Over 10,000 calls are placed to University Operations Center each year from disgruntled students complaining about the temperature of their rooms, but very few students actually know how Harvard buildings, are heated, or in very rare cases, cooled.

Here, The Crimson brings you an exclusive, behind-the-scenes look of thermodynamics at Harvard.

According to Harry A. Hawkes, director of engineering and utilities, Harvard uses "district heating," which delivers steam from the Blackstone Station power plant in Cambridge through tunnels and buried lines to multiple buildings on campus.

The plant is located at the intersection of Memorial Drive, Western Avenue and Blackstone Street and is owned and operated by the Commonwealth Energy System (COM/Energy)

"Commonwealth Energy makes steam and we buy it from them," Hawkes says. "The steam travels in underground tunnels and across the river to serve different buildings at Harvard. There are about three-and-a-half miles of tunnels extending from the Blackstone power station along Memorial Drive and north to the Law School and through the Weeks Memorial foot bridge to the Business School."

Approximately 200 University buildings are currently heated with steam although only Radcliffe and the Quadrangle have their own boiler rooms, says Hawkes.

Steam is an older method of heating that Harvard has used since the 1920s, but the College is by no means the only institution to maintain this seasoned process. According to Morris A. Pierce, district energy historian and energy manager for the University of Rochester, a recent census by the Department of Energy found more than 30,000 district heating systems in the United States and thousands more worldwide.

"This method of heating is used in various parts of the country, but mostly in Europe," Hawkes says. Chief Engineer Paul A. Parziale adds, "Harvard is the plant's biggest customer. We're a small co-generating plant. We produce electricity and steam, [and] the steam mostly goes to Harvard."

The Logistics of Heating

A co-generation plant produces both heat and power from one thermodynamic process.

Hawkes says that the plant produces steam at high pressure, runs it though turbines to create electricity and then distributes the lower pressure steam to be used for heating.

The small plant has four boilers that operate at over 400 pounds per square inch steam pressure each.

To produce steam and electricity, the plant burns natural gas or number six fuel oil, which is a residual oil, according to Parziale. He adds that the emission stacks are monitored 24 hours a day "to ensure environmental safety."

Harvard buys the steam from COM/Energy at high pressure and converts it to lower pressure through regulating valves in the tunnels.

"We buy it at 100 pounds per square inch from the plant, but the pressure is under 12 pounds when it enters the building," Hawkes says.

Once the steam enter the building, it goes into a radiator, turns into water and gives off heat in the process--the same type of reaction that causes third degree burns from steam. When the water vapor contracts into a more dense state--from gas to liquid--it gives off energy in the form of heat. Once the steam condenses to water after it has served its heating purpose, it is sent back to the plant through the same system of underground lines and tunnels.

Why Steam Still Matters

Hawkes says buying steam has advantages and disadvantages. "Nothing is a bargain," he says. "This system allows more space in [University] buildings and better use of space without having boiler rooms in each building." Hawkes also adds that steam heating is a lower maintenance system for the University.

At the same time, because the plant is not located directly on campus, the pipes lose some heat as the steam travels through the underground system. Engineers must also worry about the thermal expansion of underground pipes through junctions. "In 300 feet, [the pipes] may expand six to nine inches when they go from room temperature to steam at 400 degrees Fahrenheit," says Hawkes.

Once the heat reaches the pipes outside the building walls, control moves out of the hands of Engineering and Utilities into the domain of Facilities Maintenance Operations, and Hawkes can take a break.

"My responsibility is to bring the steam up to the wall of the building," says Hawkes.

Infiltrating the Buildings

Harvard's original steam source was the Boston Elevated Railway (now the Massachusetts Bay Transportation Authority Red Line) power house, located on Memorial Drive next to Weld Boat House. When the plant was razed to build the river houses, Harvard began to buy steam from the COM/Energy Blackstone Plant down the river.

When the plant moved down the river, Harvard had to build tunnels and lines to transport the steam. Weeks Bridge, for example, was not built for the purpose of a 'nice little foot-bridge,'" says Hawkes. "It was built to get the utilities across the river."

And despite the fact that one's room always seems overheated, Hawkes says a chilled water plant, located in the basement of the Science Center, does exist.

Unfortunately, "the chilled water plant is primarily not used for dormitories," he says. The cooling system is used mainly for libraries, laboratories and classrooms. In a similar method to steam distribution, the chilled water is produced at the plant at 42 to 44 degrees Fahrenheit and then pumped underground to about 65 buildings.

According to Hawkes, the plant works just like a refrigerator.

"Water is cooled down with a heat exchanger using freon as refrigerant," he says. "In the chiller, gas is compressed, and then as it expands, the cooling effect results."

The plant runs though the winter to cool laboratories or other locations with special needs.

"Treasure rooms, [for example], need cooling in winter to control humidity," Hawkes says.

Currently, the chilled water plant is expanding from 8,000 to 13,000 tonnage. To put this into perspective, Hawkes says a typical window air-conditioning unit in a bedroom is half a ton.

The Cost of It All

All this heating, cooling, electricity and water and sewage treatment costs the University approximately 25 million dollars each year. Heating alone amounts to about five to six million dollars, which comprises about half a percent of the University's 1.5-billion-dollar operating budget, according to Hawkes.