Greening MIT

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Energy Hogs

Amanti's time-lapse photos showed Building 18's lights glowing constantly day and night. Light-sensor readings revealed that the building was twice as bright inside as others on campus. But the lights, Amanti calculated, accounted for only 5 percent of the electricity used. The main problem--the reason this building consumed more energy per square foot than any other MIT building but one--was that it had 200 fume hoods, and researchers were leaving them open when they weren't in use.

Fume hoods are "one of the greatest energy hogs on campus," says Stone, who cochairs the Campus Energy Task Force. These cabinetlike devices use fans to pull air away from the confined environment of the laboratory, carrying traces of toxic chemicals outside so that researchers don't breathe them in while doing experiments. But in so doing, they're constantly pulling heated or cooled air out of the building. "It's like leaving your front door and your back door open all day," says Peter Cooper '70, manager of sustainable engineering and utility planning at MIT's facilities department. By one estimate, he says, a single fume hood typically accounts for as much annual energy use as two homes--and there are more than a thousand on campus.

Conventional fume hoods pump air at the same rate whether their glass doors are open or closed. The hoods in Building 18, however, had been selected because the airflow drops by two-thirds when the doors are closed, potentially making them much less wasteful. But the researchers were defeating the purpose. Amanti found that some had even disabled alarms designed to sound whenever the hoods were using more energy than necessary, "jamming the mute button with scraps of paper," he wrote.

Lab heads had little incentive to get researchers to close the hoods. Individual departments and researchers don't pay their own energy bills, Cooper says; the Institute as a whole picks up the tab. Requiring each lab to pay for the energy it uses might motivate researchers to save, he says, but the current policy is unlikely to change--for good reason. At MIT, it's easy for, say, a biologist and an electrical engineer to form a lab together. Although getting space allocated can sometimes be a challenge, "they don't have to worry about the biology department and the electrical-­engineering department combining their budgets," he says. "When we compare ourselves to other research universities, a lot of our success is because we have interconnecting corridors and a common financial system."

As it turns out, people can be persuaded to change even without a financial incentive. After the head of the chemistry department, Tim Swager, learned how energy hungry his building was, he decided to do something about it, and went looking for a way to reveal the most wasteful labs. Each fume hood is equipped with sensors that record how far open the doors are and relay that information to a system that controls the airflow. Swager found $12,000 to develop a program to convert the data into reports that compare all the labs, identifying the best performers and exposing the worst offenders.

The reports prompted researchers to close the hoods more often; that saved the Institute about $24,000 a year and reduced carbon dioxide emissions by 93 tons in Building 18 alone, according to an analysis done by Dan Wesolowski, PhD '08. Even though the chemistry department itself didn't save any money, Cooper says, "just giving them information changed behavior."