A new model for water and hydrogen
China has switched on a compact but ambitious facility in Rizhao, a coastal city in Shandong province, that turns seawater and industrial waste heat into two strategic resources, low cost fresh water and green hydrogen. Project operators say the site produces fresh water for about two yuan per cubic meter, roughly 28 US cents, which undercuts typical municipal tap rates in many cities. It also outputs high purity hydrogen as a co product, while concentrating mineral rich brine for use in marine chemicals. The installation has run continuously for more than three weeks, a key milestone in proving reliability for a new type of integrated water and energy system.
The concept is simple to describe and difficult to execute. One input, seawater, feeds three product streams. For every 800 tonnes of seawater processed each year, the plant delivers about 450 cubic meters of ultra pure water suitable for industrial cooling or household use, around 192,000 standard cubic meters of green hydrogen, and roughly 350 tonnes of brine that can be sold to chemical producers. The hydrogen is reported to require about 4.2 kilowatt hours of electricity per standard cubic meter, which puts the process in line with modern electrolyzer performance. What sets Rizhao apart is how it lowers the water cost by tapping low grade heat from nearby steel and petrochemical plants, heat that normally dissipates into the air or ocean.
How the Rizhao system works
The plant locates fresh water production right beside energy intensive industry that generates steady streams of low temperature heat. That heat drives a separation step that turns seawater into very clean water at relatively low thermal thresholds. Techniques that fit this profile include membrane distillation and humidification dehumidification, which thrive on low temperature heat. Part of the fresh water goes to users, part feeds an electrolyzer that splits water into hydrogen and oxygen. The concentrated brine that remains can be a feedstock for products such as bromine, magnesium salts, and industrial salt, which reduces the need to discharge concentrated brine back to the ocean.
Why low grade heat matters
Heavy industry leaks vast amounts of medium and low temperature heat. Steel mills and refineries are prime examples. Capturing that heat and using it to make water avoids extra electricity consumption for desalination. In coastal industrial parks, seawater is abundant, waste heat is abundant, and cooling duty is constant. Co locating desalination and electrolysis with big heat sources trims both operating cost and carbon intensity. It also shifts water use away from municipal supplies, which eases pressure on local aquifers and rivers.
What the energy numbers mean
Hydrogen energy use is often discussed in terms of electricity per kilogram. A standard cubic meter of hydrogen contains about one ninth of a kilogram. At 4.2 kilowatt hours per standard cubic meter, the figure is roughly 47 kilowatt hours per kilogram of hydrogen. That is within the band of modern alkaline and proton exchange membrane units. The innovation in Rizhao is not an extraordinary electrolyzer, it is the way the plant cuts the cost and the water footprint by pairing the electrolyzer with a seawater line that runs on waste heat. The electricity still must be low carbon to call the product green hydrogen, but the thermal side comes at a steep discount because the heat would otherwise be wasted.
Can hydrogen come straight from the sea
Direct seawater electrolysis, where electrolyzers run on seawater without a separate desalination step, is an active line of research. The appeal is strongest offshore, where wind farms and platforms can make hydrogen at sea and pipe it or ship it ashore. The challenge is chemistry. Seawater contains high levels of chloride, sulfate, and organic matter. Standard cells tend to favor the chlorine evolution reaction at the anode, which corrodes parts and generates unwanted chlorine. Sand, biofouling, and scaling also shorten equipment life. To tackle this, teams are testing new catalysts that resist chloride attack, porous separators that block ions that trigger side reactions, and designs that keep chlorine out of the reaction zone. A floating demonstration off the Chinese coast has already shown that a membrane based system can run in rough seas by isolating a clean water layer for electrolysis while pulling feed from the ocean.
Two routes, one goal
There are two main ways to combine the ocean with hydrogen. The first route is to desalinate seawater and then run a conventional electrolyzer. The second is to adapt the electrolyzer to operate on seawater, or on water that is cleaned enough on the fly. Rizhao looks like the first route in miniature, but with a twist. Instead of using large electric pumps and high pressure reverse osmosis for the water step, it uses heat from next door. Offshore and remote wind sites may favor the second route because space and maintenance are limited. Coastal industrial parks may prefer the first route because waste heat is available and it yields both water and hydrogen that industry can absorb. In labs and pilot plants, corrosion resistant catalysts, new membranes, and membraneless concepts are pushing each approach forward.
Cost and scale from pilot to industry
Pricing fresh water at two yuan per cubic meter is an attention grabber. That figure sits below many urban tap water tariffs, and it includes a degree of purification that many industrial users would otherwise add themselves. Lower water cost makes hydrogen production more attractive in water stressed provinces, since hydrogen production typically needs very clean water to protect electrolyzers. Co producing water and hydrogen also spreads capital cost across two products, while revenues from brine based chemicals can offset part of the operating bill.
The electricity cost of hydrogen depends on the power source. At roughly 47 kilowatt hours per kilogram, electricity priced at three to five US cents per kilowatt hour yields a power bill of about 1.40 to 2.35 dollars per kilogram. Equipment, maintenance, and finance add to that number, and those costs vary widely. Rizhao is a small installation, yet it points to a template that coastal China can scale. The country has dense industrial corridors where waste heat is plentiful. That makes sites like steel clusters in Shandong, Hebei, and Jiangsu suitable candidates to replicate the concept with bigger equipment.
Power availability is also improving. An ultra high voltage corridor now links large wind and solar fields in western provinces with load centers in the east. New lines connect fresh capacity in Gansu to the grid that feeds Shandong. Access to steady renewable electricity would let a future Rizhao scale up electrolyzers while keeping hydrogen low carbon during hours when waste heat alone cannot meet the load.
Why this matters for water stressed regions
Hydrogen is a thirsty molecule if the water is scarce. Making one kilogram of hydrogen typically requires about nine liters of clean water. Analysts expect new hydrogen demand to require billions of cubic meters of fresh water within the next decade. If the surge arrives in dry regions, that strains supplies unless seawater and wastewater step in. Research indicates that pairing desalination with electrolysis and recovering waste heat from fuel cells and electrolysers can trim the total energy bill by a few percent. Shifting the water source to the coast and using heat that would otherwise be dumped keeps inland water for farms and cities while cutting energy inputs at the margin.
Environmental design still matters. Brine can harm marine ecosystems if discharged without care. The Rizhao model reduces this risk by selling brine for chemical production, which limits ocean discharge. Seawater intake also needs careful engineering to avoid harming marine life. The best practice is to draw water at low velocities through fine screens and place intakes where fish and larvae are few. These are not afterthoughts. They are essential for winning permits and community support as more coastal industrial parks look to pair desalination and electrolysis.
China builds an ecosystem around hydrogen technology
Behind projects like Rizhao sits a growing manufacturing base and a pipeline of partners. In Tianjin, a major electrolyzer factory now under full control of a European firm supplies hundreds of megawatts of alkaline modules each year. That plant has upgraded automation and quality systems and has already supplied equipment to some of the largest hydrogen projects in operation. Full control means faster design adjustments, tighter logistics, and better quality assurance for global orders.
Jarle Dragvik, chief executive of HydrogenPro, framed the shift as a way to match capacity with demand from very large projects.
It is about streamlining operations and locking in a cost efficient setup ready for large scale projects.
Foreign and domestic players are strengthening links across desalination, renewables, and hydrogen in China. A global water and energy developer has opened an innovation center in Shanghai to work on photovoltaics, wind, energy storage, green hydrogen, and seawater desalination with universities and labs. Chinese companies are also exporting expertise. One is building a green hydrogen project in Egypt tied to wind and solar that targets ammonia exports. Another is partnering in Saudi Arabia to design a giant hydrogen to ammonia plant. These moves point to a supply chain that can deliver kit, services, and operating know how for projects at home and abroad.
What could come next
The next test for Rizhao and similar plants is time. Engineers will watch for fouling on heat driven membranes, scaling in pipes, and the stability of electrolyzers that start and stop with waste heat availability. More run hours will clarify the real maintenance needs and the best operating windows. On the business side, the integration of three product lines, water, hydrogen, and chemicals from brine, can buffer revenue swings and improve bankability.
Choices will also sharpen between two technical paths. Direct seawater electrolysis may find its place offshore with wind and wave power, where simplicity and compact gear are prized. Desalination followed by electrolysis may win where low grade heat is abundant and where there is steady demand for very clean process water. The end goal is the same, green hydrogen supplied at competitive cost without tapping scarce freshwater sources. The Rizhao pilot shows one practical way to get there while making something useful from heat that industry currently throws away.
Key Points
- A coastal plant in Rizhao, Shandong, produces fresh water and green hydrogen from seawater using industrial waste heat.
- Reported water price is about two yuan per cubic meter, with hydrogen energy use at about 4.2 kilowatt hours per standard cubic meter.
- Annual output per 800 tonnes of seawater includes 450 cubic meters of ultra pure water, 192,000 standard cubic meters of hydrogen, and 350 tonnes of brine for marine chemicals.
- Using low grade heat for desalination cuts electricity needs and eases pressure on municipal water supplies.
- Direct seawater electrolysis is advancing, yet materials challenges remain, so many projects still prefer desalination followed by electrolysis.
- China’s ultra high voltage grid brings new wind and solar power to Shandong, supporting larger electrolyzer fleets.
- Manufacturing capacity in Tianjin and new innovation hubs in Shanghai show an expanding hydrogen and desalination ecosystem.
- Export projects in Egypt and Saudi Arabia highlight the global reach of Chinese hydrogen and desalination know how.
- Careful intake design and brine management are essential to protect marine life as coastal projects scale up.
