The most sustainable way to make hydrogen fuel is to split water using renewable electricity—but that requires access to freshwater. Now, researchers have reported a way to make hydrogen fuel from just humidity in the air.

Their electrolyzer extracts moisture from air and splits it via renewably powered electrolysis to create hydrogen. It is the first such electrolyzer to produce high purity (99 percent) hydrogen from air that has as little as 4 percent humidity, says Gang Kevin Li, a professor of chemical engineering at the University of Melbourne, in Australia. The success could open up the possibility of producing hydrogen in semi-arid regions, which also have some of the highest solar- and wind-power potential.

Tests of the prototype direct-air electrolyzer over 12 consecutive days showed that it could produce almost 750 liters of hydrogen a day on average per square meter of electrolyzer. Li and his colleagues reported the details in the journal Nature Communications.

Hydrogen offers the prospect of clean, emission-free energy, and the hydrogen economy has gathered steam in the past few years due to increases in funding and improvements in technology. But most of the hydrogen around the world today is still produced from natural gas or coal. Green hydrogen from electrolysis is still a nascent technology because of the need for electrolyzers on a large scale.

Many teams are working on alternative ways to make green hydrogen. Solar-powered water-splitting devices, for example, use photocatalysts, which absorb sunlight to split water into hydrogen and oxygen but have a low solar-to-hydrogen efficiency of only 1 percent. To overcome the need for freshwater, there have been attempts to produce hydrogen from saline and brackish waters, but the devices have to deal with contamination and chlorine as a by-product.

Li and his colleagues decided to use moisture in the air as the water source. Globally, there are nearly 13 trillion tonnes of water in the air at any moment, they say, and even dry environments such as the expansive Sahel region in Africa have an average relative humidity of 20 percent.

To tap into that humidity, the researchers soaked a sponge or foam with a water-absorbing electrolyte liquid, and sandwich it between two electrodes. “Water extracted by the electrolyte is spontaneously transported to the electrodes by capillary force and electrolyzed into hydrogen at the cathode and oxygen at the anode,” Li explains. “The whole process is passive, and no moving parts or mechanics are involved.”

The researchers demonstrated the use of both solar panels or a small wind turbine to power the module. They tested the prototype both indoors and outdoors in the hot, dry Melbourne summer. The solar-to-hydrogen efficiency of the device is over 15 percent, Li says.

For the outdoor tests, they connected five electrolyzers in parallel, which, powered by the sun, produced 745 L of hydrogen per square meter a day, enough to heat a home. They also let the prototype run by itself for eight months to showcase durability.

The prototype is only a few square centimeters in area right now. But over the next year, with funding from investors, the team plans to make larger electrolyzers, with electrode areas of 10 square meters, Li says. They are also improving the electrolyte recipe to further increase the energy efficiency and output, he says.

Both efficiency and output should not be affected when the device is scaled up. But the main challenge the team faces is to find the right materials for the electrolyzer, he says. “How can we make it cheaper and better?”

The Conversation (7)
Kenneth Bean18 Sep, 2022

Besides danger, green H2 is a spectacularly dumb idea because to make it with solar or wind energy you can get only a 25-40% annual capacity factor. So if you build an H2 electrolyzer with capacity of 100,000 tons per year, you will get only 25,000 to 40,000 tpy; the plant will be idle or below capacity most of the time, unless you install excess solar/wind capacity and batteries. Not to mention the whole premise for switching to H2 is to stop climate change by reducing CO2 emissions - it is highly unlikely this would be effective. The good news is it also is highly unlikely that the more severe predicted climate disasters also are highly unlikely, so the whole H2 thing is a huge waste of time and resources.

FB TS13 Sep, 2022

It is extremely bad idea to use hydrogen as fuel for land/sea/air transportation because it is pretty much explosive!

Imagine a future world w/ all kinds of hydrogen vehicles, tanker trucks, gas stations everywhere!

Are we seriously thinking that there will be never any accidents/leaks/ruptures/mishandling to trigger massive explosions?

Not to mention, there is actually no need at all to use hydrogen as fuel!

All light/small vehicles are already becoming fully electric & all heavy/big land/sea/air vehicles just need us to start producing biodiesel/biofuel at large scales!

(From all possible industrial/agricultural/forestry waste/biomass & trash & sewage!)

5 Replies
This photograph shows a car with the words “We Drive Solar” on the door, connected to a charging station. A windmill can be seen in the background.

The Dutch city of Utrecht is embracing vehicle-to-grid technology, an example of which is shown here—an EV connected to a bidirectional charger. The historic Rijn en Zon windmill provides a fitting background for this scene.

We Drive Solar

Hundreds of charging stations for electric vehicles dot Utrecht’s urban landscape in the Netherlands like little electric mushrooms. Unlike those you may have grown accustomed to seeing, many of these stations don’t just charge electric cars—they can also send power from vehicle batteries to the local utility grid for use by homes and businesses.

Debates over the feasibility and value of such vehicle-to-grid technology go back decades. Those arguments are not yet settled. But big automakers like Volkswagen, Nissan, and Hyundai have moved to produce the kinds of cars that can use such bidirectional chargers—alongside similar vehicle-to-home technology, whereby your car can power your house, say, during a blackout, as promoted by Ford with its new F-150 Lightning. Given the rapid uptake of electric vehicles, many people are thinking hard about how to make the best use of all that rolling battery power.

The number of charging stations in Utrecht has risen sharply over the past decade.

“People are buying more and more electric cars,” says Eerenberg, the alderman. City officials noticed a surge in such purchases in recent years, only to hear complaints from Utrechters that they then had to go through a long application process to have a charger installed where they could use it. Eerenberg, a computer scientist by training, is still working to unwind these knots. He realizes that the city has to go faster if it is to meet the Dutch government’s mandate for all new cars to be zero-emission in eight years.

The amount of energy being used to charge EVs in Utrecht has skyrocketed in recent years.

Although similar mandates to put more zero-emission vehicles on the road in New York and California failed in the past, the pressure for vehicle electrification is higher now. And Utrecht city officials want to get ahead of demand for greener transportation solutions. This is a city that just built a central underground parking garage for 12,500 bicycles and spent years digging up a freeway that ran through the center of town, replacing it with a canal in the name of clean air and healthy urban living.

A driving force in shaping these changes is Matthijs Kok, the city’s energy-transition manager. He took me on a tour—by bicycle, naturally—of Utrecht’s new green infrastructure, pointing to some recent additions, like a stationary battery designed to store solar energy from the many panels slated for installation at a local public housing development.

This map of Utrecht shows the city’s EV-charging infrastructure. Orange dots are the locations of existing charging stations; red dots denote charging stations under development. Green dots are possible sites for future charging stations.

“This is why we all do it,” Kok says, stepping away from his propped-up bike and pointing to a brick shed that houses a 400-kilowatt transformer. These transformers are the final link in the chain that runs from the power-generating plant to high-tension wires to medium-voltage substations to low-voltage transformers to people’s kitchens.

There are thousands of these transformers in a typical city. But if too many electric cars in one area need charging, transformers like this can easily become overloaded. Bidirectional charging promises to ease such problems.

Kok works with others in city government to compile data and create maps, dividing the city into neighborhoods. Each one is annotated with data on population, types of households, vehicles, and other data. Together with a contracted data-science group, and with input from ordinary citizens, they developed a policy-driven algorithm to help pick the best locations for new charging stations. The city also included incentives for deploying bidirectional chargers in its 10-year contracts with vehicle charge-station operators. So, in these chargers went.

Experts expect bidirectional charging to work particularly well for vehicles that are part of a fleet whose movements are predictable. In such cases, an operator can readily program when to charge and discharge a car’s battery.

We Drive Solar earns credit by sending battery power from its fleet to the local grid during times of peak demand and charges the cars’ batteries back up during off-peak hours. If it does that well, drivers don’t lose any range they might need when they pick up their cars. And these daily energy trades help to keep prices down for subscribers.

Encouraging car-sharing schemes like We Drive Solar appeals to Utrecht officials because of the struggle with parking—a chronic ailment common to most growing cities. A huge construction site near the Utrecht city center will soon add 10,000 new apartments. Additional housing is welcome, but 10,000 additional cars would not be. Planners want the ratio to be more like one car for every 10 households—and the amount of dedicated public parking in the new neighborhoods will reflect that goal.

This photograph shows four parked vehicles, each with the words \u201cWe Drive Solar\u201d prominently displayed, and each plugged into a charge point.Some of the cars available from We Drive Solar, including these Hyundai Ioniq 5s, are capable of bidirectional charging.We Drive Solar

Projections for the large-scale electrification of transportation in Europe are daunting. According to a Eurelectric/Deloitte report, there could be 50 million to 70 million electric vehicles in Europe by 2030, requiring several million new charging points, bidirectional or otherwise. Power-distribution grids will need hundreds of billions of euros in investment to support these new stations.

The morning before Eerenberg sat down with me at city hall to explain Utrecht’s charge-station planning algorithm, war broke out in Ukraine. Energy prices now strain many households to the breaking point. Gasoline has reached $6 a gallon (if not more) in some places in the United States. In Germany in mid-June, the driver of a modest VW Golf had to pay about €100 (more than $100) to fill the tank. In the U.K., utility bills shot up on average by more than 50 percent on the first of April.

The war upended energy policies across the European continent and around the world, focusing people’s attention on energy independence and security, and reinforcing policies already in motion, such as the creation of emission-free zones in city centers and the replacement of conventional cars with electric ones. How best to bring about the needed changes is often unclear, but modeling can help.

Nico Brinkel, who is working on his doctorate in Wilfried van Sark’s photovoltaics-integration lab at Utrecht University, focuses his models at the local level. In his calculations, he figures that, in and around Utrecht, low-voltage grid reinforcements cost about €17,000 per transformer and about €100,000 per kilometer of replacement cable. “If we are moving to a fully electrical system, if we’re adding a lot of wind energy, a lot of solar, a lot of heat pumps, a lot of electric vehicles…,” his voice trails off. “Our grid was not designed for this.”

But the electrical infrastructure will have to keep up. One of Brinkel’s studies suggests that if a good fraction of the EV chargers are bidirectional, such costs could be spread out in a more manageable way. “Ideally, I think it would be best if all of the new chargers were bidirectional,” he says. “The extra costs are not that high.”

Berg doesn’t need convincing. He has been thinking about what bidirectional charging offers the whole of the Netherlands. He figures that 1.5 million EVs with bidirectional capabilities—in a country of 8 million cars—would balance the national grid. “You could do anything with renewable energy then,” he says.

Seeing that his country is starting with just hundreds of cars capable of bidirectional charging, 1.5 million is a big number. But one day, the Dutch might actually get there.

This article appears in the August 2022 print issue as “A Road Test for Vehicle-to-Grid Tech.”

Keep Reading ↓Show less