NYS Governor's Awards for Pollution Prevention - Cornell University
Cornell University, Ithaca, New York
Cornell University operates a large campus district cooling system to provide central cooling to about forty percent - 4 million square feet - of its core campus. Pressures on this system (CFC phaseout, load growth, aging equipment and rising energy costs) required significant change, and studies were begun in 1994 to determine what path should be taken for renewal. The Lake Source Cooling (LSC) concept was chosen from numerous options studied. LSC as an engineering concept is amazingly simple, as non-contact cooling and pumping water have been engineering basics since the Industrial Revolution. It was complicated, however, in its size and the complexity of construction. The $58 million project received all approvals necessary to proceed to final design and construction during the spring and summer of 1998. Construction began in spring of 1999, with start-up and commissioning occurring during the summer of 2000. Though it required more initial investment than replacing the system with standard refrigeration technology, LSC will save money over time by using a fraction of the energy needed with conventional electric-powered chillers and by reducing future capital and maintenance expenses for chillers (75 - 100 year life for LSC versus 35 - 40 for chillers).
Methodologies and Procedures
Lake Source Cooling (LSC) provides a passive and technologically simple cooling option for Cornell University, utilizing a natural, non-polluting, and renewable resource. It uses the cold, deep water of Cayuga Lake to cool a closed loop extension of the existing campus chilled water network without the need for mechanical refrigeration. All the heat added to the lake is released each winter. In the depths of Cayuga Lake, the water temperature remains a constant 39° F. A 63-inch diameter by 10,400-foot long intake pipeline made of high density polyethylene (HDPE) carries water from a depth of 250 feet to a heat exchange facility at the lake's shore. Here, the cold water is pumped through a bank of stainless steel heat exchangers where heat is absorbed from a second, separate flow of water coming from the campus. This second flow of water, cooled to 42 - 45° F is pumped back to campus over 3 miles away. There the chilled water is used to cool laboratories and other building spaces. The lake water is warmed to 48 - 56° F and returned to the lake about 500 feet from shore through a specially designed diffuser. Both water loops are variable flow to match cooling needs, minimizing the use of lake water and pumping energy.
LSC is a first of its kind project, with many unprecedented engineering features. It is designed to provide over 20,000 tons (240,000,000 BTUs/hr) of peak cooling capacity, circulating up to 32,000 gallons/minute.
LSC has eliminated the use of refrigerant-based chillers, reducing energy use by 86 percent. In addition, LSC has reduced emissions of pollutants produced from the generation of electricity in regional power plants, reducing the release of global-warming gases and acid rain precursors. To date, LSC has been operating at 0.1 KWH/ton-hour of cooling produced and may very well be the most efficient large scale district cooling system in the world. This compares to 0.75 KWH/ton-hour (annual efficiency) for the original Cornell district cooling system which was already nationally recognized as one of the most efficient of its kind. LSC provides the following benefits:
Reduced electrical use equivalent to 2,500 homes annually (over 22 million KWH/yr of electricity).
Eliminated the burning of over 19,000,000 pounds (8,620,000 kg) of coal annually in regional power plants as well as the associated impacts of mining, transportation and ash removal (based on a peaking coal fired power plant).
Reduced carbon dioxide emissions by over 56,000,000 pounds (25,400,00 kg) per year.
Reduced sulfur dioxide emissions by over 645,000 pounds (293,000 kg) per year.
Reduced nitrogen oxide emissions by over 55,000 pounds (249,000 kg) per year.
Accelerated elimination of 40,000 pounds (18,100 kg) of CFC refrigerants that are known to deplete the ozone and act as greenhouse gases.
The construction of LSC resulted in numerous improvements to public roadways, utilities, a town park and sidewalks, resulting in $1.3 to 1.5 million in infrastructure updates at no expense to taxpayers. In addition, the school district granted the university an easement across its property in exchange for up to 400 tons of cooling. This will save the district taxpayers over $750,000 in present value for new refrigeration and operating costs.
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This page was last modified September 25, 2002