Central Energy Facility - Cardinal Cogen

Stanford's Central Energy Facility is comprised of four plants built over five decades. The first facility constructed at this location was the Boiler Plant - the third steam plant in Stanford's over 100 year long history of centralized steam production for heating buildings. The current plant location was chosen for it's proximity to the main academic campus and the initial phase of the current Stanford Hospital that was built in the same era. Chilled water production for cooling buildings was added in the 1970s, and electrical production was added in the 1980s. In the late 1990s the Ice Plant was added to help manage peak electrical demand, and further optimize the energy production economics of the entire facility.

Stanford's Boiler Plant was constructed in 1957 and 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 now 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 1972 and has undergone several major renovations, the most recent in 2006. The plant currently consists of three 1,000 ton steam absorption chillers, one 4,000 ton steam turbine driven centrifugal chiller, and four 1,000 to 1,400 ton electrical centrifugal chillers for a total nameplate capacity of 11,600 tons. The steam powered chillers capture for productive use the excess steam generated by the cogeneration plant during the summer when campus steam loads are low and electrical rates are high. The electric chillers provide off peak and winter capacity when there is not enough steam to operate the steam powered chillers.

The Cogeneration Plant 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 42 MW generator, a waste Heat Recovery Steam Generator (HRSG), and a steam powered turbine driving a 14 MW generator. Waste heat from the gas turbine combustion process is exhausted into the HRSG to generate high pressure steam that then powers the steam turbine to generate additional electricity – hence combined cycle. Stanford uses about 60% of the electrical power generated by the plant, the balance is sold to PG&E. Stanford uses about 80% of the low grade waste heat generated by the plant, qualifying the plant under the Public Utility Regulatory Policies Act of 1978 (PURPA) as a “qualifying facility”. This designation requires the local utility company (PG&E) to purchase excess power at the utility company's alternative cost for natural gas power production. The waste heat in the form of low pressure steam is distributed to campus and hospital buildings for comfort and domestic water heating, and to Stanford's Chilled Water Plant for steam powered chillers. Should the gas turbine not be operable, steam from Stanford's Boiler Plant can be used to produce about 5 MW of emergency power from the steam turbine.

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 five 2,500 ton electric rotary screw chillers and 120,000 ton hours of ice storage coils located in a 4 million gallon tank under the Jordan Quad parking lot. Using ice storage or a combination of ice storage and chillers, the Ice Plant can produce 16,000 tons of cooling. Except under extreme cooling load conditions, the Ice Plant chillers operate only at 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 40 ° F during peak demand, effectively increasing distribution capacity by 25% with existing piping.