Lighting accounts for about a third of electrical energy consumption in commercial buildings. As advanced energy-saving lighting controls still have a minority penetration in the existing building stock, building owners have a major opportunity to reduce energy costs with lighting control.
Adoption of advanced lighting controls faces the usual hurdles affecting all energy-efficient lighting, including a focus on initial cost and lack of education about benefits. A particular challenge unique to controls, however, is estimating energy savings.
When lamps and ballasts are replaced, energy savings are easily quantified by subtracting the new lighting system power from the old system power, and then dividing that figure by the old system power. With lighting controls, many factors come into play that can affect projected energy savings, all of them specific to the application characteristics, such as occupant behavior, building design, site orientation, daylight apertures, interior reflectances, and system settings and level of commissioning.
The Lawrence Berkeley National Laboratory (LBNL) analyzed 240 energy savings estimates from 88 papers and case studies. Using filtering to focus on lighting energy savings only produced by lighting controls only in actual field installations only (as field simulations were found to overestimate savings), LBNL produced best estimates of average lighting energy savings for these strategies:
|Occupancy||Lighting status changes automatically based on presence of people||Occupancy sensors, timeclocks, energy management system||24%|
|Personal Tuning||Occupant control of light levels||Dimmers, wireless switches, workstation-specific control, preset scene control||31%|
|Daylight Harvesting||Lighting status changes automatically based on daylight levels||Photosensors||28%|
|Institutional Tuning||Light levels tuned to space needs by application, ballast tuning (reduction of ballast factor), task tuning, lumen maintenance, group controls||Dimmable ballasts, and dimmers and switches used to control group lighting||36%|
|Multiple Strategies||Any combination of the above||38%|
The methodology and results were condensed into a paper published in the January 2012 issue of LEUKOS. The authors concluded:
“This meta-analysis shows that individual control strategies save on average between one-quarter and one-third of lighting energy, and multiple controls strategies can capture up to nearly 40 percent savings on average.”
“The results of this meta-analysis, viewed in aggregate, provide strong evidence that currently available lighting controls strategies can and do provide significant lighting energy savings in commercial building applications.”
The LEUKOS paper can be viewed free here.