Jeong-In Choi

Increasing global temperatures and unpredictable weather threaten agricultural production, intensifying the reliance on greenhouse cultivation. While naturally ventilated greenhouses offer an energy-efficient solution, their thermal performance under high heat loads is a growing concern. This study developed and validated a 3D CFD model to investigate the temperature distribution inside a single-span, naturally ventilated greenhouse. The model, implemented in ANSYS Fluent, considered the influence of external meteorological conditions, including solar radiation and wind, on the internal microclimate. The model demonstrated high accuracy, with an RMSE of 0.847°C and an MAE of 0.714°C for temperature when compared to experimental data. Diurnal analysis confirmed the dominant role of solar radiation, showing a strong correlation between indoor temperature and external solar radiation (r = 0.96) on sunny days. Spatially, the simulation revealed extreme thermal heterogeneity under high solar load, with a total internal temperature variation of up to 25°C (from 296 K to 321 K). The distribution was characterized by a distinct vertical stratification due to buoyancy and a strong longitudinal gradient, with the hottest air accumulating in the upper leeward corner. These findings highlight areas of potential crop heat stress and demonstrate the limitations of side-ventilation alone. The validated model serves as a valuable tool for optimizing ventilation strategies and improving climate control system design.

Growing interest in long-duration space missions and extraterrestrial colonization has driven the development of reliable space agriculture systems essential for sustaining life during these missions. However, the effects of environmental stressors such as low atmospheric pressure on plant growth have not yet been fully elucidated, which is crucial for the design of bioregenerative life support systems. This study investigated the growth responses of kale (Brassica oleracea var. acephala) under different pressure conditions (101.3, 67, and 33.0 kPa) in a closed environment, simulating potential extraterrestrial habitats. Two weeks after germination, kale plants were cultivated in custom-made acrylic pressure chambers for 19 days. Water (20 mL) was supplied on days 1 and 9. Leaf length, leaf width, and chlorophyll content were measured on days 1, 9, and 19. No significant differences were observed among the groups on day 1 (p > 0.05). However, by day 9, significant increases in leaf growth were observed in groups A (101.3 kPa) and B (67 kPa), with group B showing temporary enhancement of leaf growth (p < 0.05). By day 19, group A exhibited the highest growth rates for all parameters (leaf length 44.72 ± 2.74 mm, leaf width 39.19 ± 5.99 mm), while group B maintained relatively high growth, and group C (33 kPa) displayed the lowest growth rates, indicating a tendency for growth inhibition under prolonged hypobaric conditions. Chlorophyll content (SPAD values) increased during the early stages, with the highest values recorded in group C, suggesting that low pressure may temporarily stimulate chlorophyll preservation and accumulation. However, by day 19, chlorophyll content decreased across all groups, indicating challenges in maintaining photosynthetic capacity over the long term. These findings suggest that while low-pressure environments may initially promote physiological activity, they ultimately lead to growth inhibition. This study highlights the importance of maintaining appropriate pressure levels for space-based crop cultivation and provides foundational data for designing bioregenerative life support systems.

This study quantitatively evaluated the disinfection performance of a low-pressure mercury UV-C system against the pathogenic bacterium Agrobacterium rhizogenes by analyzing the effect of different combinations of lamp power consumption and flow rate. Agricultural water samples were collected from three commercial farms (Sources A, B, and C) in Sacheon-si, Gyeongsangnam-do, for the first experiment, and Source D in Gunbuk-myeon, Haman-gun, Republic of Korea, for the second experiment. All water samples were artificially inoculated with A. rhizogenes prior to treatment. The experiment tested nine combinations of three lamp power consumption levels (40, 75, and 105 W) and three flow rates (10, 15, and 30 L/min). Among these, samples #10, #20, and #30 were inoculated but not UV-treated, serving as the corresponding pre-disinfection controls. In the second experiment, a fixed power of 75 W was applied under high-flow conditions (60 and 120 L/min), with samples #37 and #38 serving as the corresponding untreated controls. In all tested conditions, absence of detectable bacteria was confirmed, except for sample #33 (75 W, 60 L/min), in which viable cells were detected at 2.0×10 2 CFU/mL. However, this represented approximately a 4.9 log reduction compared to its control (#37, 1.6×10⁷ CFU/mL), indicating substantial bactericidal efficacy. These findings suggest that effective disinfection can be achieved even under high-flow conditions, provided that sufficient UV dose is delivered. The results underscore the practical applicability of low-pressure UV-C systems in agricultural water treatment through the optimal configuration of operating parameters.