Flocean’s subsea desalination pod

Flocean

Turning seawater into drinking water is so costly and energy-intensive that it’s untenable in most parts of the world, but a Norwegian company is trialling a new approach that could change that. Flocean will launch the world’s first commercial-scale subsea desalination plant in 2026, and says its system will cut the cost and energy consumption of the process dramatically.

Global demand for water is going up, driven by population growth, climate change and industrial uses like data centres and manufacturing. Meanwhile, fresh water is becoming less abundant due to droughts, deforestation and over-irrigation.

Land-based desalination currently produces about 1 per cent of the world’s fresh water supply, with over 300 million people relying on this source for their daily water needs. The biggest plants are in the Middle East, where cheap energy makes the technology more feasible and water scarcity makes it more necessary.

The leading technology for desalination today is reverse osmosis. The method pumps seawater through a membrane with microscopic holes that only allow water molecules to pass through, while salt and other impurities get filtered out. The water has to be pressurised to push it through the filters, a process that requires vast amounts of energy.

Flocean’s approach is to plunge water-filtering pods deep into the ocean, separate seawater from salt at depth, then pump the fresh water back up to land. By putting reverse osmosis pods deep underwater, the technology leverages hydrostatic pressure – the weight of all the water pressing down from above – to push the seawater through filtering membranes.

Less pumping means less energy consumption, around a 40 to 50 per cent reduction compared with conventional desalination plants, according to the company. Plus, seawater is cleaner once you get below the sunlight zone (which extends to 200 metres below the water’s surface), which means the water doesn’t require as much pre-treatment before it reaches membranes.

“It’s fundamentally quite boring down there from a process and engineering perspective,” says Alexander Fuglesang, Flocean’s founder and CEO. “It’s the same salinity, temperature, pressure. It’s dark. There’s not a lot of bacteria that can cause biofouling.” The same hydrostatic pressure that pushes water through the membranes also helps disperse the salty brine by-product, which Flocean says is free of chemicals that might harm marine life.