Despite the fact that lighting accounts for 26 percent of the energy used by a building and about 10 percent of building costs, only 1 percent of U.S. commercial buildings use cost-saving lighting-control systems says a recent study by Lawrence Berkeley National Lab, Berkeley, Calif., and the Washington, D.C.-based U.S. General Services Administration.
The Commercial Building Partnership (CBP) study was established to develop affordable advanced controls to eliminate wasted lighting energy in existing commercial buildings. The lighting team planned to achieve 80 percent lighting energy savings in existing commercial buildings with controls that cost $2 per square foot installed by 2015 and to work with industry to create next-generation controls. The CBP study then measured energy savings at 10 demonstration sites in seven federal buildings in California and Nevada.
The team replaced existing lighting with workstation-specific lighting, which consisted of an energy-efficient luminaire with a built-in occupancy sensor and individual-controlled digital dimming ballast centered over each workstation.
This system enabled users to control occupancy sensing and light-level tuning for each workstation.With data logs placed in circuits, the study obtained pre- and post-retrofit usage data for a range of scenarios for one or two years at each location. The advanced lighting controls were found to lower energy consumption and lighting energy use intensity (EUI) at all of the sites, though the installation of new fixtures resulted in similar or increased the installed lighting power density. The before-and-after energy savings in the buildings studied ranged from 26 to 66 percent.
The highest level of reductions came from institutional tuning and scheduling, then occupancy controls and, to a lesser extent, from the use of personal controls. In conference rooms and grand jury rooms, for example, occupancy controls led to huge savings—often because lighting previously had been left on before controls were installed.
The study found the lighting equipment paid off in only two out of 10 installations, because of the installation costs. If the buildings operated above the national average lighting energy use intensity, all the retrofits would be cost-effective with energy rates greater than $0.17/kWh—and most would be cost-effective at rates above $0.13/kWh, such as those found in some areas of California. The study concludes cost-efficient systems and familiarity and ease of use are the most critical considerations to ensure the installation and effective use of such systems and, in those areas, the outlook is promising.
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