# Evaluation of the Coupling of a Hybrid Power Plant with a Water Generation System
## 4 Results  
### Exergetic Analysis  
Having assumed 850 W/m\({}^{2}\) of DNI at Fuentes de Andalucia and an ambient temperature of 20 \({}^{\circ}\)C, the solar exergy received at the solar field is 138 MW. For the system under consideration, the exergetic efficiencies of the plant components are shown in Table 2. Specific properties for each stream of the power plant simulation can be found in Tables 12 and 13 of the appendix of the paper. According to the data obtained, it is noticed that the exergetic efficiencies of the majority of the power plant components generally exceed 80%.  
The highest exergy destruction is calculated in the biomass combustor, mainly due to the chemical reaction taking place there. Part of this exergy destruction can be avoided by preheating the reactants and by reducing the excess air. Another significant source of irreversibilities is the heat transfer between streams with high temperature differences. Such is the case of feedwater preheaters which tend to have lower exergy efficiencies, as a result of the high temperature difference between the steam turbine extractions and the water streams. Although the condenser is characterized by a relatively high exergy destruction, it is required to increase the total performance of the remaining plant components and allow lower pressures at the exit of the turbine.  
The overall solar efficiency of the power plant reaches a value of 15%, a value slightly lower when compared to other concentration technologies [57]. However, this value is enhanced by the use of thermal storage which provides autonomy to the plant and guarantees robust operation. Although a large part of the irreversibilities cannot be avoided, as in the case of the combustion process, actions can be incorporated to mitigate these effects. Further improvements can be achieved with the development of solar technology. In the coming years, advances within components and working fluids are expected to increase the total efficiency of power plants.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multicolumn{2}{c}{**Stream Balances**} & \multicolumn{2}{c}{**Stream Values (kW)**} \\ \hline
**Component** & \(\mathbf{E_{P}}\) & \(\mathbf{E_{F}}\) & \(\mathbf{E_{P}}\) & \(\mathbf{E_{F}}\) & \(\mathbf{\varepsilon}\) **(\%)** \\ \hline
**Air** & \(\dot{E}_{2}-\dot{E}_{1}\) & \(\dot{W}\) & 114.98 & 139.58 & 82.38 \\
**Compressor** & \(\dot{E}_{24}-\dot{E}_{51}-\) & \(\dot{E}_{Biomass}\) & 26,979.72 & 63,536.00 & 42.46 \\
**Biomass** & \(\dot{E}_{25}-\dot{E}_{23}\) & \(\dot{W}\) & 6.41 & 8.02 & 79.89 \\
**Pump 1** & \(\dot{E}_{38}-\dot{E}_{37}\) & \(\dot{W}\) & 240.87 & 286.45 & 84.09 \\
**Pump 2** & \(\dot{E}_{45}-\dot{E}_{44}\) & \(\dot{W}\) & 240.87 & 286.45 & 84.09 \\ HPST & \(\dot{W}\) & \(\dot{E}_{26}-\dot{E}_{28}-\dot{E}_{27}\) & 5,200.00 & 5,542.65 & 93.82 \\
**IPST 1** & \(\dot{W}\) & \(\dot{E}_{29}-\dot{E}_{31}-\dot{E}_{30}\) & 7,600.00 & 8,199.54 & 92.69 \\
**IPST 2** & \(\dot{W}\) & \(\dot{E}_{30}-\dot{E}_{33}-\dot{E}_{32}\) & 5,600.00 & 6,384.02 & 87.72 \\
**LPST** & \(\dot{W}\) & \(\dot{E}_{32}-\dot{E}_{34}\) & 2,100.00 & 2,605.15 & 80.61 \\
**FWH 1** & \(\dot{E}_{43}-\dot{E}_{38}\) & \(\dot{E}_{33}-\dot{E}_{40}\) & 289.91 & 347.95 & 83.32 \\
**FWH 2** & \(\dot{E}_{50}-\dot{E}_{45}\) & \(\dot{E}_{28}-\dot{E}_{47}\) & 115.39 & 151.13 & 76.35 \\
**Economizer** & \(\dot{E}_{18}-\dot{E}_{17}\) & \(\dot{E}_{13}-\dot{E}_{14}\) & 3,421.20 & 4,024.58 & 85.01 \\
**Evaporator** & \(\dot{E}_{19}-\dot{E}_{18}\) & \(\dot{E}_{12}-\dot{E}_{13}\) & 11,414.47 & 12,880.55 & 88.62 \\
**Superheater** & \(\dot{E}_{20}-\dot{E}_{19}\) & \(\dot{E}_{8}-\dot{E}_{10}\) & 7,080.78 & 7,621.87 & 92.90 \\
**Reheater** & \(\dot{E}_{21}-\dot{E}_{22}\) & \(\dot{E}_{9}-\dot{E}_{11}\) & 3,787.17 & 4,105.00 & 92.26 \\
**Cold Pump** & \(\dot{E}_{16}-\dot{E}_{15}\) & \(\dot{W}\) & 163.76 & 170.45 & 96.07 \\
**Hot Pump** & \(\dot{E}_{7}-\dot{E}_{6}\) & \(\dot{W}\) & 0.1195 & 0.125 & 95.62 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Exergetic efficiencies of power plant components.