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To capitalise on the abundant and free resources of the sun and sea, researchers at the University of South Australia have initiated a pioneering project to construct vertical sea farms floating on the ocean. These innovative sea farms possess the capability to produce fresh water for drinking and agriculture without human intervention, offering a potential solution to the impending global crises of freshwater scarcity and food shortage, anticipated to be exacerbated by the projected world population reaching 10 billion by 2050.
Led by Professor Haolan Xu and Dr Gary Owens from UniSA’s Future Industries Institute, this inventive system comprises two main components: an upper layer resembling a glasshouse and a lower water harvest chamber. The system’s functionality bears a resemblance to a wicking bed, a concept familiar to home gardeners, but with a remarkable twist. It relies on an array of solar evaporators that absorb seawater, isolate the salts within the evaporator structure, and, when exposed to the sun’s rays, release clean water vapour into the atmosphere. This vapour then condenses on water belts and is transported to the upper plant growth chamber.
In a field test, the researchers successfully cultivated three common vegetable crops – broccoli, lettuce, and pak choi – using seawater surfaces without the need for maintenance or additional clean water irrigation. The system, powered solely by solar energy, offers several advantages over existing solar sea farm designs that are currently undergoing testing.
Professor Xu highlights that other designs incorporate evaporators within the growth chamber, occupying valuable space that could otherwise be used for plant growth. Additionally, these systems are susceptible to overheating, which can lead to crop damage or death. In contrast, the innovative design developed by Professor Xu’s team distributes the evaporator and growth chambers vertically, reducing the device’s overall footprint and maximising the area available for food production. The system is not only fully automated but also cost-effective and easy to operate, relying exclusively on solar energy and seawater to generate clean water and cultivate crops.
Dr Owens emphasised that while their design currently represents a proof-of-concept, the next step is to scale it up, utilising a small array of individual devices to enhance plant production. Meeting the growing demands of food supply will necessitate both increasing the size and number of these devices.
It is conceivable that in the future, vast farm biodomes could float on the ocean’s surface, or multiple smaller devices could be deployed across expansive sea areas. Their existing prototype is also poised for modifications aimed at achieving a higher biomass output. One such modification involves using cost-effective substrate materials like waste rice straw fibre, which would further reduce operational costs.
The research team has demonstrated that the recycled water produced by their system is of sufficient quality for drinking, with lower salinity levels than the World Health Organization’s guidelines for drinking water. This innovation is timely, given the United Nations estimates that approximately 2.4 billion people are likely to face water shortages by 2050. During the same period, the global water supply for agricultural irrigation is projected to decline by approximately 19%.
Freshwater constitutes a mere 2.5% of the world’s water, and much of it is inaccessible, and trapped in glaciers, ice caps, or deep underground reservoirs. It’s not that the quantity of freshwater is diminishing, but rather that the limited available supply faces increasing demand due to population growth and the effects of climate change. In contrast, a staggering 97.5% of the world’s water resides in the oceans, readily available.
This technology harnesses the power of the sea and sun to tackle the escalating global challenges of water scarcity, food shortage, and diminishing agricultural land. Widespread adoption of the technology has the potential to enhance the well-being of billions of people worldwide.
