Maximum profit cogeneration plant - MPCP: system modeling, optimization problem formulation, and solution

摘要

The well-known CGAM optimization problem was formulated to serve as a benchmark for comparison of different thermoeconomic methodologies. The CGAM cogeneration plant produced 30 MW of power and 14 kg/s of saturated vapor at 20 bar. The objective function was the total cost rate of the system, related to thermodynamic variables and installation costs. Because the CGAM problem originates from an academic viewpoint, its models do not reflect the industrial reality of energy systems, and do not conform to important operational and technological restrictions. The objective of this work is to propose an alternative cogeneration-system optimization problem, denoted the MPCP problem - Maximum Profit Cogeneration Plant, which incorporates functional economic concepts and modern technologies. The objective function is the net present value (NPV) of the monetary gain for the period of plant operation. The optimum (i.e., maximum) NPV value is obtained using two different professional optimization toolboxes appropriate for multivariable nonlinear constrained functions. The optimal operational conditions indicate that the MPCP plant reaches the allowed physical limits of the main equipment, namely, maximum efficiency of the gas turbine generator set and minimum temperature difference inside the heat recovery steam generator. Formal findings like these help to direct efforts to improve current technologies.