U. power plant wins award for efficiency

The same type of engine that powers F-18 fighter jets also generates electricity and heat on campus.

For its efficient cogeneration process, the University power system has just won the Environmental Protection Agency's 2007 Energy Star Combined Heat and Power Award.

"It's really, really great in that it reduces the need for electricity because its so efficient," said James Kuczmarski '08, a member of the Wilson School task force "Sustainable Use of Energy at Princeton University."

To produce energy, Princeton uses a cogeneration system, a plant that provides power and thermal energy from only one input fuel. The current program burns either natural gas or diesel. Yale and Harvard also have cogeneration plants.

Ten years ago, the former setup, which imported power from an off-campus grid to generate steam, needed to be updated, so the Facilities Department decided to bring power generation onto campus. The cogeneration plan appeared to be the most economical. That meant vacating 200 Elm Drive, which previously housed the campus boilers and now is home to Public Safety.

"We felt it was a very beneficial thing that it was less detrimental environmentally," energy plant manager Ted Borer said.

The jet engine turns a turbine that then rotates a mechanism that converts mechanical energy into electrical energy, producing 15 megawatts. Exhaust is routed through the boiler to warm campus water and to produce steam for heating. By combining the two processes the University can recapture excess heat, raising the efficiency to between 70 and 80 percent.

The Energy Star award is given to cogeneration plants that use five percent less fuel than modern plants with separate power and thermal systems.

The University's cogeneration plant requires 21 percent less fuel than an on-campus boiler powered by grid electricity, and it has reduced carbon dioxide emissions by 27,936 tons per year.

"Over the past few years there has been a real push to reduce energy use," Borer said. He added that Facilities has worked to make changes such as isolating pipes or refining inefficient control — a comprehensive "recommissioning effort" that has involved checking the heat and thermal use of each building on campus.

Borer said that though "the campus is growing, we need a little less steam at any given air temp[erature] outside than two or three years ago."

In addition to the environmental benefits, Princeton chose the cogeneration plan because of its economy. Having the generator on campus increases flexibility and reliability. The plant can switch between natural gas and diesel within 90 seconds, based on changes in input price or availability.

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"We very carefully make economic decisions," Borer said. "We watch the prices on the grid very carefully."

The campus is on the simultaneous power grid with New Jersey, Pennsylvania and Maryland. Should something fail within the University's generator or should campus energy needs exceed the generator capacity, the University purchases power off the grid. It can also sell excess power back to the grid, though the campus is a net purchaser.

Total campus power use vacillates, depending on the time of day and the season. During the winter months, the campus draws about 20 megawatts during the day and 10 megawatts at night. The summer energy draw can reach a high of 25 megawatts during the day. Demand is lower in the spring and fall.