Biomass on Campus
It's a big job keeping 27,000 students warm though the winter. The University of South Carolina in Columbia looked to a new source of heat and found that the savings would be measured in the millions of dollars.
The university hired Johnson Controls Inc. to do a comprehensive energy audit of the school's campus and implement projects to increase energy efficiency, says Helen Zeigler, USC associate vice president for business and facilities. Johnson Controls is a $36 billion a year diversified company with core businesses in building efficiency and control and power technology. After four months of study, Johnson Controls submitted a list of 18 projects that would reduce the consumption of fossil fuels on campus and would pay for themselves in a 10-year period, which was a criteria set by the university. "We are trying to keep the campus warm and do it in a greener and less costly way," Zeigler says.
In July 2006, Johnson Controls began construction of the biomass-fired steam system. The original contract to build the facility was for $16 million, but changes made in response to residents' concerns over noise and dust added another $1 million to the cost. The facility was enclosed in a shell that complemented the architecture of the campus. An electrostatic precipitator was added to control emissions. The final change was that fuel deliveries were rerouted and rescheduled to minimize traffic congestion and noise in the residential neighborhoods surrounding the campus. "We decided to invest the additional money to meet those concerns and be a good neighbor while we built this," Zeigler says.
Education was the key step to gaining community acceptance of the project, Zeigler says. "First we had to educate ourselves because we had never heard of a facility like this prior to Johnson Controls proposing it," she says. "Once we were comfortable with the technology, we began meeting with neighborhood groups about what we were going to put on the site. Once we met all the concerns of the neighborhood groups, they have become very supportive of the project. They see that we are a university and if anyone is going to take a leadership role of trying new technologies, we should and will do that."
Three Nexterra Energy gasifiers supply enough syngas to provide 80 percent of the USC's peak winter heat demand plus generate 1.38 MW of electricity.
SOURCE: NEXTERRA ENERGY CORP.
The original permit for the plant didn't require air quality control equipment, although the U.S. EPA was reviewing its regulations for biomass plants as the plant was being designed. The particulate control system was added in part to anticipate it being required in the new regulations and to ease community concerns. Many other issues were also addressed in the permitting process. "The plant is in a very sensitive location as far as nearby residences, a flood plain, railroads and a nearby airport," says Ken Detwiler, senior project manager for Johnson Controls. "So we have had to address permitting issues regarding all of those things."
A Big Job
Supplying heat to the university campus was a major undertaking, Detwiler says. The campus is spread out across much of the community and includes more than 170 buildings. "All of the steam distribution system is underground and very extensive," he says.
The facility will run on wood waste from the International Paper Co. plant in Newberry, S.C., about 40 miles from the campus. The fuel will be primarily bark, which is a byproduct of the wood chipping process. "There is a tremendous amount of waste wood when they strip the trees of their bark," Detwiler says. "We are getting that bark ground up and shipped to our plant. We will store the bark on site." The facility will require 57,000 tons of wood per year-about 10 semi-trailer loads a day-for fuel.
The biomass gasifier and boiler were built by Nexterra Energy Corp., a Canadian firm. In October 2007, during the project in South Carolina, Johnson Controls and Nexterra formed a strategic alliance where the two companies will jointly develop and implement biomass gasification projects.
The USC system will have the capacity to produce enough steam to provide about 80 percent of the heating needs of the campus. The waste wood is turned into synthesis gas in a low-oxygen pyrolysis process. The gas is reformed at the top of the gasifier into a mixture of methane, hydrogen and carbon monoxide. The gas is fed into an oxidizing chamber where air is added to produce combustion. "You are actually burning gases rather than burning wood," Detwiler explains. "It is a much cleaner process when we do it that way."
The combustion process raises the temperature of the gases to about 1,900 degrees Fahrenheit. The hot gases are fed into a waste-heat boiler that generates steam at 600 pounds per square inch (psi) at 740 degrees F. The system can generate 60,000 pounds of steam per hour.
The gasifier produces steam at a higher pressure than is needed for the heating system. That extra pressure is used to turn a backpressure turbine generator to produce electricity.
The Nexterra gasifier breaks biomass down into combustible gases which are burned to heat high pressure boilers.
SOURCE: NEXTERRA ENERGY CORP.
The generators will produce enough electricity to power the biomass facility and to power another energy facility on the same side of campus. The system has a generation capacity of 1.38 megawatts. "That power offsets the amount of power in the biomass plant that we need to generate the steam," Detwiler says. "We have a little bit of excess capacity that we send up to the university grid to offset what they take off the utility grid."
The backpressure turbine reduces the pressure of the steam to 130 psi for distribution to the campus. The steam then flows through more than seven miles of pipes in the underground distribution system to dorms, classrooms, labs, offices and other facilities. "We had to add 3,300 feet of piping just to interconnect to the existing energy plants," Detwiler says.
In the original plan the facility was housed in a simple shelter leaving much of the plant equipment exposed, Detwiler says. "The university decided it wouldn't be beneficial to leave it exposed like that," he says. "They decided to enclose the whole facility and we provided quite a few architectural upgrades to make it more pleasing. It turned out to be quite a showplace and we have gotten a lot of positive feedback from the neighborhood."
The biomass facility was completed in early December 2007. The first few days of operations showed that some of the systems supporting the gasifier needed adjustments, but the core system was running well, Zeigler says. "We've been pleased when it has been up and running," she says. "It has been producing the steam just as it was designed to do. We have had to tweak the conveyer system that feeds the wood fuel into the gasifier unit. We've also had some issues with the reverse osmosis unit that treats the water that goes through the boiler. The things we have been dealing with don't focus on the primary thing, the gasification technology."
Save the Planet, Save Some Money
When the plan was finalized in 2004, the university projected it would save $2 million a year. Those savings will be used to pay for the project over 15 years. "After the debt is amortized, then the savings will accrue to the university," Zeigler says. "Actually, based on the current price of natural gas, we think the savings will be closer to $2.5 million a year."
The uncertainty of natural gas supplies made the project even more attractive to the university, Zeigler says. "Shortly after we entered this contract, there was a fairly large increase in the cost of natural gas," she says. "It has largely stabilized since then, but we never know what the next month is going to bring. It is one of the commodities that is hard to budget for because prices can change drastically with little notice."
At a cost of $10.65 per 1,000 cubic feet (Mcf), the university's annual natural gas costs topped $5.3 million. The biomass plant will provide the same amount of heat at a cost less than $1.5 million a year. That works out to an equivalent cost of $2.4 per Mcf of natural gas.
Along with the biomass project, Johnson Controls implemented many other money saving projects on campus. They upgraded the campus' existing energy plants including replacing chillers and cooling towers. The steam distribution system was upgraded with piping repair and replacement of condensate pumps and steam traps. In 100 buildings low-flow fixtures were installed to save water. Energy efficient lighting was installed in 107 buildings. Building management was improved by replacing pneumatic temperature controls with direct digital controls that can be monitored and controlled from a central location. Johnson Controls implemented many other smaller projects including thermal swimming pool covers, high-efficiency transformers, new air handlers, variable speed drives and VendingMiser power controls which power down vending machines when the surrounding area is vacant while maintaining the temperature of the vended product.
One aspect of the project that Zeigler appreciates is how it has multiple positive impacts for the people of South Carolina. The project will lower the university's energy costs which will mean lower tuition and taxes. It provides a market for what is now a waste product which will help the state's forestry industry. "It also helps our country as a whole to lessen our dependence on fossil fuels," she adds. "We are proud of having forged the way on this. We would encourage parties who would like to see this technology in place to get in touch with us."
Jerry W. Kram is a Biomass Magazine staff writer. Reach him at firstname.lastname@example.org or (701) 738-4962.