# Smart Hydroponic Cultivation System for Lettuce
## 2 Materials and Methods
### Monitoring and Control System
### Case Study Results: Proximal Analysis

Lettuce is a vegetable belonging to the Compositae family, it is low in calories and serves as a good source of folic acid, vitamins A and C, as well as dietary fiber, which has significant benefits for digestive health. However, its overall nutritional value is relatively low, as it consists mostly of water. Additionally, lettuce possesses antioxidant properties due to its carotenoid levels and phenolic compounds [46]. Table 4 presents the biochemical variable data obtained from the proximal analyses conducted on 100 g of lettuce from the different treatments with the purpose of highlighting the nutritional benefits of each treatment and determining whether they meet the basic compositional criteria. The results are presented as mean \(\pm\) standard deviation (SD). Figure 16: Box plot of chlorophyll content in lettuce leaves measured using SPAD index values during the cultivation experiment for treatments T50, T75 and T100. Each box represents the interquartile range (Q1–Q3), the central line marks the median and the whisker ends indicate the minimum and maximum values, excluding outliers. Figure 17: Comparison of the arithmetic means of chlorophyll content (SPAD index values) and leaf dry mass (g) in treatments T100, T75 and T50. No significant differences were found among the treatments in terms of carbohydrates, fats and fiber content. However, for protein content, significant differences were observed, with T100 showing the highest values and a maximum difference of 0.7 g between treatments. Regarding moisture content, a deficiency of 0.71 g was recorded for T100. No significant differences were observed among treatments for iron and magnesium content. In contrast, significant differences were found in ascorbic acid, potassium and sodium levels between T50 and T100, but not between T75. Lastly, for zinc content, significant differences were observed across all three treatments, with T50 presenting the lowest values, causing reduced nutrient concentration in this treatment. Table 5 presents a comparison of some biochemical variables from T100, T75 and T50 against 100 g of commercially available iceberg lettuce, as reported by the United States Department of Agriculture (USDA) [47]. As observed, the carbohydrate values in all three treatments are slightly lower than those reported by [47], yet remain within a comparable range, indicating that the implementation of the smart agriculture system does not negatively impact the lettuce's energy contribution. An increasing trend in protein content was observed with higher nutrient solution concentrations, with T75 and T100 exceeding the values reported in [47]. Moisture content was higher in all three treatments compared to the reference, which may be attributed to the hydroponic technique used, as it provides a greater amount of water to the plants during growth. Finally, the treatments also showed higher fiber content than the reference, with T75 exhibiting the highest value. ### Case Study Results: Energy Measurements

Energy analysis is a fundamental component in evaluating the performance of agricultural systems in controlled environments, as it helps identify critical loads and supports the development of optimization strategies [48]. An energy consumption monitoring process was conducted with a 16 s update rate for the main devices comprising the proposed system. The total energy expenditure for one day of system operation was 13.65 kWh, of which 53% (7.22 kWh) was attributed to air conditioning--this being the component with the highest energy demand due to the continuous thermal regulation required for crop development. Secondly, full-spectrum LED lamps accounted for 28% (3.82 kWh) of daily consumption, reflecting their extended