Ringside: Disruptive Desalination Technology Comes to California

OceanWell aims to bring deep water desalination to California and the world

By Edward Ring, May 29, 2025 2:55 am

29 May 2025 2:55 am

The concept of deep water desalination has been around for decades, but only in recent years has the enabling technology been available. Innovations pioneered by the oil and gas industry to better service offshore drilling platforms have matured. These include better ways to protect against corrosion of underwater equipment, and replacing hydraulic with electrical systems. Rapid advances in underwater robotic vehicles also promise to reduce construction and maintenance costs.

By using technology that is no longer ahead of its time, a California-based company, OceanWell, aims to bring deep water desalination to California and the world. Their product has the potential to dramatically reduce the energy cost, the environmental impact, and the financial cost of large-scale desalination.

OceanWell's design relies on performing desalination at a depth of around 1,300 feet, where they intend to tether pods to the sea floor. Production-sized pods will measure roughly 40 feet long and 25 feet in diameter. Ocean water will enter the pod where fresh water will pass through a filtration membrane, while a circulating pump on the salt water side of the membrane will create a cross flow that expels the brine back into the ocean. The fresh water that collects inside the pod on the other side of the membrane will feed a subsea pump and pipeline to shore that is shared by several pods.

While this description excludes countless relevant details, it is important to highlight the reasons this design has such disruptive potential. It lies in the fact that as the subsea pump pushes the fresh water up through the underwater pipe to an onshore collection facility, it creates lower pressure on the fresh water side of each pod's interior. On the seawater side of the membrane, undersea pressure at 1,300 feet is about 600 PSI, but on the freshwater side of the membrane the pressure inside the pod is lowered by the subsea pump to around 250 PSI. This is enough to pull fresh water through the membrane at a rate the company predicts will be one million gallons per day per pod.

The expected energy savings are based on a simple but fundamental difference between deep water desalination and onshore desalination: When the membrane performs the desalination process underwater, only the fresh water has to be pumped, whereas in an onshore desalination plant, ocean water - including the eventual brine which is 50 percent of the volume - has to be pumped up from the ocean intakes and pushed through the filtration membranes. OceanWell estimates their energy cost will be approximately 2,250 kilowatt-hours per acre foot of fresh water. This compares to today's commercial onshore desalination plant energy costs of around 3,500 kilowatt-hours per acre foot of fresh water.

The environmental impact of deepwater desalination is likely reduced due to several factors. The brine is less concentrated and is released from dozens of distributed pods that are deep underwater. The potential for underwater biota such as plankton or fish larvae to get trapped in the membranes is reduced not only from prescreening and cross-flow circulation pumps around the membranes, but also because the membranes perform under lower intake pressure than conventional desalination plants, and also, crucially, because the amount of bioactivity that exists at a depth of 1,300 feet is far less than at or near the surface where typical land-based desalination intakes are located.

None of this is to imply that the environmental impact of conventional desalination plants cannot be managed, which is a topic to revisit and emphasize. Primarily via conventional land-based reverse osmosis filtration, worldwide desalination capacity now exceeds 30 million acre feet per year, which represents about 1 percent of total worldwide freshwater diversions, and an impressive 7 percent of worldwide municipal water consumption - of course, not all of it is for municipal use. As discussed in a previous column, desalination at scale is already cost-competitive with many water supply options that we take for granted.

It is with construction cost, however, where deepwater desalination may offer its most disruptive opportunity. OceanWell's approach, using mass produced pods that form underwater "water farms," could dramatically lower the price of desalinated water. The company's current production cost estimates are proprietary and in any case are still dependent on testing results and variables such as the price in the future for construction materials. But imagine if the installed cost for each production pod was $5 million, and that for each pod in a large water farm, the balance of plant - subsea pumps, pipelines, onshore facilities, and so on - there was an equivalent additional cost. This means a 50 pod water farm, producing 50 million gallons per day of fresh water, would cost $500 million. Compared to traditional desalination plants - the proposed Huntington Beach desalination plant was projected to cost $1.4 billion dollars to deliver the same quantity of fresh water - this is barely one-third as much. But until we know how much these pods and other systems are really going to cost, this is speculative.

In partnership with the Las Virgenes Municipal Water District, an OceanWell prototype is being tested in a reservoir in the Santa Monica Mountains. While the testing pod is positioned at a shallow depth in fresh water, the abundant biota present in the lake will allow the engineers to quickly evaluate the systems they've developed to avoid algae and microorganisms getting trapped on the filtration membrane. The company plans to test pods in the ocean by 2028, and forecast a production-scale water farm could be operating by as soon as 2030.

We may hope California's regulatory agencies don't treat OceanWell's proposals with the same obstructionist zealotry with which they delayed, then killed, the desalination plant that was proposed for Huntington Beach. With any luck, OceanWell's systems may prove to be leapfrog technologies that silence even the most confirmed skeptics of desalination. This technology, and the company building it, merits close attention in the coming years.

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Edward Ring

Edward Ring is the director of water and energy policy for the California Policy Center, which he co-founded in 2013 and served as its first president. The California Policy Center is an educational non-profit focused on public policies that aim to improve California's democracy and economy. He is also a senior fellow of the Center for American Greatness. Ring is the author of two books: "Fixing California - Abundance, Pragmatism, Optimism" (2021), and "The Abundance Choice - Our Fight for More Water in California" (2022).

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Ringside: Disruptive Desalination Technology Comes to California

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