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EU research partners develop solid state hydrogen storage tank coupled with fuel cell as vehicle APU unit

Partners in a 42-month, €3.5-million (US$4.8-million) EU research project have developed a system comprising a solid state hydrogen storage tank coupled to a fuel cell (SSH2S). The unit was fitted for the first time into an Iveco Daily van as an Auxiliary Power Unit (APU), and was able to supply electrical energy for air conditioning, auxiliary heating and lighting.

SSH2 explored the use of a new class of material for hydrogen storage (i.e. MM'(BH4)n mixed borohydrides) as well as a known system (Li-Mg-N-H); the project investigated combining two materials in the storage solution.

The modular hydrogen tank consists of individual tubes placed side by side and filled with two different solids. These storage materials absorb the gaseous hydrogen like a sponge to which it is then bound. This property enables storage of the gas in a small volume under a pressure of 70 bar and normal outside temperature—substantially better than a conventional tank that requires the hydrogen to be kept under a pressure of 700 bar.

The use of solid materials in the tank means that hydrogen can be stored very safely; even if there is a leak, the strong bond between the gas and the storage materials ensures that hydrogen escapes at such a slow rate that there is no risk of explosion.

—Inga Bürger, Project Manager at the DLR Institute of Engineering Thermodynamics

As part of the project, the researchers connected the tank with solid materials up to a high-temperature fuel cell for the first time, delivering electricity and the heat required to release the hydrogen from the storage materials. The tank has a volume of 10 liters and offers a storage capacity of 1400 liters of hydrogen, sufficient to provide the van’s APU with one kilowatt of electrical energy for two hours.

The University of Turin (UNITO, Italy) coordinated the EU research project SSH2S. EU-wide, it involved seven research centers and companies: DLR, Karlsruhe Institute of Technology (KIT), the Institute for Energy Technology (IFE, Norway), Tecnodelta s.r.l. (Italy), Serenergy A/S (Denmark), Fiat Research Centre (Italy) and Joint Research Centre of European Commission (JRC, Netherlands).

KIT, IFE, JRC and UNITO lead the development of the storage materials. DLR cooperated with its partners, Technodelta and the Fiat Research Centre, to create the combined tank and the fuel cell coupling, and also their integration within the vehicle. The European Union provided €1.6 million (US$2.2 million) in funding.



There are several critical parameters missing:
Weight of hydrogen by mass
How fast it can be released.
How fast it can be stored.

Roger Pham

Good point, Dave. Volumetric density of 200Wh/L is 1/2 to 1/3 that of lithium battery, and gravimetric energy density is probably just as poor!

And how much power is required to induce the solid materials to release the hydrogen at a rate sufficient for the APU.


Part of this effort was a research project and there is value in knowledge gained. However, the total energy is only 2 KwHr which is not that that large for a Lithium Ion battery. And to emphasize electric-car-insider's comment, they should state the overall system efficiency.


Beyond the very pertinent questions asked in posts above, there is also a system-level question: how does this compare overall in mass, energy use and cost to powering accessories through recuperative braking? A "microhybrid" storage device that recovers energy just for accessories and start-stop/creep would have a much better figure of merit than a "fuel cell APU" under just about any trade criteria when the complete system package and performance is considered.

Beyond the braking question: why do it at all? A PHEV/BEV doesn't need it. I don't even see the point in an FCV.

I would think the only place this device has application is in a long-haul truck sleeping cabin. Even then, if the vehicle propulsion is significantly "electrified" through hybridization or otherwise, there is already storage in the form of battery or caps (a LOT of it, BTW), and a fuel cell and supporting hardware seems like a lot of extra stuff.

Roger Pham

Good point, Herman. For just 2kWh of capacity, a Lithium battery pack would be much more compact, more efficient, and can recuperate braking energy and will raise the vehicle's overall MPG, though the van must have a big enough motor/generator /inverter for energy recuperation.


1400 liters of H2 at STP is about 115 grams, so the H2 storage density of the tank is about 11-12 grams per liter.

Liquid ammonia contains about 110 grams of hydrogen per liter.  If you had a 5-liter tank of ammonia and a 5-liter sodium amide reactor to convert it to N2+H2 at 80% efficiency, you could operate the same fuel cell for about 8 hours.

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