Author evaluates various modeling approaches for large systems employing high temperature fuel cell (particularly SOFC). Paper includes a brief discussion of current trends and various designs. It goes into details discussing the crucial parameters influencing the cycle''s operation and performance. For better understanding, the basics of the fuel cell operation, involved processes and all phenonena are provided. Finaly the desired system configuration is proposed and investigated. The modeling and optimisation in the software are extensively described. Analysis of the whole system with the proposed numerical tool allows the determination of the overall system thermal efficiency with high fidelity, thus the biggest effort must be made to correctly determine all input parameters and define the proper assumptions as well as simplifications. The final discussion after performed modeling emphasises the most crucial parameters. The proposed system represents a clean energy source, which substantialy reduces the polutants flow associated with the power generation.