## 2 Methodology
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Parameter** & **Design** & **Deliefa** & **El Oued** & **Béchar** \\ \hline \multirow{4}{*}{Location} & DNI (W/m\({}^{2}\)) & 1050.00 & 750.00 & 700.00 \\  & Latitude (\({}^{\circ}\)) & 34.68 & 33.50 & 31.50 \\ \cline{1-1}  & Longitude (\({}^{\circ}\)) & 3.25 & 6.78 & \(-2.25\) \\ \cline{1-1}  & Elevation (m) & 1144.00 & 69.00 & 816.00 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Location parameters for different regions. Figure 1: Implementation of the heliostats field. Representation of the optical angle \(\alpha\). the exchange with the outside by radiation (solar and radiation losses), by convection (losses at the body of the receiver) and by conduction (losses through thermal bridges). Figure 2 shows the different heat exchanges of the receiver with the external environment. The heat flux of the receiver can be expressed by Equation (6):  
\[Q_{rec}\ =\ q_{htf}\ +\ q_{conv}+q_{rad}+q_{ref} \tag{6}\]  
\[Q_{rec}\ =\ S_{i}\cdot I_{d} \tag{7}\]  
where \(q_{htf}\) is the heat flow of molten salt; \(q_{conv}\): loss of convection heat flow; \(q_{rad}\): loss of radiation heat flux; \(q_{ref}\): loss of reflection flux; \(S_{i}\): total surface. The incidence of solar radiation \(I_{d}\) on the receiver is evaluated by the flux map radiation model. The distribution of the radiation flux is integrated by combining the effect of the different losses occurring in a heliostats filed layout (cosine effect, shadowing effect, blocking effect, atmospheric attenuation, spillage and flux image profile), based on direct radiation from \(950\ W/\mathrm{m}^{2}\)[26; 33]. The energy absorbed by the heat transfer fluid (\(q_{htf}\)) is given by the following Equation (8):  
\[q_{htf}=m_{htf}\cdot C_{htf}\cdot\left(T_{htf(x+dx)}-T_{htf(x)}\right)=US_{i} \cdot\left(T_{st}-T_{htf}\right) \tag{8}\]  
\[US_{i}=\frac{1}{R_{cond}+R_{conv}} \tag{9}\]  
\[R_{cond}=\frac{\ln\frac{D_{st}}{D_{lt}}}{2\cdot\pi\cdot L_{t}\cdot K_{t}\cdot N _{t}} \tag{10}\]  
\[R_{conv}=\frac{2}{\pi\cdot h_{htf}\cdot L_{t}\cdot D_{t}\cdot N_{t}} \tag{11}\]  
where \(q_{htf}\) is the heat flow of molten salt (W), \(m_{htf}\) is the molten salt flow rate (kg/s), \(C_{htf}\) is the heat capacity of the molten salt fluid (k/kg\(\cdot\)K), \(T_{htf}\) is the inlet temperature of the molten salt at x position (K), \(U_{Si}\) is heat transfer conductance coefficient (W/K), \(T_{st}\) is receiver temperature at the surface (K), \(R_{cond}\) is heat transfer resistance by conduction (K/W), \(R_{conv}\) is heat transfer resistance by convection (K/W), \(D_{st}\) is outer diameter of the tube (m), \(D_{lt}\) is the inner diameter of the tube (m), \(L_{t}\) is  
Figure 2: Energy balance of the external receiver. length of the tube (m), \(K_{t}\) is thermal conductivity of the receiver tube (W/m\(\cdot\)K), \(N_{t}\) is total number of the receiver tube, and \(D_{t}\) diameter of the tube (m). The losses by convection are given by Equation (12):  
\[q_{conv}=S_{i}\cdot h_{conv}\cdot(T_{st}-T_{ic-air}) \tag{12}\]  
where \(q_{conv}\) is the loss of convection heat flux (W), \(S_{i}\) is total surface/Surface total (m\({}^{2}\)), \(h_{conv}\) is the convective heat losses from each receiver tube (W/m\({}^{2}\cdot\)K), \(T_{st}\) is the receiver temperature at the surface (K), and \(T_{ic-air}\) is the temperature of the air in the inner cavity (K). The radiation losses \(q_{rad}\) have a negligible value because the absorber has a high absorption of short waves of solar radiation and the same for losses by reflection \(q_{ref}\) due to the less emissivity of the long thermal waves. The performance of a good configuration of the solar tower system is based on several parameters such as power generation injected to the grid, incident solar radiation, and storage capacity. The capacity factor and the multiple solar characterizing the performance of a central solar tower system.