Four factors dictated a substantial change to the Cornell district cooling system: compliance with federal laws that phased-out chlorofluorocarbon containing refrigerants (CFCs), replacement of aging equipment, the addition of cooling capacity to meet growing loads, and rising energy costs. New cooling loads and renovation are expected to add 10,000 to 15,000 tons over the next 35 years. Six of the original hermetic chillers could not be economically converted to non-CFC refrigerants. This would have required that the University replace six of its eight major chillers within a ten year time frame, plus construct new chillers to meet increased demand. A significant capital outlay was required by year 2010. The magnitude of these changes offered the University a unique opportunity to consider the development of Lake Source Cooling (LSC) as an alternative cooling source.
LSC provides a passive and technologically simple cooling option, 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 present campus chilled water network without the need for mechanical refrigeration (all the heat added to the lake is released each winter). LSC operates at 0.1 KW/ton which has dropped electric power use to 13% of that required by the original campus cooling system. This represents over 20 million kilowatt hours saved on an annual basis. LSC came on line in July 2000 and has reduced both Cornell's reliance on refrigerants and the pollutants produced in the generation of electricity in regional power plants, reducing the potential for global warming and acid rain. LSC also offers a 75 to 100 year system life, instead of the 30 to 40 years typical for chillers.
The Phase I Feasibility Investigation revealed that an optimized LSC plant (18,000 tons initial capacity, and up to 20,000 tons as campus return water temperature increases), in combination with non-CFC chillers, would be more economical to operate over a 30 year period than a system based exclusively on chillers. In this plan, LSC will be supplemented, at peak loads, by existing equipment - the thermal storage tank and two open-drive HFC refrigerant chillers. The other six hermetic CFC chillers will be decommissioned. The LSC plant will provide nearly all central cooling, capturing the majority of the energy savings, while the system's remaining chillers will be relegated to back-up and peaking service.
The Phase I Feasibility Investigation demonstrated that LSC represented an economic and environmentally sound alternative for cooling the campus.
Once the feasibility of LSC was determined, the project proceeded into Phase II Schematic Design and Permitting. Phase II consisted of engineering schematic design development, Environmental Impact Statement (EIS) preparation, and filing of the associated regulatory permits. Environmental findings revealed no significant adverse environmental impact to the lake, verifying earlier findings that there will be no harm to the lake from construction or operation of LSC. The Environmental Impact Statement was accepted as final by the New York State Department of Environmental Conservation (DEC) in December, 1997 and in January, 1998, the key DEC permits were issued. Upon receipt of this key approval and agreements with the local municipalities and private landowners, the Cornell Board of Trustees approved funding for Phase III Final Design and Construction in January 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 current system with standard technology, LSC will save money over time by using a fraction of the energy needed with conventional electric-powered chillers and by reducing Cornell's future capital and maintenance expenses for chillers.
