Economical Condensing Turbines?

Abstract

Steam turbines have long been used at utilities and in industry to generate power. There are three basic types of steam turbines: condensing, letdown and extraction/condensing. • Letdown turbines reduce the pressure of the incoming steam to one or more pressures and generate power very efficiently, assuming that all the letdown steam has a use. Two caveats: Letdown turbines produce power based upon steam requirements and not based upon power requirements, and if all the steam letdown does not have a use, letdown turbines can become a very expensive way of producing electric power. • Condensing turbines have the ability to handle rapid swings in electrical load. Unfortunately, they can only condense a small percentage of the steam, usually less than 14%. Therefore only a small percent of the heat of condensation is available for their use. Also equipment must be used to condense the remaining steam below atmospheric pressure. • Extraction/condensing turbines both extract steam at a useful temperature and pressure and then condense the remainder of the steam. These units have the ability to load follow also. They are often used in concert with gas turbines to produce the balance of electrical power and to keep a electric self generator from drawing electrical power from the grid. The method for analyzing the cost of the condensing steam produced power is exactly the same in all cases. This paper will attempt to provide a frame work for preliminary economic analysis on electric power generation for condensing steam turbines.