Determining the Optimal Equipment Capacities of Cogeneration System : 1st Report, Optimization Method and Its Effect

Abstract

For cogeneration systems, a planning method is proposed to determine optimal capacities of constituent equipment together with optimal maximum demands of utilities. The equipment capacities and the utility maximum demands are determined so as to minimize the annual total cost in consideration of the operational policy for the variations of both electricity and thermal energy demands. These design and operational problems are formulated as a nonlinear programming and mixed-integer linear programming problem, respectively. In consideration of their hierarchical relationship by a penalty method, they are solved by means of the generalized reduced gradient method, and the branch and bound method, respectively. Through a case study on a gas engine cogeneration system, the effect of optimization on the annual total cost is investigated to ascertain that more economical merits can be extracted by the proposed method than by the conventional trial and error method.