# Thermoeconomic Analysis of Concentrated Solar Power Plants Based on Supercritical Power Cycles
## 3 Results  
Thermal and Optical Analysis of the Solar Thermal Power Plant as a Function of the Receiver Configuration  
The results presented in this section only refer to the optical and thermal performance of STPPs that differ in the receiver configuration (number of panels and their dimensions) but that have the same thermal power, as well as the other parameters enumerated in Section 2.4. Table 6 shows the panel dimensions, heat losses, and pressure drop as a function of the number of panels in the receiver.  
As observed in Table 6, as the number of panels increases, their dimensions decrease. This ultimately leads to higher optical loss due to spillage, which decreases the optical efficiency, as observed in Figure 6a,b. On the other hand, heat losses decrease as the number of panels increases, as the view factor from the panel to the outside decreases due to a reduction in the aperture of the prism-shaped cavity. The pressure drop also decreases because the parallel fluid circuits increase as the number of panels increases, while their length, specifically the panel height, decreases. As a result, both the receiver energy and exergy efficiency improve with an increasing number of absorber panels. The overall solar subsystem performance, which is the convolution of the solar field optical efficiency and the receiver energy/exergy efficiency, exhibits maximum values for configurations between 8 and 10 panels, approximately, as observed in Figure 6a,b.  
\begin{table}
\begin{tabular}{c c c c c} \hline
**Number** & **Panel Height** & **Panel Width** & **Heat Losses** & **Pressure Drop** \\
**of Panels** & **(m)** & **(m)** & **(kW\({}_{\text{th}}\))** & **(bar)** \\ \hline
6 & 9.153 & 6.538 & 2231.465 & 5.531 \\
7 & 7.886 & 5.633 & 1490.491 & 4.750 \\
8 & 6.937 & 4.955 & 1066.124 & 4.159 \\
9 & 6.202 & 4.430 & 806.335 & 3.700 \\
10 & 5.618 & 4.013 & 636.138 & 3.343 \\
11 & 5.138 & 3.670 & 520.657 & 3.046 \\
12 & 4.739 & 3.385 & 436.343 & 2.798 \\
14 & 4.0852 & 2.918 & 312.163 & 2.4 \\
16 & 3.5756 & 2.554 & 234.591 & 2.102 \\ \hline \end{tabular}
\end{table}
Table 6: Panel dimensions, heat losses, and pressure drop as function of the number of panels in the receiver, while keeping the receiver thermal power constant.  
Finally, Figure 7 displays the overall energy efficiency of each STPP considered, which follows the same trend as the energy efficiency of the solar subsystem, since the power cycle efficiency is the same for all the configurations analysed: 48.41%, as seen in Table 1. As expected, there is also a maximum efficiency between 8 and 10 panels, which is the result of two opposing effects: on the one hand, energy and exergy efficiency, which increase as the number of panels increases, as heat loss and fluid pressure drop decrease due to shorter parallel circuits; on the other hand, there is a reduction in optical efficiency as the number of panels increases as the spillage loss increases.  
Figure 6: Thermal and optical performance of the receiver and the entire solar subsystem: (**a**) evolution of the optical and energy efficiencies as function of the number of absorber panels while keeping the receiver thermal power constant; (**b**) evolution of the optical and exergy efficiencies as function of the number of absorber panels while keeping the receiver thermal power constant.