## 6 Conclusions  
In this study, a novel combined sCO\({}_{2}\)/LiBr-H\({}_{2}\)O AHP system is first proposed and analyzed for heat and power cogeneration according to the principle of energy cascade utilization. Detailed thermodynamic and exergoeconomic analysis, parametric studies, optimizations, and comparisons are carried out among a stand-alone sCO\({}_{2}\) system, a sCO\({}_{2}\)/DH system, a sCO\({}_{2}\)/ammonia-water AHP system, and the proposed sCO\({}_{2}\)/LiBr-H\({}_{2}\)O AHP system. The main conclusions and contributions of this work can be summarized as follows:  
1. Using the LiBr-H\({}_{2}\)O AHP to recover the waste heat from sCO\({}_{2}\) cycle can significantly improve the thermodynamic and economic performances for the overall system. Based on the optimization results, the sCO\({}_{2}\)/LiBr-H\({}_{2}\)O AHP system can gain an improvement of 13.39% in the exergy efficiency and a reduction of 8.66% in the total product unit cost compared to the stand-alone sCO\({}_{2}\) cycle;
2. The exergy efficiency of sCO\({}_{2}\)/LiBr-H\({}_{2}\)O AHP system is 3.53% and 1.13% higher than those of sCO\({}_{2}\)/DH system and sCO\({}_{2}\)/ammonia-water AHP system, respectively, in the EOD case, and the total product unit cost of the sCO\({}_{2}\)/LiBr-H\({}_{2}\)O AHP system is 1.27% and 0.42% lower than those of the sCO\({}_{2}\)/DH system and sCO\({}_{2}\)/ammonia-water AHP system, respectively in the the COD case. In addition, _COHP_ of sCO\({}_{2}\)/LiBr-H\({}_{2}\)O AHP system is much larger than those of sCO\({}_{2}\)/DH system and sCO\({}_{2}\)/ammonia-water AHP system, indicating that the LiBr-H\({}_{2}\)O AHP can maximize the recovery of waste heat from sCO\({}_{2}\) cycle to provide heat for users. Therefore, the LiBr-H\({}_{2}\)O AHP is a desirable waste heat recovery system for the sCO\({}_{2}\) cycle, with which the combined system could achieve a higher exergy efficiency and a lower cost. Besides, the proposed sCO\({}_{2}\)/LiBr-H\({}_{2}\)O \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Items** & **sCO\({}_{2}\)** & **sCO\({}_{2}\)/DH** & **sCO\({}_{2}\)/Ammonia-Water sCO\({}_{2}\)/LiBr-H\({}_{2}\)O** \\  & & & **AHP** & **AHP** \\ \hline _PRc_ & 2.3693 & 2.3692 & 2.3449 & 2.3992 \\ _T\({}_{5}\)_ (\({}^{\circ}\)C) & 600 & 600 & 600 & 600 \\ _T\({}_{\text{AB}}\)_ (\({}^{\circ}\)C) & / & / & 114.31 & 96.98 \\ _T\({}_{\text{A1}}\)_ (\({}^{\circ}\)C) & / & / & 28 & 28 \\ _COPP_ & 0.3855 & 0.3855 & 0.3845 & 0.3866 \\ _COHP_ & / & 1 & 1.131 & 1.235 \\ _n\({}_{ex}\)_ (\%) & 53.38 & 58.34 & 59.26 & 59.91 \\ _ct\({}_{\text{total}}\)_ (S/GJ) & 18.819 & 17.410 & 17.262 & 17.189 \\ \hline \hline \end{tabular}
\end{table} 
Table 15: Optimized results for the cost optimal design case. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Items** & **sCO\({}_{2}\)** & **sCO\({}_{2}\)/DH** & **sCO\({}_{2}\)/Ammonia-Water sCO\({}_{2}\)/LiBr-H\({}_{2}\)O** \\  & & & **AHP** & **AHP** \\ \hline _PRc_ & 3.1641 & 3.2599 & 3.2960 & 3.2803 \\ _T\({}_{5}\)_ (\({}^{\circ}\)C) & 600 & 600 & 600 & 599.31 \\ _T\({}_{\text{AB}}\)_ (\({}^{\circ}\)C) & / & / & 115.86 & 90.30 \\ _T\({}_{\text{A1}}\)_ (\({}^{\circ}\)C) & / & / & 28 & 27.92 \\ _COPP_ & 0.3980 & 0.3979 & 0.3978 & 0.3975 \\ _COHP_ & / & 1 & 1.282 & 1.410 \\ _n\({}_{ex}\)_ (\%) & 55.11 & 60.36 & 61.79 & 62.49 \\ _ct\({}_{\text{total}}\)_ (S/GJ) & 19.603 & 18.210 & 18.054 & 17.881 \\ \hline \hline \end{tabular}
\end{table} 
Table 14: Optimized results for the exergy efficiency optimal design case. AHP system is presented to be a high-efficiency CHP system. It provides a meaningful direction for the design and improvement of sCO\({}_{2}\)-based CHP systems to reduce energy consumption and to bring considerable economic benefits;
3. The parametric study presents the influences of decision variables on the system performances, and the PSO optimization finds optimal design conditions for different cases.