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The cogeneration facility is a combined cycle power plant owned and operated by Cardinal Cogen, a subsidiary of General Electric. Commissioned in 1987, the plant consists of a natural gas powered turbine driving a 39.2 MW generator, waste Heat Recovery Steam Generator (HRSG), and a steam powered turbine driving a 10.7 MW generator. Waste heat from the gas turbine combustion process is used by the HRSG to generate high pressure steam which is in turn used in the steam turbine to generate additional electricity – hence combined cycle. Stanford uses about half the power generated by the plant, the balance is sold to PG&E. 125 psig steam is extracted from the steam turbine for distribution to the campus and the high pressure steam absorption chillers. 15 psig steam is also extracted from the steam turbine for powering the low pressure steam absorption chillers and condensate de-aerators. When the gas turbine is not operating, 125 psig steam from the CEF Boiler Plant can be used to produce about 5 MW of emergency power from the steam turbine. Stanford's Boiler Plant was constructed in 1957 and is the third steam plant in Stanford's history. The Boiler Plant consists of four 125 psig, 80,000 lb/hr boilers. The boilers can be fired with natural gas or in the event of emergencies, #2 fuel oil. Stanford stores on site enough fuel oil for three days operation. The Boiler Plant is primarily a back up for the cogeneration facility, although it is also used to generate supplemental steam during peak demand. The boilers were renovated in 1996 for low NOx operation. Modifications include low NOx burners, flue gas re-circulation, new instrumentation and electronic controls. Stanford's Chilled Water Plant was constructed in five stages between 1972 and 1991, and currently consists of five 1000 ton steam absorption chillers, and four 1000 to 1400 ton electrical centrifugal chillers for a total nameplate capacity of 9600 tons. The steam absorption chillers capture for productive use the excess steam generated by the cogeneration plant during warm weather when campus steam loads are low and electrical rates are typically high. The electric chillers provide off peak and winter capacity when there is not enough steam to operate the absorption chillers. Stanford's Ice Plant was constructed in 1999 and provides additional cooling capacity to meet Stanford's summer cooling loads without having to operate electric chillers during periods of high electrical rates. The Ice Plant houses three 2500 ton electric rotary screw chillers and 100,000 ton hours of ice storage coils located in a 4 million gallon tank under the Jordan Quad parking lot. The Ice Plant chillers operate in the middle of the night when electrical rates are low, "building" ice in the tank. The ice is "burned" the following day when electrical rates are high in lieu of operating electrical chillers. This approach reduces Stanford's peak electrical demand by 8 MW and saves Stanford about $500,000 annually. Additionally, ice storage allows us to reduce the chilled water supply temperature from 44 ° F to 38 ° F during peak demand, effectively increasing distribution capacity by 40% with existing piping.
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