In an effort to bring home the issues of energy and sustainability, a student team from the Stewart School of Industrial and Systems Engineering analyzed electricity practices and identified potential energy savings for the ISyE complex. The team's findings prompted Georgia Tech Facilities, who provided assistance throughout the project, to enact a more sustainable nighttime lighting policy in the ISyE buildings.
Graduate students Seth Borin, Todd Levin, and Cauvery Patel performed the calculations this spring as a project for their "Quantitative Analysis of Energy and the Environment" class led by Dr. Valerie Thomas, Anderson Interface Associate Professor of Natural Systems. The team observed that the three buildings that comprise the ISyE complex - the Groseclose Building, the ISyE Main Building, and the Instructional Center (IC - account for almost $200,000 in annual energy expenditures. They decided to focus primarily on the electricity consumed by the buildings' lights, vending machines, and computers.
The students identified lighting as the area with the largest potential for energy savings. Their methodology divided ISyE floor space into common areas and private areas. Common areas such as hallways, lounges, and restrooms receive sporadic activity throughout all hours of the day while the use of private areas such as offices and classrooms is largely constrained to daytime hours. The team observed the lighting and traffic patterns of the ISyE complex and defined a low-activity period from 7:30pm to 7:30am during which occupancy sensors could be used to regulate the facilities' lighting.
Combining infrared and ultrasonic technology, occupancy sensors detect human activity and control luminosity accordingly. By the team's estimations, a two-thirds reduction in default lighting intensity coupled with the use of regulatory sensors could produce savings in excess of $7,000 annually, recouping the initial investment in as little as three years. In some areas, the potential energy savings are even more profound; the installation of sensors in the IC's Tennenbaum Auditorium, which consumes an estimated 25 megawatt hours (MWh) of electricity annually while not in use, could pay for itself in less than one year.
For ISyE, the students' diligence will not go unrewarded. At the end of the spring semester, Georgia Tech Facilities installed occupancy sensors in the bathrooms, hallways, and lounges on all four floors of the Groseclose and Main Buildings. In the past, no policy existed to adjust common area lighting output during the low-activity period.
In a similar fashion, the graduate students examined the viability of "smart" vending machines that make use of occupancy sensors to regulate the activity of their motors and compressors. Fitting the ISyE complex's seven vending machines with sensors could reduce the units' energy costs by 46 percent, equating to $500 in annual savings.
The team also measured the energy usage of the computers in the IC classrooms, the Undergraduate Lab, and the Graduate Lab. An average computer consumes 88 watts while in use but only 43 watts while idling with the monitor off. Furthermore, an offline computer left plugged into its power strip still draws one watt of power. The team estimates that computer utilization drops to 11 percent between the nighttime hours of 6pm and 9am, and their recommendation to shut down machines after given periods of inactivity could amount to $2,000 in annual energy savings.
Overall, the team identified the potential for the ISyE complex to decrease its yearly energy consumption by 137 megawatt hours, a five percent reduction equivalent to the annual carbon dioxide emissions of 14 households. The students' recommendation also urges Georgia Tech Facilities to meter energy consumption on a departmental basis in order to incentivize a reduction in energy usage.
For more information contact:
Barbara Christopher, Industrial and Systems Engineering
Contact Barbara Christopher bchristopher@isye.gatech.edu
404.385.3102