A Cornell-led team built a 10 centimeter by 10 centimeter prototype device that produces carbon-free “green” hydrogen via solar-powered electrolysis of seawater, with an important byproduct: potable water.
Researchers at Cornell University are making the most of abundant resources on Earth: sunlight and seawater.
They have created a device for the production of carbon-free, green hydrogen through solar-powered electrolysis of seawater. The innovative technology also generates potable water as a beneficial byproduct.
This 10 by 10 centimeter (3.94 by 3.94 inches) device is called hybrid solar distillation-water electrolysis (HSD-WE).
The current prototype impressively produces 200 milliliters of hydrogen per hour with a promising 12.6% energy efficiency.
“Water and energy are both critically needed for our everyday life, but typically, if you want to produce more energy, you have to consume more water,” said Lenan Zhang, assistant professor in the Sibley School of Mechanical and Aerospace Engineering in Cornell Engineering, who led the project.
Zhang added: “On the other hand, we need drinking water, because two-thirds of the global population are facing water scarcity. So there is a bottleneck in green hydrogen production, and that is reflected in the cost.”
Production of green hydrogen
Typically, green hydrogen is produced by splitting pure water molecules into hydrogen and oxygen through electrolysis.
However, this process is expensive due to the requirement of an excessive amount of clean water.
The research team created a small prototype device that taps into the limitation of photovoltaics solar panels – the low efficiency.
While most solar cells only convert about 30% of sunlight into electricity, the remaining energy is released as waste heat. The team’s device captures much of this waste heat and uses it to warm and evaporate seawater.
A key component is the capillary wick, which holds a thin film of seawater in direct contact with the solar panel. This allows for efficient heating and evaporation, leaving the salt behind.
The resulting clean water vapor is then condensed and fed into an electrolyzer, powered by the solar panel, to split the water molecules into clean hydrogen and oxygen.
“This is a highly integrated technology. The design was challenging because there’s a lot of complex coupling: desalination coupled with electrolysis, electrolysis coupled with the solar panel, and the solar panel coupled with desalination through solar, electrical, chemical and thermal energy conversion and transport,” Zhang explained.
“Now, for the first time, we can produce a sufficient amount of water that can satisfy the demand for hydrogen production. And also we have some additional water for drinking. Two birds, one stone,” Zhang added.
Reducing hydrogen cost
According to Zhang, the current cost to produce green hydrogen is about $10 per kilogram.
However, he believes that with the abundance of sunlight and seawater, their team’s device could reduce this cost to $1 per kilogram within 15 years.
Beyond hydrogen production, this technology holds further potential. Integrating it into solar farms could even help cool the photovoltaic panels, boosting their efficiency and extending their lifespan.
“We want to avoid carbon emission, avoid pollution. But meanwhile, we also care about the cost, because the lower cost we have, the higher market potential for large-scale adoption. We believe there is a huge potential for future installation,” Zhang concluded.
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The findings were published in the journal Energy and Environmental Science.
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