In spring 2012, the Department of Facilities tapped one of MIT’s greatest resources—its students—to learn more about electricity consumption on campus.
Working with Lecturer Stephen A. Hammer of the Department of Urban Studies and Planning, Facilities tasked a team of undergraduates to conduct a study of plug load on campus—the energy consumed by the appliances and electronic devices plugged into outlets.
Plug load estimates are important in determining the size of a building’s heating, ventilation, and air-conditioning (HVAC) system, because lab and office equipment generates heat. Yet Facilities has found that industry standards tend to inaccurately estimate plug load, which can lead to oversizing the HVAC system and paying higher energy costs, according to Peter Cooper, manager of sustainable engineering and utility planning for Facilities and a member of the MIT Energy Initiative’s Campus Energy Task Force (CETF).
“The energy consumed via plug load has changed dramatically in the last 20 years,” says Julia Ledewitz, sustainability and LEED coordinator for Facilities, who also participates in the CETF. “In classroom and office spaces we’re seeing three times what we used to see at the plug load level. The amount is now closer to the energy consumed by lighting and the heating and cooling of spaces.”
This uptick has occurred because the use of electronics has skyrocketed—now accounting for an estimated 20% of the electricity consumed in US commercial office buildings. At the same time, plug load has become increasingly important because efforts to insulate buildings and improve lighting systems have reduced other major energy demands.
But the only way to know the exact plug load of a space is to measure it—which is where the students came in.
“This [plug load study] was a very quick and easy, low-cost way to get at this information—while giving students exposure to how one does this kind of field work,” says Hammer, who reached out to Facilities to develop this project for a class called Re-Energizing MIT. The class, supported by the S.D. Bechtel, Jr. Foundation and the d’Arbeloff Fund for Educational Excellence, gives students hands-on experience as energy consultants working with MIT to improve campus energy management.
Erica Lai ’14, a materials science major who is minoring in energy studies, teamed up with Jennifer Liu ’14, an electrical engineering and computer science major, to conduct the study, which involved metering outlets and analyzing usage in E62, the new Sloan School of Management building.
The students tracked all the power consumption in eight discrete spaces—seven offices and a copy room—for one week and found that the average weekday peak load in this densely plugged area did not exceed the average year-round peak load projected for the building. “They found the estimates were a little conservative,” Hammer says, suggesting that the building’s designers expected higher plug loads than have materialized.
“It’s a small sample size, so the findings are still inconclusive, but what’s important is that we now have actual field measurements that Facilities can add to over time,” Hammer says, noting that the information will help when MIT is designing or retrofitting buildings in the future.
The students also found that computer equipment was the primary driver of plug load, with laptops consuming “between 2 and 13 times less power in a 24-hour period than desktops due to lower usage patterns and the energy-efficient nature of laptops,” according to their report.
Laxmi Rao, IT energy coordinator for Information Services & Technology (IS&T) and a member of the CETF, says the students’ measurements confirm IS&T’s understanding of energy usage. “Across campus there is a noticeable trend toward laptops and energy-efficient monitors that—as they note—will contribute to a significantly lower load factor.”
The students presented their work to Executive Vice President and Treasurer Israel Ruiz and other members of the CETF in May, and the work was very well received. “The rigorous, data-driven, student-led research projects open up a myriad of exciting opportunities to expand the good work of the Campus Energy Task Force and increase the range of energy efficiencies on campus,” says Ruiz, CETF co-chair. “The students did a great job.”
Going forward, Hammer and Ledewitz both say they plan to expand the plug load project to evaluate usage elsewhere on campus. “We’ll continue to invite students to conduct these valuable [energy] studies,” Ledewitz says. “Each project helps us to understand how the campus and its community are using energy and how best to plan ahead.”
This article appears in the Autumn 2012 issue of Energy Futures.