## 3 Results and Discussion  
The summarized results of the water recovered from the exhaust air are shown in Table 2. The calculations were performed including water storage in a tank with a capacity of 2 m\({}^{3}\). The system has a 100% effectiveness in the cold period (months from December to March). During months from June to August the effectiveness of the water recovery system is significantly reduced to average values ranging from 11% to 19%. Months such as May and September are transition months, during which large fluctuations in the effectiveness of the system from minimum values of 24% to maximum values of 75% are observed.  
In 2012 the maximum effectiveness of system performance was registered. The characteristic parameters describing the operation of the system are shown in the Figure 4. In winter season, a high inflow of water to the reservoir is observed (Figure 4a). The overflow is recorded for 191 days (Figure 4b) till day 110 th and from day 284 th till the end of the year. It shows a high potential for aerial water recovery in the growing halls. Excess water could be used for other purposes.  
In the warm season it is also possible to recover water, but the daily amount of recovered water does not exceed 1 m\({}^{3}\) (in the period from day 140 th to day 284 th of the year see Figure 4a). That is why, during this period of time water is not stored (see Figure 4c) and the system effectiveness varies from 0% to about 48% (Figure 4d).  
System operation analysis showed that 2018 is a year in which the lowest system effectiveness equal to 61.08% was recorded. It shows that the exhaust air, which has constant parameters during the year, is a stable source for water recovery. In 2018, the period in which there is no excess water is longer (day 93 rd to 297 th). The range of 182 days in which the effectiveness of the system is 100% is also lower as confirmed by Figure 5d. For comparison, in 2012 this time lasted for 191 days.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Month**} & \multicolumn{4}{c}{**Performance, \%**} & \multicolumn{4}{c}{**Performance, m\({}^{3}\)**} \\ \cline{2-7}  & **Min** & **Mean** & **Max** & **Min** & **Mean** & **Max** \\ \hline I–XII & 61.08 & 67.12 & 69.48 & 229.62 & 252.50 & 261.91 \\ I & 100.00 & 100.00 & 100.00 & 31.93 & 31.93 & 31.93 \\ II & 100.00 & 100.00 & 100.00 & 28.84 &  
The calculation results of the water recovery system effectiveness for the entire analyzed period are presented in Figure 6. In the cold period, the system has an effectiveness of 100% (blue color). In the warm season, the effectiveness of the systems decreases even to 0%, which is indicated by the red color. It can be concluded that the proposed system is a promising solution in hydroponic growing halls because it allows providing enough water for watering the plants for most of the year. The system also generates excess water, which can be used for other purposes. To create an independent system for recovering water for watering the crop, a supporting system or solution would have to be proposed, the effectiveness of which would be satisfactory during the warm period (e.g., rainwater harvesting [36]).  
Figure 4: Maximum system effectiveness equal to 69.48% occurred in 2012. (**a**) Inflow of water to the tank. (**b**) Overflow of water. (**c**) Accumulated water in the tank. (**d**) System performance.  
Figure 5: Minimum system effectiveness equal to 61.08% occurred in 2018. (**a**) Inflow of water to the tank. (**b**) Overflow of water. (**c**) Accumulated water in the tank. (**d**) System performance.