The Case Against Hydrogen Trucks

This article is a companion to my recent article about why I think battery electric trucks are the future of freight:

Electric Trucks- the Future of Freight

TL&DR: hydrogen trucks are largely just a retreat position for people who previously thought hydrogen cars were going to be a thing. They won’t be. There is no realistic value proposition for hydrogen trucks, whether powered by fuelcells or, even dumber, by IC engines running on hydrogen.

How We Got Here

We all know, or should know, that the hydrogen fuelcell car is deader than a doornail.

Comparing the Mirai to the Model 3- Tesla Wins

Whereas it looked like the only game in town for cars without a local toxic tailpipe back in the 1990s, the battery EV has come along, sold millions, and driven a nail into the fuelcell EV (FCEV)’s tanks. Fortunately there was just a loud hiss, not an explosion, but the result was the same.

Why Are We Still Talking About Hydrogen Trucks?

Those who were pushing hydrogen cars, weren’t going to just pack up and go home. They retreated into the use case of trucks, arguing the following:

1) Batteries are heavy, and since trucks carry loads which are limited in weight by the total gross weight of the vehicle plus its load, and because hydrogen has better energy density per unit mass, a truck of adequate range to be practical for freight haulers needs hydrogen if it is to be decarbonized.

2) Batteries are intrinsically more efficient than if we were to use electricity to make hydrogen for use as a transport fuel (by roughly a factor of THREE). But if we can make hydrogen cheaply enough, the added effectiveness of faster refueling and longer range will make the inefficiency irrelevant.

3) Hydrogen will be cheap because electricity will be cheap, and hydrogen will be needed for all sorts of things old and new so scale will make hydrogen cheap.

4) The grid can’t handle EVs. But we can put hydrogen in pipes- maybe even in pipes currently used for natural gas. So hydrogen is more practical to distribute than electricity. And hydrogen offers the advantage of energy storage. Storing 3 kWh worth of hydrogen is cheaper than storing 1 kWh worth of electricity in a battery.

This stuff finds its way into studies, largely done by people who benefit from the hydrogen attempt whether it succeeds or fails. And sometimes, by academics who are jumping on the square-wheeled bandwagon- and who haven’t read papers from the likes of Ulf Bossel and Reuel Shinnar from the 1990s, when all the fundamental issues for why there wasn’t going to be a hydrogen economy, were already spelled out, in gory thermodynamic detail.

But hey, let’s take these notions apart, and see if they are valid. Just because we’ve got nothing better to do.

Hydrogen Light, Batteries Heavy, Therefore Hydrogen

As my article about electric trucks points out, per the North American Centre for Freight Efficiency, 75% of freight loads aren’t limited by maximum gross vehicle weight, but by trailer volume or floor area.

Hydrogen’s energy density per unit mass- 33.3 kWh of LHV per kg- is awesome- especially if you forget about the mass of its containers. Those containers are pressure vessels typically designed to withstand 350 bar for trucks, rather than 700 bar for cars. And those tanks, even made cleverly using aluminum bottles over-wrapped with kevlar and carbon fibre, are heavy because they must safely contain an enormous amount of mechanical potential energy. They also have a limited cycle life, just like a battery- you can only safely fill and empty them so many times before they become unsafe, whereas a battery just loses capacity the more you cycle it. So is there really a huge savings to be had, switching from small battery plus fuelcell and hydrogen tanks, to big battery? Not really. And a little extra weight will affect only 25% of loads anyway- many of which are tanker trucks full of fossil fuels.

On the other hand, hydrogen’s energy density per unit volume is not so awesome. Hydrogen at 350 bar is about 21 kg/m3. If you were to feed a 60% efficient fuelcell with hydrogen, the resulting 20 kWh of electrical energy returned per kg x 21 kg/m3 is about 420 kWh/m3, or about 420 Wh/L. That’s almost exactly the same as the Model 3’s battery pack. Except much worse, because the tanks are cylinders with hemispherical heads- they don’t pack together nicely. And no, we’re not expecting BEV tractors to be substantially larger than the diesels they replace, due to battery volume. Getting rid of the diesel components leaves sufficient room for quite a large pack.

Of course you could increase the energy density of hydrogen to 71 kg/m3 by using liquid hydrogen- at 24 degrees above absolute zero. That would unfortunately cost you about 30% of the energy in your hydrogen (making the efficiency markedly worse), but you’d need to put that in via electricity to run the Claude cycle compressors to make that liquid. That’s a pretty terrible tradeoff. And in tanks the size of a tractor trailer tanker, liquid hydrogen boils off at more than 1% per day- in tiny tanks that you might want to put on a truck, the boil-off would be ridiculous. You’d need to burn that hydrogen any time the truck wasn’t demanding it, as its global warming potential (GWP) is 11.5x that of CO2 on the 100 yr time horizon. It’s not toxic, but its flammability and high GWP mean you can’t just vent it like we did in the bad old days.

There is no hydrogen-derived “new LNG” in the future- here’s why!

And no, there’s no solution to these fundamental problems- no magic graphene absorbent that will make hydrogen denser than it is as a liquid. High pressure hydrogen is chosen because of all the bad options for hydrogen storage for transport applications, it is the least bad!

The reality is that hydrogen as a transport fuel is neither efficient nor effective. Its inefficiency makes it structurally expensive, and its ineffectiveness (arising from its low energy density per unit volume) makes it expensive to store, distribute and dispense.

Fundamentally. For reasons you can’t change with innovation.

Efficiency Doesn’t Matter, Therefore Hydrogen

Hydrogen trucks will take three times as much energy from source as BEV trucks to go the same distance- round numbers. You might get that down to two times with massive improvements in both electrolyzers and fuelcells, but that’s about as good as it will ever get. But hey- three times zero is zero, right? If electricity is cheap enough, why would we care about wasting it?

Well…hydrogen is three times as expensive for energy per mile driven. In an industry which charges its customers a fuel surcharge, that alone should be a deal killer. But it’s way, way more than that by the time you’ve figured in the cost of making hydrogen (the equipment and labour needed to convert electricity and water to hydrogen), distribute it to fueling stations, and dispense it.

Hydrogen Distribution and Dispensing Both Suck

Hydrogen’s low energy density per unit volume means that currently, we don’t move or store much hydrogen at all. 92% of hydrogen moves essentially no distance- it’s made right where, and when, it is consumed. Why is that? Because it’s cheaper to move whatever we’re going to make the hydrogen from, to where hydrogen is needed. There are some hydrogen pipelines, but they exist more for outage prevention, to connect a bunch of hydrogen reformers to a bunch of refineries and chemical plants within a short distance from one another.

And no, it ain’t so simple to just switch which gas we put in the natural gas transmission network. That’s just not on, despite how hard the people who own that network, are selling you on the idea (because the alternative is to admit they’re going out of business).

Hydrogen to Replace Natural Gas? Forget About It!

What about tube trailers? Oh yeah, just forget those. A full Class 8 DOT certified tube trailer contains 380 kg of hydrogen.

380 kg of hydrogen i a whole truckload- if you have a scavenger compressor that can go down to atmospheric pressure that is!

A full Class 8 DOT certified gasoline or diesel tanker contains 11,000 gallons of these fuels- and to a 1st approximation, 1 kg of H2 is about the same LHV as 1 gallon of gasoline or diesel. That means we’re looking at around 30 tube trailers for hydrogen for every one tanker of diesel we delivery today. Yes, there are people working on composite tube trailers which would run at higher pressures. Sadly, they’ve been leaking and catching fire. But one day, they might drop that to ten trailers instead of thirty. Still deader than doornail as a distribution method!

Everybody has a model in their head of hydrogen refueling as being as simple as plugging a hose into the truck and turning a valve. That’s of course far simpler than reality. Reality is hiding behind the curtain, and there’s a lot of complexity there. First, you need to get the gas there, and as discussed above, that’s hard and expensive, because it implies either building new, bespoke hydrogen pipelines from some large scale centralized hydrogen production facility- in North Africa, say- and then distributing that hydrogen to every refueling station. Or else you’re talking about distributing three times as much electricity to each refueling station and then running comparatively tiny electrolyzers at each one. The problem with tiny electrolyzers is that they are fundamentally incapable of ever making cheap hydrogen. And of course they make the grid problem, three times as hard as if we just used BEVs instead!

Breakthrough in Electrolyzer Efficiency!

Even once it’s on site, you need to compress it to 350 bar. And because the tanks on the truck are composite tanks, they can’t handle much heat. So you need to chill the hydrogen so that as it expands and heats up (a weird property that it shares with helium), it doesn’t cook the tank it’s being fed into. Want to do that fast? You need a really big chiller. And it needs to be sitting there on standby in case a truck rolls up and needs refueling.

I’ve been involved in designing hydrogen storage and dispensing systems, and I can tell you that anybody who thinks that the capital cost for hydrogen refueling is going to be lower than that for megawatt chargers, has another thing coming.

Faster Refueling- Really?

The reality is that hydrogen refueling also gets harder the larger the vehicle you intend to refuel. So whereas you might refill a Tesla Semi from 20% to 80% battery state of charge (SOC) in ~30 minutes using a megawatt scale charger, the best you’re going to do with a hydrogen truck in practical terms is around 20 minutes on the pump. Not five. And no, it will absolutely not be faster if you use liquid hydrogen, either.

Hmm: (much) more than three times as much energy cost, in return for saving 20 minutes of refueling. Yes, I know that 20 minutes of truck and driver productivity are worth money- but are they worth that much money?

But You Can Store Hydrogen!

Yeah, and the battery on the truck is what, chopped liver?

The notion that hydrogen storage onsite at refueling stations, plus intermittent operation of electrolyzers on site, will save demand charges that would drive up the cost per kWh of BEV charging is also popular. But the notion that it’s worth throwing away 2 out of every 3 kWh you feed such a system, just to store energy, is very questionable indeed. Worst case, megawatt chargers would need to be paired with larger grid storage batteries on site, which would do the same thing as hydrogen would, but at 90% instead of 33% efficiency! And of course any time you operate an expensive asset like an electrolyzer intermittently, its cost per kg of product goes up- way up.

Scale Will Make All Problems Go Away!

No, folks, it won’t.

First, most of the “hydrogen economy” rubbish is just as dumb as hydrogen for transport. So while I do see a great need for green hydrogen to replace the black stuff that’s keeping us alive and fed via ammonia production etc., and a few new uses to decarbonize iron production (also an existing use of hydrogen that just needs expanding),

I don’t see a hydrogen economy coming.

Ever.

Transport fuel use of hydrogen is only one of several dumb use cases being proposed, but yeah, it’s a real stinker.

Yes, scale will help make electrolyzers and fuelcells cheaper. No, electrolyzers aren’t going to get as cheap as some are dreaming, because they don’t understand economy of scale and Wright’s Law properly- and I do, because I spent decades as a specialist in scaling up chemical processes and equipment.

Scaling Example #2: Water Electrolysis

And while scale will help with fuelcells just like it will help with electrolyzer stacks, not their balance of plant, without the scale of cars and light trucks, there simply won’t be sufficient doublings available to make fuelcells cheap enough if we use them only in class 8 trucks and heavy equipment.

And no, we won’t be using them in aircraft, either. Talk to Bernard van Dijk about that- he’s one of my co-founders of the Hydrogen Science Coalition, and he’s forgotten more about aircraft than I’ll ever know.

Hydrogen for Aircraft- HSC Explainer Video

Nor for ships.

Nor for stationary power.

No, scale won’t come to the rescue here. Hydrogen as a transport fuel is just broken. It’s a cart with square wheels.

Image credit: Michael Sura

The Bottom Line

Battery electric trucks aren’t a pin for pin replacement for diesels. And thank goodness! They drop GHG and toxic emissions, are easier to drive (no 18 gear transmissions), quieter, and will have less maintenance (particularly for brakes). But that will leave some transport truck use cases, unserved. Can hydrogen fill those, at least?

Let’s consider remote and rural transport. The example I like to use is ice road trucks which resupply First Nations communities in northern Canada. They’re not going electric, for sure. Are those going hydrogen?

Forget about it. Fuel logistics kills the idea deader than a doornail.

Remember those tube trailers?

Nope. Those will either need to keep running on fossil diesel, or if we’re worried about the 3/4 of eff all GHG emissions that are produced by that tiny fraction of tonne-miles of freight, we can make them use biodiesel instead. That would work, and would cost only modestly more than fossils. Hydrogen wouldn’t work, period.

What about Hydrogen Engines?

Hydrogen engines make all this stuff worse. Fuelcells are selected, despite extra cost, because they are more efficient and hence lessen hydrogen’s problems of cost and energy density per unit volume. Engines don’t help, and hydrogen engines will generate both particulate emissions from combustion of lubricant oils in the engine, and NOx- the inevitable result of burning anything in air.

This excellent video talks about Toyota’s hydrogen car engine, and how ridiculous it is, in unambiguous and clear terms, with all calculations provided.

The Unbearable Lightness of Hydrogen

What About E-Fuels?

In a recent debate, where I basically cleaned the floor with the arguments of the executive director of the Canadian Hydrogen and Fuelcell Alliance, the great hope apparently isn’t for hydrogen, but for hydrogen-derived fuels- so called e-fuels such as ammonia or methanol. These are all attempts to a) keep using engines b) make hydrogen more effective, but also c) make hydrogen even less efficient. And I freely admit, for aircraft and ships, we might be so desperate, and sufficiently rich, to reach for some e-fuels- or, at least, to use green hydrogen to run the hydrogenolysis reactions necessary to make drop-in fuels out of biomass. We’ll need to be rich though. And for land transport, where BEVs are a real alternative that is cheaper in energy cost than fossils already, that just makes no sense to me at all. E-fuels for land transport are really the sport of Porsche owners- because only Porsche owners will be able to afford them.

Ammonia as a transport fuel is horrifying. I spent decades designing and building systems which handle and store chemicals, sometimes chemicals so hazardous that they make ammonia look like mother’s milk. But ammonia isn’t just a poison gas, with a concentration immediately dangerous to life and health (IDLH) of only 300 ppm- it’s also extremely corrosive to eyes, the linings of the mouth, nose and throat, ears etc. etc. One tanker truck of ammonia in 1970s Houston was the cause of Houston’s most serious chemical incident in its history. One tanker, scores of deaths and grievous injuries. Anybody recommending ammonia as a vehicle fuel had better be ready to put on their level A pressurized SCBA chemical protection suit and go in there to repair a leak, or they’d better shut up about it right quick. I know I’m not- I’ve been in one of those suits. Truck transport with ammonia would be bad, but ammonia to fuel ships at sea is, to me, next level idiocy.

Ammonia? Pneumonia!

I don’t think we’ll even need biofuels here. It’s a certainty to me that virtually every use case for land vehicles is going electric. For the better.

Disclaimer: I’m human, and I make mistakes even when I don’t write my articles with a glass of home-made scrumpy in hand. Point out where I’ve gone wrong, with references, and I’ll gladly correct my work.

If however you just don’t like what I’ve written because I’ve sh*t on your company’s precious idea, feel free to contact my employer, Spitfire Research Inc. They’ll be more than happy to tell you to piss off and write your own article. Or, just block me- that’ll be your loss.

Why Direct Air Capture (DAC) Sucks- and Not in a Good Way!

UPDATED August 8, 2023

You’ve likely heard the sales pitch before:

  • there will be fossil CO2 emissions we simply cannot eliminate
  • even once we do reach actual or near-zero fossil CO2 emissions, we’ll need to “draw down” CO2 from the atmosphere to avoid the need to cope with global warming long-term
  • renewable energy will be super-abundant and super-cheap one day, so designs predicated on the notion of wasting vast quantities of it aren’t as stupid as they might seem on their face
  • yeah, I know, that last point wasn’t convincing, and it really is stupid right now, but we need to work on it so it’s ready when we need it

What am I talking about? Direct air capture- the act of using active mechanical/chemical equipment and vast quantities of renewable energy, in a totally pointless fight against entropy, to try to suck CO2 out of the atmosphere for either durable burial or “use”.

You’ve all seen the images- CGIs of vast rows of giant vacuum cleaners, fixing the problems of history. Hurray! The deus ex machina solution to climate change has arrived. Go on sinning, folks- keep burning fossils with wanton abandon! Because some day, some bright propellor-heads will find a way to just suck our sins back out of the atmosphere!

Do you see the danger of that fantasy? I certainly do. And as a chemical engineer, I realize how preposterous it is to even think about moving minimum 1600 tonnes of air around mechanically to have the hope of removing 1 tonne of CO2 from it at 416 ppm.

DAC: The Idiot Cousin of Carbon Capture and Storage (CCS)

Let’s be crystal clear here: you’ve likely heard people say things like “CCS doesn’t work”. They’re wrong. CCS works just fine in terms of its real objectives, which are captured in this, the most accurate and concise reference in relation to CCS that I’ve yet come across:

(Warning- language might make a sailor blush!)

Yes CCS works just fine, in terms of extending social license for fossil fuel use, and as a marketing tool for the fossil fuel industry, and in terms of regulatory capture etc.

Update: don’t take my word for it- take the fossil industry’s word for it!

“We believe that our direct capture technology is going to be the technology that helps to preserve our industry over time,” Occidental CEO Vicki Hollub told an audience at CERAWeek, an oil and gas conference, earlier this month. “This gives our industry a licence to continue to operate for the 60, 70, 80 years that I think it’s going to be very much needed.”

Even if you are to look at it technically, CCS works just fine- you just can’t afford it, even under nearly ideal conditions.

The UN Wants Big Oil’s Help on Climate, Good Luck With That

This video does a good job of taking the mickey out of the whole “clean coal” thing, which was predicated on CCS “working”. It’s worth a watch, and is a good laugh- though not quite as good as the Juice Media one above:

How do I know that CCS works “just fine”? Because the “capture” part is done routinely by the fossil fuel industry day in, day out, as a normal part of business. Every hydrogen generation unit on earth does it. Every liquefied natural gas (LNG) plant does it. Most of the fossil gas processing plants do it too, removing some CO2 to get the gas up to pipeline spec in terms of energy content. And a great many chemical plants remove CO2 from either feedstocks or product streams, because the gas gets in the way otherwise.

In chemical engineering terms, the capture part is childsplay, because CO2, aside from being bigger and bulkier, also has a “handle” on it that other gases in the atmosphere like N2 and O2, and the methane that makes up most of fossil gas, don’t have. CO2 is an acid gas, and so it chemically reacts with bases. And that reaction can be made reversible, too. So we can use that “handle” to separate it out selectively from mixtures of other gases.

Of course if the atmosphere can be treated as a free or very cheap public sewer, you don’t bother with the “S” part- you simply vent the gas once you’ve collected it. And if that alternative is on the table, there’s no big impetus to put a whole lot of effort and energy into making sure your “CCS” project meets its design objectives- so, sometimes these projects don’t. And often, it’s for reasons other than the “capture” part. Gorgon, for instance, is having trouble with the “storage” part, because the reservoir they want to dump the CO2 into, needs to have water pumped out of it- and the receiving reservoir for that water is clogging up with sand. Or something like that- anyway. Ask a geologist.

The Basics of CCS

Any time you try to take a dilute mixture and make it into a concentrated mixture, you’re going in the opposite direction to the one the 2nd law of thermodynamics says that things go spontaneously. The spontaneous direction is for concentrated things to become dilute, hot things to become cold etc. etc. By trying to go in the other direction, you’re locally decreasing entropy, by pushing something up a concentration gradient. No problem, says the 2nd law- you simply have to pay your tithe in terms of energy, and ensure that the entropy of the entire universe increases in net terms when you’re done. The bigger the concentration gradient, the greater the entropic “tithe”- the more energy you need to use to make it happen.

It stands to reason. Imagine you’re given 100 golf balls- all white, except one. You can look at each ball, but only one at a time, and you can’t stop looking when you’ve found the orange one- once you’re in, you’re committed to looking at all 100. Wow, what a pain! But you could do it, if for some reason you really wanted that one orange ball.

Now let’s say that instead of 100, it was 10,000 balls, and still only one orange one…

You can see that the lower the concentration, the more of a pain in the @ss this is going to be. That’s the 2nd law.

In terms of gas mixtures, the thing that really matters is the partial pressure. The partial pressure is the product of the volumetric concentration of the gas, and the total pressure.

Take, for instance, the syngas stream coming out of a steam methane reformer. The gas mixture is about 15-20 volume % CO2, at a pressure of about 25 bar(g). The partial pressure of CO2 is therefore about 0.15*26 =~ 3.8 bar.

Let’s compare that to the atmosphere. It’s 416 ppm CO2 at a total pressure of 1 bar(a). That’s a partial pressure of 0.000416 bar.

Hmm- looks like getting the CO2 out of the 1st one is going to be quite a bit easier than the 2nd one, eh? Yup. Way, way easier. You need to process 3.8/0.000416 or around 9100 times as much gas volume in the case of the atmosphere, to obtain a tonne of CO2- assuming that you captured it all.

But in fact the partial pressure we’re most concerned about is the partial pressure at the discharge, not the inlet. So doing 90% capture (removing all but 10% of the CO2 in the incoming gas stream) takes considerably more energy than doing 50% capture- not just because you have to process more gas, but you have to do a better job of “sifting” it.

There are other complexities, but to a first approximation, the following are borne out when you look at CCS projects in the world:

1) The stuff you’re removing the CO2 from, has to be worth money, and the CO2 must be a problem, otherwise you won’t bother removing it.

2) The partial pressure of the CO2 has to be pretty high to make it worth the bother of removing it.

3) That means either the concentration of CO2, the total pressure, or preferably both, need to be high, or you won’t bother doing it

4) That means process streams, rather than waste gas streams, are the main thing you’re going to remove CO2 from, because they’re easy, i.e. they require less expensive energy

5) Combustion equipment usually doesn’t operate at high pressure, and is usually carried out using air (which is 79% useless nitrogen), resulting in low CO2 partial pressures- so post-combustion CO2 capture is unusual (though it is done- when the desired product is CO2, for instance for carbonating drinks)

When you look at “CCS” projects therefore, what you usually find are projects like Sleipner and Gorgon, where there’s a lot of CO2 in an otherwise valuable fossil gas stream coming up from the ground under pressure, which must have its CO2 removed before it can be monetized, and where the CO2 is being buried rather than vented for regulatory reasons (i.e. venting isn’t allowed by the local government).

Rarer are projects like Quest, the blackish-blue bruise-coloured hydrogen project in Alberta which is burying 1 million tonnes of CO2 per year which must be removed from the hydrogen, but which ordinarily would be vented- except instead, the Canadian public through their tax dollars are paying to bury it instead.

Blackish-Blue Bruise Coloured Hydrogen

What you rarely see are post-combustion CCS projects, where CO2 produced from energy production such as burning fossil gas or coal is captured and then buried. Why not? Low partial pressure, meaning high energy cost, and extra cost due to loss/destruction of the bases (amines) used in the carbon capture equipment. In those cases where post-combustion CO2 capture is carried out, invariably the proponents seek to monetize the CO2 by doing enhanced oil recovery. And that, folks, really isn’t CCS- it’s a way to “dryclean” an existing oil reservoir to recover more oil, and only a fraction of the CO2 injected remains buried. EOR is an attempt by the fossil fuel industry to be paid twice for its CO2- and while post combustion CCS is better than mining naturally occurring CO2 for this purpose, the even better choice is to stop mining fossils for the purpose of burning them.

Forget About CO2 Re-Use

And please, for once and for all, let’s forget about the “use” thing, i.e. CCUS. Let’s be clear about what CO2 is: it’s a waste material. The very thing that makes CO2 (and water) a valuable product of energy producing reactions like combustion, makes it a poor starting material from which to make much of anything useful. What is that thing? Low Gibbs free energy, i.e. low chemical potential energy. Think of fuels as sitting on top of a chemical potential energy cliff. Throw them down the cliff by reacting them with oxygen to make products like CO2 and water, and you liberate chemical energy. But the 1st law of thermodynamics says that you must put back all that energy if you want to start with CO2 and water and use them to make fuels again- and the 2nd law says that each energy conversion is going to come with losses. As it turns out, the losses involved in climbing that particular cliff are very, very steep indeed.

Of course some readers are scratching their heads or perhaps throwing chicken bones at their computer screens right now, yelling that CO2 (and water) is the basic building block of life on earth. And yeah, you’re right. Plant life takes CO2, water and the energy from sh*tloads of visible light photons, collected and stacked up on top of one another in an incredibly complex chemical shuttling process called “photosynthesis”, to produce carbohydrates- the stuff from which plants are made and the stuff (nearly) the entire rest of the ecosystem uses as a source of chemical energy (i.e food).

Nature’s been at this for about a billion years, and has managed some shocking leaps forward in the efficiency of photosynthesis. The energy efficiency, after all that time, is about 2% at best.

Why? Because it’s frigging hard to do. Nature does this because a) the sun is a limitless source of energy b) to nature, time is irrelevant and c) it has no choice.

There are a handful of highly oxygenated chemicals which might be worth making from CO2, water and electricity in the future. The only one of them which is a “fuel” in meaningful terms, is methanol- and right now, all the methanol in the world is made from fossil gas via the manufacture of syngas, without CO2 capture. Fortunately, most of the methanol produced in the world is like almost all the hydrogen- it isn’t wasted as a fuel, but rather is used as a chemical.

Reference Costs

Shell Quest provides a great reference. The article I wrote about Quest, linked above, provides links to the public sources of information about the project. It was done by experts, not dummies- it was designed and executed by Shell and the giant EPC Fluor. Conditions are ideal- high partial pressure CO2 in process syngas is all they go after, capture percentage target is modest (80% of the CO2 in the syngas), and they have an ideal hole in the ground to stuff the resulting CO2 into, only 60-ish km away.

What does it cost? $145 CDN per tonne of CO2 emissions avoided. Shell claims on the project website that they could do the next project “for 30% less”, but that was before COVID/wartime inflation. And in facilities terms, net of the energy (heat and electricity) used to run the CCS equipment, capture is terrible- only 35% of the CO2 in net terms is captured. Figure in the methane emissions and CO2e capture is even worse- by my estimates, only about 21%.

Too expensive. By the time a reasonable payback on capital, realistic costs of energy and some profit are included, the cost of doing this is north of what carbon taxes will be in Canada even in 2030- even assuming we keep electing pro carbon tax governments (and I sincerely hope we do!). Unless carbon tax levels are both high and very certain, nobody is going to do this without additional government “help”. That means taking money collected in taxes on things we want, or should want, i.e. people and businesses making goods and services of real value- and using those funds to pay the likes of Shell to bury its effluent.

So much better to just reduce how much effluent we generate, by buying less of Shell’s products!

Why does DAC Suck?

As you might have concluded from the foregoing, DAC sucks not just because of its obvious use as an insincere strategy to keep us burning fossils for longer based on a false hope- but also because the partial pressure of CO2 in the atmosphere, though higher than we can tolerate in climactic terms, is very low indeed in absolute terms: only 0.000416 bar. That means you’re involved in not only an entropic fight, requiring lots of energy to capture even a little CO2, but you also generally have to move a lot of air around mechanically to make it work out. And there’s a lot of other stuff in air- dust and dirt, water vapour and the like- which can screw up your equipment, depending on how you do it.

As badly as “blackish blue” hydrogen looks, doing that would be much smarter than doing DAC. And capturing the CO2 from calciners making cement from carbonate rocks, would make even more sense- especially if those calciners were electrified using renewable electricity.

The energy use inherent to the thermodynamic foolhardiness of DAC means that DAC is, until we stop burning fossils as a source of energy, basically an energy-destroying Rube Goldberg apparatus to rival something out of an OK Go video:

Here’s a hilarious bit of inadvertent accuracy on the part of the National Renewable Energy Laboratory (NREL) in relation to DAC- an image which is missing only the wire connecting the polluting power plant to the useless DAC machine!

As I’ve said many times: over here, on the left hand side of the image (most of the world sadly!) we’re burning fossils to make energy. Over there, on the right hand side of the image, we apparently have vast amounts of renewable energy which we want to waste by running an energy-destroying Rube Goldberg apparatus. The obvious solution is to connect “here” and “there” with a WIRE, and throw away the worthless, energy-sapping molecular middleman!

DAC’s Biggest Players

There are plenty of players trying to suck up the credulous, foolish funding for DAC approaches being offered both privately and through government agencies, but the two main proponents at present are the (regrettably) Canadian company Carbon Engineering, and the Swiss firm Climeworks (whose image I modified for this article). There are also “passive” DAC approaches, such as people trying to grind up silicate rocks so they can “weather” and become carbonate rocks quicker than they would naturally. Those approaches have their own problems, but they’re not the target of this particular missive on my part- you’ll need to wait for a future article for me to take them on. In this one, my sights are set firmly on the big, iconic, CGI-generated vacuum cleaners- my target is the “meme” of DAC.

Carbon Engineering’s approach is to use a two step process. A strong base (potassium hydroxide) is used to capture the CO2 in the big vacuum cleaner thingies, making their DAC equipment quite a bit smaller and more practical than if a weaker base were used- but at the cost of making regeneration of that base, harder and more energy-intensive (thermodynamics sucks, doesn’t it?). Their solution is to use the calcium oxide cycle, generating calcium carbonate as their strong base is recycled. The calcium oxide is regenerated from the calcium carbonate- get this- by burning fossil gas…

Their principal investors, Chevron and Oxy Petroleum, are interested in using DAC to produce CO2 for use in EOR, while also harvesting credulous government money for CCS credits. Wonderful! Michael Barnard has done a marvelous job of bashing this dumb scheme already, so I don’t need to bother doing any more than pointing you to his excellent work. He calls Carbon Engineering “Chevron’s Fig Leaf”, and I cannot disagree.

Chevron’s Fig Leaf Part 1: Carbon Engineering Burns Natural Gas To Capture Carbon From The Air

The other guys, ClimeWorks, use a “highly selective filter material”- what this is, is not clear, but it appears to be a base fixed to a solid. The base is then heated to 100 C to drive off the CO2. No, they get no entropic benefit from any magic beans in their “filter”- they’re fighting the same pointless battle that Carbon Engineering and the rest are fighting, just using different tools. But at least ClimeWorks doesn’t burn fossil gas to regenerate their “filter”- they power their units with “100% renewable energy or waste heat”. Their big showcase project is in Iceland, where clean-ish geothermal electricity and heat is used to run their DAC machine. The resulting CO2 is injected into water returning to a volcanic aquifer rich in silicates. Over a period of years, the CO2 in this water “weathers” the silicates, converting them to carbonates.

ClimeWorks seems to have settled on the business model of voluntary carbon credit harvesting. Pay us to capture and bury your CO2, at the low low price of $1,100 USD per tonne!

Wow- imagine the real emissions reductions we could do for way, way less than $1100/tonne…Like electric vehicles, where the car costs more, but the total cost of ownership to the vehicle owner- and hence the cost per tonne of CO2 emissions abated- are in fact negative to the vehicle owner…

But hey, I get it. The big vacuum cleaners to the rescue will let some people drive their big, dumb pickup trucks with a little less guilt- even if those DAC units are just proposed and not actually built…

Carbon Negative Technologies Which Work

I can hear the complainers already. “You just sh*t on everything everybody else is doing- what are your solutions?”

I’ve laid out my solutions very clearly. I’ve even mis numbered them, so your solution can be slotted in where you see fit:

What Are the Energy Solutions?

What are the solutions? Read the $)(*@#$ article! But in summary:

1) Make CO2 emissions cost something- a high and durable price

2) Stop wasting precious, finite fossil resources as fuels. Use them instead to make the 10s of thousands of molecules and materials every bit as essential to modern life as is energy, but which are far, far harder to make starting with biomass much less CO2 and water and electricity! Electrify everything instead. And if you think you can’t electrify it, try harder.

3) We’ll need some liquid fuels in the future, for applications like long distance aviation which simply cannot do without. Don’t make them the lugubrious way using CO2, water and electricity, because that’s nuts. Instead, start with biomass. Yes, the cheapest way is using food biomass, because all of agriculture so far in human history has been optimized around getting plants to put as much energy into the parts we harvest for food as possible. But we can also start with cellulosic materials- wood waste, corn stover, sugarcane bagasse, rice and wheat straw etc. Make those fuels via pyrolysis, produce biochar and return that to the fields and forests the source biomass came from, closing the inorganic nutrients loop and providing a service formerly provided to the ecosystem via wild fire- something humans simply cannot tolerate. Yes, the resulting fuels will cost a fortune, but they’ll be cheaper than e-fuels, and every mile flown by rich people on jets will have the net result of taking carbon OUT of the atmosphere and tying it up for centuries if not millenia in the soils. But don’t expect that to happen voluntarily- you’ll need to force it via regulation or it just will not happen. I like this char approach much better than other bioenergy plus carbon capture and storage schemes (BECCS). Burning wood and doing post-combustion CCS is pretty much a non-starter based on my analysis, though some like Drax in the UK are betting big on it.

Disclaimer

This article was written, pro bono as a public service, by a human who was sipping home-made cider and writing about something he thinks is important, on a Friday evening, instead of watching Netflix. That human has no money riding on any of this one way or another- he has no EV company stock, nor is he shorting Carbon Engineering etc. But because a human was involved in the writing, there is some emotion in there, as well as the possibility of error. Show me where I’ve gone wrong, with references, and I will gratefully edit the piece to reflect my more fulsome knowledge.

E-Methane: Exergy Destroyer, On Steroids

TL&DR: grinding up electricity to make heating fuel is just a way to waste energy and capital, by destroying exergy (the potential to do thermodynamic work). It’s obviously worse than just making hydrogen. It is wasteful, and wasteful means expensive. It also means higher emissions than if you did something sensible, like feeding a heatpump.

There’s been a lot of recent news about projects by a firm called TES, in both the US and Canada. A proposed TES project in former Canadian Prime Minister Jean Cretien’s region of Shawinigan, Quebec, has been making major news here in recent days. No surprise, one of the project’s proponents is Jean Cretien’s daughter, France Cretien Desmarais, is a major proponent of the project.

When I wrote my lengthy tome about the various ideas of using hydrogen as an energy export commodity-

Hydrogen to Replace Natural Gas- By the Numbers

– I looked at all the various options for transporting hydrogen- as a gas, as an ultra-cryogenic liquid, as ammonia, methanol, solid metal hydrides, and in the form of hydrogenated molecules (liquid organic hydrogen carriers). All of these looked pretty stupid, due to capital costs and losses. But one real stinker missed the list- the idea of reacting CO2 with hydrogen to make methane. I had to add that to the article later, because it seems to be mentioned more and more often as people contend with the very real problems of distributing hydrogen itself. The simpleminded notion that you can just change which gas is sold in the natural gas network was put to sleep in another of my articles-

The Myth of Hydrogen as an Energy Export Commodity

– and that notion too remains alive, like a zombie, kept that way by the natural gas industry who knows that they are out of business post decarbonization without it.

Some clever folks just say, “Why don’t we put biogas into the natural gas network”? And why not? It’s a mixture of methane and CO2, about equal amounts. While most end-use devices won’t like all that extra CO2, removing it should be easy enough- certainly dead easy compared to removing CO2 from the atmosphere at ~400 ppm…

https://www.linkedin.com/pulse/why-direct-air-capture-sucks-good-way-paul-martin/

Sadly, aside from a few places where agriculture is very intense, there simply won’t be enough. And despite the fact that biogas is made from a waste, by the time you have the CO2 out of it, biogas methane costs a multiple of what we are used to paying for fossil natural gas. It’s also distributed across the landscape, so collecting the source material, producing the gas, and inserting it into the existing gas network is no easy task. Small scale makes it expensive, and physical distribution across the landscape means that you either have to transport waste to larger facilities, or build lots of small, capital-inefficient ones.

So of course the bright sparks who think we’ll be positively drowning in green hydrogen because that’s just frigging inevitable, because electrical grids are hard and whatnot (insert other nonsense as you see fit- the green hydrogen crowd has lots of it, and #hopium smokers the world around seem to be gobbling it up)…well, they think maybe we should react that green hydrogen with CO2 and make…methane.

You know, the exact reverse of the process by which substantially all the world’s hydrogen is actually made today. Whereas we run steam or coal reformers to react these fossils with steam over some catalysts to produce, ultimately, CO2 and hydrogen, these folks want to do the opposite- react CO2 with hydrogen to make…methane.

The Sabatier Reaction

We’ve known about the Sabatier reaction, also known in the industry as “methanation”, for a long time. It is commercially used sometimes as a way to back-treat dangerous CO and CO2, which can destroy fuelcell catalysts, to inert methane, as a treatment method in hydrogen purification.

CO2 + 4 H2 ===> CH4 + 2 H2O

Basically, the reaction involves “un-burning” CO2, by reacting off both oxygen atoms with hydrogen and then replacing the vacant bonding sites with even more hydrogen.

The reaction is spontaneous and exothermic- thermodynamics doesn’t mind if we’re dumb enough to want to do this. And if you were to convert 100% of the energy in the feed hydrogen to the higher heating value of product methane, the ultimate thermodynamic efficiency would be about 78%. That’s actually pretty good, considering.

No real reaction goes that perfectly, though. For instance, another reaction we’ve known about for a long time is this one: one of the methanol synthesis reactions:

CO2 + 3 H2 ===> CH3OH + H2O

That one is also spontaneous and exothermic. And its ultimate thermodynamic limit efficiency is 85% on a higher heating value (HHV) basis-not surprising perhaps, because it wastes one fewer H2 molecule than the Sabatier reaction does, making worthless water. But in reality, you can’t do it for any more than about 60% efficiency in a real plant- which is, unshockingly, the approximate efficiency by which natural gas LHV can be converted to methanol LHV in a world scale black methanol plant.

Another way to put that, is that real methanol systems fed CO2 and H2, only get to about 70% of the ultimate efficiency that thermodynamics sets as a limit. Why is that? Well, lots of reasons, but the big one is that conversion per pass sucks, because the real reaction going on is via carbon monoxide and the water-gas shift reaction pathway rather than directly from CO2 to methanol. That means we end up spending a lot of energy making CO and water out of CO2 and H2, and then running the whole shebang around in a loop, cooling it down, removing the methanol and water products and then re-compressing and re-heating the gas to feed it to the reactor again. Real processes don’t approach thermodynamic perfection very often, and the closer you push them toward that ideal, the more capital cost you end up spending trying to recover energy that would otherwise be wasted.

So: why is e-methane seductive: because a) a giant transmission and delivery system exists for the product, which unlike hydrogen, can actually be fed to that network in any proportion desired b) the reaction is fairly brainless, just requiring a series of fixed bed catalytic reactors with heat and water removal between them. Methanol is a lot more complex in terms of the technology and the plant required.

It’s simple, but that doesn’t stop e-methane from being dumbass. We’ll get there.

CO2 Sources Matter!

If we are planning to make methanol (which might be sensible) or methane (which probably won’t be!) using energy entirely in the form of green hydrogen, and we’re planning to use these molecules as fuels, then it matters a lot where we get the CO2 we use for that purpose.

Some focus on the notion that only the source of enthalpy (chemical potential energy) matters. They think it’s OK to capture fossil CO2 produced by burning or, say, black hydrogen production, and get away with the fact that when the fuel is burned, the captured fossil CO2 ends up in the atmosphere anyway.

I don’t.

We need to stop burning fossils as fuels, because we need to stop emitting fossil CO2 into the atmosphere.

Period.

Getting a 2nd pass on CO2 from burning fossils by capturing (some of it) and using (some of) it in a fuels production process is, at very best, a 50% reduction in the carbon intensity of the original fossil fuel use. That’s just not good enough.

So if you want to call your product an e-fuel, you need, at minimum, to be using pure biogenic or (well…no, this won’t happen) direct air captured CO2.

Evaluation of the TES Shawinigan Project

TES has been granted a 150 MW Hydro Quebec block of power- very green, cold water hydroelectric power with very high capacity factor. Power that should be fed to decarbonization efforts in Quebec- real ones, like electrification of transport, or, at least, fed to hungry electricity consumers in the US so they can shut off their coal and gas fired power plants.

TES apparently plan to add a large amount- hundreds of megawatts more in the form of wind and solar projects that they would build themselves.

Their plan is to convert that electricity to hydrogen, and then react it with biogenic CO2, presumably captured from combustion of wood and wood byproducts in the forestry industry, or perhaps from the CO2 portion of biogas methane etc.

Let’s take this sucker apart and see if it makes sense!

Energy Efficiency Chain for e-Methane

First, we start with electricity. Let’s feed it to an electrolyzer which takes 52.5 kWh/kg of hydrogen. That’s 75% efficiency on the higher heating value (HHV basis), or about 63% efficient on the lower heating value (LHV) basis. That’s a little lower than the 70% LHV basis I usually use in these calcs, but I’ve chosen this for two reasons:

1) To be consistent with what David Cebon used in his hydrogen for heating graphic produced for the Hydrogen Science Coalition (below) and,

2) Because in numerous projects done as a consultant in the past few years, I’ve never, ever seen a real electrolyzer quotation which achieved better than this on a total balance of plant basis. Most fall between 55 and 65 kWh/kg.

Let’s throw in a 1% grid electricity loss, just to show that we didn’t use a big loss here. This is basically an “islanded” project, consuming its own power and electricity made at a nearyby hydro dam.

We’ll also throw in a 95% efficiency (i.e. 5% loss) for hydrogen compression, storage and losses associated with moving hydrogen around on the site.

Next, let’s apply a 92% efficiency, i.e. an 8% loss, to supply the energy necessary to capture and compress the required CO2. That’s a very, very optimistic figure, based on the 2.1 MJ/kg CO2 which is used to capture 78% of the 3.8 bar partial pressure CO2 at Shell Quest. We’re using that figure despite its obvious optimism, just because the figure is publicly available. Any post combustion CO2 capture, and any capture that requires transport of the CO2, is going to take a lot more energy than that!

Now we feed this hydrogen and CO2 to the Sabatier reactor. And remember, best case that converts 78% of the HHV of hydrogen fed, to HHV of methane. Let’s assume that it operates better than methanol, and achieves 75% of maximum theoretical energy efficiency, with the balance going to yield losses, energy to run pumps and compressors, gas separation equipment, cooling to remove the produced water etc. This is based on optimistic comparison to other processes. Based on a ratio of what their project could achieve at best case using the 78% perfect conversion, and how much methane they think they’ll be making, TES seems to be taking this figure as 85%- but hey, they’re bound to be optimistic about their efficiency, I guess. 78% x 75% = 59% overall conversion from hydrogen HHV to methane HHV.

Now we put the gas into the gas transmission system. Compression for transport is about 97.5% efficient, and then transport/distribution itself is about 97.5% efficient per the ANL GREET model. That’s another 95% efficiency or 5% loss in terms of the gas energy we send to customers.

And now, we feed it to a gas boiler or furnace at 90% AFUE.

If we feed 1 MWh of electricity to the front end, we end up with 0.32 MWh of low grade comfort heat, in a home heated with the resulting e-gas. 32% cycle efficiency- but worse than even that…because we fed work (electricity) and got out heat…

But it’s even worse than that when we consider EXERGY, i.e. the potential to do work. And the best way to consider that, is to look at what else we might do instead.

Let’s say we fed the same 1 MWh of electricity into the electrical grid. Distribution is about 95% efficient based on US average data from EIA (i.e. 5% grid loss)- in fact in Ontario where I live, it’s less than 3% loss. The electricity is now already at your home’s meter, where we feed it to an air source heat pump with a coefficient of performance of 2.5 (we’re not expecting 3 out of a unit in most of Quebec, though most Quebecois live along the St. Lawrence, not way up north- just as most other Canadians live within 100 miles of the US border.

1 MWh of electricity then delivers 2.4 MWh of heat into the home. This one is so simple we don’t even need a Sankey diagram to see how awesome it is.

2.4 MWh divided by 0.32 MWh is a factor of 7.5 times. We can heat 7.5 times as many homes for the same amount of electricity if we just leave the molecular middlemen out of it!

And we haven’t even begun to talk about cost!

What Does This e-Methane Cost?

Well, it’s 7.5 times what it would cost to run a heatpump using the same energy, right? Well, it’s not quite that simple- but almost. In fact, it’s far, far worse than that!

Figures in this section and elsewhere are in Canadian dollars unless otherwise noted. $1 CDN = $0.74 USD as of today.

Figuring this out in detail is a little trickier than doing an efficiency chain diagram. But let’s do it, just because we’re bored!

First, let’s assume that TES gets electricity, on average between the 150 MW they get from Hydro Quebec and the wind and solar they make for themselves, at $0.05/kWh. That’d be pretty amazing, but let’s be hopeful here! That’s $13.89 per GJ of electricity, i.e. considerably more expensive than the ~ $7/GJ Energir is reportedly paying today for wholesale natural gas HHV energy. As of today, the US Henry Hub wholesale price for gas is $US2.78/MMBTU which is about $3.70 CDN/GJ. So already, even at an amazing 5 cents per kWh, that’s a lot of money going down the drain, to waste it as heat!

Now, let’s assume a few figures to estimate the cost of green hydrogen. $0.05/kWh x 52.5 kWh/kg is $2.63/kg H2 just for electricity. Add in a $2 million CDN/MW electrolyzer which lasts 10 yrs, which costs us nothing for operating labour or other O&M, and which is given to us by benevolent people who don’t want a return on their investment- they’re satisfied with simple payback when the electrolyzer turns into a pumpkin. And let’s assume a capacity factor for our power of 100%. It won’t really be that high, because only 150 MW is firmed hydropower. But again, let’s be blissfully hopeful here. That drives up our best case price for green hydrogen to $3.82/kg. That’s $27/GJ for hydrogen HHV.

Doubleplusnotcheap!

Now we feed it to a conversion process which makes it into e-methane at 59% efficiency. We don’t know what Sabatier reaction systems cost, so let’s assume they’re free, and have no other operating costs. The result is still $27/GJ divided by 59%, or about $46/GJ of methane HHV. We also need to supply about 0.32 GJ worth of energy to satisfy other energy losses in the chain, but let’s assume they’re supplied as cheaper 5 cent per kWh electricity. That adds another $4.50/GJ, taking us to, round numbers, a blue sky ridiculously hopeful cost of e-methane to TES- NOT to the consumer- of $50/GJ. 50/7 is about 7.1 times the cost of gas currently being paid for by Energir, wholesale.

Relative to the heatpump…well, it’s a lot more than 7.5 times more expensive for energy. Remember, the heat pump eats $13.89/GJ electricity but pumps out 2.4 GJ for every GJ you feed it. So its cost for heating is only $5.80 or so per GJ of heat delivered to your house. Cheaper than what Energir is paying for fossil gas! (But of course, we homeowners pay a lot more than 5 cents retail per kWh of electricity, so let’s forget about how cheap this could be for a second!)

That $50/GJ wholesale cost for e-methane doesn’t include all sorts of things that will be very, very real costs- we’ve just eliminated them from consideration because we don’t have good estimates for how much they’ll cost, or are too lazy to bother to figure them out. And it doesn’t include profit, or any return on investment for anyone. It assumes the project is run by altruists.

And, as it turns out, it doesn’t matter. Even without those unknown costs in there- all of them at zero- the result is ridiculously expensive e-gas.

So…WTF Would We Ever Do This?

It turns out that the motivation behind this project is likely a mandate by Energir to use a certain percentage of low or zero emissions gas in their network. And they can’t get enough biogas…apparently…even though it is vastly cheaper than this e-gas ever will be.

And the other reason is as clear as day to me: subsidy harvesting. One can imagine not only attracting a substantial “tax credit” from the federal government for making green hydrogen (effectively reducing capital cost by getting the government to pay for it!) , then more still for making green gas out of it- and then it wouldn’t surprise me if they thought they could get CO2 capture credits of some kind here too. Nevermind the fact that any CO2 captured, ends up in the atmosphere when the gas is burned…

Well, there you go, folks. e-methane is an exergy destroying machine on steroids. And if it is built, this TES project will be a very efficient extractor of money out of likely both the federal and provincial governments AND out of the pockets of Energir gas consumers.

What it isn’t, is a sensible decarbonization strategy.

References:

1) Data from real projects for electrolyzer efficiency, proprietary (I can’t share the quotations with you, sorry)

2) Moioli et al, Renewable and Sustainable Energy Reviews, 107, 2019

3) My own calculations for the ultimate conversion efficiency for methanol and methane from CO2 and hydrogen, validated against ref 2) above

4) Experience with e-fuels projects in terms of approach to ultimate energy conversion efficiency, again confidential (most figures in the academic literature are very significantly over-estimated relative to reality)

Disclaimer: This article was written by a human, and humans make mistakes. If I’ve made one, please feel free to call me out on it and to provide references if possible to set me right. I’ll be grateful for the correction.

If I’ve just upset you because I’m shitting on your pet idea, feel free to contact Spitfire Research Inc. They’ll be happy to tell you to piss off and write your own article.

Breakthrough in Electrolyzer Efficiency!

“FOR IMMEDIATE RELEASE

🔬REVOLUTIONARY BREAKTHROUGH SETS HYDROGEN ENERGY IN A WHOLE NEW LIGHT

[City, Date] – Today marks an unprecedented achievement in the sphere of renewable energy! We’re incredibly excited to announce a thrilling breakthrough in hydrogen electrolysis that could totally redefine the landscape of the global energy sector. Brace yourselves, friends of tech, because you’re about to be blown away by this game-changing, phenomenal advancement.

This isn’t just a step forward; it’s a colossal leap towards a future brimming with sustainable energy! Our team of wizard-like scientists and technical magicians have unlocked the secrets of hydrogen electrolysis, achieving unprecedented levels of energy efficiency that were previously considered the stuff of dreams.

The newly discovered process, affectionately dubbed “Hydrogen 2.0,” operates at breathtakingly high efficiency levels. We’re not just talking 20%, 50%, or even 80%… Nope! Our revolutionary Hydrogen 2.0 is astonishingly hitting near-perfect efficiency rates! Imagine the capabilities of an energy source that delivers virtually no energy waste – it’s mind-boggling!”

(The preceeding delicious #hopium emission was courtesy of ChatGPT as expertly wrangled by human intelligence Michael Barnard)

In the past few years there have been at least two prominent and at least somewhat credible claims that people have 95% (HHV) efficient electrolyzers working in the lab.

So that’s my argument against hydrogen on the basis of inefficiency shot to pieces, isn’t it? Guess it’s time to pack up the @hydrogen science coalition and jump on the hydrogen as a fuel bandwagon, eh?

Let’s be clear: the problem with hydrogen isn’t that electrolysis is inefficient, or fuelcells are inefficient, or storage is inefficient. The problems with hydrogen as a fuel or energy storage medium are a) exergy destruction b) too many steps, each with efficiency limits and c) the properties of the H2 molecule.

Exergy Inefficiency

Exergy has a more complex definition to a thermodynamicist, but to a layperson or an average engineer, it’s safe enough to just call it “the potential to do work”. While a joule of room temperature heat and a joule of electricity are both 1 joule of energy, the former has ZERO exergy and is basically worthless if you have more of it than you need, and the latter is nearly pure exergy. You can convert electricity with very high (nearly 100%) efficiency into thermodynamic work, i.e. mechanical energy. As Michael Liebreich says, riffing on Orwell’s Animal Farm: “All joules are created equal, but some joules are more equal than others!”. Or as I say, “Committest though NOT the 2nd Sin of Thermodynamics!”. The 2nd sin is to confuse a joule of heat with a joule of work as if they’re of equal value- rather like confusing an American dollar with a Jamaican dollar because they’re both units of money measured in dollars!

I have a device which can convert electricity to 1000 C heat with 100% efficiency! Is that magic? No, the device is called a resistance heater. Converting pure exergy to even high temperature heat with 100% efficiency is no problem, because that heat has a lower exergy value. The 2nd law says, “that’s fine- thou shalt pass”.

On the flipside, one can use a joule of work to PUMP 3 joules of heat from a cold place to a hot place. The 2nd law is OK with that too, with the temperatures of the hot and cold places determining the maximum efficiency (called, for heat pumps, a coefficient of performance).

An electrolyzer is no more magical than- and in fact, in thermodynamic terms, it’s fairly similar to- a resistance heater. It converts pure exergy (electricity) into a fuel, which is chemical potential energy- a proxy for heat. That process is in the 2nd law’s natural direction, the direction of increasing universal entropy and decreasing useful exergy.

This is the fundamental problem with using hydrogen derived from electricity, as a fuel or energy storage medium. Even at high ENERGY efficiency, making hydrogen from electricity is a massive step backward in EXERGY efficiency.

The current state of the art of water electrolyzers is about 83% HHV (ultimate, thermoneutral) efficiency on the stack level. That means to produce 1 kg of H2 with a HHV of 39.4 kWh/kg- the total heat energy produced when you burn that 1 kg again, including the (useless in exergy terms) 6.1 kWh/kg worth of heat of condensation of the product water vapour- you need to put in 39.4/0.83 or 47.4 kWh of electricity.

Of course a hydrogen plant contains much more than just an electrolysis stack- it has “pumps and tanks and sh*t” too- as my old boss used to say about stuff that looks complicated but really is pretty routine. That stuff- compression equipment, hydrogen deoxygenation and drying, electrolyte management, heat rejection, water treatment etc. etc., a) consumes electricity too, b) costs money and c) is already mass produced, so learning curve savings in cost or big improvements in its efficiency are both unlikely. Add in these “balance of plant” and “outside battery limits” energy uses and hydrogen costs somewhere between 50 and 65 kWh/kg to make from water.

Scaling Example #2: Water Electrolysis

The Efficiency Bargain

Recent claims by two firms- Hysata, with a capillary water electrolyzer, and H2Pro with a complex multi-stage semi-batch electrochemical water splitting scheme, are that they can make 1 kg of hydrogen for 39.4/0.95 = 41.5 kWh. That’s a savings of 5.9 kWh/kg. What percent improvement that is, depends on what denominator you choose, and is hence not all that useful.

These new electrolyzers are both a) new, so no learning curve yet to make them cheaper and b) more complex than state of the art electrolyzers. Both are early stage, i.e. low technology readiness level. To know if either will EVER be useful for making hydrogen at scale, we’d need to know lots and lots of things:

  • capital cost now, ie. complexity, ease/difficulty of manufacture, raw materials cost etc.
  • how the capital intensity per kg of H2 produced might be reduced when production is done at scale (ease of mass production, basic complexity (how simple is it, and can it be made simpler to reduce cost), ability to scale rather than number up units etc.), and threats to the supply chain (availability of catalytic metals is a big risk for PEM units for instance)
  • durability, i.e. how many hours on stream the stack or catalysts will last before requiring replacement
  • efficiency loss: how quickly the catalysts or other components lose effectiveness and hence drop efficiency
  • etc. etc. etc.

Some of these things won’t be known until a unit has been in industrial service for ten years. Some, we can get good guesses at fairly soon, but only if we’re under an NDA with the company so they open their technical kimono and show us the technology away from the investors and stock promoters, warts and all- so no, you’re not going to find that stuff in a media article!

The fundamental bargain here however is really simple: how much extra cost is it worth to save 5.9 kWh/kg H2?

Taking an electrolyzer which is found in working order, free in a ditch somewhere, which magic elves install free of charge on borrowed land, and with a system efficiency of 50 kWh/kg, to make $1.50/kg hydrogen, it would need to be fed electricity at 3 cents per kWh, i.e. $30/MWh. Add any capital cost at all, and this price of electricity must fall even further, or the price of hydrogen must rise to pay back the capital investors, and the non-magic elves who expect a salary, and the people who don’t give away land for free. If the capital is more than zero, then it will also matter how frequently that electricity is available at a low cost. Even if it’s free part of the time, if it’s not cheap most of the time, your electrolyzer is going to make expensive hydrogen.

5.9 kWh x 3 cents = about 18 cents per kg. You’re not going to pay for much additional capital cost with those savings. Mind you, the 50 kWh/kg electrolyzer is already a pretty expensive beast, because it’s running at a low current density to be so efficient. Real ones you can afford are going to be closer to 60 kWh/kg on a system basis. But who knows what current density Hysata and H2Pro’s claims are made at? I wouldn’t trust the figure even if I could find it in print. And we’ve already established that the capital cost will be higher, because these systems are more complex than the current state of the art- in one case because of complex microstructure (capillaries) and in the other, because it’s a sequential semibatch operation, with oxygen evolution happening separately from hydrogen generation. That takes more “tanks and pumps and valves and sh*t”…

So: are Hysata or H2Pro “breakthroughs” that will revolutionize hydrogen production? Doubtful. They may, or may not, marginally help. But they don’t fix the fundamental problem with electrolysis- they don’t stop it from being, fundamentally, a massive destroyer of exergy.

Steam Electrolysis: SOECs

If you electrolyze steam rather than water, you can actually make hydrogen for even less than 39.4 kWh/kg input electrical energy. You can actually take some heat and convert it to hydrogen chemical potential energy. Of course the device is a stack of metals and ceramics glued together with glass, which operates at around 700 C, so you’re not getting off scot free here. Even if you can find somebody who will boil water for you for free, rather than paying another 6.1 kWh/kg H2 to do that, you have the problem of running at 700 C. And given that 7/8 of the mass coming out of the electrolyzer is oxygen, recovering heat from what amounts to a cutting torch is, well, tricky. SOEC stacks are small, don’t like thermal cycling so have to be electrically heated to keep them hot when they’re not operating, and today cost considerably more per MW of capacity than water electrolyzers- for reasons that should be obvious. Are SOECs a magical solution? Depends- does your process need both hot oxygen and hot hydrogen? Then, maybe. Otherwise, doubtful in my view, unless somebody makes a huge leap forward in making SOEC run efficiently several hundred degrees cooler.

Cycle Efficiency

The problems with hydrogen as a fuel or energy carrier show up when you do a cycle- from electricity to hydrogen, hydrogen to storage, and storage to a fuelcell or turbine or other device to make electricity again.

Of course the ridiculous commentators say that the cycle is 100% efficient! And they’re right- it’s 100% efficient at turning electricity into heat, most of which is worthless. Sadly, a chunk of heat (electrolysis waste heat, and compression or liquefaction waste heat, or ammonia/methanol/LOHC hydrogenation/e-LNG waste heat, is made where you already have energy in excess (and hence are throwing away electricity). So yeah, that waste heat is GONE- it rarely has a meaningful use, except perhaps in complex process units i.e. with the waste heat used to run the Rube Goldberg apparatus known as direct air capture or the like. Affording the capital to recover this heat is a different matter, and a value proposition there is absolutely NOT guaranteed. The smaller the scale, the less likely that source heat recovery will be useful.

Using best case figures: electrolysis at 83% HHV efficiency is really about 70% LHV efficiency (subtracting the 6.1 kWh/kg of heat energy which no fuelcell or engine can put to use). Best case, compression for storage is about 90% efficient, at scale- at smaller scale, this efficiency falls rapidly. And the best case for either a fuelcell or combined cycle gas turbine power plant is about 60% on a LHV basis. 0.7 x 0.9 x 0.6 is 37%, i.e. buy 3 kWh, get 1 back. That’s just fundamentally a terrible battery- even worse, because the energy density of hydrogen per unit volume is absolutely terrible. And on top of that craptastic efficiency, you end up needing to pay for a bunch of expensive capital equipment. Note there’s nothing in that simple calc for transmission of electricity, transmission of hydrogen product, or innumerable other energy-sucking factors in real systems. It’s an idealized best case. And no, changing that 70% LHV efficiency to 80% (i.e. 95% HHV efficiency) doesn’t help all that much- the cycle increases to 43%. On the same basis, a lithium (or sodium) ion battery is 90%. And that battery is very, very much simpler.

A nice visual example, because people like pictures: here’s David Cebon‘s graphical explanation of why it is so much more sensible to use the exergy of wind electricity to pump heat into homes, than to use it to make hydrogen to replace fossil gas in existing boilers. There we’re talking about a ~ 5-fold difference in useful energy delivered per joule of feed energy.

Poor cycle efficiency is what kills hydrogen’s use as a fuel, whether for transport or heating or what have you. Poor efficiency which is NOT offset by much greater effectiveness (i.e. ease of storage, transport or use of energy) is just a recipe for economic failure. It’s putting money into two piles on the floor and setting one of them on fire. That might make you money under some rare circumstances, but generally only if the money you’re burning, isn’t yours!

Disclaimer: I’m human and so I make mistakes. I don’t know everything, either. Where I’ve gone wrong, provide me with good references to the contrary and I’ll amend my text with gratitude. Don’t like it because I’m slaughtering your precious idea with my analysis? Feel free to complain to Spitfire Research Inc., who will tell you to shove off and write your own article.

Scaling Example #2: Water Electrolysis

Old electrolyzer stacks from Norsk Hydro, now NEL, 1920s

Scaling Object Lesson #2: Water Electrolyzers For Hydrogen Production

We learned about vertical scaling in the 1st article in this series:

Economy of Vertical Scale

…and about horizontal scaling or “numbering up” in the 2nd:

Horizontal Scale- Numbering Up

Now we’ll use these tools to examine the scaling future of an extremely important decarbonization technology: electrolyzers for producing hydrogen from renewable electricity.

My readers will know that I think hydrogen is a massive decarbonization problem, and that I think we must focus our efforts on making green (electrolytic) hydrogen to replace the 98.7% of the stuff that is made from fossils without carbon capture- the ultra-black hydrogen that dominates the market today.

Hydrogen From Renewable Energy- Our Future?

In a decarbonized future, we’ll need a lot of green hydrogen, even if we aren’t stupid enough to waste any as an inefficient vehicle or heating fuel! I estimate that 90 of the current ~ 120 million tonnes/yr of hydrogen we use today, is durable in a decarbonized future. And in reality we’ll need more than that, because there are some uses for hydrogen as a molecule which are also a very good idea: for instance, using H2 to replace the carbon monoxide used in the direct reduction of iron ore to iron metal.

Replacing that 90 million tonnes of H2 per year would take a monumental effort. Optimistically, it would take 4500 TW h of green electricity– more than twice as much as all the wind and solar made on earth in 2019. Given that today we’re making less than 0.03% of world H2 production by the on-purpose electrolysis of water, we’re really at ground zero on the important task of decarbonizing hydrogen itself.

If we had renewable electricity available to us at 100% capacity factor, we’d need only ~ 513 GW worth of electrolyzers to make that hydrogen- but since renewable electricity isn’t available with such high capacity factors, we’ll really need 1000-1500 GW of electrolyzers.

How much on-purpose electrolyzer capacity is there on earth today? Less than 1 GW. We need to increase electrolyzer capacity by at least 3 orders of magnitude and probably more.

Hmm: how can we apply what we learned about vertical and horizontal scaling to this most important decarbonization problem?

Electrolyzer Basics

There are two main water electrolysis technologies which are front-runners today: the alkaline electrolyzer, and the proton exchange membrane (PEM) electrolyzer. They differ in details, features, benefits, disadvantages etc in important ways, but for our purposes we don’t need to worry about that. Let’s look at the basic components of an electrolysis system.

The electrolyzer itself consists of a “stack” of electrolysis cells, each with an anode and a cathode (and many other parts, depending on which technology). Cells are arranged in physical parallel, meaning that each cell is fed water/electrolyte and the products (hydrogen and oxygen gas) are collected from each cell.

(schematic of an electrolyzer stack- image credit, IRENA)

The cells may be arranged electrically in series, parallel, or series/parallel arrangements to allow us to select DC current and voltage inputs of a manageable level. High currents mean big conductors, expensive power controls, and high ohmic losses- high voltages mean lower currents, but also the potential for currents flowing where we don’t want them to- so we are involved in a balancing act.

Electrolysis is an area-based process. The key parameter for electrolyzer design is current density, i.e. the current, in amperes, which flows through each unit of electrode/cell area. Lower current density means lower voltage per cell and hence higher efficiency, but also means more capital cost per unit of H2 production (or power input) because each unit of electrode area produces less value (less hydrogen) per unit time.

While we could build complete cells individually, and connect each one up to the others with individual tubes and wires or buss bars, that would be very expensive- and we’re smarter than that. Designs vary, but you won’t go far wrong as a basic mental model to think of a stack of plates held together with draw bolts, with internal manifolds and process connections at each end, arranged rather like a plate and frame heat exchanger.

It is advantageous to produce the hydrogen product under pressure, so that less mechanical compression is needed prior to transport or storage of the bulky gas. While pressure forces the equilibrium the wrong way (back from H2 toward water) which costs us some voltage, it also makes the gas bubbles smaller and hence leaves less electrode area blocked by nonconductive gas. Smaller bubbles mean lower current density and hence higher efficiency- to a limit. That means we get a certain amount of gas compression out of an electrolyzer basically “for free” in energy terms- very desirable! Unfortunately, pressure acting on a unit of area generates a force that wants to separate our plates and make the electrolyzer leak- so the bigger we make each plate, the stiffer it must be and the larger and more numerous the bolts that draw the plates together. Ultimately, this basic physics puts practical limits on how big we can make each plate.

Balance of Plant

The electrolyzer stack or stacks are only part of an electrolysis plant. Everything outside the stack which supports it, is called the “balance of plant” or BoP.

(balance of plant for an alkaline electrolyzer: image credit, IRENA)

Each electrolyzer needs a supply of pure water- at least 9 kg per kg of H2 produced. You can use freshwater or seawater, but in either case you must use reverse osmosis to purify it first- a process which takes a trivial amount of electricity (only 0.035 kWh/kg of H2 even starting with seawater) relative to the 50 kWh/kg it takes to make 1 kg of H2 from water. Impurities in the water can (significantly) sap efficiency by carrying stray currents, can make products like chlorine which contaminate the product gases and destroy materials of construction, deactivate cell catalysts etc. Water purification is a no brainer here- and trying to electrolyze dirty or saline water as a way to make hydrogen, is a fool’s errand.

Electrolyzers need DC electricity of controlled current and voltage. Large variable output DC power supplies referred to as “rectifiers” (but much more complex than a bunch of diodes!) are therefore required, along with all their safety gear, measurement instrumentation and controls, and heat removal systems (because these power supplies are not 100% efficient).

Electrolyzers themselves are not 100% efficient, which means that they convert some of the electricity they are fed, into heat. While a little heat is good (improves efficiency), too much wrecks materials of construction or boils the feed water. Accordingly, heat removal systems are required, and the amount of heat generated at scale is a) is not trivial and b) generally produced in places which already have excess energy available, and which hence have little use for low-grade heat. That means we need pumps and heat exchangers to manage this heat, and yet more heat exchangers to reject this heat to the atmosphere.

The product hydrogen is saturated with water vapour and also contains some oxygen. Generally the hydrogen is passed over a catalyst which burns out the oxygen, forming more water. Drying is accomplished in stages with compression and cooling, and for some processes, more complex drying (based on regenerable adsorbents) may be required. So here too, we’re talking about catalyst beds, heat exchangers, compressors, refrigeration equipment, adsorbent beds etc.

The product oxygen is usually vented, but if it is to be compressed and monnetized, it too needs drying, hydrogen removal and compression.

Finally, the product(s) need to be compressed for transport or storage. Whereas electrolyzers might operate at 30-70 bar, storage is generally at 250 bar or higher. That’s more compressors, piping and storage tanks.

“Outside Battery Limits” (OSBL) Equipment and Infrastructure

An electrolysis plant is like any chemical plant making any other chemical product, in that there are support systems outside the “battery limit” of the chemical plant itself. Some examples include:

  • electrical substations, switchgear etc.
  • Control and data acquisition system and human/machine interface
  • pipeline connections, trailer loading facilities
  • water supply and wastewater management
  • emergency relief systems, flares, vent stacks etc.
  • Buildings or weather enclosures
  • facilities for operators or maintenance staff
  • roads, parking, civil works

That’s just a partial list- but every such project has to take the OSBL into account, and pay for it.

Scaling of Electrolysis Systems

Assuming that what we want is to make hydrogen as cheaply as possible per kilogram, how should we proceed with scaling up an electrolysis system?

From the discussion about the basic physics of a cell and cell stack, a few things are clear:

  • cells are repeating identical units consisting of parts which we might mass produce
  • making each cell larger in area will allow each cell to consume more current and hence produce more H2
  • making each cell larger in area makes it more likely to leak and requires stronger materials
  • arranging cells in fluidic parallel in stacks makes more sense than building innumerable tiny cells and connecting each one

The first point gives us some hope that Wright’s Law can come to the rescue. It is entirely possible to imagine cell components being made in automated factories, and then robotically assembled into cells, and cells into stacks, in a true mass-production environment. And as we do that, with every doubling of production, we should expect the units to get cheaper.

It’s fairly clear that cells of larger electrode area are going to be desirable, but that larger cells will require stronger materials and will be more likely to leak. An optimum size should exist, but that size will vary depending on many things, including the limitations of our mass production scheme.

It’s also fairly clear that it would be desirable to stack up as many such cells into a “stack” as practical, so we have as few stacks as possible- but that there will likely be a practical physical maximum based on mechanical properties, fluid mechanics, and dimensional limitations for transport etc.

And so, the electrolysis industry has concluded. While stack sizes are pushed upward yearly, right now the biggest single stack has a capacity on the order of about 10 MW of input power. A 1 GW electrolyzer therefore would consist of 100 such stacks, arranged in physical parallel, likely in a number of “trains”.

So: what’s our scaling conclusion about electrolyzer stacks? I think we can conclude:

a) Wright’s Law will likely be applicable to the stack

b) since just to replace black hydrogen, we’ll need to increase the capacity of electrolyzers on earth by at least 1000x, there’s lots of room for Wright’s Law to run down the cost of each stack

c) both the cells and the stacks of cells will likely have an optimum size, but people will be motivated to increase that optimum size by clever design

d) the optimum size of stack will require that multiple stacks be “numbered up” to achieve plants of sufficient scale

a) and b) are good, hopeful signs for future electrolyzer stacks to become cheaper with time- assuming somebody will pay for the initial stacks which are expensive per unit of production and not mind doing so.

d) however means that projects of substantial size will involve lots of stacks in physical parallel, and that means that there will be limited economy of vertical scale for the electrolyzer portion of the project

What about the balance of plant?

That consists of “tanks and pumps and sh*t”, as my old boss used to say whenever he was confronted with something that looked complicated and scary, but wasn’t really. Conventional stuff, nothing magical. Nothing we shouldn’t be able to scale vertically to kingdom come. And as we scale that stuff- as an electrolysis project gets bigger in capacity- we should expect the marginal cost of the balance of plant to drop per kg of H2 for the good reasons given in my first article in this series. However, we should also expect nearly zero Wright’s Law benefit in relation to the balance of plant. The same for the OSBL: as a proportion of cost per kg of H2, it should drop as the scale of the project increases, but there should be little to no Wright’s Law learning curve to save our bacon. It’s not like pumps, tanks, heat exchangers, buildings, parking lots, electrical substations etc get cheaper as we make more of them- we’ve made too many of them already, and getting to the next “doubling” takes decades.

The Current State of Electrolyzer Scaling

The major players in electrolyzer manufacture have grown up making fairly small units. Prior to the most recent hydrogen #hopium pandemic, the whole role for electrolysis was either to make high purity hydrogen for specialist applications, or to make quantities of hydrogen to rescue users of small quantities of the gas from the high prices being charged by gas suppliers for tube trailer deliveries from a commercial hydrogen plant. Anybody who needed hydrogen at a meaningful scale, simply bought their own small SMR and made it themselves instead from much cheaper fossil gas.

Often, electrolysis supported pilot projects or provided hydrogen as a utility to an existing facility. Accordingly, many of the electrolysis suppliers designed modular products, often based around “seacans” (shipping containers) which served as both environmental enclosure and support for the equipment. Some units were self contained in a single container, while others required several containers for a complete unit.

(container modular electrolyzer system: image credit- Plug Power)

What do you think about the idea of mass producing containerized complete small electrolyer systems in containers? What are the economic prospects for such a design?

In my opinion, based on the type of analysis we’ve used in the past two articles, the prospects for such an approach are very poor indeed. I see this design as a hangover from the industry’s history.

While the stacks will still have Wright’s Law cost learning benefit, complete containerized packaged systems could benefit from factory fabrication but likely would have minimal to no Wright’s Law learning based cost reduction benefit. The economy of vertical scale for the balance of plant would be abandoned due to the very small maximum scale of complete units stuffed into containers of a limited size, and the resulting marginal capital cost per kg of H2 would be higher than necessary. Furthermore, shipping containers, though themselves mass produced (for use AS shipping containers…) are an inefficient use of steel, an inefficient way to enclose space relative to constructing a building, they offer poor access for operation and maintenance, and are (greatly!) suboptimal in size relative to (considerably) larger modular frameworks which can ALSO be moved by road and sea to most locations. In modular systems, the optimal size of a module is the biggest piece you can move down the road without excessive “heroics”, so you have to re-assemble as few modules as practical on site: this maximizes one of the key benefits of modularization, which is minimizing expensive site work by doing as much in the factory as practical.

The ridiculous extension of this approach is the proposed path to scale of Enapter, a company developing a technology called anion exchange membrane electrolysis. Though the AEM technology has an interesting combination of desirable properties of both alkaline and PEM units, with some of the downsides of each removed, Enapter’s publicly announced strategy is to mass produce complete 2.3 kWh electrolyzers, each including its own complete balance of plant. Thousands of such factory mass-produced units would be physically paralleled to produce an electrolysis project at scale. Sadly, I think this is an object lesson in how not to scale up an otherwise potentially promising technology. It shows to me a lack of understanding of fundamentals of engineering economics.

https://www.rechargenews.com/energy-transition/-our-unique-aem-electrolysers-will-produce-cheaper-green-hydrogen-than-any-rival-tech-/2-1-1042573?utm_content=buffer0a93c&utm_medium=social&utm_source=linkedin.com&utm_campaign=buffer

Fortunately, there are smarter people in the electrolyzer space, both among the market leaders and a number of their rivals. They have a clear view of what it would take to make electrolysis cheap enough to make cheap green hydrogen at scale, and are pursuing development projects for equipment that are consistent with good engineering economics. Some of them are even smart enough to be Spitfire Research customers! But in the interest of maintaining confidentiality, I won’t mention their names, unless they want to “out” themselves in the comments.

Insights for the Future Cost of Green Hydrogen

To become truly inexpensive, truly green hydrogen requires the following things:

  • a) very cheap renewable electricity available at high capacity factor, which means hybrids of wind and solar in places which have sunny days and windy nights
  • b) projects of very large vertical scale
  • c) electrolysis plants that are inexpensive at scale
  • d) to make green hydrogen production into a business, you also need a way to get the green hydrogen to market.

(Sharp readers will notice that I never mentioned efficiency- and that might make some people suspect I’ve been smoking some #hopium myself. Why is efficiency not on that list? Because the existing state of the art of electrolysis is already 83% HHV efficient, which sadly is only 70% LHV efficient- though hard to afford at that low current density. The incremental benefit from 83% to 100% on an HHV basis- the limit for water electrolysis set by thermodynamics- is, in my view, much less important than the other factors!)

To achieve a), you need large hybrids of wind and solar, located far away from electricity markets (or else you’ll simply make and sell electricity instead!)- locations such as western Australia, Chile etc. That unfortunately collides with d)- locations far away from electricity markets are also far away from places which can use hydrogen, and moving hydrogen across transoceanic distances is a bear of a problem. Accordingly, those projects will need to make something you can move, such as ammonia, direct reduced iron,, methanol or the like. And, hopefully, we’ll be smart enough not to waste those materials as ways to make hydrogen again…

The Myth of Hydrogen as an Energy Export Commodity

To achieve c), you need somebody willing to buy expensive electrolyzers- and the expensive hydrogen they produce- sufficiently to get electrolyzer production far enough along the Wright’s Law learning curve to make the cells and stacks cheap enough. That’s possible but it will take deep pockets- our public pockets. So it’s my hope that we aren’t stupid enough to waste any of that precious, expensive but truly green hydrogen on dumb uses that are better served by electrification directly or via batteries, or which can be eliminated, or which can be solved more effectively by other means (biofuels etc.)

What you also need is b), ie for the balance of plant and OSBL to be done at large vertical scale, because it won’t be subject to Wright’s Law and hence won’t get cheaper as a result of learnings. And sadly, there’s only so much that vertical scale can do to reduce the costs of this part of the cost of a total hydrogen plant.

Will green H2 get cheaper? Absolutely! But only because it is insanely expensive at the moment.

Will it get cheap enough? Depends on what you mean by cheap enough, and for what purpose.

Will it get cheap enough to replace black hydrogen? That depends more on what we do in relation to carbon taxes and emission bans than it does in relation to the scaling of electrolysis technology. I dearly hope so- our lives are depending on it, if we want to keep eating that is. Dumping CO2 to the atmosphere for free, or nearly free, is a giant subsidy on the backs of our childrens’ futures that we must END, TODAY.

Will it get cheap enough to go head to head with the electricity it is made from? No. That should be obvious.

Will it get cheap enough to use as a fuel, for transport or heating? I doubt it. I think there are better options that will achieve decarbonization of these functions, at far lower cost to society. That goes even moreso for so-called e-fuels derived from hydrogen. Fighting thermodynamics all the way back from water, CO2 and electricity is a fool’s errand- one that should be undertaken only if we are both rich and desperate.

Scaling Example #1: Small Modular Nuclear Reactors

Now, let’s used the tools we’ve learned, to took at some examples from the effort to decarbonize our economy.

The first example to take a swing at with our new understanding of vertical and horizontal scaling is the small modular nuclear reactor, or SMNR for short. SMR means something else to me- steam methane reformer- a technology which pre-dates the entire nuclear industry.

First, a disclaimer. I am not a nuclear engineer. I have no nuclear design experience, and I claim no special expertise in relation to nuclear power. I am however a chemical engineer with decades of experience helping people scale up- and down- chemical process technology. I have also spent decades designing and building small modular chemical plants in a factory environment, and have more than a passing familiarity with their engineering economics.

Let’s also be clear: I think nuclear power can be made adequately safe, and that its use in the 1970s and 80s undoubtedly saved countless premature deaths in my home province of Ontario relative to its true market competitor at the time- burning coal to make electricity. Nuclear is also very clearly a dispatchable, or at least reliably available, source of electricity which also has very low GHG emissions. While I acknowledge that the both the decommissioning of nuclear plants and the storage of nuclear waste are major political and public relations problems, I think that they both have quite practical technical solutions- though the cost of those solutions is unclear to me. That’s a long list of pluses for nuclear power- rather big ones. There is some argument as to whether or not that list of pluses is worth whatever nuclear might cost us, but I’m not of that opinion. Nuclear is just one option- and there are others. We need a societal discussion about what those options are, and what their costs and impacts are.

Nuclear Power’s Present: Giant Vertical Scale

The modern nuclear reactor power plant is the epitome of “go big or go home”- of maximizing vertical scale in an (often seemingly vain) effort to keep the cost per kWh low for consumers. Initially, nuclear reactors were small as we learned how to use them. Engineers understood the economy of vertical scale just as well in the 1950s as they do today, and so it was quite clear that if nuclear power were to become cheap, it would do so by building nuclear reactors at considerable (vertical) scale. And as the industry grew, and project experience was gained, reactors got bigger- not smaller.

It is important to realize what a nuclear reactor is, at its essence. It is a steam power plant with a nuclear fission heatsource, and associated safety and controls equipment to operate and keep that heatsource safe. Given that there’s nothing magical about a steam power plant, surely the steam power plant portion of the project should benefit from ordinary economy of vertical scale.

What about the fission reactor itself?

There have been plenty of examples in the recent past of cost and schedule over-runs in nuclear power projects in numerous locations around the world- in fact, it’s much harder to find examples of nuclear power projects which are anything close to on time and under budget (though nuclear apologists always have a few of those to trot out as examples). The preponderance of cost/schedule over-runs has led people to conclude, perhaps not unreasonably, that nuclear went too far into a giant, megaproject vertical scale that was larger than truly practical.

The current scale of reference is, round numbers, 3 GW of thermal output, or about 1 GW of electrical output per reactor. The cost/schedule overruns would imply that an optimal scale for nuclear power deployment might be at some scale smaller than the current scale- a scale requiring fewer “heroics”.

A nuclear power plant generally has several reactors of around 1 GW electrical capacity, sited together. An example is the Darlington nuclear power station located east of Toronto. It consists of four units with a total generation capacity of 3.5 GW of electricity- roughly 20% of Ontario’s electricity demand. The units are operated independently but share common infrastructure, again to save capital cost.

Darlington’s construction started in 1982 with unit 1, and ended in 1993 when unit 4 was completed. The original budget of $4 billion was exceeded, considerably- the plant cost $14.4 billion, or roughly $23 billion in 2020 dollars. Some of that overage resulted from financing costs arising from project delays caused by government “interference” etc. – the story is a long and sordid one, which likely is an object lesson in why projects like this should not be allowed to become political footballs. In 2021, the 30 yr refit project for the plant was started, at a cost of another $13 billion. If we’re honest, that refurbishment cost was “baked in” when we decided to build the project in the first place.

In 2013, Ontario went out to tender on a “twinning” of Darlington. Prices came back so eye-wateringly high that nuclear ambitions in Ontario came to a screeching halt.

Until 2021, that is…

A new project, referred to as “Darlington New Nuclear”, hit the headlines. The plan is for a new 300 MW (and it looks like that means 300 MW electrical capacity) Hitachi boiling water reactor for the Darlington site.

The moniker “small modular nuclear reactor” has been attached to the project- but the plant, at 1/3 the size of the existing units, is not small in objective terms- it’s in fact bigger than the 200 MWe Douglas Point plant, the prototype for the CANDU reactors later built at Darlington and elsewhere, constructed in the 1960s.

It’s also not modular in the sense that most people understand. It will not be completely assembled in a factory and delivered in sections that are easy to put back together, on the back of a truck or trucks. The plant, if ever built, will be substantially site constructed, just as the larger Darlington units were.

But I digress…

Here’s the SMNR pitch, being made by many firms today:

  1. The reason nuclear power plants are so expensive is that they’re always a brand new, 1st of kind design. There’s no steady crew of people with the specialist skills to efficiently build them, because we never build the same design twice nor do we build them one after another. No common design means people spend more time engineering, and less time building.
  2. A “new” nuclear fission reactor technology will be used. Sometimes, that’s just a new twist on the existing “boiling water” reactor. Sometimes, they’re talking about a totally different technology, such as a molten salt fuel cycle.
  3. The units will be built at much, much smaller scale than the existing state of the art. NuScale, for instance, the project which seems to be farthest along in the USA, has a capacity per unit of about 77 MW electrical per reactor. Twelve (12) units operating in physical parallel would be required to replace a single Darlington-scale unit.
  4. The smaller scale is claimed to be small enough to be “intrinsically safe”, or something near enough to that, so the hope is they will be simpler to build, and easier and quicker to permit.
  5. The units are small enough that they can be built (and apparently, also fuelled) in a factory, and shipped to site “largely assembled”- in NuScale’s case, in three truck-shippable pieces per reactor, totalling 700 tonnes per reactor. The claim is that will make projects faster to begin producing some power, and hence much cheaper.
  6. Because the factory will make the same unit again and again, what the unit lacks in economy of vertical scaling, will be more than compensated for by a) factory fabrication by a trained team b) “mass production” and c) “simplicity” arising from the smaller scale
  7. The small units will be perfect for use on remote sites like mines, small remote communities etc.

Let’s examine the claims one by one, using NuScale as a reference case because its information is quite widely available to the public, not because it is especially worthy of either praise or criticism:

  1. To me, this is a popular myth, not a reflection of the real reason nuclear power plants are expensive. Like all myths, there’s a grain of truth there: nuclear is a specialist industry with a heavy certification burden. The real reason they’re expensive is that they are massive capital projects with extremely long design life, a high risk profile, and accordingly a long permitting, approval and construction process. Projects which must be done at positively massive scale to deliver sufficient economy of vertical scale to make each kWh seem cheap enough for ratepayers to afford, for reasons made obvious in my 1st article in this series. And the regulatory attention is inescapable, because the risk profile means that only the public has deep enough pockets to insure these projects against accidents.
  2. To my non-nuclear eye, NuScale isn’t really a new nuclear technology- it’s just a small boiling water reactor with a different cooling scheme involving a thermosiphon and water immersion rather than active pumping. And, shockingly, from a brief review of NuScale’s website, it seems that the plan is to connect each unit to its own (tiny) “skid mounted” (modular) steam plant, such that even the steam plant part of the job will lack economy of vertical scale.
  3. At 77 MW electrical output per unit, the unit definitely qualifies as “small”. Therefore, numerous individual units will need to be installed, either in physical parallel on the same site with common infrastructure, or on numerous sites, to supply equivalent amounts of power to the units they seek to replace. Which of these two options will be cheaper? Obviously the former, and by a lot!
  4. “Intrinsic safety” is obviously something which is easy to claim, but quite hard to demonstrate to the satisfaction of a regulatory body who knows that the public, not a private entity, will be providing insurance against an accident. By “hard”, I mean “will cost a lot and take a long time to achieve”
  5. Certainly the pieces of each NuScale reactor look to be small enough to be shipped by a number of different means, including by heavy logistical truck/trailer units- but by no means would those be “routine” shipments given the diameter and weight, even if they didn’t also contain active nuclear material. The project is, however, still modular in the way people typically understand that term in the industry.
  6. Until orders of such reactors are so common that maintaining a dedicated factory full time for their fabrication is a practical option, each unit will be built more or less by hand, albeit in a factory environment. Subcomponents and sub-assemblies will be made in other dedicated factories, just as all plants are built today, whether they’re modular or “stick built”. But the project would have access to the benefits of modular fabrication. Calling that “mass production”, however, is more than a small stretch of the definition of that term! Such a factory would have almost nothing in common with, for instance, a factory making cars. People, not robots, will be doing most of the work. The notion that sufficient savings in labour and schedule would be possible to overcome the rather obvious lack of economy of vertical scale of each unit is therefore very questionable.
  7. It is clear that the lack of economy of vertical scale will not be compensated for adequately by modular fabrication even if the units are ganged in parallel on a common site with common infrastructure. The notion that putting tiny units alone or in small groups on numerous different sites could yield affordable kWh for consumers is just preposterous.

Let’s look closely at claim 6) – that mass production in a factory environment would overcome the conventional economy of vertical scale.

Let’s take the unit cost of one NuScale 77 MW unit as x units of capital cost. What would we expect 12 such units, factory modular, to cost if they were all ordered at the same time? I’d guess 12^0.9 x at best, to be generous, or about 9.3x. It could easily be higher.

What should, in comparison, one unit of 12*77 = 924 MW electrical output, cost? About x * 12^0.6, or 4.4x…

For a project which hinges on capital cost per unit of value production, that’s a death sentence. On the basis of decades of experience doing it for a living, there’s no way that factory modular fabrication is going to drop the price per unit sufficiently to make up for that ocean of a difference.

Now let’s look at a few other issues which seem obvious even to me as someone who absolutely makes no claim to be a nuclear power expert:

  1. From a nuclear proliferation, security, terrorism etc perspective, distributing nuclear reactors on numerous sites, particularly remote/rural ones, is far riskier than larger centralized sites which can be better planned and protected. Power distribution costs won’t be reduced unless we also decide to site these numerous little nukers much closer to population centres- something that is unlikely to go over well with the people who would be living next door. You can claim that such fears are unjustified, but that doesn’t mean they won’t present themselves with pitchforks and torches at every public meeting.
  2. Because fuelling costs are low, and capital costs are (very) high, nuclear power is generally operated as close to 100% capacity factor as physically possible, generally being given preferential access to serve loads on the grid. The issue isn’t that nuclear power plants can’t be “turned down” in output- the issue is that you can’t afford to operate them that way. And that fact means that nuclear doesn’t play well with intermittent wind and solar power, which are cheaper when they are available and simply not available when they aren’t. Making the plants smaller won’t change that, at all. The putative benefit of having 12 units you can individually control, really adds not very much to that economic equation.
  3. Could Wright’s Law really be counted on to make each subsequent reactor cheaper than the last? Can SMNRs become like solar panels or Li ion batteries? That depends on how applicable you think Wright’s law is to fairly conventional equipment- heat exchangers, welded pipe systems, steam power plants etc. My bet is that it’s not very applicable because manufacturing processes for such equipment are already very well understood- we make enormous numbers of pieces of such equipment in the world yearly already. The potential for Wright’s Law “doublings” which lead to learning-based cost reductions, seems small, though I don’t doubt there would be a learning rate if there were sufficient doublings.
  4. For Wright’s Law to kick in, we’d need to have a single design which is the obvious favourite, and to build that one only. Does such a design exist? No- rather, there are many designs being proposed, for both conventional and new fuel cycles, with no clear winner.
  5. If a particular future fuel cycle (molten salt, thorium, what have you!) is somehow limited to a small maximum scale due to its nuclear physics, to me that’s a flaw, not a feature. It means that the technology will have challenges to achieve a low cost per unit of production, ie. per kWh it makes for consumers. It also means that each technology will make its cheapest kWh when built out to its largest practical scale- just like all other technologies which produce commodity products.
  6. Can the smaller units be refurbished? What’s their design life, and how would one extend that to maximize the number of kWh each unit generates before it becomes a pile of (low level) radioactive waste? I sincerely don’t know the answer to these questions, but I’m sure others might.
  7. Is a nuclear reactor really a great tool to site at a remote location like a mine or remote community? Are such locations ideal in terms of emergency response, skilled and trained maintenance staff etc. Etc.? And does the power use of such sites, and the resulting GHG emissions, really make a big difference to total world GHG emissions? Is this a “hard to decarbonize sector” or just an excuse to sell units to places already accustomed to paying high prices for power from diesel generators and the like?
  8. It is sometimes claimed that SMNRs provide greater possibility to provide combined heat and power than conventional nuclear power plants, given that heat can’t be shipped over distances as great as electricity can in economic terms. However, that’s only true if we put them on numerous sites which are each closer to populated centres, and then we’re willing to spend the money to build district heating etc.. That is, as already noted, not a recipe for low capital cost.

From this analysis, and based on long discussions with nuclear advocates and nuclear critics, I can say that I consider the small modular nuclear reactor to be basically nearly pure nuclear #hopium. It’s a concept that fails a basic economic “sniff test”- a proposed solution that seems incapable of solving nuclear’s really big problem, which is its enormous capital intensity- not its tendency to draw out “no nukes” protesters.

It also seems to run quite contrary to the learnings of the past. And you know what they say about that: doing the same thing over again and expecting a different outcome is a fairly accurate definition of delusion.

Why are SMNRs So Popular, Then?

Lots of smart people, and entire companies with world class pedigrees such as Rolls Royce, are lined up in opposition to what I’m telling you in this piece. Why am I so sure that they’re wrong and I’m not?

Simple. It’s a concept known as “moral hazard”.

When I was in the business of designing pilot plants for new processes for clients, on occasion the client or their investors might ask me whether I thought the process was “worth piloting”, i.e. Did it have a likelihood of economic success? I would (rightly) refuse to answer such questions, and if pressed, I would simply repeat the client’s own claims to them and say, “If A, then B”. Why did I give such a cagey answer? Because, as a designer/builder of pilot plants, I benefited financially from designing and building the pilot plant, whether the process had any chance of economic success or not! Any opinion I offered to such questions was therefore offered from a position of an actual conflict of interest- and I was in a position of “moral hazard”. As an aside, I love the fact that as an independent consultant, I can now tell clients straight up about every strength and every weakness I see in their plans- with no moral hazard.

Clients who can’t take the truth as I see it, I’m quite happy to part ways with- I even advertise this as a feature of my consultancy on my website.

Now put yourself in the shoes of a nuclear engineer: you’re coming to the end of your career in what is basically otherwise a dying industry. Very few at-scale nuclear projects are being built, so maybe you’re working on a refurbishment project- the last one on that plant. To you, the chance to work on a SMNR project, probably one lasting many years, especially one funded by governments or by people who will pay your salary whether the project achieves its goals or not, is likely a very pleasant one relative to trying to find a new industry to work in late in your career. You’re an expert in nuclear power, certainly- but do I give your opinion about its potential for success of SMNRs, any real weight? Or do I consider that opinion to be one offered from a position of moral hazard?

That’s certainly not an accurate description of everyone who supports SMNRs, by a long shot. There are many people of such high personal integrity that they will tell the truth, when asked, and the whole truth, even if that truth is contrary to their personal economic interest. But it describes a lot of them, especially many of the ones advocating the concept most loudly in public.

There are some people who are absolutely not in a position of moral hazard who also think SMNRs are the bee’s knees. They may genuinely believe that SMNRs have a real chance to make cheap kWh one day, if we only finally standardize on one design and then build them by the thousand every year. I just don’t think those people are thinking clearly. I think they’ve smoked a little too much #hopium for their own good. Doesn’t make them bad people- doesn’t make them right, either.

Finally, there’s the even more cynical group of people. People like Doug Ford, recently re-elected premier of the province of Ontario. Doug is many things- aside from being the older brother of the imfamous late crack-smoking former mayor of Toronto Rob Ford, Doug is quite likely also a closeted climate change denialist, although he is far too cagey to ever admit that publicly.

Let’s say you’re our dear leader DoFo. You have lots of people clamouring at you about climate change, and since you fancy yourself to be a populist, you don’t want to appear to be doing nothing. But you don’t believe in it, so you don’t want to spend any real money dealing with it. Especially not on “green power” projects which you ran against as costly boondoggles and a blot on your rural voters’ landscape- projects which you cancelled, then passed legislation preventing the project’s proponents from seeking the cancellation fees former governments had agreed to. You also know that the Pickering nuclear power plant is scheduled to close down in 2024, for good, because it’s finally too many years past its best-before date to extend any further.

So: what do you do?

How about planning a 300 MW “small modular nuclear reactor”? Are you troubled that it’s not really small, nor modular? Nope. You talk about all those Ontario jobs. And you know that it will be quite happily studied- by people largely in a moral hazard position- until you’ve retired from office. The money spent on this gives you plausible deniability about the whole AGW issue as you see the province build more fossil gas-fired power plants to replace Pickering. “Just wait”, you say- “the SMNRs are coming to save the day!” Doug can add #hopium dealer to his long resume…

Recommended Reading: you can’t go far wrong in reading @Michael Barnard ‘s treatment of the same topic, which was informed in part by discussions we had about the topic but which also contains Michael’s usual, top notch research and analysis.

https://medium.com/the-future-is-electric/small-nuclear-reactor-advocates-refuse-to-learn-the-lessons-of-the-past-8ca1af3293c3

Horizontal Scale- Numbering Up

An article written while I worked at Zeton may be instructive in relation to this topic as a backgrounder:

https://www.linkedin.com/pulse/scaling-up-down-paul-martin/

Once we reach a certain maximum practical vertical scale for a particular piece of equipment, it becomes impractical to build a bigger unit, or to transport and erect it once it’s built, as noted in the previous article. At that point, we shed a few tears, because we know that the continually decreasing capital cost per unit of value created is now more or less over for that unit. But generally, this is not encountered in every unit on a plant at the same scale. When we’ve got the largest pump, filter, reactor etc. that can be made in practical terms, the next step isn’t to build two complete twin plants on the same site, much less two complete plants on two different sites to save on distribution. Rather, we will usually “number up” the largest practical thing, running several of them in parallel.

Sometimes we do that even though we’re below the maximum practical scale. Some plants have “trains” of duplicated units which run in parallel, such that one train can be shut down for maintenance, or because the market dries up. Common infrastructure is maintained, and that gives us some of the benefit of vertical scale- just not to the same extent as if we made each unit bigger.

An example is the Shell Pearl GTL project pictured in the 1st article.

(Shell Pearl GTL- a mammoth gas to liquids plant installed in Qatar- photo credit, Shell)

That project produces liquid hydrocarbons ranging from LPG to waxes, starting with fossil gas. The process, known as Fischer Tropsch, takes CH4 apart to CO and H2 (and lots of CO2) and then back-hydrogenates CO to -CH2- and H2O. It is so inefficient, as a result of wasting all that hydrogen “un-burning” CO to make water, that the only way it can make money is:

  1. You must do it at positively mammoth scale to drop the marginal capital cost of the overall plant to the lowest practical level
  2. You must pair it with a gas source which is both enormous and basically free
  3. You must be able to dispose of fossil CO2 to the atmosphere, again basically for free

Accordingly Pearl GTL is positively mammoth- it must be to make money for its owners, at prices of products that the market are willing to pay. Capital cost was on the order of $20 billion.

It is in fact so huge that it “numbers up” its reactors.

Each reactor is a giant pressure vessel- weighing 1,200 tonnes- containing 29,000 catalyst tubes in a common shell from which the heat is removed. Each reactor is as big as Shell could make them, without what Shell considered to be excessive “heroics”.

There are two trains of reactors. And in each train, there are 12 reactors operating in physical parallel.

Shell Pearl’s reactors, installed. Photo Credit www.oilandgasmideast.com

This is basically an object lesson in “numbering up”. Each catalyst tube is as big as it can be without making the wrong products. As many such tubes are put into a single pressure vessel as practical, to make the cost of physical paralleling of these tubes as low as practical. And then, large numbers of these pressure vessels are installed again in physical parallel, arranged in trains.

The rest of the plant is similarly divided up into single or multiple units in accordance with the maximum practical scale at which the process itself can be carried out. If I recall correctly, it has two of the largest air separation plants ever built, a huge autothermal reformer etc.

Shell didn’t pursue this giant scale for fun and games. Apparently they looked at this project numerous times over more than a decade, before deciding to pursue it. They ran the numbers and convinced themselves, quite correctly, that the only way to make money from Fischer Tropsch, even with a nearly free gas supply, is to go big- so big in fact that numbering up the reactors was the only practical option.

“Numbering Up” to Minimize Scale-Up Risk

There’s another reason some people give for pursuing a “numbering up” rather than scaling up strategy. Sometimes, making the bigger unit with higher production capacity is easy- but sometimes, it’s very risky indeed. The larger unit we design might not work at all, or might make a different product, or undesired byproducts etc.- even if you retain experts to help you make the best stab at building the larger unit that you can. The risk here isn’t just money, it’s time. A development project for a larger unit, can take considerable time. And if customers are knocking down your door already today, you may not want to wait. Under those circumstances, numbering up small units which have already been proven to work, seems a tempting option.

The Downsides of Numbering Up

Unfortunately, for every unit we have to run in physical parallel (because we had to number up rather than scaling up), we now have multiple devices to procure, install, connect, control and test. That means more valves, more switches, more wires, more instruments and controls, more installation labour, quality control, testing etc.- and more cost. It also means more likelihood of an individual failure of some kind, even though the failure of one unit might only reduce production by a small amount of the total (that’s an advantage of numbering up in “trains” as noted above).

If making a larger unit is possible, even with some risk, it’s likely worth doing- if the market can support that much product. What we are unlikely to get away with is to instead build multiple identical smaller units and operate them in physical parallel- especially if the individual units are a small fraction of the total production that the larger plant could produce.

Of course if we take “numbering up” or “horizontal scale” to its logical conclusion, we see some of the many things we use on a daily basis- articles that are mass produced in plants which themselves take advantage of as much vertical scale as possible, so that each commodity product item (computer, solar panel, car etc.) itself is as cheap as it can be.

This is where the proponents of certain schemes, fall into the ditch. They frequently confuse the apparatus making the commodity goods, with the commodity goods themselves!

Why “Mass Production” – of the Means of Production- Can’t Win

But surely if we mass-produce entire plants to make our commodity, those plants will get cheaper and their capital cost per unit of production will drop?

No, they won’t. Because S^0.6 is an exponential function. It positively destroys any benefit which mass production of the plant itself could possibly generate.

Furthermore, the sorts of things we’re talking about here aren’t suitable to true mass production.

Modular Construction

Sure, you can build a complete chemical plant in a factory, in pieces of a size and weight suitable to be shipped by whatever means you like. Such construction is referred to as “modular”, and I was in the business of designing and building small modular chemical plants used as pilot and demonstration and small commercial units for over two decades. Modular construction offers many advantages- faster schedule, better build quality, and higher labour productivity among others, when it’s done right.

https://www.linkedin.com/pulse/designbuild-approach-modular-construction-paul-martin/

And despite this, I can say, unequivocally, on the basis of that considerable experience, that nobody would ever achieve lower cost per unit of production by getting ten modular plants of identical design, built at the same time as modular projects, if building a 10x larger plant on site (referred to as a “stick built” rather than modular plant) was a practical alternative. Whereas a modular design/build operation might be able to offer ten plants of unit cost 1 for 10^0.9 = ~ 8.1x the cost of the first one, the 10x larger plant- including the extra cost associated with “stick building” the parts of it that were too big to modularize, would cost only 10^0.6 = 4x. These figures are, of course, very rough, but they give you the basic idea.

If you want real mass production, order 10,000 of them at the same time…but how likely are you to do that?

Where Horizontal Scale is Your Only Choice

The first article in this series examined the conditions under which the economy of vertical scale was valid. If any of those conditions are violated, horizontal scale may be your only choice.

If your product is unstable, i.e. ozone, you have no choice but to put an ozone generator on every site that needs ozone. That those ozone generators are mass produced, however, does not make ozone a cheap chemical! Its cost is high not just because it is energy inefficient to make, but also because the need to make it on site in tiny ozone plants makes inefficient use of capital, even though the ozone units themselves are built in factories. That inefficiently used capital cost makes every kg of ozone that much more expensive.

If your feed or product can’t be distributed readily, you may also have no choice but to go for horizontal scaling, on separate sites. Of course that is no guarantee whatsoever that the resulting product, made using equipment with poor capital utilization efficiency (high marginal capital cost), is worth enough to make the enterprise into a business.

And no, “mass production” of the necessary plant equipment, absolutely won’t save you.

In the next articles we’ll use these concepts to evaluate a number of claims in the renewable/alternative energy world, to see whether or not they make sense.

Economy of Vertical Scale

Shell Pearl GTL project in Qatar- a project which can barely make money despite giant scale

There are lots of proposals emerging seemingly every day, based around the notion that we will mass produce some device, plant or process, and then use those mass-produced devices to produce some commodity product- frequently a product made by devices, plants or processes already operated commercially at much larger scale. A few examples seemingly popular at the moment include:

  • small modular nuclear reactors for power generation
  • distributed hydrogen generation (particularly for refuelling vehicles)
  • small units to generate value from fossil gas that would otherwise be flared, by converting it to fuels or chemicals
  • distributed units to process a distributed resource- waste products from agriculture, municipal solid waste, batteries- you name it

The idea is simple enough: we all know that when things are made in large numbers, a couple things happen. One is that we get better at making them, and that learning drives down the cost of each unit produced. The first one costs a lot because it’s a prototype. The 2nd, if it is identical, is easier and hence cheaper because we’ve already proven the concept. And so it goes, with capital cost falling by a certain percentage with each doubling of production- a principle known as Wright’s Law.

Another is that when we increase the scale of the manufacturing plant (made possible by increased numbers of units being sold), we can benefit from the savings associated with automation etc. This is actually one of the features which enables Wright’s Law for the manufacture of certain types of devices.

The fundamental thesis of the sorts of schemes I’m going to take on in this article series can be stated more or less as follows: building big plants is hard. It takes time and lots of capital. So instead, we’ll make a very small plant, do it very well, and then mass produce the very small plant and operate many of them in physical parallel, either on the same site or on a plentitude of sites, the latter to save the costs of distributing the product (or to eliminate the need to build infrastructure to distribute the product). And it’s my job in this series, to explain to you why this idea has a rather tall stack of engineering economics- arising from basic physics- in the way of its success.

It’s important to provide a little context here, so that people can make sense of where such approaches are necessary, where they make sense, and where they’re just somebody playing around with your lack of knowledge of engineering economics and hoping you won’t notice.

Economy of Vertical Scale

You’ve probably noticed that we make many things in large, centralized plants. We distribute feeds of matter and energy and labour to those plants, and we distribute products from those plants to the people/businesses who need them. Why do we do that?

The answer comes from very basic physics, which leads in a very direct way to engineering economics.

Take the simplest example: a piece of pipe to carry a fluid from point A to point B.

Let’s say we’re moving a commodity with that pipe- doesn’t much matter what commodity. Let’s compare two pipes: one has a diameter of X, and the next has a diameter of 2X.

The first pipe can carry a given amount of product per unit time at a particular amount of energy input per unit time lost to friction. The correct size of pipe is determined based on what’s referred to as an “economic velocity”- the flowrate which gives a linear velocity which is an optimum balance of the cost of pumps/compressors and their energy lost to pressure drop in the pipe (higher for smaller pipes) and the capital cost to build, test and maintain the pipe (higher for larger pipes). A different optimal velocity exists for a chemical plant’s piping, for instance, than for a pipeline carrying fluids across a country (with the latter favouring lower velocities).

When we compare pipes with diameter X and 2X, we find right away that we can move four times as much material per unit time in the larger pipe, because the cross sectional area varies as D^2. Indeed it’s even more than 4x, because we get a benefit from an improved ratio between wetted perimeter (where wall friction happens), which varies with D, and cross sectional area which varies as D^2.

But the real benefit is this: the pipe capital cost doesn’t increase by anything near four times.

We’ve just discovered the physical basis for the economy of vertical scale, or “economy of scale” for short. It arises because relationships such as the surface area to volume ratio, become more favourable with increasing scale.

Similar physics are active for all things on a project- every pump, valve, tank, heat exchanger, transformer, motor- you name it. The bigger you make it, the cheaper it gets (in capital cost) to produce a unit of value from that device.

Capital Cost Versus Scale

Let’s say we have two plants: the first plant produces 1 unit of production (doesn’t matter if that’s tonnes per day of a chemical, MW of electricity etc.), and the 2nd one produces 10 units per day of the same undifferentiated thing. We say that plant 2 is 10/1 = 10 times the scale of plant 1, ie. we have a scale factor of 10.

To a first approximation, because of relationships like the one for the pipe example, it can be shown that:

C2 =~ C1 S^0.6

Where C2 is the capital cost of the larger plant, C1 is the capital cost of the smaller one, S is the scale factor (the ratio of production throughput of plant 2 to plant 1), and 0.6 is an exponent which is the average for a typical plant. In fact, each thing in the plant has a similar relationship, with an exponential factor which ranges from between 0.3 (for centrifugal pumps) to 1 (for things like reciprocating compressors above a certain minimum size). Normalized over the cost of a typical plant, the exponent of 0.6 gives the best fit.

Let’s say that 1 unit of production generates 1 unit of revenue per day. Ten units would generate 10 units per day. But let’s say that 1 unit of production rate costs us $1 million in capital. Ten units of production would therefore cost us 10^0.6 x $1 million = ~ $4 million in capital. The cost of capital per unit produced is therefore $1 million/unit/day for the first plant, and $4/10 = $0.4 million/unit/day for the 2nd plant.

The marginal capital cost per unit of production is dramatically lower for the larger plant- assuming:

  • there’s a market big enough to consume all the production of the larger plant
  • there’s feedstock sufficient to feed the larger plant
  • the product and its feedstocks are both legal and possible to transport by practical means
  • we’re within the limits of the scaling equation, meaning that each thing we’re using in the plant, simply gets bigger
  • we’re making a commodity which is fungible, meaning that it’s interchangeable with the same product made elsewhere

We’ve just discovered the reason we do stuff at large scale! It doesn’t matter what undifferentiated fungible commodity product we’re making, as long as it meets our assumptions above (or only bends them a little), every unit of production (every tonne of product, or kWh of electricity etc.) becomes cheaper if we make it in a plant of larger scale.

Limits of Vertical Scaling

Of course there ultimately will be an optimization here too. We rarely think it’s a good idea to make all the world’s supply of any one thing of value in a single plant at one location on earth. That’s putting too many eggs in one basket. Distribution isn’t free of charge, much less free of risk, and logistics limits how far you can move a particular product before the cost of distributing it overwhelms the capital savings. Similarly, the feedstocks are often distributed and their logistics matters too.

Some products- and some starting materials – are too voluminous or unstable or dangerous to make the trip. Doesn’t matter how badly we want to make ozone, for instance, in one centralized plant to make it cheaper, because in 90 minutes, even under ideal conditions, it’s gone- it falls back apart to oxygen again. If you want ozone, you must make it on site and use it as it’s made.

With hydrogen as a feed, unle\ss we’re using a tiny amount, it is generally better (in economic terms) to either set up production near an existing hydrogen plant, or to transport something else to make hydrogen from and then build a small to medium sized plant of our own- because the infrastructure to economically move more than very small quantities of a bulky gas like hydrogen doesn’t exist beyond a few “chemical valley” type situations where large number of plants are co-located in the same geography. Bespoke new infrastructure suitable for moving pure hydrogen is very costly and slow to build.

The same with hazardous wastes: we may find it very efficient to process them in one giant plant, but there are often rules about transporting wastes across borders etc that make it impossible to do so.

Vertical scale, within those limits, is king. It’s the reason we have centralized power plants, oil refineries, chemical plants, car manufacturing plants etc., rather than having one in every town, or every home. The resulting economy of scale can pay for considerable distribution infrastructure too- within limits.

Additional Advantages to Vertical Scale

Many other factors tend to generate lower costs of capital for larger projects rather than smaller ones. The proportion of a project spent on factors like engineering, permitting, controls and instrumentation, accessory facilities, civil/structural work, utilities etc. all tend to be lower per unit of production rate for larger rather than smaller plants, with exceptions of course.

When capital cost intensity decreases, so does the incremental cost of improvements to save energy such as heat integration. Whereas small projects often heat using fuel and cool using a cooling utility, heat integration becomes economically possible as projects become larger. And when plants are integrated into even larger facilities, energy integration from one plant to another becomes possible. Plants can share utilities such as steam, such that surplus steam from one plant is used for motive power or heating by another.

Is There Such A Thing As “Too Big”?

Absolutely. At a certain point, things are just too big to build in practical terms. With some pieces of equipment, you get to the point where there’s only one company in the world who would even try, and they get to name their price and delivery schedule. Sometimes, the issue is shipping the finished article to the site. Sometimes it’s a matter of not being able to afford to build the thing in place, because doing so requires basically building a factory with specialized equipment only for the purpose of building the one unit, squandering much of the benefit of greater scale.

All of these factors lead to the conclusion that there is a maximum practical scale for most things. And beyond that maximum practical scale, you’re pioneering- you’re going one larger, and taking onboard all the learnings of doing so on just your project. Future projects might look at your ruins and laugh, or they may benefit from your suffering, but you’re going to suffer either way.

A certain amount of “heroics” in terms of specialized logistics, heavy cranes, special crawler trailers, or site construction, is necessary in any big project. But when a project goes too far, the result can be a higher cost than if you’d simply built two or even four smaller units which didn’t require heroics to the same extent. You bet that major projects teams suffer over these details, in an effort not to become a signpost on the road of project development which says, “go no further”.

In the next article in this series, we’ll discuss what you do when you reach the limits of vertical scaling.

Recommended Reading: “Capital Costs Quickly Calculated” – Chemical Engineering magazine, April, 2009

Are German Gas Pipelines “Fundamentally Suitable” for Hydrogen?

leaking hydrogen pipeline by DALL E

Update: my peer reviewed article in Energy Science and Engineering (Aug 2024) summarizes some of the points in this piece.

https://scijournals.onlinelibrary.wiley.com/doi/10.1002/ese3.1861

A recent study https://www.dvgw.de/medien/dvgw/forschung/berichte/g202006-sywesth2-steel-dvgw.pdf

carried out by Open Grid Europe GmbH with the assistance of the University of Stuttgart, paid for by DVGW (Deutscher Verein des Gas- und Wasserfaches- the German Association for Gas and Water) did rather careful, extensive and thorough testing of a wide and characteristic variety of pipeline steels in hydrogen atmospheres of various pressures. 

The report draws a shocking conclusion that has been parroted on high by the #hopium dealers at Hydrogen Europe and various other pro-hydrogen lobby groups:

“Hence, all pipeline steel grades investigated in this project are fundamentally suitable for hydrogen transmission.”

Well that’s it- case closed then!  All gas transmission pipelines are fundamentally suitable to transmit pure hydrogen!  The fossil gas distribution industry is saved! The “sunk cost” of all that infrastructure is rescued!   And all those worry-warts like myself who were pointing out the hazards of such a conversion were just wrong!

While I’m totally happy to find out when I’m wrong, so I can change my opinion to be consistent with the measured facts, I’m afraid that in this case, the answer is rather more complex than just “Paul Martin is wrong- gas pipelines are safe for use with hydrogen”.

TL&DR Summary: extensive materials testing in this study proves that molecular hydrogen does cause pipeline materials to fatigue crack faster (up to 30 times faster than they would in natural gas) and to lose as much as 1/2 their fracture toughness (making them more likely to break). But if you reduce the design pressure of the pipeline substantially- to 1/2 to 1/3 of its original design pressure- the gas industry would consider that “safe enough” under the rules intended for designing new hydrogen pipelines. That would of course drop the capacity of the existing gas pipeline by a lot, requiring that either the lower capacity be accepted or the line be “twinned” or replaced if it were switched to hydrogen. And a host of other problems per my previous article on this topic, are also unresolved.

Hydrogen to Replace Natural Gas- By the Numbers

What Was Studied

Modern gas transmission pipelines are generally made of low alloy, high yield strength carbon steels typified by API 5L grades X42 through X100.  The study examined steels commonly used in pipeline service in Germany, ranging from mild steels of low yield strength such as historical grade St35 (35,000 psi yield), through API 5L X80 (80,000 psi yield strength), including some steels used in the manufacture of pipeline components such as valve bodies.  In many cases, specimens were prepared in such a way that the bulk material of the pipeline, a typical weld deposit and the heat affected zone of the parent metal were all tested.  Thorough, careful work.

The specimens were tested in a cyclic (fatigue) testing apparatus which could be filled with hydrogen atmospheres of varying pressures.  The major factors examined were fatigue crack growth rate and fracture toughness, because these parameters are known, not merely suspected, to be affected in a detrimental way in these steels by the presence of hydrogen.

What They Found

To hopefully nobody’s surprise, the testing found that the presence of hydrogen does greatly accelerate fatigue crack growth, and significantly negatively affects fracture toughness in the tested steels.

Specifically, they were able to build a good model of the fatigue cracking behaviour of these materials.  They found, to quote p. 169 of the study:

  • At lower stress intensities and hydrogen pressure, crack growth is comparable with crack growth in air or natural gas
  • At higher hydrogen pressures, crack growth very rapidly approaches the behaviour at a partial pressure of H2 = 100 bar (~ 1500 psi) , even at lower stress intensities
  • The position of the transitional area from “slow” crack growth to H2-typical rapid crack growth (my emphasis) depends on the hydrogen pressure, although it cannot be predicted exactly

They also found that fracture toughness Kic was negatively affected by the presence of hydrogen.  Fracture toughness was, as expected, reduced even in low yield strength steels like St35, even when small amounts of hydrogen were added.  Fracture toughness was strongly reduced in higher yield strength steels such as L485 (a common modern pipeline steel used in Germany).  Even 0.2 atm H2 dropped fracture toughness greatly, and fracture toughness continued to drop steeply as pH2 was increased.  

fracture toughness vs H2 concentration per DVGW study
(source: DVGW study p. 176)

Hmm…so how did they draw the conclusion that these steels are “fundamentally suitable for hydrogen transmission”?

By comparison against the requirements of the hydrogen pipeline design/fabrication code/standard, ASME B31.12. 

The study found that the crack growth rate was consistent with the assumptions used in the hydrogen design de-rating method used in B31.12. They also found that in  all the steels tested at pH2 = 100 bar, the minimum required Kic value of 55 MPa/m^½ was exceeded.

The TL&DR conclusion here is as follows:  yes, hydrogen causes pipeline steels to fatigue crack faster and to lose fracture toughness to a considerable extent, relative to the same steels used in air or natural gas.  But that’s okay…because it doesn’t crack faster or lose more fracture resistance than expected in a design code used for dedicated hydrogen pipelines.

A design code that fossil gas pipelines are not designed and fabricated to, by the way!

What Does This Mean?  Hydrogen’s Impact on Pipeline Design Pressure

Transmission pipelines are designed, fabricated and inspected in accordance with codes and standards which vary from nation to nation.  The common standards in use in the USA, which serve as a reference standard in many other nations, are ASME B31.8 for fossil gas and other fuel pipelines, and ASME B31.12 for bespoke hydrogen pipelines.  While the latter do exist (some 3000 km of dedicated hydrogen pipelines in the USA alone), the former are much more extensive (some 3,000,000 km of them in the USA).  And if you a) own such a pipeline or b) depend on it to supply the gas distribution network you own, and c) know that without hydrogen, you’ll be out of business post decarbonization, you will be very motivated to conclude that you can re-use your gas pipeline to carry hydrogen in the future.  Hmm, sounds like a bit of a potential conflict of interest, no?   

In both ASME standards, the design pressure of the pipeline is determined via a modification of Barlow’s hoop stress equation, involving the specified minimum yield strength of the piping (S), the pipe nominal wall thickness (t), pipe nominal outer diameter (D), a longitudinal joint factor (E), a temperature de-rating factor T, and a design safety factor  F, which depends on service class/severity and location.  For hydrogen per B31.12, a new factor Hf, a “material performance factor” is applied to effectively de-rate carbon steel pipeline material design pressure to an extent rendering it (arguably) safe for use with hydrogen:

P = 2 S t/D F E T Hf

These helpful tables excerpted from ASME B31.8 and B31.12 were borrowed from Wang, B. et al, I.J. Hydrogen Energy, 43 (2018) 16141-14153

Tables of Hf and F from Wang et al
from Wang et al (reference above)

Design factor F, used in both codes, varies between 0.8 and 0.4 in ASME B31.8 based on “location class”, which is based on factors including proximity to occupied buildings.  

B31.12 for hydrogen has two design factor tables:  one for new, purpose-built hydrogen pipelines, with F values matching those in B31.8 for fossil gas (option B), and one for re-use of pipelines not originally designed to B31.12, which uses a lower (more conservative) table of F values ranging from 0.5 to 0.4 (option A).  The latter, option A, would apply to any fossil gas pipeline repurposed to carry hydrogen.   

For many existing gas pipelines, repurposing the line to carry hydrogen would require de-rating of the design pressure from the current level which is often 72% or 80% of specified minimum stress, to perhaps 40-50%.  

For hydrogen piping, the material de-rating factor Hf ranges from 1 for low yield stress piping materials used at low pressures, to 0.542 for high tensile, high yield strength materials operating at high system design pressures.  No such material de-rating factor is required in ASME B31.8 for the design of fossil gas pipelines.

In the extreme case, a pipeline designed and fabricated for fossil gas per ASME B31.8 in a low criticality (class 1 division 1) location far away from occupied buildings, made of a high yield strength steel, would have its design factor reduced from 0.8 to 0.5, and an Hf applied of 0.542.  The result would be a reduction in design pressure to 34% of the original value, i.e. a reduction of almost three-fold.

A reduction in design pressure represents a very significant reduction in pipeline energy carrying capacity and would require either “twinning” of the line with new pipe, or replacement with new pipe. 

So:  Can We Use Existing Gas Transmission Pipelines for Pure Hydrogen?

The answer is much more complicated than a simple yes or no! 

Can they be re-used?  Maybe- but the pipe material isn’t the only issue.  There are many others, covered in my paper here:

Hydrogen to Replace Natural Gas- By the Numbers

(which I will shortly update with this new information in relation to piping materials- that’s why I love LinkedIn as a publishing medium, because it makes updates easy!)

Can they be re-used at their existing design pressure and hence at their existing energy carrying capacity?  The answer to that is almost certainly NO.  At bare minimum, de-rating of the design pressure would be required, likely to a significant extent.  This would necessitate either twinning the line with new pipe to carry the same amount of energy, replacing the existing pipe, or accepting the reduced capacity.

Will they blow up and kill people if used for hydrogen?  Well…they will crack much faster, even at reduced stress, and will be much more likely to break, than if they carried fossil gas without hydrogen in it. Gas pipelines are often operated at a pressure which varies with respect to time, cycling frequently, whereas dedicated hydrogen pipelines tend to be run at more constant pressures, resulting in less rapid fatigue.   But if the design criteria of a code (B31.12) not used in the design and construction and testing of the original pipe are retroactively applied to the existing pipeline, the industry might consider that to be “safe enough”.  The DVGW testing demonstrates that the design assumptions used in the hydrogen pipeline design code to set its “hydrogen design de-rating factor” are met, in metallurgical terms.

Let’s just say, that’s far from a ringing endorsement for the concept.  If I were a regulatory body in charge of ensuring that gas utilities keep their pipelines safe, I’d be paying very close attention to any pipeline being re-purposed for hydrogen. The gas industry itself is in at very least a potential conflict of interest in regard to this matter, and the regulatory bodies will need to step up and ensure that if any pipeline is converted to carry hydrogen- even hydrogen blends- that this is done in a way that is truly safe.

The Myth of Hydrogen as an Energy Export Commodity

The Suiso Frontier, transporter of coal-derived #hopium in bulk from Australia to Japan!

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.  It seems that the hydrogen #hopium purveyors are rarely satisfied with the notion that any particular place- my home and native land of Canada for instance- might make enough green hydrogen to satisfy its own needs for hydrogen, but rather, push on to sell the idea that we will become a hydrogen exporter too!

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.

The Energy Beggars

There are also places in the world with large, energy-hungry populations, on small landmasses, who aren’t particularly fond of their nearest land neighbours:  South Korea and Japan come immediately to mind- the option of importing HVDC electricity via a cable which can be “stepped on” by an unfriendly neighbour every time they’re irritated with you is clearly not appealing, if the lessons of the Ukraine war and Russian gas supply are of any use!  And there are numerous other places in the world which don’t want the cost and inconvenience of building out huge renewable and storage infrastructure, for renewables with poor capacity factor and hence need broader grids and storage and overbuilding.

These places also have a long history of importing fossil fuels by ship or by pipeline from distant countries- and, usually, a long history of trying unsuccessfully to get un-stuck from that situation for strategic reasons. 

The simpleminded approach to decarbonizing their economies is to import chemical energy, just in another form, this time without the fossil carbon- assuming that is both technically possible and affordable- as long as it’s by ship, so they can switch suppliers in an emergency.  

Hydrogen Exports to the Rescue!

Matching that obvious source of supply with that obviously thirsty demand, seems a no-brainer.  And at first glance, hydrogen seems to fit the bill as a way to connect the two.  It is already produced at scale in the world: we make 120 million tonnes of the stuff per year as pure H2 and as syngas, albeit almost all of which is produced from fossil fuels, without carbon capture, right next to where it is consumed. 

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.  And whereas there are about 3,000 miles of hydrogen pipeline in the USA, which sounds like a lot, that compares with 3,000,000 miles of natural gas pipeline in the USA.  Most hydrogen pipelines are used for outage prevention among refineries and chemical plants, and to serve smaller chemical users, in “chemical valley” type settings such as the US gulf coast, where you can’t throw a stone without hitting a distillation column.  The long distance transmission of hydrogen is, with very few exceptions, basically just not done.  It’s not impossible- we do know how to design and build hydrogen pipelines and compressor stations- it just doesn’t make sense to do it, relative to moving something else (natural gas, for instance), and then making the low density, bulky hydrogen product where and when it’s needed.

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.  We won’t be able to simply repurpose the old natural gas transmission network, as desperately as the fossil fuel want us to believe we can. We can’t, even if we were to manage to take care of all the problems with the distribution network and all the end-use devices for natural gas that are also not compatible with pure hydrogen.

I had a careful look at a recent academic paper, which compared the shipment of hydrogen and other fuels by pipeline, against the shipment of similar energy via high voltage DC (HVDC):

Energy transmission costs from deSantis paper

Costs of transmission only, from De Santis, Lyubovsky et al Cell Press 2021 https://www.cell.com/iscience/fulltext/S2589-0042(21)01466-8

However, the paper commits what I have been calling the 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…Note in the figure below, electricity and fuels are compared per unit of LHV (lower heating value).  Convert that back to equivalent units of exergy and you’ll see that hydrogen, at $2-4/kg, is vastly more expensive as a commodity than the on-shore wind electricity it would presumably be made from to compare with.

The paper’s authors make other confusing choices, such as running the hydrogen at a considerably lower velocity in the line than indicated by normal pipeline design methods, and these choices affect the conclusions considerably.  So whereas the energy loss for H2 versus natural gas should be three times as high per unit of energy delivered, they conclude it is actually lower than for natural gas.  The losses stated for HVDC, of 12.9% per 1000 miles, are also considerably over-stated relative to the industry’s metrics of performance (see JRC97720 as just one example). 

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.  The pipeline itself isn’t actually the controlling variable!

Another paper I recently reviewed;  d’Amore-Domenech et al, Applied Energy, Feb. 2021

This paper looked at both subsea pipelines for carrying 2 GW of energy to distant locations, and at 0.6 GW delivery from offshore to onshore locations.  This is getting closer to the sort of thing which might be considered to move hydrogen from North Africa to Europe, or perhaps one day from Australia to anywhere else.

It turns out that both subsea pipelines and HVDC cables on the order of 1000 km, already exist.  In fact, much longer HVDC lines are currently under study, including one proposed from Darwin, northern Australia, to Singapore, and another from Morocco to the UK.

The paper’s authors assume that HDPE pipe would be used to transmit the hydrogen at electrolyzer discharge pressures of ~ 50 bar(g), to avoid subsea compressor stations ($$$$$).  The pipeline loses hydrogen by permeation through the HDPE pipe (resulting in losses of high GWP potential hydrogen to the ocean and hence the atmosphere), and the pipe is increased in diameter along its length as the hydrogen expands due to frictional pressure loss.  

Sadly, the paper’s authors also commit the 2nd Sin of Thermodynamics, comparing a MWh of delivered electricity (pure exergy) as if it were worth the same as a MWh of hydrogen higher heating value (HHV).  This is a rather glaring error that seems to have passed right through peer review without comment, and it affects the conclusions significantly.

The authors include an 80% (state of the art best case) efficiency for converting electricity to hydrogen HHV at 50 bar(g), and look at this over a 30 yr lifetime.

The energy lost over 30 yrs for HVDC is 1.2×10^4 TJ

The energy lost over 30 yrs for the H2 electrolyzer and pipeline is 1.2x 10^5 TJ, i.e. ten times higher.

Despite this, they conclude that the lifecycle cost of transmitting energy in the form of hydrogen is a little lower for a pipeline than for HVDC at > 1000 km in length.  That is, of course, entirely cancelled out by the 50% conversion factor and the cost of the device at the end of the pipe, required to convert hydrogen HHV back to electricity again, which were ignored in the paper entirely.  In other words, entirely opposite to their conclusion, their paper leads us to conclude that HVDC is actually considerably cheaper on a lifecycle basis.

For distances longer than 1000 km, the paper concludes that liquid H2 transport is the better option.  We’ll deal with that one next…

We won’t even discuss the shipment of compressed gas in cylinders.  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.

No alt text provided for this image

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/

Here’s my stab at evaluating the export of hydrogen as a cryogenic liquid.

Hydrogen becomes a liquid at atmospheric pressure at a temperature of around -249 C, or 24 kelvin, i.e. 24 degrees above absolute zero.  At that mind-bogglingly low temperature, it is still not very dense.  Whereas compressed hydrogen at 10,000 psig (700 barg) is about 41 kg/m3, liquid hydrogen is only 71 kg/m3.  The improvement in energy density per unit volume is not spectacular.  And whereas to compress hydrogen from the 30-70 bar pressure at the output of an electrolyzer,  to 700 bar(g), can be accomplished for about 10% of the energy in the hydrogen (in the form of work, i.e. electricity, mind you!), liquefying hydrogen takes a mind-boggling 25-35% of the LHV energy in the product hydrogen- again, in the form of electricity to run the compressors- that compares to ~ 10% for liquid methane (LNG).  

Take the exergy of the hydrogen itself into account by applying a conversion efficiency of 50% to the hydrogen at destination to convert it back to electricity, and even without the energy involved in transport of the liquid hydrogen (i.e. whatever energy it takes to move the ship etc.), you get a loss on the order of 50-60%, i.e. you are making very poor use of electricity at the source from which you’re making hydrogen and then liquefying it.

Today, we use liquid H2 as a hydrogen transport medium only very rarely.  The major uses for liquid hydrogen are cooling NMR magnets, and the upper stages of rockets.  That’s about it- there’s no other meaningful use which justifies the extreme complexity and cost of involving a 24 kelvin liquid gas.

The problems of hydrogen liquefaction are considerable, and very technical.  First, hydrogen heats up when you expand it, any time you start at a temperature above about -73 C (200 K)- this behavior arises from hydrogen’s unusual negative Joule-Thomson coefficient above 200 K.  That means, if you want to liquefy hydrogen, you first have to cool it down considerably as a gas.  Generally liquid nitrogen precooling is used for this purpose, necessitating an air liquefaction plant as part of the works.  After precooling, the hydrogen can be liquefied by either a helium refrigeration cycle or a hydrogen Claude cycle (where hydrogen itself is the refrigeration fluid).  

No alt text provided for this image

(image source:  Linde)

The energy input required  is considerable as a result of the difficulty of rejecting heat to the ambient world when starting at such a low temperature.  And although that would be bad enough, hydrogen has another wrinkle:  spin isomerization.  The electron spins of the two hydrogen atoms in a hydrogen molecule can be either aligned (ortho) or opposite (para).  When you condense gaseous hydrogen, you get a mixture of about 75% ortho and 25% para-hydrogen.  As the liquid sits in storage, ortho gradually converts to para, releasing heat.  And that released heat escapes the only way it can- by boiling hydrogen you’ve spent so much energy to cool and condense.  A catalyst is required to carry out the conversion more quickly so the heat can be recovered prior to storage, rather than causing excessive boil-off while the H2 is being stored.

Keeping heat out of liquid hydrogen at 24 kelvin, however, is easier said than done.  Vacuum insulated “dewar” type tanks can be constructed, and for applications like this, spherical containers are the optimal shape with the lowest surface area per unit volume.  A land-based LH2 dewar tank about as big as you can make it, reportedly has excellent performance, where only 0.2% of the hydrogen in the tank,boils off each day.  Any tank smaller than that, or of a less optimal cylindrical shape, allows even MORE than 0.2% hydrogen to boil off per day.  And in transit, on a ship or truck, recapture and re-condensation of the boil-off gas is not possible.  The best you can do is to burn it, hopefully as a fuel, or if in port, to just burn it to prevent it from becoming a greenhouse gas- H2’s global warming potential (GWP) is at least 11x as great as CO2 on the 100 yr time horizon and it is even higher on the relevant 20 yr time horizon.

Once you get to the size of tank possible to put on a truck, 1% boil-off per day is about the best you can do.  Want to make it worse?  Just use a smaller tank!  

Hydrogen’s low density, even as a liquid, is another problem.  Liquid hydrogen, at 2800 kWh/m3 HHV,  contains only about 44% of the HHV energy per unit volume of liquid methane (6300 kWh/m3), i.e. LNG.  On an LHV basis, i.e. if we need work or electricity at the destination instead of heat, it’s even worse- 2364 kWh/m3 for hydrogen versus 9132 kWh/kg for LNG, i.e. about ¼ the energy density per unit volume.  That means either larger energy cargo ships, or several ships to carry the same amount of energy- even if boil-off is managed.

Converting Hydrogen to Other Molecules for Shipment

Confronted with these obvious difficulties, which make hydrogen rather a square wheel for the transport of energy across transoceanic distances, hydrogen proponents don’t give up!   Naturally, they try to shave the corners off hydrogen’s square wheel by converting it to another molecule with more favourable transport properties.  The four main candidates are ammonia, methanol, liquid organic hydrogen carriers (LOHCs), and metal hydrides.  We’ll take these one at a time.

Ammonia

While making green ammonia to replace the black ammonia we rely on to feed about half the humans on earth is inarguably a high merit order use for any green hydrogen we might afford to make in the future, some have gone on to suggest ammonia as a vector by which hydrogen itself may be transported.  

Ammonia is discussed in some detail in my paper here:

https://www.linkedin.com/pulse/ammonia-pneumonia-paul-martin/

The advantage is that it is made from nitrogen which can be collected anywhere from the air.  The downsides are many:

  • Heat is released at the point of manufacture, where energy is already in excess, hence it is likely this energy will be wasted
  • The Haber-Bosch process, while efficient after ~ 110 yrs of optimization, must be operated continuously to have any hope of being economic.  It is high pressure and high temperature, and hence not suitable to cyclic operation as energy supply rises and falls.  This necessitates considerable hydrogen storage if the feed source is renewable electrolysis
  • Breaking ammonia part again to make hydrogen takes heat, at the place where you’re short of energy, and at fairly high temperature (so waste heat from fuelcells isn’t likely to be useful)
  • Ammonia is a poison to fuelcell catalysts
  • When burned in air, ammonia generates copious NOx, requiring yet more ammonia to reduce these toxic and GWP-intensive gases back to nitrogen again (NOx consists of N2O- a 300x CO2 GWP gas which is persistent in the atmosphere, NO- a transient species, and NO2, the toxic one which is water soluble and not persistent in the atmosphere but a precursor of photochemical smog etc. Burn ANYTHING- hydrogen, ammonia, gasoline, your old boss’s photograph etc., and you get all three)
  • Ammonia itself is dangerously toxic, especially in aquatic environments
  • Large shipments of ammonia would be insidious targets for terrorism
  • Cycle efficiencies, starting and ending with electricity, for processes involving ammonia, are on the order of 11-19%, meaning that you get 1 kWh back for every 5-9 kWh you feed

Because substantially all ammonia used in the world is of fossil origin, made from black hydrogen which itself is made from fossils with methane leakage and without carbon capture, and its use literally feeds the people of the earth, I see any use of ammonia as a fuel before black ammonia is replaced with green ammonia, as being basically energetic vandalism.  It has an objective clearly different than that of decarbonization in my view.

Methanol

Methanol, which is currently exclusively made from natural gas or coal by gasification to produce syngas (mixtures of H2 and carbon monoxide), can also be made by producing an artificial syngas by running the reforming reactions backward- starting with CO2 and H2 and catalytically producing CO and H2O.  While that energy loss, generating water by basically “un-burning” CO2, is substantial, as long as a CO2 source of biological or atmospheric origin can be used, methanol has a series of attractive properties:

  • It is a liquid at room temperature, not just a liquefied gas, so its cost of storage is very low per unit energy (though tanks do need inerting, which is unnecessary for gasoline or diesel)
  • It is toxic, but nothing even close to the toxicity of ammonia
  • Its energy density is lower than that of gasoline and diesel, but once made, it is considerably more favourable as an energy transport or storage medium than ammonia or hydrogen
  • It may be reformed at modest conditions back to synthesis gas again
  • It is a versatile chemical used to make many other molecules, including durable goods such as plastics, and if we are not foolish enough to burn those materials at end of life, it can be a mechanism for carbon sequestration

The big challenge for methanol is that source of CO2.  Direct air capture wastes too much energy in a needless fight against entropy, so forget about it as a source of CO2 to make methanol in my opinion.  Unless a concentrated source of non-fossil CO2 (a brewery, anaerobic digester or biomass combustor) is colocated with the source of electricity and hence hydrogen, the shipment of liquid CO2 by sea to make methanol from, replicates many of the economic challenges of LNG and liquid hydrogen.

While making green methanol is also a clearly no-regrets use of any green hydrogen we may happen to make, methanol as an “e-fuel” is a challenging issue for the above-noted reasons.  Obtaining decent economics per delivered joule would seem very challenging indeed.  Therefore, the hopes of companies like Maersk that they will be able to fuel their ships on fossil-free methanol in the near future, seem perhaps decades premature at best.

The use of methanol as a vector for the transmission of hydrogen for use as hydrogen, makes no sense to me at all.  Reforming the resulting CO back to CO2 and more H2 again using water is possible, but too costly and lossy to make energetic sense to me.   

Liquid Organic Hydrogen Carriers (LOHCs)

These are liquid organic molecules like methylcyclohexane, which can be dehydrogenated to produce hydrogen and toluene.  The toluene, also a gasoline-like liquid, can be shipped back to wherever hydrogen is in excess, and hydrogenated to produce methylcyclohexane again.  Numerous molecule pairs are candidates, each with its suite of benefits and disadvantages.

The big disadvantages of LOHCs are similar to those of ammonia:

  • Parasitic mass is considerable – for MCH/toluene, only 6% of the mass of MCH is converted into hydrogen at destination, and the other 94% of the mass has to be shipped in both directions.  On this basis alone, LOHCs are not good candidates as transportation fuels (i.e. fuels for use to move ships, trucks etc.) in my view
  • Like with ammonia, heat is produced at the place where you have energy in excess, and energy is required (again at high temperature) to supply the endothermic heat of dehydrogenation at destination.  The temperatures required are too high for waste heat to be used
  • There will inevitably be some loss of the molecules in each step.  Yields will never be 100%
  • Considerable capital and operating/maintenance cost will be required at both ends, for the hydrogenation/dehydrogenation equipment.  These are chemical plants, not simple devices like fuelcells or batteries, and hence they will be economical only at very large scale if ever

LOHCs don’t seem to have a good niche in my view. They are useless as sources of hydrogen for transport, below the size of perhaps a ship.  While some, such as Roland Berger in a recent report:

https://www.rolandberger.com/en/Insights/Publications/Transporting-the-fuel-of-the-future.html

…tend to conclude that LOHCs are a better way to do “last mile” transport of hydrogen under certain circumstances than some of the other options, that is again really a desperate reaction to the impracticality of hydrogen itself as an energy distribution vector, rather than a vote of confidence in the technology itself.

Solid Metal Hydrides

Hydrogen reacts with both the alkali metals (Li, Na) and alkaline earth metals (Ca, Mg) as well as with aluminum and other elements, to form hydrides, i.e. where hydrogen is in the form of H- ion.  These hydrides can form at the surface of the metals, providing a means of “chemi-sorption” for the storing of hydrogen at lower pressures than that required for pure compressed gas.  However, the cost of the lower storage pressure is greatly higher (parasitic) mass, i.e. useless for transport applications, and the need to use heat (generally provided by electric heating) to desorb the hydrogen when required.  

The hydrides themselves can also be made as pure solid substances, such as “alane” (AlH3), magnesium hydride (MgH2) or NaBH4 (sodium borohydride).  These metal hydrides react with water, producing twice as much hydrogen as is found in the original hydride molecule.  For instance:

MgH2 + 2 H2O ⇒ 2 H2 + Mg(OH)2

Sadly, there’s the rub:  aside from the considerable problem of parasitic mass, in each case, the re-formation of the original hydride involves two steps:

  • Production of the metal again from its hydroxide, and
  • Production of the hydride by reaction with hydrogen at high temperature and pressure

The energy cycle efficiency of all such schemes involving metal hydride reactions with water are therefore negligible, tending to be in the single digits, because the process of re-making the metal and then the hydride is so energy-intensive.  Wasting 10 joules merely to deliver 1 joule at destination is not something we’re going to do at scale, or at least that’s my hope!

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!)

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.  What kind of cars they drive is really irrelevant:  the energy-intensive industry that is the basis of their economies, will simply need to move offshore, given that their economic competitors would be using energy which costs 1/10th as much per joule, and using that energy directly rather than through a lossy middleman.  Either that, or they’ll need to switch to a service economy and focus on extreme energy conservation- which might be best.

However, what concerns me is that neither the Japanese nor the Koreans are ignorant in these matters.  If I saw both countries building out renewable offshore wind generation like mad, or even going nuts building new nuclear plants, perhaps I’d believe that their interest in decarbonization via hydrogen was truly in earnest, to sop up even at great cost, the residual that they can’t manage to supply locally as electricity.  Rather the focus on hydrogen looks more like an attempt to put off the energy transition until some future date when hydrogen becomes “economic” as an option, burning fossils and fooling around with meaningless pilot projects (JERA burning ammonia in 30% efficient coal-fired power plants, anyone? Or worse still, this brown coal gasification with liquid hydrogen shipment nonsense?) in the meantime.  Because, frankly, looking at the various importation options, the future in which hydrogen as an energy transport vector becomes “economic” across transoceanic distances is likely “never”, relative to more sensible options.

Disclaimer: whereas I always try to be accurate, I’m human and therefore fallible. If you find anything wrong in my article, which you can demonstrate to be wrong via good, reliable references, I’ll be happy to correct it. That’s why I publish on a vehicle like LinkedIn, rather than in journals that remain unedited and therefore preserve my errors in amber!

Oh, and if you don’t like my opinion on these matters, by all means feel free to contact my employer, Spitfire Research Inc.

The president (i.e. myself) will be happy to tell you to get lost and write your own article, with even better references, if you disagree.