Quote: “ One of the most pressing challenges facing the use of hydrogen is its storage, which typically requires extremely low temperatures (−252.8 °C) and high pressures (350 to 700 bar). ”

I know I am just an amateur

In the PicoBalloon hobbyist world, we are generating our own hydrogen. You can buy the equipment for cheap from China and generate it from water. It doesn’t require extreme temperatures to store. Are we generating dirty hydrogen?

Why does this paper suggest storing at extreme temperatures and pressure?

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philipkglass 3 days ago | parent | next [-]

Hydrogen gas has very low density at standard temperature and pressure. 1 kilogram of gaseous H2 occupies 11,100 liters at STP. This is great for ballooning, where the low density is the whole point, but it means that hydrogen stored for energy is excessively voluminous in the form of uncompressed gas.

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crote 3 days ago | parent | prev | next [-]

Storing hydrogen in general isn't very difficult. The problem is in storing enough hydrogen that having it react with air in a fuel cell can power something meaningful.

For example, the Hyundai Nexo has a range of 611 km (380 mi), which requires it to store 6.3 kg of hydrogen. At atmospheric temperature and pressure hydrogen has a density of 0.08988 g/L, so that would require a tank with a volume of 70 m3. For reference, a semi-trailer has a volume of about 100 m3.

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naasking 3 days ago | parent [-]

> Storing hydrogen in general isn't very difficult.

That's not accurate, storing hydrogen is very difficult. The atoms are so small that they pass into the molecular matrix of storage containers, sometimes even when kept at extreme temperatures and pressures, causing "hydrogen embrittlement", which eventually destroys the container and releases all of the hydrogen.

The only truly reliable way to store hydrogen over appreciable time frames is when it's bound in molecular forms, like fossil fuels or ammonia.

	▲	senectus1 2 days ago \| parent [-]
		hydrogen embrittlement is only really an issue if the container regularly changes temperature and the metel has to expand and or contract. granted this is most real world scenarios. but not always.

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ricardobeat 3 days ago | parent | prev | next [-]

For hydrogen to be useful as fuel, we need it to produced at scale, transported and stored, it is not feasible to generate it on demand (even if you could, you would still need a battery for electrolysis).

The 300+ psi pressure is needed to achieve similar power density as gasoline/electric. At atmospheric pressure you need about 15 liters of hydrogen gas to match the energy in one small AA battery.

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dleary 3 days ago | parent | prev | next [-]

You're using hydrogen in a balloon. Where its very low density is a boon.

Hydrogen gas also has very low energy density. To store enough of it to be useful, it has to be pressurized/liquified, which requires the expensive storage solutions.

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brnt 3 days ago | parent | prev | next [-]

Did you not give your own answer? "Pico" balloons hold tiny amounts of the stuff. And mainly for flotation (ie non consumable), as opposed to a (consumable) fuel.

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AnotherGoodName 3 days ago | parent | prev [-]

You're getting terrible efficiency in the production of hydrogen which you don't care about since it's a hobby.

You're also getting terrible energy density with gaseous hydrogen. Liquid hydrogen has great energy density but requires active cryogenics to store or it'll blow open even the thickest walled container.

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CamperBob2 3 days ago | parent [-]

Why not store it in hydride form? (Edit: my bad, should read article first, then the comments.)

That's said to be even more energy-dense than liquid H2, and it's obviously much safer.

Guessing the answer is that it requires heat to liberate the gas, and/or makes us even more dependent on rare earths.

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AnotherGoodName 3 days ago | parent | next [-]

That's better. In fact the best option is to store it as methane. Electricity to methane production has the same efficiency as hydrogen. It's just a small step across to allow the hydrogen to bond to free carbon when producing it and doesn't really hurt the overall efficiency of hydrogen production from electricity since the biggest losses are in the production of the hydrogen itself. Both methane and hydrogen production from electricity have the same efficiency.

As methane it's reasonably easily liquified. You also already have a network of natural gas systems that you can utilise this in right now. There's literally fleets of natural gas vehicles today as well as pipelines everywhere. If making hydrogen from electricity was in any way viable we'd already be doing it for the methane networks we have today.

Of course if we start talking like this the myth of hydrogen being green gets blown right out of the water and we realise that storage isn't even the biggest issue of hydrogen. "Hey Toyota why don't we just use your existing CNG cars instead, it'll save us making hydrogen from methane and if we ever do start making it from electricity in bulk couldn't we just make methane similarly?".

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CamperBob2 3 days ago | parent [-]

How do you get rid of the C in the CH4, though?

By the same token, I've always thought it would be interesting if someone came up with a way to retrofit gas stations with something that could split the hydrocarbon molecules without burning them. Then we'd really be able to reuse existing infrastructure (handwaving away the storage-density problem of course, which the subject of this article might help with.)

But same problem... the carbon and the hydrogen really, really like to hang out together.

	▲	AnotherGoodName 3 days ago \| parent [-]
		You take c from the co2 when producing ch4 synthetically. You then reform the co2 on combustion. Fwiw methane to hydrogen and back again is trivial. It’s how hydrogen is predominantly made today. You can indeed make a hydrogen fuel station from methane. It’s just that it’s really really dumb to do that when hydrogen is so inefficient in an engine and so hard to store. You should just use methane all the way.

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philipkglass 3 days ago | parent | prev | next [-]

Improved hydride storage is exactly what the submitted article discusses.

A hydrogen battery that operates at just 90 °C has been developed by researchers from Japan, overcoming the high-temperature and low-capacity limits of earlier methods. The device works by moving hydride ions through a solid electrolyte, allowing magnesium hydride, which acts as the anode, to repeatedly store and release hydrogen at full capacity.

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timerol 3 days ago | parent | prev [-]

TFA is about storing hydrogen in magnesium hydride