Advanced BioFuels USA

(Spitfire Research)  There is a popular myth in the marketplace of ideas at the moment:  the notion that hydrogen will become a way to export renewable electricity in a decarbonized future, from places with an excess of renewable electricity, to places with a shortage of supply and a large energy demand.

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And like all myths, the notion of hydrogen as an export commodity for energy is separated from an outright lie by a couple grains of truth.

The Lands of Renewable Riches

There are places in the world which have huge potential to generate high capacity factor renewable electricity, and which have no significant local use for electricity (hint- that’s not Canada, folks! Any hydroelectricity we have in excess, has a ready market in the USA)  This is particularly true of special locations- deserts with oceans to the west- which are also so distant from electricity markets that the option of transporting electricity via high voltage DC (HVDC) is costly and challenging to imagine.  Places like Chile, Western Australia, Namibia and other points on the west coast of Africa, come to mind.  Remember that high capacity factor renewables are essential if green hydrogen production is ever to become affordable – electrolyzers and their balance of plant are unlikely to get cheap enough to ever make cheap hydrogen from just the fraction of renewable electricity that would otherwise be curtailed.

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We do know how to move and store it, though we don’t do much of either.  Only about 8% of world H2 production is moved any distance at all, and most hydrogen is consumed immediately without meaningful intermediate storage.

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If you have energy already in the form of a chemical- particularly a liquid- moving that liquid by pipeline is the way to move it long distances with the lowest energy loss, lowest hazard and lowest cost per unit energy delivered.  When your energy is already in the form of a gas, it’s almost, but not quite, as good.  So at first glance, pipelines look appealing as a way to move hydrogen around- assuming that you already have hydrogen, that is! 

The re-use of existing natural gas pipelines for transporting hydrogen, either as mixtures with natural gas or as the pure gas, has been dealt with in another of my papers:

https://www.linkedin.com/pulse/hydrogen-replace-natural-gas-numbers-paul-martin/

…and so we won’t re-hash the argument here.  But I concluded, with good evidence:

1.  The re-use of natural gas long distance transmission pipelines for hydrogen beyond a limit of about 20% by volume H2, is not feasible in most pipelines due to incompatible metallurgy.
2. 20% H2 in natural gas represents about 7% of the energy in the gas mixture, and hence isn’t as significant as it sounds in energy or decarbonization terms.
3. Hydrogen, having a lower energy density per unit volume than natural gas, consumes about 3x as much energy in transmission as natural gas does in a pipeline, and would require that all the compressors in the pipeline be replaced with compressors of 3x the suction capacity and 3x the power.

We are therefore really talking about using new long distance transmission infrastructure to move hydrogen around.

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2nd Sin of Thermodynamics:  it confuses electrical energy (which is pure exergy, i.e. can be converted with high efficiency to mechanical energy or thermodynamic work), with chemical energy (i.e. heat, which cannot), just because they are both forms of energy with the same units.  They’re not equivalent, any more than American dollars and Jamaican dollars are equivalent simply because they’re both money, measured in units of dollars!  There’s an exchange rate missing…

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When you consider that the energy loss involved in just making hydrogen from electricity is on the order of 30% best case (relative to H2’s LHV of 33.3 kWh/kg), and that this energy needs to be fed as electricity (work), it soon becomes quite clear that the cost of transmission by pipeline versus HVDC is quite foolish if what you’re really looking at is the cost to move exergy (the potential to do work) from one place to another.  If you start with electricity, the cost of using hydrogen as a transmission medium for that electricity includes an electrolyzer and a turbine or fuelcell at the discharge end of the pipeline. 

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A US DOT regulated tube trailer carrying hydrogen at 180 bar(g) (2600 psig), i.e. the biggest tank of hydrogen gas permissible currently to ship over US roads, contains a whopping 380 kg of H2.  While one day US DOT may permit pressure to increase to 250 or even 500 bar(g), it should be clear that shipping BILLIONS of kilograms of hydrogen as a compressed gas in cylinders across transoceanic distances is just utterly a non-starter.

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Liquid Hydrogen (LH2)

Michael Barnard’s article on the subject is well worth a read, 

https://cleantechnica.com/2021/12/20/shipping-liquid-hydrogen-would-be-at-least-5-times-as-expensive-as-lng-per-unit-of-energy/

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Converting Hydrogen to Other Molecules for Shipment

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The four main candidates are ammonia, methanol, liquid organic hydrogen carriers (LOHCs), and metal hydrides.  

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Conclusions

The export of hydrogen, either as hydrogen itself or as molecules derived from hydrogen for use as fuels directly or as sources of hydrogen to feed engines or fuelcells, seems to be an idea which although technically possible, is extremely difficult to imagine becoming economic.  The energy losses and capital costs and other practical matters standing in the way of hydrogen or hydrogen-derived chemicals being used as vectors for the transoceanic shipment of energy, seems to be rather more a result of #hopium addiction being spread by interested parties, than something derived from a sound techno-economic analysis.

What Should We Do Instead?

It’s clear to me that the opportunity of high capacity factor renewables from hybrid wind/solar installations along the coasts in places like Chile, Western Australia etc. is considerable, and so is the potential for these green energy resources to decarbonize our society.

In my view, however, we’re thinking about it wrong.

We should be thinking about Chile, western Australia etc., becoming hubs for the production of green, energy-intensive molecules and materials- things that we need at scale, which represent large GHG emissions because we currently make them using fossil energy or fossil chemical inputs.  The list includes:

• Ammonia, and thence nitrate and urea, for use as fertilisers (NOT as fuels!)
• Methanol, for use as a chemical feedstock, again not as a fuel
• Iron (hydrogen being used to reduce iron ore to iron metal by direct reduction of iron (DRI), which can then be made into steel at electric arc mini-melt mills wherever the steel is needed
• Aluminum, and perhaps one day soon, magnesium too- neither of which involve hydrogen really, but both of which will need electricity in a big way if we want to decarbonize them
• Cementitious/pozzolanic materials- though these are such bulky and low value materials that shipment across transoceanic distances is hard to imagine we’ll be able to afford
• who knows- maybe diamonds and oxygen! (Just kidding!)

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For locations such as north Africa, the obvious solution is to skip the hydrogen and indeed the molecular middleman entirely, and simply to export electricity via HVDC directly to Europe.  Although that doesn’t address the need for energy storage, the resources predicated for the manufacture of economical green hydrogen already suggest high capacity factor, and proximity to the equator makes their seasonal variation considerably lower as well.  Clearly, in my view, making hydrogen simply to permit electricity to be stored for later use is very hard to justify, given the best case cycle efficiency of hydrogen itself- without hydrogen long distance transport and distribution taken into account- is on the order of 37%.  That is far too lossy a battery to be worth major investment. Drop that even further by adding lossy things like hydrogen liquefaction or interconversions to yet other molecules and it looks just too bad to take seriously.

What About Fossil Energy Importers?

Countries like Japan and South Korea, frankly, are in big trouble in a decarbonized future, especially if they make themselves dependent on importing energy in the form of hydrogen or hydrogen-derived molecules.  READ MORE