OPTIMUM OPERATION OF COGENERATION PLANTS WITH ENERGY PURCHASE FACILITIES

The paper presents an optimization scheme for the economic dispatch of electric and steam demands to a cogeneration plant with a tieline and auxiliary boiler facilities. The objective is to share both the electric and thermal load demands among the in-plant generating units and the energy purchase facilities to minimize the total energy cost. Depending on the cost parameters, optimum cogeneration can result in selling electricity during utility peak demand hours while purchasing electricity during the local peaks of either and/or steam to reduce the overall cost of the unit product. The optimization scheme is based on generalized network programming which can often solve problems with more variables and constraints that can be solved by other techniques. This scheme is capable of handling the nonlinear cost functions and the dependent relations between the electric power and steam generation for the cogeneration unit.