SYNTHESIS AND OPERATIONAL PLANNING OF UTILITY SYSTEMS FOR MULTIPERIODOPERATION

A mixed-integer (MILP) formulation is presented for the synthesis and operational planning of utility systems for multiperiod operation with varying demands. The design of the utility system optimizes the confi guration choice and equipment sizes from a superstructure of alternati ves. The optimization problem takes into account the investment costs, operating costs of units for all periods, and the planning for schedu led maintenance of equipments. The multiperiod formulation includes bi nary variables for the choice of units for design, as well as binary v ariables for operational status of existing equipment during each peri od, producing a model that is computationally expensive to solve. A bi level decomposition method is proposed that consists of solving a high er level design problem for choosing the design configuration in a red uced space that excludes the operational binary variables in each time period. For the choice of units obtained from the first level, the lo wer level planning problem consists of optimizing their operation and operational status (on or off) for each period. A new concept of desig n cuts is introduced to tighten the gap between solutions obtained fro m both levels. Numerical results are presented for several example pro blems. (C) 1998 Elsevier Science Ltd. Ail rights reserved.