|Princeton University hopes to get a green light this year from New Jersey’s Department of Environmental Protection to run its heating plant on 99.9 biofuel.
The system provides heat for 150 buildings amounting to approximately 9 million square feet of climate controlled-space. The campus has a daytime population of 10,000.
The university conducted a test in the fall of 2007 in which it ran its General Electric gas turbine on the 99.9 biofuel, said Ted Borer, Princeton University’s energy plant manager. It was the first time in the world that biofuel was used to fuel the GE LM1600 gas turbine, which originally was developed as the engine for the Stealth Fighter and the Navy FA-18. The turbine is used to generate steam for heating and 15 megawatts of electric power for the campus.
The test went so well that the university plans to apply to the state this spring for a permit to run the system on biofuel.
Currently the system runs primarily on natural gas, with No. 2 heating oil as the backup, or secondary fuel. But if the state approves use of biofuel, that would become the secondary fuel, ahead of the heating oil.
“It burns better,” he said of the biofuel. The boilers operate with more stability on biofuel, but on heating oil, “even with very slight impurities, the boilers tend to rumble and shake a little bit.”
Princeton’s energy plant received a 2007 Energy Star CHP Award from the U.S. Environmental Protection Agency and the U.S. Department of Energy for its efforts to reduce pollution and improve energy efficiency. CHP stands for combined heat and power, also known as cogeneration. Princeton installed its natural gas-fired cogeneration system in 1996 to support electricity, heating and cooling and research needs on campus.
The university is striving to reduce its carbon dioxide “footprint” while simultaneously aiming for cost effectiveness. Adding the capability to heat Princeton buildings by burning biofuel suits this overall aim because it requires only minor changes to the plant’s equipment and results in much lower emissions.
Before embarking on the pilot project in the fall, Borer’s department conducted a thorough engineering analysis. “We looked at every component that the fuel touches to make sure it’s okay with that fuel,” he said.
Some other institutions are using biofuel blends with much smaller percentages of biodiesel. Taunton State Hospital in Massachusetts, for example, is using B10 (see “A B10 Success,” January 2008 Fuel Oil News). Why did Princeton choose to go with close to 100 percent biofuel?
The university chose a blend of 99.9 percent biofuel for two reasons. One was to maximize reduction of carbon dioxide emissions. Secondly, “If you use 100 percent biofuel, you don’t get the blender’s credit because you’re not blending anything,” Borer pointed out. “If we’re going to switch fuels – do all the analysis that’s involved – we might as well go all the way.”
To prepare for the test run last fall, “we did an extensive engineering review,” Borer said. “We looked at every single component, every fitting that the liquid fuel touches, to confirm that it would not have material compatibility issues. And we worked extensively with General Electric on the engine.”
In the engineering analysis, material compatibilities were closely scrutinized, and it was decided best to avoid use of copper, brass and bronze components. “There are a few lines in the plant that we’re going to change from copper to stainless steel,” he said.
Borer said he’s optimistic that the state’s DEP, once it receives Princeton’s application to burn biofuel, will approve it. If the application is submitted as currently planned, in April or May, an approval could be forthcoming some time in the fall. Then it will be time to identify biofuel suppliers.
“We’ll try to work out contract terms so we can be confident we’ll get supply in any conditions,” Borer said. The biofuel suppliers who participated in the project last fall were Fuel Bio, Elizabeth, N.J. and Keystone Biofuels, Shiremanstown, Pa.
As for the cost of biofuel, it differs somewhat depending on the feedstock that it comes from. Discussing soy-based biofuel, he said in an interview in February, “Right now it’s a good bit above the ULSD, but with some of the state and federal [incentives] it looks like we can bring it down” close to the cost of ultra-low sulfur heating oil. By contrast, biofuel from waste kitchen oil “looks like it could come in at the ULSD price.”
Borer said, “I’m hopeful we’ll be able to come close to the cost of the ULSD.”
The combustion process can be tweaked to squeeze out more BTUs per gallon. “We found it to be a very good fuel from an operating standpoint,” he said. Gelling was not a problem during the test, possibly in part because he chose to conduct the test in a two-week period spanning the end of September and the beginning of October.
“We ran the test during the fall when there are no temp issues,” Borer said. “But if we operate this long term, we definitely want to get a fuel oil heater to bring the fuel up to between 100 and 150 Fahrenheit. That’ll knock down the viscosity a little bit and keep us out of any gel point issues. We always have a ready source of steam, so it would be pretty easy to put in a little steam heat exchanger.”