OPTIMAL MULTIPERIOD OPERATIONAL PLANNING FOR UTILITY SYSTEMS

In this paper, the operational planning problem for utility systems is formulated as a mixed-integer linear program (MILP). For multiperiod operation with piecewise constant varying demands for utilities, the o ptimal choice of units for each period is determined. The objective fu nction accounts for both the operating costs for each period and chang eover costs for startup/shutdown of units each between periods of oper ation. A two-stage approach is proposed that requires the solution of MILP subproblems coupled with a shortest path algorithm, resulting in orders of magnitude reduction in computation time as compared to a dir ect MILP solution using branch and bound enumeration. The computationa l requirements of the algorithm are linear with respect to the number of periods and global solution of the MILP is guaranteed. Solution of three sample problems yield savings up to 5% in total annual cost of o peration with the main advantage being the simplicity of the proposed plan (few startups and shutdowns). (C) 1997 Elsevier Science Ltd.