To take one calorie of heat out of a hot classroom in the summertime, or to add a calorie to a cold space in the winter, Ball State University’s boilers, all from the middle of the last century, have to burn one calorie of coal. But in a few months, the university’s heating and cooling system will become seven times more efficient by dumping heat or gathering it, depending on the season, from the dirt around six feet under the campus.
It seems that universities are competing more and more these days in the efficiency of heating and cooling. New York University recently unveiled a heating and cooling system that it says is 90 percent efficient. Ball State, in Muncie, Ind., says its technology — called a ground source heat pump — is not new, but that its system will soon be the largest installation of its kind in the country, if not the world.
As with a conventional air conditioning or heating system, water is heated in winter or chilled in summer and moved through pipes that have room air blowing over them. Yet the heart of the technology is machinery that can transfer heat in either direction.
In the summer, it can take heat out of the piping that runs to the room air and put it in a separate water loop that can be sent to a cooling tower. In winter it can draw heat from a separate loop and add it to the piping for room air.
The key to the system is a series of pipes buried below the frost line, which in Indiana means about six feet under the ground. In the summer, water carrying heat from the air conditioning system can give off that unwanted energy to the soil, which is at 55 degrees. This expends considerably less energy than giving it off to the warm, muggy air. In the winter, it can pull out water at 55 degrees and extract heat from it to warm the rooms.
“When you’re heating or cooling, everything is about transferring energy,’’ said James W. Lowe, the director of engineering, construction and operation at Ball State, where he oversees the heating and cooling of some 5.5 million square feet.
The system will eliminate almost all of the university’s $3 million annual bill for fuel but will take about $1 million a year in electricity to run.
The installation, which will take several years, will cost $75 million to $80 million, Mr. Lowe said.
That would seem to imply a payback time of about 40 years. But two of the university’s boilers date from 1940 and another two from 1955, and all are due for replacement. The university priced out new boilers, which could have burned coal but also up to 30 percent wood or other biomass, but those would have cost $65 million to $70 million, Mr. Lowe said. So the additional cost involved in cycling energy into and out of the ground is at most $15 million, he said.
The New York Times