## 3 Result and Discussion
### Simulation  
Figure 3 shows the PVT performance in thermal efficiency \(\eta_{t}\) versus the reduced temperature parameter \((T_{i}-T_{a})/I\) for wind loss effect; (a) T-mode and (b) PVT-mode. From Figure 3a, the T-mode simulation is represented by the black circle markers while the T-mode experiments by the white circle markers. The trend line for both T-modes crossed each other, with the slope \(\eta_{t}/(T_{i}-T_{a})/I\approx 1726.0\) for the simulation and 1726.2 for the experimentation. For Figure 3b, PVT-mode simulation is represented by the black rectangle markers, while the PVT-mode experiment is by the white rectangle markers. The trend line for both T-modes also crossed with the slope \(\eta_{t}/(T_{i}-T_{a})/I\approx 3049.5\) for the simulation and 3025.1 for the experimentation. Based on Equation (20), the \(RMS_{s-r}\) values of the \(\eta_{t.sim}\) to \(\eta_{t.reg}\) were 0.82% for T-mode and 0.00% for PVT-mode, giving an average of 0.4%, whereas the \(RMS_{s-e}\) values of the \(\eta_{t.sim}\) to \(\eta_{t.\exp}\) for T-mode and PVT-mode were 16.3% and 10.9%, with an average of 12.9%. Figure 4 shows the PVT performance of thermal efficiency \(\eta_{t}\) versus the reduced temperature parameter \((T_{i}-T_{a})/I\) for without wind loss effect; (a) T-mode and (b) PVT-mode. In Figure 4a, the T-mode simulation is represented by the black diamond markers, while the experiment is by the white diamond markers. The trend lines for both T-modes crossed each other, with the slope \(\eta_{t}/(T_{i}-T_{a})/I\approx 1556.0\) for the simulation and 1556.7 for  
Figure 3: Thermal efficiency vs. the reduced temperature for the wind loss effect: (a) T-mode simulation vs. T-mode experiment; (b) PVT-mode simulation vs. PVT-mode experiment. the experiment. For Figure 4b, PVT-mode simulation is represented by the black triangle markers, while the PVT-mode experiment is by the white triangle markers. The trend lines for both T-modes also crossed, with the slope \(\eta_{t}/\left(T_{i}-T_{a}\right)/I\approx 2921.5\) for the simulation and 2900.0 for the experimentation. Based on Equation (20), the \(RMS_{s-r}\) values of the \(\eta_{t.sim}\) to \(\eta_{t.reg}\) are 0.02% for T-mode and 0.74% for PVT-mode, giving an average of 0.4%, whereas the \(RMS_{s-e}\) values of the \(\eta_{t.sim}\) to \(\eta_{t.exp}\) for T-mode and PVT-mode were 10.2% and 14.0%, with an average of 12.1%. Figure 5 shows the PVT performance of thermal efficiency \(\eta_{t}\) versus the reduced temperature parameter \(\left(T_{i}-T_{a}\right)/I\) of simulation results for (a) wind loss effect and (b) without wind loss effect of T-mode vs. PVT-mode. From Figure 5a,b, the trend line of T-mode versus PVT-mode crossed each other. For the wind loss effect, the crossing point was \(\eta_{t}=39.8\%\) and \(\left(T_{i}-T_{a}\right)/I=0.0056\), whereas for the without wind loss effects, at \(\eta_{t}=46.4\) and \(\left(T_{i}-T_{a}\right)/I=0.0049\). The cross point was not much different compared to the results of the experiment; \(\eta_{t}=40.0\%\) and \(\left(T_{i}-T_{a}\right)/I=0.0055\) for the wind loss effect, or \(\eta_{t}=46.7\%\) and \(\left(T_{i}-T_{a}\right)/I=0.0047\) for the without wind loss effect [13]. The total efficiency of PVT, \(\eta_{pet}=\eta_{t}+\eta_{e}\), at these crossing points are approximately 52.3% and 58.9% for wind loss effect and without wind loss effect, respectively. The area between 0 and the crossing point was called the effective region [13]. Figure 6 more specifically describes electrical efficiency versus thermal efficiency for the PVT-mode (simulation) versus the T-mode (simulation). Using Equation (25) to calculate \(\eta_{e}\) based on \(T_{S}\), which was conducted simultaneously [2]. \(\eta_{e}\) as a function of \(T_{S}\) was plotted into the graph \(\eta_{t}\) versus \(\left(T_{i}-T_{a}\right)/I\) as the X-axis, as well as \(\eta_{e}\) versus \(\left(T_{i}-T_{a}\right)/I\). As shown in the graphs, \(\eta_{e}\) also decreased for \(\left(T_{i}-T_{a}\right)/I>>0\), as well as for \(T_{S}>>0\) in Equation (25).