The cruel reality is that only about 3% of the world's fresh water is available, and only a small portion of it is readily available. But as droughts intensify in the world's arid regions, more and more people are turning their attention to the remaining 97% that roam the oceans.
Islands, cities, and water districts have used desalination to remove salt from seawater for more than a century, but it wasn't until the 1970s that the technology became more widespread. Producing water through reverse osmosis, the most widely used technology, requires approximately 1.5 kilowatt-hours of electricity for every 100 gallons. As of 2022, approximately 26 billion gallons (100 billion liters) of water are produced through desalination every day.
However, reverse osmosis is energy-intensive and requires powerful pumps to force water molecules through a specially designed membrane, leaving behind a salt-water solution. Pressures often reach up to 800 psi, which is about 20 times more than a typical car tire. Approximately 70% of a reverse osmosis plant's energy use comes from operating these pumps.
Experts are looking for other ways to speed up this process, and one promising approach they've begun to consider is known as deep sea reverse osmosis (DSRO). In it, a reverse osmosis device is dropped into deep water, approximately 1,300 to 2,000 feet deep, where naturally occurring pressure forces water through a membrane. Pumping fresh water from the deep ocean and returning it to shore requires only relatively small pumps and consumes only a fraction of the electricity used in land-based desalination.
This idea has been around since the invention of reverse osmosis desalination itself, but it never caught on because the ocean can be a foreboding place for complex technology. That has changed recently, with a handful of companies now in the race to perfect the technology.
This convergence can be traced back to advances made by the oil and gas industry, which has been working on deep-sea power, communications, and robotics for decades. “The timing is perfect because the cost curve and the experience curve are completely taken into account,” Alexander Fuglesang, co-founder and CEO of Flocean, told TechCrunch.
Until now, deep-sea reverse osmosis has not been limited to harsh marine environments. Robert Bergstrom, Oceanwell's founder and CEO, said it was difficult to power the pods to run the pumps and sensors. He previously founded Seven Seas Water Group, a traditional desalination company now owned by Morgan Stanley.
OceanWell's pods connect to a central hub that provides power and data while collecting fresh water. Image credit: OceanWell
Over the past 10 to 20 years, oil and gas companies have “electrified the ocean floor,” said Michael Porter, Oceanwell's chief technology officer. “This is really a game changer for us.” Previously, pumps and equipment were powered by hydraulic systems, which were inefficient and prone to failure. “But now with the advent of electric pumps, it's much cheaper and easier to operate,” he said.
Oil and gas companies are also helping make remotely controlled submersibles cheaper and more effective. For DSRO startups, these submersibles have made the setup and maintenance of deep-sea equipment much easier. “You don't have to pull up all your equipment to turn one bolt,” says Bergstrom.
At depth, desalination pods operate small pumps that slowly move water through the membrane. The slow speed means most marine life can escape by swimming. For those who are unable to do so, Oceanwell is developing a method to periodically reverse the flow of the pump to flush microorganisms from filters and membranes. It should not only protect marine life, but also help keep filters and membranes free of obstructions for longer.
Similar to terrestrial desalination, DRSO releases brine that is more salty than the surrounding seawater. But for DRSO, the problem is less serious. For one thing, rather than doubling terrestrial desalination, it produces a more dilute brine that's only about 10% to 20% more salty than seawater, and the dispersed pods release that brine into the water column. “It spreads within 10 to 30 meters of the pods, which are tiny micro-plants on our ocean floor,” Fuglsang said.
Installing equipment on the ocean floor remains costly, including bringing power, water and communications lines to the site and installing the desalination pods themselves. “We obviously can't build smaller plants because of this big backbone that we're building,” Bergstrom said. “It's a huge capital investment just to install it. But once you get from 10 million gallons to 100 million gallons per day, the rest of the costs start to come down.”
The Flocean team stands in front of one of the deep-sea reverse osmosis pods. Image credit: Flocean
Fuglesang said Flocean plans to deploy one to 10 pods per site. Oceanwell is targeting similar numbers.
After implementation, the savings should start to add up. OceanWell, Flocean, and another DSRO startup, Waterise, all predict that this technology will allow them to produce water using 30% to 50% less energy than land-based reverse osmosis. Additionally, the water that comes out is often colder than where it is used, so it can be used to absorb heat from large air conditioners first. “This is a really powerful energy-saving device that you can bolt on,” Fuglesang says.
Investors are starting to pay attention. In November, Oceanwell announced it had raised $11 million in Series A funding from investors including Kubota. On Tuesday, Flocean announced a $9 million Series A, the company exclusively told TechCrunch. Flocean's round was led by Burnt Island Ventures, Freebird Partners, and Nysnø Climate Investments, with participation from Katapult Ocean and MP Pensjon.
Although Froshan has signed contracts to deploy demonstration systems in the Maldives and Jordan, Fuglsang said the company intends to focus on the Mediterranean and Red Sea basins. Waterise currently has a contract to supply a mining company in Jordan, while OceanWell is initially targeting California.
As the water crisis grows around the world, both companies are optimistic that their technology can help fill the gap. “Roughly speaking, we think we can impact a billion people and prevent them from falling into water poverty,” Bergström said.