CASE STUDY SERIES: COLLEGE CAMPUS CHP
THE UNIVERSITY OF NORTH CAROLINA AT CHAPEL HILL ENERGY SERVICES DEPARTMENT
UNC turns to coal-fired cogeneration to meet growing campus energy needs.
ENVIRONMENTAL BENEFITS AND ENERGY SAVINGS • • • •
Reduced NOx output by 308 tons annually Decreased SO2 output by 650 tons annually Cut CO2 output by 10,620 tons annually Provides 18,000 tons of ash annually, which is recycled as material for structural fill and other projects CHP SYSTEM SPECIFICATIONS •
ELECTRIC CAPACITY: 28 MW
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HEATING CAPACITY: 900,000 lbs/hour
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COOLING CAPACITY: 33,100 tons
SEARCH WORDS: DISTRICT ENERGY, CHP, COGENERATION, COAL FIRING, CIRCULATING FLUIDIZED BED, PLANT SITING, ENVIRONMENTAL PERMITTING
INTERNATIONAL DISTRICT ENERGY ASSOCIATION www.districtenergy.org
OAK RIDGE NATIONAL LABORATORY www.ornl.gov
UNITED STATES DEPARTMENT OF ENERGY www.eren.doe.gov
PROJECT BACKGROUND
CHP SYSTEM METRICS
ower generation has a long history on the campus of the University of North Carolina at Chapel Hill. A man named Joshua Gore brought the first dynamo to the campus in 1890, and the first plant was built soon after in 1895. The present power generation facility has its roots in a plant built in 1940 on West Cameron Avenue, a half mile from the main campus. This plant was fired by coal and supplied electricity to both the university and the surrounding towns of Chapel Hill and Carrboro. In the early 1970’s, the state legislature decided that UNC should not be in the electric power business and ordered the university to divest its electric utility assets to Duke Power. After the divestment, UNC generated only 20% of its power needs, purchasing the remainder from Duke Power. In the 1980’s, the university revisited on-site power generation, and in 1988 decided to build a coal-fired cogeneration plant that would provide a clean, reliable source of energy for the UNC campus and hospital.
COGNERATION: Coal-fired boilers generate steam and electricity
P
CHOOSING COAL AS A FUEL SUPPLY The university conducted a study of its utility options from 1983 to 1985. The recommendation was to build a replacement cogeneration facility on the same site as the old West Cameron Avenue plant. This decision provided both utilization of existing infrastructure and reasonable economic payback. The old plant site had links to the rail system, facilitating deliveries of fuel, and was already connected to campus distribution piping. When it came time to choosing a fuel source, several factors came into play. The university had previously burned coal in its plant, but coal was generally dirtier than natural gas, which had become the fuel of choice for most new plants. But when asked about the availability of natural gas to fuel the new cogeneration plant, the local utility replied that supplies were not available on a costeffective basis. Coal, however, was still available, and at low cost. Furthermore, the university was familiar with the technicalities of burning coal from its previous experience. Therefore coal was chosen to fire the new plant. The university anticipated new source environmental performance standards and was aware of the need to design a plant that would be clean
HEATING CAPACITY: 900,000 lbs/hr • 2 coal-fired atmospheric circulating fluidized (ACFB) boilers @ 500,000 lbs/ hour total • 2 oil/gas package boilers @ 400,000 lbs/hour total (for standby & peak) • 40 miles of steam piping, supply & return • Auxiliary fuels: 100% MCR natural gas; 70% MCR No. 2 fuel oil ELECTRIC CAPACITY: • 28 MW steam turbine generator COOLING CAPACITY: • 3 plants with total capacity of 33,100 tons • Chilled water supply temp.: 42-45°F • 10 miles of chilled water piping, serving approximately 100 buildings
enough to overcome both regulatory hurdles and the stigma of burning “dirty” coal. These criteria left the university with a choice between implementing circulating fluidized beds (CFB) or using pulverized coal with scrubbers. The economics pointed to using CFB. CFB reduces emissions of acid rain-producing components such as NOx and SO2. The reduced NOx output is the result of the low combustion temperature (1600° F). SO2 output is reduced by using a limestone additive to precipitate it as calcium sulfate (Figure 2).
PUBLI PUBLIC C REVIEW PROCESS The proposed site of the project was the location of the existing UNC steam plant. There was much opposition to the proposed site, primarily from people who lived in a neighborhood that surrounded the plant. A map of the plant and its surroundings can be seen in Figure 3. Despite the opposition, the site proved to
CASE STUDY SERIES: COLLEGE CAMPUS CHP
UNC CHAPEL HILL
be the best place to locate the new plant. It was the only location with existing connections to the electrical substation, the campus steam supply grid, and the railroad. There was also space available on the parcel for construction of a new facility. In 1986, after much debate, the project was issued a special use permit with 24 conditions. The conditions included, among other stipulations:
PROJECT CONDITIONS • •
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Planting trees and shrubs to minimize aesthetic impact of the new facility Designing structures such that all handling of coal, ash, and limestone is done within enclosed structures Transporting waste ash from the plant in covered trucks or rail cars only after it has been wetted down Limiting visible emissions from truck unloading of plant material into the landfill to less than 20 percent opacity Limiting visible emissions from coal handling at the plant to no more than 10 percent opacity Ensuring that no fugitive particulate matter emissions are visible beyond the property line of the plant Working with the town to design the external appearance of the plant such that its impact on the neighborhood is minimized
The university moved forward with design and construction, and in 1992 commenced operations at the new plant. The new building featured blue-tinted windows, totally enclosed coal handling, and active coal storage in silos. The only major issues involved noise abatement. The decorative glass exterior did not provide adequate sound insulation, upsetting some neighbors. The town and UNC worked with an acoustical consultant to minimize the sound emanating from the plant, and succeeded in reducing levels to 50 dB at the property line. The plant now generates steam for the campus and hospital and provides one third of the electricity needed on campus. The remaining amount is purchased from Duke Power.
Figure 1. Aerial view of UNC’s CHP plant. Source: UNC.
The UNC facilities department has been recognized for its leadership in cogeneration. It is a founding partner of the EPA Combined Heat and Power Partnership, and it is the only plant not fired by natural gas to have been awarded an Energy Star Combined Heat and Power Certificate of Recognition.
PROJECT IMPACT Annual Savings •
Reduces NOx output by 308 tons
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Reduces SO2 output by 650 tons
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Reduces CO2 output by 10,620 tons
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Provides 18,000 tons of ash which is recycled as material for structural fill and other projects
Other Benefits •
Utilizes coal, a cost-effective energy source that is currently cheaper than natural gas or other alternative fuel sources, to keep costs low
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Extracts twice as much energy from a pound of coal by using cogeneration to achieve 69% efficiency
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Provides reliability in excess of 99.85%
CASE STUDY SERIES: COLLEGE CAMPUS CHP
UNC CHAPEL HILL Stanford University
Figure 2. Circulating fluidized beds keep NOx levels low by burning coal at lower temperatures. They also limit emissions of SO2 by mixing limestone with the coal in the combustion chamber, converting the SO2 into an inert part of the residual ash. Source: UNC Chapel Hill.
Figure 3. The University of North Carolina cogeneration plant is surrounded by an off-campus residential area. This increases the importance of clean coal handling and burning operations, as well as that of noise control. Source: UNC Chapel Hill.
CASE STUDY SERIES: COLLEGE CAMPUS CHP
UNC CHAPEL HILL
CASE STUDY CONTACTS AND SPONSORS FOR MORE INFORMATION, PLEASE CONTACT:
UNC CHAPEL HILL
Raymond DuBose Director of Energy Services CB#1800 Chapel Hill, NC 27599-1800 (919) 966-4100 phone (919) 843-4567 fax
[email protected] http://energy.fac.unc.edu
Robert Thornton, President International District Energy Association 125 Turnpike Road, Suite 4 Westborough, MA 01581 (508) 366-9339 phone (508) 366-0019 fax
[email protected] www.districtenergy.org
THIS CASE STUDY REPORT MADE POSSIBLE BY:
AND
INTERNATIONAL DISTRICT ENERGY ASSOCIATION www.districtenergy.org
OAK RIDGE NATIONAL LABORATORY www.ornl.gov
CASE STUDY SERIES: COLLEGE CAMPUS CHP
UNITED STATES DEPARTMENT OF ENERGY www.eren.doe.gov
UNC CHAPEL HILL
