Multi-objective optimization model for fuel cell-based poly-generation energy systems

Although the layout of combined cooling, heat and power (CCHP) systems is well known from a technical perspective, the optimal operating strategy and sizing of such systems are relatively complex, due to the high number of variables and constraints involved. To address this research gap, the present paper describes the formalization, implementation, and validation of an innovative multi-objective optimization model for CCHP poly-generative energy systems. As a novelty, the model uses two levels of optimization: a first level to optimize the best operating strategy of the system for different unit sizes, minimizing an economic cost function, maximizing the performance of the plant, and minimizing polluting emissions; the second level to optimize the size of the plant, through a technical-economic optimization function based on the Net Present Value. The model is highly flexible, allowing the execution of sensitivity analyses. The analyzed energy system is composed of a cogeneration unit, namely solid oxide and polymer electrolyte membrane fuel cells, and of heat pumps, electrical storage, and traditional auxiliary boilers. In order to prove the reliability of the CCHP units, the modeled performance curves for the fuel cell systems have been validated with existing commercial units, resulting in a degree of correlation mostly over 90%.