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First UAV test flight with Cella solid-state hydrogen storage and fuel-cell power system

The Scottish Association for Marine Science (SAMS) recently completed a UAV test flight using Cella Energy’s hydrogen-based power system. The system is based on Cella’s solid, nanostructured chemical hydride hydrogen storage material which is capable of releasing large quantities of hydrogen when heated. Cella Energy is a spin-off from STFC’s Rutherford Appleton Laboratory in the UK. (Earlier post.)

Cella designed and built a gas generator using this material, which when combined with a fuel cell, creates electrical power. The complete system—Cella gas generator along with a fuel cell supplied and integrated by Arcola Energy—is considerably lighter than the lithium-ion battery it replaced.

The work was funded by a grant from Innovate UK and has enabled Cella and Arcola to design and build a power system that could be incorporated into the Raptor E1, built and designed by Trias Gkikopoulos of Raptor UAS.

This flight used a small prototype system and we were pleased with the initial flight with another flight scheduled to take place in the near future. The larger versions of this system that we are already designing will have three times the energy of a lithium-ion battery of the same weight.

—Stephen Bennington, Cella’s Managing Director

Cella’s production process takes ammonia borane (NH3BH3) with 12 wt% hydrogen content and incorporates a polymer to produce a composite. The material forms a microporous plastic-like solid which can be pressed, shaped or extruded into any form and to fit any space. Accordingly, the material can also be pelletized to form a solid fuel with fluid properties. Each gram of Cella material produces up to 1 liter of hydrogen gas.

The material production uses commercially scalable methods and Cella is currently capable, through toll manufacture, of making many tons of the material per year.

Cella’s solid-state hydrogen storage technology also addresses the issues that surround the transportation of compressed gaseous hydrogen. Cella’s material is a solid and is not under compression, is stable in air and at temperatures below 500 ˚C.

Because it is a chemical hydride, a chemical processis required to recycle the material; Cella says it is working with chemical industry partners to take the known recycling methods and scale them into a cost-effective industrial process.

Cella is also working on aerospace systems with its partner, Safran’s Herakles division (earlier post), which is soon to become part of Airbus-Safran Launchers, a joint venture between Safran and Airbus. The two have been working together to prove the feasibility of using Cella’s hydrogen storage material for aerospace applications. They have built a working system, and have gone a long way to understanding many of its safety, performance and certification requirements.

Arcola Energy supplies, deploys and supports off-the-shelf fuel cell products from vendors including Ballard and Horizon. Arcola will source and integrate fuel cell stacks or systems from leading developers worldwide.


A genuine breakthrough. Kudos! I wonder what the production version pricing level would be.


This is the future of air travel; albeit, a long away future. As I have said before, the airliner of tomorrow will be powered by ducted elctric motors, gimbaled to provide attitude control instead of high drag control surfaces, with a buffer battery and power provided by fuel cells to generate the electricity. A water byproduct at altitude is better than jet exhaust.


Three (3) times the energy of lithium batteries per weight is interesting for drones and light/small e-planes.

Depending on refill ease and cost, a more advanced version could become interesting as home/office energy source and for FCEVs?


Definitely an interesting technology but it is not going to provide an easy transition to the hydrogen economy.

"Because it is a chemical hydride, a chemical processis required to recycle the material; ..." It is not something that you can easily fill up with at your neighborhood hydrogen station.

It may have a short time benefit for certain military applications but longer term, I would place my bet on better batteries. If you could get lithium air to work, I believe that it would have a higher energy density and lithium sulfur should also have a comparable energy density and is probably closer to being commercially available


Here are tables showing what that energy density means in absolute terms:

So it looks like, using the figures for metal hydrides, it runs at around:

metal hydride 0.58kwh/kg 3.18kwh/litre

That is quite a bit better than the best batteries can do, and three times is in the ball park

That might be good enough for light and recreational aircraft, and for ancillary power, but I am a long way from convinced for passenger planes.


U.A.V's requiring sustained deployment may be better off with P.V. and battery.


"3.18kwh/litre" ? If I'm crunching the numbers right this is a better way to store hydrogen than LH2. Which is only 2.37kwh/l. [Somebody double check that, please.] However, it's about the same as liquid ammonia at 3.22kwh/l. [Again, someone best double check. I'm trying to convert between kwh and MJ.]



From my link:

liquid (-253°C) 33.3kwh/kg 2.36kwh/litre

So you are spot on.

However the energy by mass,~60 times less than liquid hydrogen, and more importantly around 20 times less than jet fuel at around 12 kwh/kg:

explains my reservations about using it for fuel for large planes.

As against that, the use of electrics would in itself enable the use of different designs, with more propellers making for a lot better efficiency.

Lets see how we get on with small aircraft before making plans for transatlantic jumbos!


GCC tweets today.

This makes so much sense.
Bring on line H2 electrolysis at industrial locations where large scale and time sensitive demand is highest.

Storing H2 on site at industrial plants.

There is likely trained personal or the ability to provide same.

There are simply not enough disposable homeless people to operate a dangerous H2 infrastructure owing to much demand from the Japanese nuclear power industry failure at Fuckishima
Russia is running out of heroes too since Chernobyl.

There would be much (critical) incentive to maintain the infrastructure. If people are talking LH2,or almost any pressurised flamable gases, then the caution should read.

'Do not to try this at home'

Use either for e production chemical process and directly for heat? or is process heat a relic from days gone by.

Roger Pham

@sd and Arnold,

The chemical hydride by Cella here can be made into micro beads of a few microns diameter. As such, they can be used to fill the car's unpressurized fuel tank like liquid fuel. Spent fuel beads can be collected and stored for later rehydrogenation at the H2 hydrogenation plant.

"The polymer micro-beads can be moved like a fluid; this fluidized hydride offers several opportunities for transportation storage:

It is no longer necessary to try and rehydrogenate the material within the vehicle. For most hydrogen storage materials this releases megajoules of energy. If the refuelling is to be done in a few minutes, this requires cooling to remove several hundred kilowatts of power. To facilitate rehydrogenation in the 3-4 minutes that the DOE targets stipulate, the thermodynamics require high temperatures and pressures of around 100 bar.

With a fluidized hydride, it is possible to quickly fill or remove the material from the vehicle so that it can be recycled or rehydrided elsewhere.

It is possible to move the material within the vehicle making it possible to separate the storage unit from thermolysis. One implementation of this concept would be storing the beads are stored in a fuel tank, which, because it does not need to contain high pressures or be heated and cooled, could be a simple lightweight plastic tank of complex shape similar to that used in current vehicles.

The hydride beads would then pumped to a hot cell where waste heat from the engine exhaust is used to drive the hydrogen into a small buffer volume. The hydrogen buffer is maintained at a pressure suitable for the internal combustion engine ICE or fuel cell and which is sufficient in volume to be able to restart the vehicle. Once the hydride has been heated and the hydrogen driven off, the waste beads are moved to and stored in another lightweight plastic tank.

In some senses hydrogen is the perfect fuel; it has three times more energy than petrol per unit of weight, and when it burns it produces nothing but water. But the only way to pack it into a vehicle is to use very high pressures or very low temperatures, both of which are expensive to do. Our new hydrogen storage materials offer real potential for running cars, planes and other vehicles that currently use hydrocarbons on hydrogen, with little extra cost and no extra inconvenience to the driver.

—Professor Stephen Bennington, lead scientist on the project for STFC and Chief Scientist at Cella"


To save space and weight, could a dual purpose/compartment tank be used to store both the fresh hydride hydrogen material and the used material?

The relative size of each compartment would be gradually and automatically changed (with a moving separator) as required.

Draining and refilling both compartments could be done simultaneously, with an appropriate dual conduit draining/feeder hose, in a few minutes?

Roger Pham

Yes, indeed, Harvey.
For a 300-mi range, the light-weight and non-pressurized H2 fuel tank requires about 50 liters, and thus takes about the same volume as the gasoline fuel tank of a comparable ICEV.

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