New Carrier Fluid Makes Hydrogen Way Easier to Transport

Imagine pulling up to a refueling station and filling your vehicle's tank with liquid hydrogen, as safe and convenient to handle as gasoline or diesel, without the need for high-pressure tanks or cryogenic storage. This vision of a sustainable future could become a reality if a Calgary, Canada-based company, Ayrton Energy, can scale up its innovative method of hydrogen storage and distribution. Ayrton's technology could make hydrogen a viable, one-to-one replacement for fossil fuels in existing infrastructure like pipelines, fuel tankers, rail cars, and trucks.

The company's approach is to use liquid organic hydrogen carriers (LOHCs) to make it easier to transport and store hydrogen. The method chemically bonds hydrogen to carrier molecules, which absorb hydrogen molecules and make them more stable-kind of like hydrogenating cooking oil to produce margarine.

A researcher pours a sample of Ayrton's LOHC fluid into a vial.Ayrton Energy

The approach would allow liquid hydrogen to be transported and stored in ambient conditions, rather than in the high-pressure, cryogenic tanks (to hold it at temperatures below -252 C) currently required for keeping hydrogen in liquid form. It would also be a big improvement on gaseous hydrogen, which is highly volatile and difficult to keep contained.

Founded in 2021, Ayrton is one of several companies across the globe developing LOHCs, including Japan's Chiyoda and Mitsubishi, Germany's Covalion, and China's Hynertech. But toxicity, energy density, and input energy issues have limited LOHCs as contenders for making liquid hydrogen feasible. Ayrton says its formulation eliminates these trade-offs.

Safe, Efficient Hydrogen Fuel for Vehicles

Conventional LOHC technologies used by most of the aforementioned companies rely on substances such as toluene, which forms methylcyclohexane when hydrogenated. These carriers pose safety risks due to their flammability and volatility. Hydrogenious LOHC Technologies in Erlanger, Germany and other hydrogen fuel companies have shifted toward dibenzyltoluene, a more stable carrier that holds more hydrogen per unit volume than methylcyclohexane, though it requires higher temperatures (and thus more energy) to bind and release the hydrogen. Dibenzyltoluene hydrogenation occurs at between 3 and 10 megapascals (30 and 100 bar) and 200-300 C, compared with 10 MPa (100 bar), and just under 200 C for methylcyclohexane.

Ayrton's proprietary oil-based hydrogen carrier not only captures and releases hydrogen with less input energy than is required for other LOHCs, but also stores more hydrogen than methylcyclohexane can-55 kilograms per cubic meter compared with methylcyclohexane's 50 kg/m^3. Dibenzyltoluene holds more hydrogen per unit volume (up to 65 kg/m^3), but Ayrton's approach to infusing the carrier with hydrogen atoms promises to cost less. Hydrogenation or dehydrogenation with Ayrton's carrier fluid occurs at 0.1 megapascal (1 bar) and about 100 C, says founder and CEO Natasha Kostenuk. And as with the other LOHCs, after hydrogenation it can be transported and stored at ambient temperatures and pressures.

Judges described [Ayrton's approach] as a critical technology for the deployment of hydrogen at large scale." -Katie Richardson, National Renewable Energy Lab

Ayrton's LOHC fluid is as safe to handle as margarine, but it's still a chemical, says Kostenuk. I wouldn't drink it. If you did, you wouldn't feel very good. But it's not lethal," she says.

Kostenuk and fellow Ayrton cofounder Brandy Kinkead (who serves as the company's chief technical officer) were originally trying to bring hydrogen generators to market to fill gaps in the electrical grid. We were looking for fuel cells and hydrogen storage. Fuel cells were easy to find, but we couldn't find a hydrogen storage method or medium that would be safe and easy to transport to fuel our vision of what we were trying to do with hydrogen generators," Kostenuk says. During the search, they came across LOHC technology but weren't satisfied with the trade-offs demanded by existing liquid hydrogen carriers. We had the idea that we could do it better," she says. The duo pivoted, adjusting their focus from hydrogen generators to hydrogen storage solutions.

Everybody gets excited about hydrogen production and hydrogen end use, but they forget that you have to store and manage the hydrogen," Kostenuk says. Incompatibility with current storage and distribution has been a barrier to adoption, she says. We're really excited about being able to reuse existing infrastructure that's in place all over the world." Ayrton's hydrogenated liquid has fuel-cell-grade (99.999 percent) hydrogen purity, so there's no advantage in using pure liquid hydrogen with its need for subzero temperatures, according to the company.

The main challenge the company faces is the set of issues that come along with any technology scaling up from pilot-stage production to commercial manufacturing, says Kostenuk. A crucial part of that is aligning ourselves with the right manufacturing partners along the way," she notes.

Asked about how Ayrton is dealing with some other challenges common to LOHCs, Kostenuk says Ayrton has managed to sidestep them. We stayed away from materials that are expensive and hard to procure, which will help us avoid any supply chain issues," she says. By performing the reactions at such low temperatures, Ayrton can get its carrier fluid to withstand 1,000 hydrogenation-dehydrogenation cycles before it no longer holds enough hydrogen to be useful. Conventional LOHCs are limited to a couple of hundred cycles before the high temperatures required for bonding and releasing the hydrogen breaks down the fluid and diminishes its storage capacity, Kostenuk says.

Breakthrough in Hydrogen Storage Technology

In acknowledgement of what Ayrton's nontoxic, oil-based carrier fluid could mean for the energy and transportation sectors, the U.S. National Renewable Energy Lab (NREL) at its annual Industry Growth Forum in May named Ayrton an outstanding early-stage venture." A selection committee of more than 180 climate tech and cleantech investors and industry experts chose Ayrton from a pool of more than 200 initial applicants, says Katie Richardson, group manager of NREL's Innovation and Entrepreneurship Center, which organized the forum. The committee based its decision on the company's innovation, market positioning, business model, team, next steps for funding, technology, capital use, and quality of pitch presentation. Judges described Ayrton's approach as a critical technology for the deployment of hydrogen at large scale," Richardson says.

As a next step toward enabling hydrogen to push gasoline and diesel aside, we're talking with hydrogen producers who are right now offering their customers cryogenic and compressed hydrogen," says Kostenuk. If they offered LOHC, it would enable them to deliver across longer distances, in larger volumes, in a multimodal way." The company is also talking to some industrial site owners who could use the hydrogenated LOHC for buffer storage to hold onto some of the energy they're getting from clean, intermittent sources like solar and wind. Another natural fit, she says, is energy service providers that are looking for a reliable method of seasonal storage beyond what batteries can offer. The goal is to eventually scale up enough to become the go-to alternative (or perhaps the standard) fuel for cars, trucks, trains, and ships.