# Thermoeconomic Analysis of Concentrated Solar Power Plants Based on Supercritical Power Cycles
## 3 Results
### Economic Analysis of the Solar Thermal Power Plant as a Function of the Receiver Configuration  
A comparative economic analysis of the entire STPP has been conducted for each receiver configuration considered in the previous section. For this purpose, the Total Capital Cost (\(TCC\)) [33], the Payback period (\(PB\)) [34,35], and the Levelised Cost of Electricity (LCOE) [33] of each STPP have been estimated. The \(PB\) is the length of time that it takes to recover the initial capital investment in a project, and it is calculated by means of Equation (11). \[PB=\frac{TCC}{AEP\cdot(CE-OMC)} \tag{11}\]  
In Equation (11), \(AEP\) is the Annual Electricity Production, which is estimated assuming that the plant has a Capacity Factor (CF) of 25%, as it is a stand-alone CSP plant [36]. Based on this, the annual production for all plants is equal to 109.5\(\cdot\)10\({}^{3}\) MWh\({}_{\text{e}}\)/year. \(CE\) is the electricity cost, 124.9 $/MWh\({}_{\text{e}}\), which is based on the average market price at USA [37]. Finally, \(OMC\) is the O&M costs per MWh\({}_{\text{e}}\), taken as 23 $/MWh\({}_{\text{e}}\)[1]. The LCOE is calculated using Equation (12):  
\[LCOE=\frac{CRF\cdot TCC}{AEP}+OMC \tag{12}\]  
In Equation (12), \(CRF\) (%) is the Capital Recovery Factor, calculated as Equation (12):  
\[CRF=\frac{WACC\cdot(1+WACC)^{n}}{(1+WACC)^{n}-1}. \tag{13}\]  
In Equation (13), \(WACC\) refers to the Weighted Average Capital Cost, which is assumed to be 8%; and \(n\) represents the economic lifetime, which is assumed to be 30 years. With the aforementioned values, the \(CRF\) is calculated to be 0.088 years\({}^{-1}\). Figure 7: Evolution of the overall energy efficiency of the STPP, as function of the number of absorber panels. The \(TCC\) of the sCO\({}_{2}\) partial-cooling cycle has been calculated using the methodology described in [38; 39]. Table 7 summarises the \(TCC\) for the primary heat exchanger, recurserators, precooler, and turbomachinery. This \(TCC\) is constant for all the STPPs analysed in the previous section, as the power cycle is the same for all of them. The \(TCC\) of the solar field has been calculated according to the equations and reference values provided in the SolarPilot program. The most significant costs are associated with the heliostat field, the receiver, and the tower, as shown in Equations (14)-(16):  
\[c_{heliostat,total}=c_{heliostat}\cdot A_{sf} \tag{14}\]  
\[c_{rec}=c_{rec,ref}\cdot\left(\frac{A_{rec}}{A_{rec,ref}}\right)^{k_{rec}} \tag{15}\]  
\[c_{tower}=c_{tower,fixed}\cdot e^{k\cdot h_{tower}} \tag{16}\]  
In the previous equations, \(c_{heliostat}\) is the cost of the heliostat per square meter of heliostat reflective area, with a default value in SolarPilot of 145 $/m\({}^{2}\); \(A_{sf}\) is the total reflective area in the field, which depends on the number of heliostats in each STPP; \(c_{rec,ref}\) is the receiver reference cost, with a default value in SolarPilot of 103 Mio. $; \(A_{rec,ref}\) is the receiver reference area, with a default value in SolarPilot of 1571 m\({}^{2}\); \(k_{rec}\) is the receiver cost scaling exponent, equal to 0.7 in SolarPilot; \(A_{rec}\) is the receiver area, which depends on the number of absorber panels and their size; \(c_{tower,fixed}\) is the fixed tower cost, with a default value in SolarPilot of 3 Mio. $; \(k\) is the tower cost scaling exponent, equal to 0.0113 in SolarPilot; and \(h_{tower}\) is the tower height, equal to 109 m for all the cases analysed. As seen in Table 8, as the number of absorber panels increases, the receiver area decreases, and, consequently, its cost decreases, since its energy and exergy efficiencies increase, as discussed in the previous section. The tower height and its cost are constant, while the total reflective area increases as the receiver size decreases because of the larger optical losses due to spillage.