A recent census for the United States Department of Energy (DOE) found that CHP systems on US campuses presently supply more than 967 MW of generation, with another 675 MW in planning or building. The heating and air-conditioning thermal loads of most college campuses make them perfect for CHP systems. Many college campuses already have district energy piping systems capable of combining thermal requirements.

New Jersey is home to the beautifully landscaped cogeneration plant at Princeton University. The twin cooling towers of the chilled-water plant reach toward the sky in the background.

A study by the International District Energy Association (IDEA) states that the average campus CHP was 15 MW in size and the median system size was 7.4 MW. The systems installed on campuses ranged from 0.18 to 85 MW. Campus district cooling systems were identified as holding a total of 900,000 mt of cooling capacity.

IDEA also documented 1.7 million lin. ft. of chilled-water distribution networks in campus district cooling systems. These cooling systems often use steam-driven chillers. Substantial growth is being reported in campus cooling systems due to construction of new campus buildings.

Why are colleges and universities installing and/or using CHP systems? They are doing so in an effort to meet increasing campus load growth and to accommodate the shift toward year-round operations, as well as to meet the growth of attendant air-conditioning loads in an environmentally responsible manner. An IDEA study has identified the capacity for an added CHP system potential of 472–662 MW, based on the recent DOE census and supplemented by considerable growth in district cooling project development.

The University of Texas at Austin (UT), the University of North Carolina at Chapel Hill (UNCCH), and the University of Iowa (UI) are three examples of institutions of higher learning that have CHP systems hard at work on their campuses. These three schools are not alone; they are in very good company. Princeton uses a CHP system, as do Cornell, Massachusetts Institute of Technology, and Rutgers.

When asked to comment on the facilities in use at Princeton, Tom Nyquist, the school's director of facilities engineering, succinctly states, "Our CHP plant provides the university with reliable heat and power in a very cost-effective manner, especially in this era of electric deregulation."

UNCCH and UT both have large boilers making steam for assorted uses. Each campus links the boilers to a steam turbine, which generates electricity, and a heating system. This reduces the campuses' dependency on the local grids and reduces operating expenses. Then this less-expensive electricity also can be used to operate electric chillers for cooling, which in turn reduces cooling costs. The rest of the steam is used to heat domestic water and the campuses' office, classroom, and dormitory areas. Chillers used to cool campus living spaces also can use steam produced by the boilers.

The UNCCH coal-fired cogeneration facility uses 9% less fuel and saves 16,000 tons of coal annually, when compared to separate heat and power generation. The school has been generating its own electricity since 1895. It began cogeneration in 1939. In 1992, UNCCH replaced its old cogeneration system with circulating fluidized-bed combustion technology to meet the increasing heating/energy needs of its campus. By 1997, the operating budget of the facility was about $17 million, and it sold more than $4 million of electricity to Duke Power Company during the 1996 fiscal year.

The new plant employs two atmospheric, circulating fluidized-bed (CFB) boilers, which can produce up to 500,000 lb./hr. of steam; a single steam-driven turbo-generator rated at 28 MW, which is capable of generating one-third of the campus' electric requirements; and a backup gas- and oil-fired boiler, which provides a safety blanket for the campus. The annual reliability rate of the system has maintained a range between 99.61% and 99.99%.

Bituminous coal is used as the primary fuel for the two CFB boilers, with natural gas and fuel oil as backup. The backup boiler is used during peaking when necessary and for emergency situations. Steam at 1,300 psig drives the turbogenerator before being extracted through dual variable extraction points. After extraction, this steam is directed for end use on campus.

The low-pressure steam derived from this process is used across the 13 million-ft.2 campus and by UNCCH hospitals for water heating, space heating, cooking, cleaning, humidification, and space cooling. Slightly higher pressurized steam is used to sterilize medical equipment at the UNCCH hospitals. This steam travels through 45 mi. of underground piping. There is an additional 10 mi. of piping that carries the chilled water supplied by the system.

UT has a central plant for both heating and cooling. Natural gas is used as the primary fuel, with oil as backup. The facility purchases $17,535,573 worth of fuel on an annual basis.

Table 1 shows the boilers operating at the plant.

According to Juan Ontiveros, P.E., the director of utilities and energy management at UT, this plant has a total installed heating capacity of 1,146,000 lb./hr. Ontiveros adds that this meets 100% of the university's heating-energy demand and heats 97% of the university's buildings' square footage.

UT also has a central chilled-water system in multiple locations with a total installed capacity of 40,800 tons. Ninety-seven percent of UT's buildings' square footage is served with cooling from the central plant. The central plant meets 100% of UT's cooling-energy needs.
Table 2 describes the system.

Ontiveros explains that the first boiler plant was commissioned in 1910. It started generating 100% of the power by 1928. It was in the 1930s that the first tunnel systems developed, and their use continues to this day. The process actually began as a project developed by the mechanical engineering department. The catalysts for self-generation were improved reliability and the cost benefit, Ontiveros adds.

Juan Ontiveros, P.E., is director of utilities and energy management at UTA.

Regarding the future of UT's power plant, Ontiveros states, "We have become dependent on steam for chilled water and heating. Since the source for 165-psig steam is from generation, we are tied to the self-generation approach. Therefore our approach has been to optimize plant efficiency and operational effectiveness. We have improved our overall system efficiency from 65% to 75% in about five years. We have other initiatives underway to better this, including a new 25-megawatt steam turbine, a dump condenser, an optimum dispatch model, and a study to add a new gas turbine."

UI is looking toward the future with the use of a rather unusual fuel: oat hulls, or plant casings. The use of this biomass fuel began with a phone call from the Quaker Foods & Beverages cereal mill in Cedar Rapids, IA. The mill is the largest of its kind in the world and is left with 100,000 tons of oat hulls each year.

Quaker was using these oat hulls to make chemicals for petroleum companies. The leftover material was being sold to a power plant. Business conditions changed, however, and Quaker's oat hull byproduct market was no longer viable. So Quaker stopped making chemicals.

In 2001, Quaker mill officials called Ferman Milster, UI's associate director of utilities, with a mutually beneficial proposition. The folks at Quaker were wondering if Milster might be able to use the oat hulls as a source of fuel for the campus cogeneration operation. Seeing a chance to help both the environment and the local community, Milster seized the opportunity.

UI was no stranger to seeking environmentally sound practices. The power plant had burned tire-derived fuel (TDF) for several years in an effort to reduce the state's inventory of scrap tires. Burned in a stoker boiler, the TDF was mixed with coal to a maximum of 5% by weight. The TDF program, excluding coal costs, was funded by the State of Iowa.

On an almost daily basis, trucks now travel 20 mi. across Iowa from the Quaker mill to UI to deliver tons of oat hulls to the power plant. The UI power plant burns approximately 60 tpd—but has burned as much as 100 tons in one day. The UI power plant's goal is to burn an average of 50,000 tpy of oat hulls. Reaching this goal would reduce UI's yearly dependence on coal by about 25%.

A unique partnership between Quaker Foods & Beverages and UI helps fuel the CFB boiler at this UI power plant.

What other benefits are there to burning oat hulls? Substituting oat hulls for gas or coal helps lower carbon dioxide emissions. An annual reduction of 60 tons of sulfur dioxide will be achieved. A decrease in NOx is expected. Landfill space is being saved.

Quaker Oats is saving money on waste disposal, and UI is saving money on fuel.

At first, Quaker was extracting a chemical from the oat hulls called furfural, which is used by the petroleum industry. It then shipped the leftovers of the oat hulls, or resifil, to UI. Resifil is a dense brown powder that can be burned as a biomass fuel.

The early resifil project encountered several problems, however. Power plant staff noted that using a 50% coal/50% resifil blend, the resifil began to ignite much too soon when added to the furnace with the coal. The early combustion radically increased the temperature in some areas of the furnace and spread superfine dust throughout the plant. There was also the added problem of the resifil collecting moisture, becoming acidic, and causing corrosion to the fuel-handling equipment. Due to these problems, the UI power plant was able to burn only a 70% coal/30% resifil blend safely.

UI engineers tried adding the resifil at a later stage in the combustion process, which helps keep temperatures down. They also teamed up with Foster-Wheeler to design a new pneumatic injection system for their CFB boiler. This helps keep the fuel-loading process much cleaner.

The next problem Quaker and UI faced was transporting the resifil to UI quickly enough to sustain UI's need for fuel. Quaker was using a railcar system to load waste oats, but UI was not equipped to receive these railcars. The power plant was on a small, restricted area at UI, and regulations called for dust-free unloading at the power plant. Quaker adapted to make transportation of the biomass fuel less of an issue.

Pneumatic tanker trucks were the solution. Vacuum loaded at the mill, the trucks make the 20-mi. trek to the UI power plant, and their cargo is unloaded in a safe, dust-free manner.
Just as the resifil problems were solved, the market for furfural all but disappeared. Quaker wondered if the raw oat hulls—instead of resifil—could be used as a biomass fuel. If so, Quaker could stop producing furfural and just sell its oat hulls to UI.

UI resolved to try to burn raw oat hulls. This required that a new silo be designed specifically for holding grain to feed the plant. In January 2003, the plant began burning raw oat hulls in place of resifil.

The pneumatic injection system held its own and even exceeded expectations, according to Milster. In fact, UI was burning oat hulls quicker than Quaker could deliver them. This was just one more puzzle for Quaker and UI to solve. The pneumatic tanker trucks just couldn't deliver the oat hulls fast enough. Work began on a system of transportation that would use 53-ft. box trailers.

Milster remarks, "The discovery process took place one baby step at a time. No one else was doing this. We would try something, have a problem, and fix what needed to be fixed as we learned. We spent a lot of time testing, discovering, and moving forward. Currently, however, all of our permits are in place. We are also in final negotiations with Quaker for a multiyear contract with them. Our natural gas and coal supplies come from out of state, so we are very pleased that our money is staying in the state of Iowa when we purchase these oat hulls from Quaker. This partnership is good for all concerned. It's good for the local economy, it's good for Quaker, and it's good for us." The CHP campus biomass project promises to one day save UI about $500,000 a year, according to Milster.

UI has tackled these challenges without increasing the size of its workforce. Today the plant actually has fewer operators than it did 12 years ago. This is primarily due to an automated plant system. The computerized system allows workers to operate boiler, turbine, and other plant equipment with just one click of a computer mouse.

The UI campus is seated on 1,900 ac. of land. There are 119 buildings and 14.5 million ft.2 of building space. It is located in Iowa City.

UI began its central plant operations in 1926. At that time, the current plant was built. It originally had three coal boilers and two hydroelectric generators. Later, in 1947, the plant was introduced to cogeneration. This occurred with the addition of a controlled-extraction steam turbine.

The plant's primary source of fuel is coal. The plant buys 110,000 tons of coal each year and splits it among three contracts: One is for stoker coal. Another is for washed bituminous coal used in the CFB boiler. The third is for the emergency pile of coal, which weighs 10,000 tons.

Backup steam-production needs are serviced by natural gas. Natural gas also services peaking. Approximately 15% of UI's annual steam production is produced using natural gas.
The UI power plant heats 100% of the campus. It also cools 50% of the campus and meets 30% of the campuswide electrical demand (see Table 3).

Regarding the pros and cons of the new system, Milster notes, "The program was not cheap. We had to get people to trust us. By nature, power plants and academic environments do not go hand in hand philosophically. Key administrative people had to trust us. We knew, however, there would be a potential payback only two years into the risk. We're already seeing the payback now."

UI's goals were to reduce its purchased fuel prices, reduce their need for purchased energy on campus, and reduce environmental damage done by greenhouse gases. UI is seeing more environmental benefits to burning oat hulls, other than just the reduction of greenhouse gases. A very pleasant surprise, according to Milster, is that all pollutants go down when the oat hull biomass fuel is burned.

Milster goes on to say that the campus and more than 7,000 students depend on the reliable energy produced by the power plant. "If we're not making steam, the university can't open its doors," Milster states. "We're constantly evaluating our plant for best practices policies. We wish to remain economically and environmentally responsible as we continue to grow to meet the increasing needs of our expanding UI campus. Our constant challenge is to be ready to provide energy for the ever-increasing load demand of UI."

The CHP system at UT meets 100% of the university's heating energy demand and heats 97% of the university's buildings' square footage.

Wheaties may claim to be the "Breakfast of Champions," but Quaker oat hulls are helping to heat and cool the Iowa Hawkeyes' recreational complex, which hosts many major Big 10 sporting events. They also are helping heat and cool dormitories, academic buildings, a large medical center, and administrative offices on the UI campus. Now there's a cereal byproduct with power!

Quaker's emergency contingency plan called for the oat hulls to be taken to the landfill, as they are biodegradable. Unfortunately the hulls trap air and are difficult to pack. They are also expensive to ship. Quaker wanted to find a way to use these oat hulls to its benefit rather than continue to pay for their transportation and disposal.

"The district energy industry—and specifically college and university campus systems—offers ideal conditions for combined heat and power. Campus energy systems employ central utility plants to meet the aggregated thermal and electric loads of multiple buildings. The close proximity and common ownership helps make connecting the buildings with piping for heating and air-conditioning services very cost-effective. Additionally, many universities and health centers are owner-occupied buildings where critical research functions create high load factors that demand a high degree of comfort and reliability. District energy systems are recognized for delivering highly reliable power and thermal services to critical load centers," relates Robert P. Thornton, president of the International District Energy Association, in regard to the rationale behind district energy systems on campuses in US.

"Often universities are significant users of electricity and natural gas. Some universities, like the University of Texas at Austin, house more than 50,000 residents. In many instances, the university owns the piping, wires, and infrastructure on campus. The scale of operations and the combination of thermal and power requirements makes for very attractive load factors for cogenerating electricity and steam, which can be used for heating space and driving central chiller plants in summer. In fact, the aggregated thermal loads of multiple buildings is what makes CHP economically attractive.

"The strong growth in CHP for the campus market is driven by load growth from new buildings under construction on campuses, planned capital replacement and expansion of facility plants, high reliability needs, and good project risk and credit profiles in the institutional market. In some cases, campus CHP systems have been operating for over 110 years, and the financial markets appreciate the ‘blue-chip' quality of the CHP project locations," Thornton concludes.

IDEA is hosting the 17th Annual Campus Energy Conference in San Diego, CA, February 11–13, 2004. More information is available at www.districtenergy.org.

Guest author COLLEEN MADONNA FLOOD WILLIAMS writes for several business magazines.

DE - Jan/Feb 2004