Innovative solutions are crucial in a world where the demand for freshwater and food is rapidly increasing due to a projected population of 10 billion by 2050. 

Researchers from the University of South Australia have introduced an unprecedented concept – floating sea farms that harness the power of the sun and sea to produce freshwater and crops.

To ensure freshwater and food supplies in the decades ahead as the world's population grows and available agricultural land shrinks, a unique project creates vertical sea farms floating on the ocean that can produce fresh water for drinking and agriculture. 

How it works:

The vertical floating sea farm developed by Professor Haolan Xu and Dr Gary Owens from UniSA’s Future Industries Institute comprises two chambers: an upper layer similar to a glasshouse and a lower water harvest chamber.

This could help address looming global shortages of fresh water and food in the decades ahead, with the world’s population expected to reach 10 billion by 2050.

Innovative technology:

“The system works much like a wicking bed that household gardeners might be familiar with,” Dr Owen says.

“However, in this case, clean water is supplied by an array of solar evaporators that soak up the seawater, trap the salts in the evaporator body, and, under the sun’s rays, release clean water vapour into the air, which is then condensed on water belts and transferred to the upper plant growth chamber,” he adds.

Crop Growth and Sustainability:

In a field test, the researchers grew three common vegetable crops – broccoli, lettuce, and pak choi – on seawater surfaces without maintenance or additional clean water irrigation.

The system, which is powered only by solar light, has several advantages over other solar sea farm designs currently being trialled, according to Prof. Xu. 

“Other designs have installed evaporators inside the growth chamber, which takes up valuable space that could otherwise be used for plant growth. Also, these systems are prone to overheating and crop death.” 

Floating farms, where traditional photovoltaic panels harvest electricity to power conventional desalination units, have also been proposed, but these are energy-intensive and costly to maintain.

“In our design, the vertical distribution of evaporator and growth chambers decreases the device’s overall footprint, maximising the area for food production. It is fully automated, low cost, and extremely easy to operate, using only solar energy and seawater to produce clean water and grow crops.” Prof. Xu says.

Scalability and Future Prospects:

Their design is only proof-of-concept at this stage, but the next step is to scale it up, using a small array of individual devices to increase plant production. Meeting larger food supply needs will mean increasing the size and number of devices.

“It is not inconceivable that sometime in the future, you might see huge farm biodomes floating on the ocean or multiple smaller devices deployed over a large sea area,” says Owens.

Water Purity and Global Impact:

Their existing prototype is likely to be modified to produce a greater biomass output, including using low-cost substrate materials such as waste rice straw fibre, to make the device even cheaper to run.

The researchers have shown that the recycled water produced this way is pure enough to drink and has less salinity than the World Health Guidelines for drinking water.

The United Nations estimates that by 2050, approximately 2.4 billion people will likely experience water shortages. In the same period, the global water supply for agricultural irrigation is expected to decline by around 19 per cent.

Dr Owens says, “Freshwater accounts for just 2.5 per cent of the world’s water and most of this is not accessible because it’s trapped in glaciers, ice caps or is deep underground,” adding, “It’s not that freshwater is dwindling either, but the small amount that exists is in ever increasing demand due to population growth and climate change.”

The fact that 97.5 per cent of the world’s water is in our oceans – and freely available –is an obvious solution to harness the sea and sun to address growing global water, food, and agricultural land shortages. Adopting this technology could improve the health and welfare of billions of people globally.

The design experiment is published in the Chemical Engineering Journal.

Floating sea farms represent a beacon of hope in a world facing imminent challenges in freshwater and food supply. As we look ahead to 2050, the integration of this technology could not only alleviate global shortages but also improve the well-being of billions of people worldwide.