## 3 Results and Discussion  
The HD solar desalination system is modified in three ways to test the effectiveness of each modification, as well as testing which modification best suits the required purpose of the system. To check the policy, we ran simulations with a C++ program. The results describe the variation in the production of fresh water under each modification. The working of the system and the simulated results for the three modifications are shown in Figure 9. The graph illustrates that the maximum mass of fresh water presented by any of the three modifications is about 18 kg/day. Specifically, the highest mass is received from the third modification. The order of preference of the three modifications is from the third to the first. The second modification is more efficient than the first modification, whereas the third is more efficient than the first andthesecond. Therefore, the third modification was chosen to be the most efficient and reliable modification. Given the complexity of the process and the practical impossibility of varying one parameter, the system requires several modifications. Furthermore, setting the others because of meteorological fluctuations and having an optimal flow rate of water as it enters the evaporation tower with the highest possible temperature and better air flow rate is required for leveraging the production. Besides, the third configuration is essential if a law that controls the variation in the solar flux (\(I\)) and that controls the flow rate of the water into the water solar collector (\(m_{\rm w}\)) is put in place. Finally, the amount of water to be recycled (\(m_{\rm recy}\)) should always respect the optimal operating temperature (\(T_{\rm II,ev}\)) as well as the water flow rate (\(m_{\rm lev}\)) in the evaporation tower. The regulation consists of setting the set-points of the temperature of the water at the solar collector outlet (\(T_{\rm west}\)), the temperature of the water at the evaporation tower (\(T_{\rm II,set}\)), and the water flow rates (\(m_{\rm w}\) and \(m_{\rm recy}\)), as follows:  
Figure 9: The effect of the different design configurations on the freshwater production. * Set-point of the outlet of the temperature of water: \[T_{\text{\it{u}set}}=\left\{ \begin{array}{l}32\ ^{\circ}\text{C}\ \text{for}\ t<1\ \text{hand}\ t\geq 7\ \text{h}\\ 42\ ^{\circ}\text{C}\ \text{for}\ 1\ \text{h}\leq t<7\ \text{h}\end{array} \right.\]
* Set-point of the inlet of the temperature of water in the evaporation tower: \[T_{\text{\it{l}set}}=\left\{ \begin{array}{l}T_{\text{\it{u}set}}-3\ ^{\circ}\text{C}\ \text{in}\ \text{case of recycling}\\ T_{\text{\it{u}set}}\ \text{otherwise}\end{array} \right.\]  
To adjust the high water temperature set-points, the rate of flow of the water ranges between 0.01 and 0.5 kg/s. Figures 10 and 11 describe the variation in the rate of flow of water in the water solar collector and the quantity of recycled water for a given solar radiation model, respectively. The amount of recycled water satisfies the desired condition imposed on the water flow rate in the evaporation tower, \(m_{\text{\it{r}recy}}\). For a water flow rate higher than 0.2 kg/s in the water solar collector, the amount of water to be recycled is equal to zero. When the water flow rate drops below 0.2 kg/s, \(m_{\text{\it{r}recy}}\) takes a nonzero value to compensate for the decrease in the water flow rate. Figure 12 illustrates the behavior of the water temperature at the outlet of the collector and that at the inlet of the evaporation tower. \(T_{\text{\it{w}o}}\) follows its desired value carefully. Likewise, \(T_{\text{\it{l}1,ev}}\) retains the assigned value. Figure 11: Variation in the amount of recycled water. Figure 10: Variations in solar radiation and the rate of flow of water in the water solar collector.