## 6 Results and Discussion
### Energy and Exergy Efficiencies of the System  
The vessels require 3800 kW of electric power and hot water for seafarers' purposes. The utilization factor and energy efficiency of the SOFC were 0.85 and 56.8%, respectively. After applying the thermodynamic model introduced above to analyze the proposed integrated system, the output power of the integrated system was estimated as 5185.46 kW, which is sufficient to drive a vessel and provide additional power for other purposes. This comes from six different power components, including the SOFC fuel cells, gas turbine, and three turbines of the bottoming cycles. Out of this, 73.3% of the total power is produced by the SOFC while 26.7% is generated by the subsystems, which indicates that subsystems  
Figure 3: Hot and cold composite curves of sequential optimization for the SOFC–GT–SRC–KC-ORC system.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Node** & **Temperature** & **Pressure** & **Molar Flow** & **Mass Flow** &
\begin{tabular}{c} **Liquid** \\ **Volume Flow** \\ \end{tabular} \\ \hline
29 & 101.40 & 1450.00 & 34.95 & 602.00 & 0.90 \\ \hline
30 & 47.31 & 1446.55 & 34.95 & 602.00 & 0.90 \\ \hline
31 & 48.76 & 6500.00 & 34.95 & 602.00 & 0.90 \\ \hline
32 & 20.00 & 201.33 & 288.65 & 5200.00 & 5.21 \\ \hline
33 & 49.51 & 194.43 & 288.65 & 5200.00 & 5.21 \\ \hline
34 & 39.59 & 12,500.00 & 42.39 & 2800.00 & 3.04 \\ \hline
35 & 223.00 & 12,496.55 & 42.39 & 2800.00 & 3.04 \\ \hline
36 & 76.48 & 700.00 & 42.39 & 2800.00 & 3.04 \\ \hline
37 & 30.26 & 693.11 & 42.39 & 2800.00 & 3.04 \\ \hline
38 & 18.00 & 201.33 & 832.63 & 15,000.00 & 15.03 \\ \hline
39 & 32.28 & 197.88 & 832.63 & 15,000.00 & 15.03 \\ \hline \hline \end{tabular}
\end{table}
Table 9: _Cont._control the operation of the proposed system as anticipated. Considering the entire system in Table 10, the overall energy and exergy efficiencies were 60.4% and 57.3%, respectively.  
It is interesting to note that the SRC subsystem is energetically more efficient than both the ORC and KC. Its energy and exergy efficiencies are 25.6% and 40.4%, respectively, which lies between those of ORC and KC, whose exergy efficiencies are 42.76% and 18.58%, respectively.  
In Figure 5, the key components of the proposed system are examined in terms of exergy destruction rates associated with the thermal processes occurring within them. The two uppermost exergy destruction rates of 2102.79 and 938.18 kW correspond to the SOFC and afterburner, respectively. This high exergy destruction rate implies that the afterburner, rather than other equipment, has significant potential for improvement.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Subsystem** & **Energy Efficiency** & **Exergy Efficiency** \\ \hline SOFC–GT & 61.4 & 58.2 \\ \hline SRC & 25.6 & 40.4 \\ \hline KC & 11.86 & 18.58 \\ \hline ORC & 22.49 & 42.76 \\ \hline Total System & 60.4 & 57.3 \\ \hline \hline \end{tabular}
\end{table}
Table 10: Energy and exergy efficiencies of the systems.  
Figure 4: Heat exchanger network for the sequential optimization of the SOFC–SRC–KC-ORC system. (**a**) Heat load; (**b**) Driving force plot.  
The third one is three heat exchangers (heat exchanger E-100, E-101, and E-102) and gas turbine with values of 151.82, 132.83, 127.94 and 101.52 kW, respectively. The lowest exergy destruction corresponds to the turbine of the KC owing to higher entropy generation at lower temperatures with a constant heat transmission rate.