Sunlight and seawater lead to low-cost green hydrogen and clean water

A Cornell-led collaboration has hit the trifecta of sustainability expertise: The group developed a low-cost methodology to supply carbon-free “green” hydrogen by way of solar-powered electrolysis of seawater. A cheerful byproduct of the method? Potable water.

The workforce’s hybrid photo voltaic distillation-water electrolysis (HSD-WE) gadget, reported in Vitality & Environmental Scienceat present produces 200 milliliters of hydrogen per hour with 12.6% energy efficiency immediately from seawater beneath pure daylight. The researchers estimate that inside 15 years, the expertise may cut back the price of inexperienced hydrogen manufacturing to $1 per kilogram—a key step in attaining net-zero emissions by 2050.

“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,” stated Lenan Zhang, assistant professor within the Sibley College of Mechanical and Aerospace Engineering in Cornell Engineering, who led the undertaking.

“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.”

Inexperienced hydrogen is produced by splitting “high purity”—i.e., deionized—water molecules into hydrogen and oxygen via electrolysis. The excessive price outcomes from the huge quantity of fresh water that the method requires; the price of manufacturing inexperienced hydrogen could be roughly 10 occasions larger than that of normal hydrogen.

“That’s why we came up with this technology,” Zhang stated. “We thought, ‘OK, what is the most abundant resource on Earth?’ Solar and seawater are basically infinite resources and also free resources.”

As a analysis scientist on the Massachusetts Institute of Expertise, Zhang started exploring methods to make use of solar power to transform seawater into potable water via thermal desalination—an effort heralded by Time journal as one of many “Best Inventions of 2023.” By the point Zhang arrived at Cornell in 2024, he had acquired help from the Nationwide Science Basis to broaden the expertise to supply inexperienced hydrogen.

Working with researchers from MIT, Johns Hopkins College and Michigan State College, Zhang’s workforce devised a ten centimeter by 10 centimeter prototype gadget that leverages one of many drawbacks of photovoltaics: their comparatively low effectivity. Most PV cells can solely convert as much as roughly 30% of photo voltaic power into electrical energy, and the remaining dissipates as waste heat. However the workforce’s gadget is ready to harness most of that waste warmth and use it to heat the seawater till it evaporates.

“Basically, the short-wavelength sunlight interacts with the solar cell to generate electricity, and the longer wavelength light generates the waste heat to power the seawater distillation,” Zhang stated. “This way, all the solar energy can be fully used. Nothing is wasted.”

To ensure that the interfacial thermal evaporation to happen, there’s a essential element, known as a capillary wick, that traps the water into a skinny movie that’s in direct contact with the photo voltaic panel. This fashion, solely the skinny movie must be heated, quite than a big quantity of water, and the evaporation effectivity is boosted to greater than 90%.

As soon as the seawater evaporates, the salt is left behind, and the desalinated vapor condenses into clear water, which passes via an electrolyzer that splits the water molecules into 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 stated.

“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.”

The present price of inexperienced hydrogen manufacturing is roughly $10 per kilogram, based on Zhang, however given the plenitude of daylight and seawater, over the course of 15 years, his workforce’s gadget may carry the associated fee right down to $1 per kg. Zhang additionally sees the potential of incorporating the expertise into photo voltaic farms to chill PV panels, which might enhance their effectivity and extend their lifespan.

“We want to avoid carbon emissions, avoid pollution. But meanwhile, we also care about the cost, because the lower cost we have, the higher market potential for large-scale adoption,” he stated. “We believe there is a huge potential for future installations.”