One might call the first three weeks of operations for a new, state-of-the-art seawater desalination plant in coastal China a ‘watershed’ moment for the industry.
Long held back by fundamental difficulties in turning seawater into pure water, this new installation beats out previous flagship desalination plants in Saudi Arabia and California in terms of cost-effectiveness, while adding a new valuable output—green hydrogen fuel.
The plant is located in the city of Rizhao, literally meaning ‘sunshine.’ It’s one of China’s most renewably-powered cities, one in which all urban water heaters are powered by solar panels. It was ranked by the UN as one of the most habitable cities in the world in 2009.
According to South China Morning Post, reporting on the facility for a Hong Kong audience, for every 800 metric tons of seawater, the system delivers 118,877 gallons of pure fresh water, 192,000 standard cubic meters of green hydrogen fuel, and 350 metric tons of mineral-rich brine for marine chemical production.
That hydrogen is enough to power 50 city buses for around 4,600 zero emission-miles of routes each. The process of creating pure hydrogen fuel relies on electrolysis, which uses an electrical current to separate the oxygen atoms from the hydrogen atoms in water. If this process is done through renewable energy, then the result is ‘green’ hydrogen. If it’s powered by fossil fuels, it’s referred to in the industry as ‘grey’ hydrogen.
The Rizhao desalination and hydrogen facility creates green hydrogen by using the waste heat from a nearby steel foundry, making it not only green, but free—so long as China remains the steel manufacturing powerhouse that it is.
“This is not just about producing a canister of hydrogen; it opens up a new path for ‘extracting energy from the sea,’” Qin Jiangguang, a senior engineer at the Laoshan Laboratory, a marine research center in the large port city of Qingdao, told the Dazhong news outlet which first reported the story.
This usage of waste heat for hydrogen fuel is a focus of Chinese industrial policy, as not only does China boast extensive coastlines, but no shortage of industrial facilities along that coast which can be leveraged to power electrolysis on mass.
Beyond the hydrogen fuel, the cost per cubic meter—the unit used by most of the world to measure water consumption for billing purposes—is a measly US$0.28. This is half the price of the water produced from the Saudi Water Authority’s massive desalination plant, which produces 52-times the amount of fresh water as the Rizhao plant.
It’s a fraction of the cost of water from the Carlsbad Desalination Plant in California, which charges around $2.20 per cubic meter.
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Desalination is one of the most effective strategies to alleviate water scarcity, but existing processes consume massive amounts of energy, leaving a large carbon footprint.
Other problems plague the production of fresh water from the sea, including the necessity to de-scale membranes used in the reverse-osmosis desalination process with chemicals that are toxic to sea life. Furthermore, once the water is produced, the briny byproduct is so overly rich in salt that it has the effect of an ecological contaminant if released into the water.
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It needs to be disposed of properly, which involves specialized sites, treatment facilities, or trained staff which can all increase the cost of the final, fresh water product. According to SCMP, the Rizhao facility sells the brine as a product for chemical manufacturing.
Previously, these challenges have been overcome by Australian researchers who found a way to more-than-double the evaporation rate of seawater by introducing clay minerals into a solar-powered hydrogel implant that’s adaptable to the thousands of desalination plants worldwide.
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