Hydrogen Storage in a Box!

Cylindrical tanks no longer are the only solution for storing high-pressure hydrogen gas. The future is looking decidedly square – and better for vehicle range and packaging. Experts from Forvia explain.

Symbio rectangular pressure tanks would be packaged in multiple-tank ‘cartridges’ within the same footprint as a BEV battery pack. Their internal design remains a secret. (Faurecia)

Until recently, there was only one practical solution for storing gaseous hydrogen for onboard vehicle use: the cylindrical storage tank. Spiral-wound, carbon fiber cylinders are the proven form factor for reliable containment of 350-bar (5000-psi) and more commonly, 700-bar (10,000-psi) hydrogen used in the latest fuel-cell electric and hydrogen-fueled IC-engine vehicles. Forvia and Symbio, the hydrogen-technologies joint-venture with partner Michelin, are in the process of changing the cylindrical-tank paradigm with a new approach that looks downright … square.

A traditional cylindrical hydrogen tank arrangement for medium-duty commercial vehicles. (Faurecia)

“This hydrogen storage system is our modular, conformable, 700-bar tank,” Rob Steele, product line manager at Faurecia, part of the Forvia group, told SAE Media while viewing a concept ‘skateboard’ chassis at the 2023 Innovation Day at the company’s suburban Detroit tech center. At first glance, the display chassis appeared to be a pack of battery modules. Then the concept struck.

This was an advanced hydrogen fuel-cell vehicle platform, but not one with the typical line of pressure cylinders aligned horizontally and set longitudinally within perimeter frame rails. Instead, rows of 700-bar, nearly square rectangular fuel cells were carried in a structural grid.

Forvia hydrogen storage systems chief engineer Tarek Abdel-Baset. (Faurecia)

“Our focus is to reduce overall architecture complexity, from the OEMs’ perspective, by offering the same footprint for hydrogen-fueled and battery-electric platforms,” explained Tarek Abdel-Baset, Forvia’s hydrogen storage systems chief engineer, zero emissions. He said the modular concept is designed to be flexible, stackable (Forvia uses the term ‘stack pack’) and adaptable according to the vehicle architecture.

“Whatever your skateboard concept is, and every OEM’s is different, we’re able to swap out your battery pack and put our hydrogen storage system in — or give you both,” Abdel-Baset noted. The solution aims to attract vehicle makers and end users seeking to optimize a single chassis architecture for both BEV and H2FC propulsion systems and their fueling/charging infrastructures.

The ubiquitous global Class 3 through 6 commercial vehicles come to mind in this strategy. Some fleet customers might need hydrogen’s rapid refueling advantage for a portion of their vehicles’ duty cycles. Others may prefer battery power for a different set of use cases. Growing interest in hydrogen for both fuel-cell and H2-fueled diesel trucks has accelerated, due in part to California’s recent ruling to ban sales of new diesel medium- and heavy-duty trucks starting in 2036. Large fleets also must convert to hydrogen or electric models by 2042.

Hydrogen fuel cells currently are the closest alternative to diesel engines for commercial-vehicle applications, according to Dan Nicholson, VP of global electrification at GM and a veteran powertrain engineer.

Abdel-Baset and Steele argued that cylindrical tanks supported with a “ganged” frame construction limit vehicle range and total onboard energy capacity. “The [rectangular] tanks put 40 to 50 percent more hydrogen on board,” Abdel-Baset said, “and that equates directly to 40 to 50 percent more operating range. It really separates you from the BEV,” he said.

So, what’s behind the Forvia-Symbio tank design? Is it a casting? A fabrication? “That’s part of our ‘secret sauce,’ Abdel-Baset said with a laugh. “This is still very much an innovation from the Faurecia R&D team in Banvans, France, so I can’t talk in great detail. But it is real,” he said.

Beneath the tank’s skin is “a lot of open structure” but with internal scaffold-like bars, he revealed. “Imagine a building with many columns in it. But instead of being in compression, they’re in tension,” he explained. The tank exterior is carbon fiber. Inside, there is a proprietary nylon liner, similar to that of a traditional hydrogen tank. The liner material and fit are engineered to eliminate permeability, keeping the tiny hydrogen molecules from escaping.

Faurecia has significant intellectual property and resources invested in the new hydrogen tanks’ development. “We can’t talk in detail because we’re finalizing a lot of it,” Abdel-Baset said. “There is a real prototype in use. We’ve taken it up to 700 bar. Now we’re working on scaling it and getting it optimized.” He said the tanks will be part of a “cartridge” system that includes the entire frame and auxiliaries, also developed in house.

“Potential customers can go with any combination of tanks, from one all the way to an entire cartridge,” he said. Faurecia customers who have been shown the cartridge configuration with the rectangular tanks have praised the design’s package efficiency and mass reduction compared with a cylindrical-tank setup, he added.

Faurecia and Symbio engineers also are engaged with various parallel innovation activities related to the hydrogen tank technology, including carbon-fiber cost-reduction projects.