Greening MIT

Continued from page 3

Some of the changes rely on more advanced technologies, at least to identify the problems that need fixing. MIT's large buildings use heating, ventilation, and air-conditioning systems very different from those used in homes. Enormous air handlers regulate temperature with steam coils for heating and chilled-water coils for cooling--both fed by MIT's central cogeneration plant, which captures the waste heat from electricity generation to make steam that can be used directly or harnessed to drive compressors and refrigerators. Such air handlers are often controlled by a system that records data such as temperatures and flow rates of air and water, and pressure differentials in the ductwork.

MIT's control system, one of the largest in North America, collects and sends about 50,000 data points every 15 minutes. Typically, this kind of information isn't preserved or analyzed; it's used only to control air handling from moment to moment. But lately a few companies have started to set up systems that translate measurements originally recorded in different terms so that certain data can be archived and analyzed comprehensively with the help of computer models and algorithms devised by mechanical engineers and other experts. This type of analysis helps companies determine whether a building is operating the way it's designed to. They can then identify problems and estimate how much it will cost to fix them.

MIT has enlisted one of these companies, Boston-based Cimetrics, to monitor and analyze some of its buildings. The company has so far identified ways to save more than $500,000 a year; about half of these projects have been completed. In Building E25, for example, the readings revealed that a new system designed to capture some of the heat being pumped out of the building by the ventilation system wasn't working properly. "Our guys went crawling through the ductwork and found that it had collapsed," Cooper says. Without the analysis from Cimetrics, "this might never have been found--and certainly not soon enough to be fixed under warranty."

But while most buildings on campus are on the building control system, analyzing all of the captured data "is hard, expensive, and almost impossible to do by hand for over 100 buildings on MIT's campus," says Stephen Samouhos '04, SM '06, a mechanical-engineering doctoral student involved in several energy projects on campus. "Even for one building, control data analysis is very challenging to perform." Samouhos speaks from experience, having studied the information science and technology building (N42) to identify opportunities to conserve energy. But within days of installing sensors in N42, he found ways to reduce energy consumption by 25 percent. One source of waste: the lights stayed on all night. "If you walk around that building, you can't even find where the light switches are," he says. He also discovered that because the building was designed to hold a never-installed data center, which would have generated a lot of heat, it has a bigger air conditioner than it needs. And even though that air conditioner can cool the building in about 20 minutes, it's switched on four hours before anyone arrives for the day. The fix is simple, Samouhos says: just uncheck one box in the control software.

And in building 6C, Samouhos discovered that occupancy sensors--designed to shut off the lights when no one was around--had been mistaken for light switches and turned off. "It's the last mile of finishing a project that prevents us from capitalizing on projected savings," Samouhos says. Labeling sensor switches "is not very hard to do," he points out. "You just have to have somebody to do it."

Taking care of such details will be important in new campus construction, which is being guided in part by a process called integrated design, says Leon Glicksman '59, PhD '64, a professor of building technology and mechanical engineering, who cochairs the Campus Energy Task Force. In integrated design, efficiency measures--such as more thoroughly insulated windows with better coatings to keep heat out in the summer and in during the winter--are considered at the same time as basic systems such as heating and air-conditioning. That way, for example, a smaller-than-usual air conditioner can be chosen in anticipation of lower cooling requirements. The new Sloan Building, which Glicksman says will probably be the most energy efficient building on campus, will use windows that will enhance energy savings in the winter by capturing more solar energy and yet reduce the amount of heat lost through the windows at night. But integrated design pays off only if building managers make sure that the energy-saving designs work as planned. So the new buildings will be monitored to confirm energy savings.