The innovative, self-sustaining system designed by the University of South Australia’s Future Industries Institute utilizes solar power to evaporate seawater and subsequently recycles it into freshwater, marking a pioneering approach that enables crop cultivation without human intervention.

The world's population is projected to reach 10 billion by 2050, raising concerns about impending global shortages of freshwater and food. To tackle these challenges, the Future Industries Institute’s Professor Haolan Xu and Dr. Gary Owens have devised the vertical floating sea farm. The system comprises two chambers: an upper layer resembling a glasshouse and a lower water harvest chamber.

The system resembles a wicking bed, a concept familiar to household gardeners. However, in this instance, clean water is supplied via an array of solar evaporators that absorb seawater, trap the salts, and, under the sun's rays, release clean water vapor into the air. This vapor is then condensed on water belts and conveyed to the upper plant growth chamber.

In field trials, the researchers successfully cultivated three common vegetable crops — broccoli, lettuce, and bok choy — on seawater surfaces, requiring no maintenance or additional clean water irrigation. Notably, the system operates solely on solar energy, offering distinct advantages over other solar sea farm designs currently under evaluation.

Professor Xu pointed out that alternative designs incorporate evaporators within the growth chamber, consuming valuable space intended for plant growth and being susceptible to overheating and crop damage. Moreover, floating farms powered by conventional photovoltaic panels for electricity generation are energy-intensive and costly to maintain.

"Our design, featuring the vertical distribution of evaporator and growth chambers, reduces the device's overall footprint, maximizing the area available for food production. It is fully automated, cost-effective, and exceptionally user-friendly, relying solely on solar energy and seawater to produce clean water and cultivate crops," Professor Xu said in a statement.

Dr. Owens noted that the current design serves as a proof-of-concept, and the next phase involves scaling it up by deploying a small array of individual devices to enhance plant production. To meet larger food supply demands, both the size and quantity of these devices will need to increase.

He envisioned a future where vast farm biodomes might float on the ocean or numerous smaller devices could be dispersed over expansive sea areas. Modifications to the existing prototype are also being considered to boost biomass output, including the utilization of low-cost substrate materials like waste rice straw fiber to enhance cost-efficiency.

The researchers have demonstrated that the recycled water produced through this method is pure enough for consumption and possesses lower salinity levels than the World Health Organization's guidelines for drinking water.

The United Nations predicts that by 2050, approximately 2.4 billion people could face water shortages, while global water supply for agricultural irrigation may decline by about 19 percent during the same period. With approximately 97.5 per cent of the world’s water contained within its oceans, harnessing freely available sea and sun through technologies like that developed by the Future Industries Institute will be critical to addressing mounting global shortages of water, food and arable land.

The results of their design experiment have been published in the Chemical Engineering Journal.

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