Air moisture harvesting in soil for indoor agriculture: A comparative study of moisture dynamics in shallow porous beds

Indoor farming can mitigate water scarcity, declining crop yields, and excessive chemical use in agriculture. However, it demands innovative solutions to reach its full potential. This paper presents a novel indoor plant cultivation technique that leverages atmospheric moisture. Shallow soil bed cooling from below can induce condensation within the soil pores, providing a sustainable water source for plant growth. We tested this method on wheat seed cultivation, observing a 40% growth increase in seedlings with cooled soil beds. We conducted a detailed study of moisture dynamics in porous sand beds to understand the underlying mechanisms of this technique. Choosing sand as a medium isolated the effects of porosity, temperature, and capillary action on moisture condensation. Sand's inertness allows a concentrated analysis of moisture dynamics without interference from chemical reactions or microbial activity. Experiments with cooled sand of varying particle sizes showed moisture condensation levels of 0.025, 0.042, and 0.092 kg/kg for coarse, fine, and superfine sand over 11 days. In soil, moisture reached 0.124 kg/kg over 22 days, highlighting the impact of porosity, temperature, and capillary forces. Our findings reveal exponential moisture increase over time and a linear relationship between bed water content and specific heat. The method is practical and adaptable, especially for remote locations and arid regions, as renewable energy sources can power it. This approach could revolutionize indoor agriculture, particularly in controlled environment systems. Controlling soil temperature can optimize growth conditions, increase yields, and minimize environmental impact. It offers versatility and scalability for various crops and systems.