By Steve Rizer
Could energy consumption in office buildings soon plummet through the widespread adoption of advanced power strips (APSs)? Considering the results of a recent U.S. General Services Administration (GSA) evaluation of the new technology and the fact that plug-loads account for approximately one-quarter of total electricity use in office buildings, the potential for making such structures significantly greener could be enormous.
APSs are designed to save energy by controlling plug-in devices according to a schedule or based on a given device crossing a power threshold. Through its Green Proving Ground (GPG) program, GSA assessed the effectiveness of APSs managing plug-load energy consumption in eight agency buildings. Three types of plug-load-reduction strategies were evaluated: schedule timer control, which allows a user to set the day and time when a circuit will be energized and de-energized; load-sensing control, which monitors a specific device’s (“master”) power state and de-energizes auxiliary devices (“slaves”) if the master’s power consumption dips below a predetermined threshold; and a combination of the two.
Results underscored the effectiveness of schedule-based functionality, which reduced plug loads at workstations by 26 percent even though advanced computer power management was already in place, and nearly 50 percent in printer rooms and kitchens, according to GSA.
For the project, GPG personnel worked with a team from the National Renewable Energy Laboratory (NREL) to identify buildings with office setups and equipment distributions typical of the wider GSA building stock. Eight buildings from GSA’s Mid-Atlantic Region, where plug loads average 21 percent, were selected. In each building, approximately 12 standard power strips with no control capability (the incumbent technology) were replaced with APSs, which monitored and provided power to an array of devices. More than 295 devices were monitored during the study, which consisted of three separate test periods, each four weeks long. All buildings selected had workstation power management in place.
The APS selected for the evaluation provides web-based control, monitoring, and data collection. Using this technology, NREL gathered three months’ worth of energy-usage data for each control strategy. Based on this information, researchers were able to determine overall performance at the end of each test period, compare that performance to baseline energy consumption, and adjust control strategy parameters in an effort to achieve maximum energy savings. Results were annualized and extrapolated for whole buildings. Researchers also surveyed occupant reception of the new technology.