# PV Tracking Design Methodology Based on an Orientation Efficiency Chart
## 2 Materials and Methods
### Selection and Design of the Mechanisms for Dual-Axis Tracking  
This step consists primarily of the selection of the mechanism, in accordance with the capacities required for the solar tracker prototype, using comparison matrices that facilitate the selection of devices according to the evaluation criteria. Here, \"H\" is assigned to high values, \"M\" to medium values, and \"L\" to low values. In addition, calculations including arithmetic, finite element analysis (FEA), and computer-aided design (CAD) tool computations are performed on the structures and  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Position** & **Schedule of Tracking (Hours)** & **Azimuth (\({}^{\circ}\))** \\ \hline P1 & 06:01 and 10:00 & 30 \\ P2 & 10:01 and 14:00 & 90 \\ P3 & 14:01 and 18:00 & 120 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Azimuth schedule of tracking.  
Figure 3: General operation of the solar tracker prototype.  
mechanisms required to develop the prototype. The first component of the design for the solar tracker is the PV system support structure, which corresponds to a 1 kW PV system composed of four panels with dimensions of 0.95 \(\times\) 1.05 m and a power of 250 W. This supporting structure is designed using CAD software and FEA. FEA to determine which structure exhibits better resistance against wind action is performed using a wind speed of 33.3 m/s, which was chosen based on the maximum wind speed records at the installation location [26]. According to the FEA, the most appropriate structure uses structural steel (PTR-14, PTR-20) and \(\frac{1}{2}^{\prime\prime}\) tubing. Moreover, the authors of [8] analyzed and established a better location of the azimuth as shown in Figure 4.  
Next, the tracking mechanism is selected based on the decision matrix presented in Table 3. The most viable option is a direct current (DC) gear motor adapted to a transmission because of its low cost and high availability.  
The transmission is designed (Figure 5) to achieve the proposed resolution without affecting the previously proposed structure. A level gear transmission with a total gear ratio of 8:1 that is composed of a gear-motor coupling dart (1), an upper panel support (2), and level gears for transverse coupling (3 and 4) is proposed. The transmission uses A36 steel due to its mechanical resistance.  
Figure 4: Proposed structure for the solar tracker.  
Figure 5: Proposed azimuthal solar tracker mechanism.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Mechanism** & **Cost** & **Availability** & **Maintenance** \\ \hline \hline Gear motor and linear actuator & L & H & M \\ Two slew drives & M & M & L \\ Two indexed motors & H & L & H \\ \hline \hline \end{tabular}
\end{table}
Table 3: Actuator selection for mechanism tracking.  
According to the calculations for a gear motor and linear actuator (such as the example shown in Figure 6, which is a worm-rack type system with a torque of 80 N-m coupled to a transmission with a step ratio of 12 and is 0.2 m in diameter), it is possible to withstand the torsion moments caused by wind action over the PV system area.