Chilled Water Plant I
The original plant, Chilled Water Plant 1 (CWP1) was built on the northern endowed campus and commissioned in 1963 with two 1,200 ton Carrier model 19C centrifugal chiller. The plant was expanded in 1965 to include another 1,200 ton Carrier model 19C centrifugal chiller for a total of 3,600 tons capacity (Chillers-1, 2, 3). Each chiller used R-11 as the refrigerant. Beebe Lake (Fall Creek) is a nearby natural water source that is used as a heat sink for the condenser water loop. Free cooling, via a plate and frame heat exchanger, was added in 1989 using the same natural heat sink. This allowed Cornell to meet all the winter cooling demand without mechanical refrigeration using 38°F water cooled naturally by outdoor air from Beebe Lake. This plant was totally automated in 1989 when free cooling and variable speed pumping was added. The automation allowed the plant to cycle from one chiller to three without operator intervention. Today, only the winter lake based free cooling is used as a backup to Lake Source Cooling. Also located in CWP1 is the Central Campus Energy Management and Control System (EMCS). This system provides alarming and monitoring of campus HVAC and electrical systems as well as central data collection of utility energy usage.
Chilled Water Plant II
Chilled Water Plant 2 (CWP2) was constructed in 1973-74 to meet the cooling loads on the statutory campus and included one 2,000 ton Carrier model 19CB centrifugal chiller (Chiller-5). Another 2,000 ton Carrier model 19CB centrifugal chiller (Chiller-6) was added in 1984. Both use R-114 refrigerant and evaporative cooling towers for heat rejection. The Statutory distribution system was interconnected to the Endowed system in 1984. CWP2 underwent an upgrade to include variable speed pumping and a current digital control system in 1992. This plant is now decommissioned and will be used in the future as loads grow.
Chilled Water Plant III
Chilled Water Plant 3 (CWP3) was constructed in 1974 on the southern portion of the endowed campus and included one 1,450 ton Carrier model 19FA centrifugal chiller using R-500 as the refrigerant (Chiller-4). A major expansion was completed in 1987 when a 4,000 ton Carrier model 17DA Centrifugal chiller, using R-12 refrigerant, was added (Chiller-7). An additional plate and frame heat exchanger was also added as well as variable speed drives on the distribution pumping. This new chiller increased the system capacity by 44% and was the system's workhorse until Lake Source Cooling came on line in 2001.
The unique feature of Chiller-7 was it's variable speed compressor, which at the time, was the latest concept in large chiller efficiency. This was done using a 3,500 HP wound rotor motor and slip energy recovery AC drive and used 40% less energy annually than conventional chillers. The incremental cost for the drive was offset within two years by the increased energy savings that amounted to over 4-million kilowatt-hours per year.
Another plant expansion was completed in 1991 which included a 4.4 million gallon stratified Thermal Storage Tank (TST). This expansion provided an additional peak capacity of 4,000 tons and was also a demand side management tool for decreasing the University's expenditure for electricity. The TST, acting like a large thermal flywheel, shifts cooling load on the chillers to off-peak times by charging the water in the tank. The tank volume is cooled at night with spare chiller capacity and warmed by the campus cooling load during the day. It allows the use of less-expensive overnight electricity rates, and reduces the need for additional chilling capacity. The TST was tied into CWP3 in a way such that Chiller-7 and the TST can be hydraulically isolated from the rest of the system for dedicated charging. This project not only was capable of shifting up to 4 megawatts of demand to off-peak hours; the total system efficiency increased by over 10%. Most of this increase in efficiency was attributable to increasing the annual production by Chiller-7 and also taking advantage of the variable efficiency of this chiller using more favorable condensing conditions at night. One of the other unique aspects of this upgrade was the ability to change the evaporator on Chiller-7 from a single pass (43° LCWT) to a two pass (39° LCWT) on the fly. At the time, Carrier knew of no other end user who had accomplished this. This project won several awards including an ASHRAE society level Technology Award, the New York State Governors Award for Energy Excellence and was also the feature story in the 1992 second quarter District Heating & Cooling Journal.
The demand for cooling is highly variable. Cornell was a pioneer in the application of variable speed drives for distribution pumping which has greatly reduced annual energy consumption.
A third plant expansion was completed in 1996 when a 2,000 ton Carrier model 17EX centrifugal chiller was installed using R-134a as the refrigerant (Chiller-8). This chiller was selected for 39° LCWT duty and tied directly into the TST system rather than the distribution system. Chiller-8 enhances the use of the TST through predominantly night-time operation with off-peak electricity and cool condensing water temperatures. Chiller-8 included a beta version of Carrier's new "BAClink" gateway tied into CWP3. This was the first time, in a commercial setting, Carrier successfully utilized the new ASHRAE BACnet standard for interface to the chiller control. Another unique aspect of this project was the ability to use Chiller-7 for split duty, using part of its capacity for satisfying the system demand while using the remainder supplemented Chiller-8 for tank charging.
Chiller-7 was retrofitted to use R-134a as the refrigerant in 1998.
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