavior.
A new testing device is under construction that will help design and measure the efficiency of advanced centralized lighting distribution systems. An example of such a system is a single light source attached to one to four hollow light guides that distribute the light to four task planes at the same time (see photo). Researchers will measure the system efficacy and optical efficiency, as well as the quality of light cast by such advanced lighting technology.
Looking to the future, researchers are constructing a gonio-photometer to measure the optical distribution of light from various luminaire systems. With this device, they will produce industry-standard photometric reports on new lighting systems.
The Lighting Systems Group works closely with the U.S. lighting industry to transfer its efficient fixture technology. Over the years they have established joint research and training programs with manufacturers such as Osram, GE Lighting, Lithonia and Cooper Lighting. It is also cooperating with Southern California Edison and other California utilities, lamp and fixture manufacturers, LBL' s in-house energy management group and the National Institute for Standards and Technology on efficient lighting demonstration projects.
Lighting Systems Group
Results from the Lighting Laboratories include:
On to more information about the Lighting Research Laboratory
EETD Newsletter Home Page
CBS Newsletter Home Page
Table of Contents for this Issue