CHP System: Turbine Reduces Greenhouse-Gas Emissions

CHP, also known as cogeneration, is the simultaneous production of electricity and heat from one fuel source. CHP systems generate more efficient and reliable power, compared to electricity provided by utilities and an overloaded grid. CHP also is designed to reduce commercial and institutional facilities' carbon footprint and lower electricity and fuel costs.

The Central Utility Facility at Fairfield University, which houses the CHP system, came online in 2007. The facility is interconnected with the university's central plant. The system generates 85-87 percent of the university's power needs, Romatzick says, while the remaining amount is delivered in traditional fashion — utility to end user.

"We run parallel with (the utility)," he says. "We constantly import 100 kW (kilowatts), and then we produce the rest of the university's electricity. That keeps the switch open, so that if the CHP plant does go down, the university doesn't even feel it. On the other hand, if the utility company goes down and we have enough capacity in the generator, the university also doesn't feel it."

Facilities that use CHP must decide between a handful of fuel sources to power the equipment, including natural gas, oil, biomass, or coal. The two most common CHP configurations are a steam boiler with a steam turbine and a gas turbine or engine with a heat-recovery unit, according to the U.S. Environmental Protection Agency's Combined Heat and Power Partnership.

The university decided to use natural gas, and the project team specified a recuperated gas turbine to power the system.

"This particular technology on this turbine is extremely low," Romatzick says of its greenhouse-gas emissions. "They only make one size in this turbine, and it has a recuperator on it. It pre-heats your combustion gases before it ignites it. On top of that, they run at a very tightly controlled temperature, which reduces the emissions."

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