An LP model for assessing congeneration strategies

A linear programming model is described which is designed to assist in the assessment of optimum operational strategies for industrial plants with cogeneration facilities. A concise format is provided for linking together basic elements such as boilers, valves, turbines and processes with steam and electricity demands with steam, fuel and electricity balance equations. The model should prove particularly useful for assessment when electricity tariffs have time-of-use energy or demand charges or when tariffs have conditions which require consideration of strategies over an extended period. The model has been applied to a paper mill which utilises pass-out turbines for cogeneration of electricity and process steam. Results indicate that savings in fuel costs of the order of 400,000 dollars per year could be obtained by implementing optimal strategies for operating the present turbines. Savings of the order of one million dollars per year could be obtained by converting the turbines to give high pressure pass-out steam and then operating optimally.