In the coastal city of Rizhao, a new industrial pilot is treating seawater as a multi-layered resource rather than a disposal challenge. This 110-kilowatt direct seawater electrolysis prototype ocean refinery couples low-temperature waste heat from nearby steel and petrochemical facilities. It produces ultra-pure water at a fraction of traditional costs while simultaneously splitting seawater into green hydrogen.
Official science reporting from China and a national technology brief have confirmed the ocean refinery pilot’s durability milestones. This success signals a shift in strategy: pairing water treatment with clean fuel production directly where seawater and recoverable heat converge.
By integrating waste heat into desalination, the ocean refinery system achieves a ‘one-in, three-out’ flow. It takes in raw seawater and outputs fresh water, hydrogen, and mineral-rich brine. This approach sidesteps the high costs of traditional desalination and offers a scalable template for coastal industries facing dual pressures of decarbonization and water stress.
Rizhao’s 110 kW Ocean Refinery: Desalination, Green Hydrogen, Mineral Brine
Pilot Specifications
- Launch Details: A 110 kW heat-coupled unit in Rizhao has achieved over 500 hours of continuous operation.
- Why it Matters: The plant reports fresh water near 2 yuan per m³ while co-producing green hydrogen. Recent press coverage attributes this outcome to the unique heat integration in Rizhao.
- Early Performance Signals: Independent hydrogen trade coverage highlighted the week-scale stability and efficiency, while a detailed sector analysis describes the ‘one-in, three-out’ co-product flow.
Performance and Science Context
- Scientific Breakthroughs: New peer-reviewed studies describe a triple-defense electrocatalyst for chlorine-resistant seawater oxidation and protective oxide armor that repels chloride during operation.
- Context for the Heat Link: Liquid-phase thermodiffusive desalination shows that low-grade heat can separate salt without membranes. New thermodiffusive desalination research maps multichannel designs suited to industrial by-heat, building on a multichannel study of liquid-phase separation.
Why a Seawater Hydrogen Plant Starts with Water Stress
Coastal Scarcity is Real, Even Next to an Ocean
Coastal industries often occupy water-stressed basins, making reliance on municipal freshwater expensive and politically sensitive. Engineers therefore pursue sea-compatible designs ranging from salt-management electrodialysis to ultra-low-energy solar stills.
Rizhao’s approach contrasts with a portable solution that turns sunlight directly into drinking water without pumps or membranes. This alternative design is focused on humanitarian and off-grid use rather than heavy industry, contrasting with solar desalination innovations for remote communities.
Why Tap Water is Not “Free” for Hydrogen
Electrolyzers need extremely clean feedwater to protect catalysts and membranes. Refining municipal water to this standard increases both operational costs and logistical complexity. In coastal clusters, using the ocean itself as the feedstock becomes attractive if chloride chemistry is controlled.
Earlier research pointed to paired desalination-plus-electrolysis trains, including lab demonstrators harvesting lithium and hydrogen from seawater while producing desalinated water in a single stream.
Waste Heat is a Resource Hiding in Plain Sight
Rizhao’s pilot capitalizes on low-temperature waste heat rejected by nearby steel and chemical plants. Academic teams have shown that gentle, steady temperature differences can drive thermodiffusion, a membrane-free separation where salts drift to the cold side of a liquid gradient. That principle allows desalination with modest heat rather than high-pressure pumps or boiling, which helps explain why industrial parks with both seawater intake and waste heat are logical hosts.
Cities are also learning to conserve fresh water by trimming thermal loads via modern dry-cooling data center designs that minimize evaporative losses.
How the Heat-Coupled ‘Ocean Refinery’ Works
How the “One-In, Three-Out” Co-Production Works
Local and trade coverage describes a flow where raw seawater enters a heat-integrated treatment block. The ocean refinery process yields three distinct outputs: ultrapure water for electrolysis, hydrogen at the stack outlet, and a concentrated brine that can be steered to chemical recovery. The reported price of 2 yuan per m³ reflects the efficiency gained by using recovered heat, rather than electricity, to drive salt separation.
Where the Heat Comes From
Rizhao’s industrial belt creates large volumes of low-grade exhaust heat that usually dissipates to air or water. The site cuts electrical parasitics of pretreatment by routing that heat through compact exchangers and liquid-gradient separators first. This process happens even before the electrolyzer ever sees the fluid. A 500-hour continuous run confirmed by an expert review panel suggests the overall thermal-electrochemical train has sufficient stability for multi-week-scale operation.
First Engineering Numbers to Watch
- Electrical Size: 110 kW, consistent with a pilot-scale alkaline or AEM stack.
- Run Time: More than 500 hours continuous as of early December 2025, per the expert review cited in Chinese technical briefings.
- Integration Efficiency: The system matches conventional alkaline unit efficiency by eliminating a separate desalination stage, according to independent trade coverage photographed at the Shandong pilot site.
How this Compares with Other Sustainable Desalination Methods
Recent coverage highlights several technologies that offer complementary routes for different scales and use cases. These innovations include:
- Electricity-free solar desalination, which focuses on off-grid resilience.
- Photomolecular water transport, offering novel efficiency pathways.
- Hybrid photothermal-photocatalyst systems, which co-produce fuels and drinkable water.
Overcoming the Three Critical Failure Modes of Seawater Electrolysis
Calcium and Magnesium Scaling: The Precipitate Problem
Hardness ions precipitate near hot, alkaline interfaces. This reaction clogs channels and buries active sites. Bubble and precipitate management protocols help maintain gas removal under seawater conditions and extend stability at practical current densities.
Practical Fixes Engineers Use
- Tailored flow fields that sweep bubbles and fines away from the anode face.
- Antiscalant surface chemistries or sacrificial capture layers that immobilize Mg/Ca away from active sites.
Anode Protection: Fighting Chloride Corrosion
Chloride aggressively attacks oxygen-evolution catalysts, binding at defect sites and causing rapid degradation. Protective “armor” layers such as vanadium oxides have been shown to repel chloride and alkaline earth ions while preserving conductivity under load.
A protection layer study in Science Advances demonstrated how these layers preserve conductivity under load, extending life at ampere-level current density. An Energy & Environmental Science review summarizes additional tactics. These include:
- Self-reconstructing nitride cores
- Phosphate-rich shells that slow halide ingress
Practical Fixes Engineers Use
- Conformal oxide or oxycarbide coatings that suppress chloride adsorption without raising overpotential too much.
- Alkaline operation with controlled chloride activity to favor oxygen evolution over chlorine evolution.
Chlorine Evolution: Managing Competitive Reactions
At certain potentials, anodes evolve chlorine instead of oxygen. This creates corrosive byproducts and significantly reduces hydrogen yield. Recent decoupled seawater electrolysis research shows how separating oxygen evolution reduces parasitics from side reactions.
At the catalyst level, Shandong-based authors have reported a triple-defense design. It combines composition tuning, lattice control, and surface barriers to hold activity while resisting chloride attack in seawater oxidation.
Practical Fixes Engineers Use
- Bias windows and pH regimes that suppress chlorine pathways in the anode compartment.
- Decoupled oxygen modules and mediator cycles to keep chloride away from the highest potentials.
From Lab Reviews to Pilot Plants: Why 110 kW Matters
Bridging Tens of Hours to Hundreds
For years, direct seawater electrolysis lived in lab cells where catalysts ran for tens or low hundreds of hours under controlled conditions. A broad Science Bulletin survey of direct seawater electrolysis mapped key failure modes:
- Chloride corrosion
- Scaling
- Chlorine evolution
These reviews also cataloged fixes ranging from phosphate-rich shells to self-reconstructing nitrides. A 110-kilowatt ocean refinery pilot that holds steady past 500 hours in natural seawater signals that materials and flow management are crossing into advanced engineering territory, not just chemistry.
Why Waste-Heat Integration is Not a Footnote
By folding heat recovery into the process, the Rizhao train avoids a separate, power-hungry desalination stage and reuses thermal energy that would otherwise dissipate. Technical briefings emphasize that this coupling eliminated the need for a standalone cooling unit while producing high-quality freshwater. This efficiency helps explain the 2 yuan per m³ water figure reported in the press.
What Still Needs to Be Proven
Scaling from hundreds of kilowatts to tens of megawatts will stress electrodes, coatings, and pumps far beyond pilot duty. Long-duration tests must demonstrate that triple-defense catalysts and protective oxide layers can keep chlorine in check. These systems need to maintain oxygen evolution selectivity in real seawater for months, not just days. Transparent LCAs and brine-mineral market analyses will also be needed to validate the “one-in, three-out” economics at commercial scale.
How an Ocean Refinery Compares to Solar Desalination
Different Architectures, Different Strengths
Rizhao’s design utilizes the low-temperature waste heat already discarded by coastal industries. That heat preconditions seawater and supports liquid-gradient separation before electrolysis. This process trims electrical demand for pretreatment while co-producing fresh water.
By contrast, reverse osmosis relies on high-pressure pumps and specialized membranes, while thermal desalination uses boiling or multi-stage flash. A third path, thermodiffusive desalination, separates salt in the liquid phase using gentle temperature gradients.
Where Solar Fits
Decentralized solar evaporators and photothermal devices shine in off-grid settings and disaster response where grid power is scarce. Solar-powered evaporators for remote communities convert sunlight directly into evaporation using capillary wicks and selective absorbers to reach high solar-to-vapor efficiency.
Trade-Offs Readers Should Watch
An ocean refinery can co-produce water and hydrogen when a nearby site has abundant waste heat and seawater intake. If the goal is household drinking water for isolated villages, simpler tech like salt-free electrodialysis metathesis is far better suited for local maintenance. For cities already building renewable microgrids, pairing low-grade heat recovery with thermodiffusion offers another route to push water costs down while lowering brine impacts.
Solving the Water Justice Question in Green Hydrogen
Why Seawater Electrolysis Changes the Conversation
A common critique of green hydrogen is that electrolyzers “steal” freshwater from people and farms. The plant in Rizhao challenges this notion by utilizing raw seawater and generating ultra-pure water as a byproduct, all while generating hydrogen for the local industry.
Who Gets the Water, and on What Terms?
Water co-produced in an ocean refinery can be routed to cooling loops, process water, or municipal supply. Policy choices decide the split. However, export-first economics can leave nearby communities negotiating for both electricity and water access. Current analyses of green hydrogen export build-outs and local energy-justice debates highlight the tension between industrial needs and community access.
The Liters-Per-Kilogram Reality
Electrolysis consumes roughly 9 to 20 liters of water per kilogram of hydrogen, depending on stack type and polishing. In a heat-coupled seawater system, this water demand is met on-site, not drawn from municipal supplies. The precise split is project-specific, which is why public reporting of water balances and brine handling should be standard in future deployments.
Are Ocean Refineries the Future of Coastal Industry?
Rizhao’s pilot suggests a practical template. Where seawater intake, low-grade heat, and hydrogen demand already cluster, an integrated plant can turn a waste stream into value. This lowers the water burden on cities. Longer-term hydrogen pipeline networks will shape how coastal hubs connect to inland users.
The strategy also aligns with earlier work that turned seawater into freshwater, hydrogen, and even lithium, echoing lithium extraction from seawater and brine strategies. However, this concept will not completely replace all methods of desalination or hydrogen production. Instead, it introduces a vital coastal archetype that complements community solar desalination and inland renewable electrolysis.
Future builds must publish clear water allocation plans, monitor marine impacts from brine, and adopt community-first water priority. If they do, ocean refineries could help industrial coastlines meet climate targets and produce essential critical tech minerals and hydrogen while improving local water resilience.
Frequently Asked Questions About Seawater Electrolysis, Desalination, and Green Hydrogen
How Does Direct Seawater Electrolysis Differ from “Desalinate then Electrolyze”?
Direct seawater electrolysis integrates purification and hydrogen production into a single train, often using waste heat to skip power-hungry pretreatment. The traditional route requires running a full desalination plant before feeding a standard electrolyzer.
Is the Reported Fresh Water Price of About 2 Yuan per Cubic Meter Realistic?
Yes, but it is highly site-specific. That low figure depends entirely on the availability of “free” waste heat from nearby industry to drive the separation process.
Does Seawater Electrolysis Eliminate Brine Problems?
No. The “one-in, three-out” model still creates a concentrated mineral brine. While this can be harvested for chemicals, environmental monitoring of salinity plumes is still essential.
How much Water does Electrolysis Use per Kilogram of Hydrogen?
Expect to use 9 to 20 liters of water per kilogram of hydrogen. Integrated systems generate this water on-site, relieving pressure on local municipal taps.
Where do Smaller Community Systems Fit In?
Ocean refineries are massive industrial-scale solutions. For villages or islands, simpler tech like solar desalination or electrodialysis metathesis is far better suited for local maintenance and budgets. For a concise survey of field-ready options, six innovative technologies that create clean water offer distinct alternatives.
What are the Next Milestones to Watch?
Watch for pilots breaking the 1,000-hour mark and third-party audits of stack performance. Public data on brine handling and lifecycle assessments will be the real proof of scale.
