## 4 Results and Discussion  
Figure 9 shows \(Q_{loss}\) and \(t_{igt}\) in the SGTC with an air layer (Figure 9a) and SGTC with a vacuum layer (Figure 9b) for previously adopted \(t_{abs}\), \(t_{o}\) and \(W\) values. All diagrams (Figure 9) were formed by varying the following three values: \(t_{abs}\) (40 \({}^{\circ}\)C, 50 \({}^{\circ}\)C, 60 \({}^{\circ}\)C, 70 \({}^{\circ}\)C, 80 \({}^{\circ}\)C and 90 \({}^{\circ}\)C)--first variable, \(t_{o}\) (10 \({}^{\circ}\)C, 20 \({}^{\circ}\)C, and 30 \({}^{\circ}\)C)--second variable, and \(W\) (1 m/s, 3 m/s, and 5 m/s)--third variable. Figure 9 shows that the heat losses in the SGTCs (SGTC with an air and SGTC with a vacuum layer) increase with the increase in the temperature of the absorber and the increase in the wind speed. A higher absorber temperature increases the temperature difference with the environment, so the driving force of the heat losses increases. When the wind is faster, convective component Equation (6) is higher, and heat losses increase. Wind speed also determines the temperature of the glass (these values are proportional). Contrary to that, higher ambient temperature causes the opposite effect. When the ambient temperature increases, the temperature difference between the environments decreases [53; 54]. When \(t_{o}\) = 10 \({}^{\circ}\)C and \(W\) = 1 m/s (Figure 9a), heat losses in the SGTC with an air layer are between 17.17 W (for \(t_{abs}\) = 40 \({}^{\circ}\)C) and 56.27 W (for \(t_{abs}\) = 90 \({}^{\circ}\)C). The heat losses are higher 8.54-9.25% (\(W\) = 3 m/s) and 13.17-14.49% (\(W\) = 5 m/s) for the same ambient temperature. If the second variable is \(t_{o}\) = 20 \({}^{\circ}\)C, the heat losses are within the following limits: 11.14-49.37 W (\(W\) = 1 m/s), 12-53.65 W (\(W\) = 3 m/s), and 12.47-56.11 W  
Figure 9: Characteristic temperatures and heat losses for SGTC with an air layer (**a**) and SGTC with a vacuum layer (**b**). (\(W\) = 5 m/s). Maximum (for \(t_{abs}\) = 90 \({}^{\circ}\)C) heat loss values are the lowest when \(t_{o}\) = 30 \({}^{\circ}\)C: 42.37 W (\(W\) = 1 m/s), 45.82 W (\(W\) = 3 m/s), and 47.81 W (\(W\) = 5 m/s). The highest and lowest internal glass tube temperatures for the SGTC with an air layer are (Figure 9a): \(t_{\text{tgt}}\) = 47.5 \({}^{\circ}\)C (for \(t_{o}\) = 30 \({}^{\circ}\)C, \(t_{abs}\) = 90 \({}^{\circ}\)C, and \(W\) = 1 m/s), and \(t_{\text{tgt}}\) = 14.49 \({}^{\circ}\)C (for \(t_{o}\) = 10 \({}^{\circ}\)C, \(t_{abs}\) = 40 \({}^{\circ}\)C, and \(W\) = 5 m/s). The calculation algorithm (Figure 4) for the SGTC with a vacuum layer is simpler due to the elimination of the convective component of Equation (4). The same effect explains the reduction of the heat losses (Figure 9b). For example, from 64.42 W to 27.11 W (\(t_{o}\) = 10 \({}^{\circ}\)C, \(t_{abs}\) = 90 \({}^{\circ}\)C, and \(W\) = 5 m/s) is the best case scenario. In this case, the value \(t_{\text{tgt}}\) is in the following range: \(t_{\text{tgt}}\) = 11.87 \({}^{\circ}\)C (for \(t_{o}\) = 10 \({}^{\circ}\)C, \(t_{abs}\) = 40 \({}^{\circ}\)C, and \(W\) = 5 m/s) and \(t_{\text{tgt}}\) = 39.3 \({}^{\circ}\)C (for \(t_{o}\) = 30 \({}^{\circ}\)C, \(t_{abs}\) = 90 \({}^{\circ}\)C, and \(W\) = 1 m/s). Analogous to the previous figure (Figure 9), the next figure (Figure 10) shows \(Q_{\text{loss}}\) and \(t_{\text{tgt}}\) in the DGTC with an air layer (Figure 10a) and DGTC with a vacuum layer (Figure 10b) for previously adopted \(t_{abs}\), \(t_{o}\) and \(W\) values. When it comes to the DGTCs (DGTC with an air layer and DGTC with a vacuum layer), the conclusions are the same as in the case of the SGTCs (Figure 10): heat losses are proportional to the absorber temperature, heat losses are proportional to the wind speed, and heat losses are inversely proportional to the ambient temperature.