Iowa State has four boilers in the power plant that are used to produce steam, two of the boilers burn coal and two of the boilers burn natural gas. All boilers produce steam at 400 pounds pressure and 750 degrees F. Typically three of the boilers are operating all the time and the fourth boiler is added as needed due to campus energy demands. The boilers are operated in a manner to maximize efficiency and minimize emissions. The power plant staff makes a choice of burning coal or natural gas to minimize energy costs for the campus.
Iowa State has four turbine-generators. These machines convert the energy in the steam into electricity. Some of the steam produces electricity first, and then is extracted from the steam turbine at 90 lbs pressure. The 90 lb steam is either sent to campus or is used to produce chilled water. As more and more 90 lb steam is extracted from the turbine-generators, the cost of electricity generated is reduced.
90 lb. Steam
90 lb. steam is extracted from the turbine-generators, after it has produced electricity. This process is called co-generation. Co-generation is defined as using a single fuel source to simultaneously produce electricity and supply thermal loads. The process is highly efficient and has been used at Iowa State University since 1891.
Electricity produced by the co-generation process can be produced at approximately one third of the cost of more conventional power generation methods. Power Plant operators maximize the amount of co-generated power to minimize electricity costs for the university. 90 lb steam is either sent to campus or is used to produce chilled water.
Iowa State has five chillers used for cooling the campus buildings. The chillers use steam or electricity to produce cold water which is sent to the campus buildings. Two chillers use 400 lb steam turbines, two use 90 lb steam turbines and one uses an electric motor to drive large compressors. Four of the chillers are located in the main power plant. One of the 90 lb steam turbine chillers is located in the North Chilled Water Plant.