Hydrogen produced from air could provide low-carbon fuel in deserts

Hydrogen has been produced from the humidity in the air, using a new approach that can even extract enough water from the atmosphere to make the fuel in deserts.

Low-carbon hydrogen is seen as a key tool for decarbonising heavy industries such as steel-making. However, efforts to make the gas by using renewable electricity and electrolysers to split water into its constituent parts, hydrogen and oxygen, face a problem: many parts of the world with the most solar power potential to do this don’t have sufficient water.

This mismatch led Gang Kevin Li at the University of Melbourne, Australia, and his colleagues to develop a prototype device that can absorb water from the air and use electrolysis to make hydrogen, powered by solar panels or a wind turbine. His team found that sulphuric acid was the best material for acting as a sponge to capture the water, and successfully used it to make high-purity hydrogen.

“This is the first technology able to produce high-purity hydrogen out of the air directly, and you can do it anywhere on Earth as long as you have energy,” says Li.

The team’s device was able to capture water even down to a humidity of 4 per cent – the humidity seen in deserts is often about 20 per cent. The researchers say this could make hydrogen production viable in places such as central Australia and the Middle East. It could also work in remote locations, allowing the hydrogen to help off-grid villages balance intermittent solar energy supplies, they add.

Li says the technology could easily be scaled up, either by making bigger versions of the roughly metre-tall prototype or by stringing many of them together in a modular fashion. He thinks the approach would be complementary to existing production methods – which include making hydrogen from fossil fuels using a process called steam methane reforming – rather than acting in competition with them.

The device was largely used indoors, so the next step for the team will be to test outdoors at greater length, including in a desert, to see how it handles real-world challenges like dust.

This is a surprising new approach that seems worth exploring, says Simon Bennett at the International Energy Agency. He says the prototype seems to produce roughly less than half the hydrogen per square metre that he would expect from a commercial system with access to fresh water in the same location. “That’s not super, but not bad considering they run on humidity. I hope they get the chance to test how a device would work in practice at the larger scales where we think hydrogen will find its competitive advantage,” says Bennett.

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