Computer program for determining optimal running conditions of a steam turbine cogeneration system

Abstract

Cogeneration is an efficient way of using energy and at a national level permits an important saving in primary energy. Different systems include those with a back-pressure steam turbine and those with a pass-out condensing steam turbine. This paper deals with the basis and structure of a software pack that enables the user to determine the optimal running conditions in either case. The program is interactive, written in FORTRAN 77 and composed of six program blocks. Each block is responsible for one basic aspect of the analysis process. Because the objective function is non-linear and only point values are available, instead of algebraic expressions, the complex optimization algorithm is used. The object of the function is to minimize the hourly fuel and electricity costs during operation. Finally, the program has been applied to a cogeneration installation with a 970 kW back-pressure turbine. The results indicate that the system sometimes produces more steam per hour than required, the excess being due to the fact that the profit from the sale of electricity is greater than the cost of steam production.