One thing they didn’t mention is energy used for round trip per unit of H2 and cost of the material itself. Neither was discussed there. Many similar materials exist already.
Many CO2 neutral pathways with other molecules exist. Amonia, methanol, ethanol, DME, urea, formic accid and so on.
PS: If you’re into this stuff, keep an eye on the Fraunhoffer institude. They have many cool projects. (I am not affiliated with them in any way)
I also did not see anything about recycling the carrier materials which seems suspiciously odd in a context so closely related to environmentalism.
But the big picture news is that this is another datapoint that shows how, like you said, the solution space for what I like to call "bound hydrogen" is apparently not exhausted at all yet. In recent months I have seen (all on hn) power-to-ammonia, that Dutch group that proposes iron powder as a heat fuel of roughly coal performance that is recycled by reducing the returned iron oxide powder with hydrogen (and started to fuel a brewery as a pilot) and now this "powerpaste" which sound like straight out of the back to the future future. The claimed energy density is absolutely amazing! If the required infrastructure hardware is small enough it could be a gamechanger for BEV: size the battery to be sufficient for 80% of driving days and install the "1000 miles extra" block where it can be accessed for replacing, e.g. where an ICE car would have it's engine. Chances are the extra miles fuel won't be cheap, but you'll surely be able to buy a lot of RX refills for the battery cost saved if a strong majority majority of your driving can be done on battery only.
I always considered the term "hydrogen economy" silly because of how annoying H2 is to deal with at scale, but "bound hydrogen" can change that in so many ways. It's almost as if hindsight was trying to win a bet or something wrt how we look back at George W. Bush, first him appearing so unexpectedly presidential compared to a certain successor, then suddenly hydrogen economy ceases to be a joke. What's next, discovery of actual WMD so they could have well stayed honest had they just looked a little harder? Harris becoming president after "pretzel incident 2"? Bound hydrogen is the most exciting technology field since many years.
The only chemical substances that can approach hydrocarbons in energy density must be composed of light elements, preferably able to lose many electrons by oxidation.
So aluminum hydride would be better from this point of view than the magnesium hydride and ammonia is a very good solution if it is desired to avoid making hydrocarbons from carbon dioxide.
Nevertheless, nothing practically usable beats hydrocarbons in energy density. However it is unknown yet whether another form of storage, e.g. ammonia or another hydride a.k.a. "bound hydrogen", would not be better for the efficiency of a complete cycle of storing the energy by chemical synthesis, then recovering it using a fuel cell or a thermal engine.
Specific energy of magnesium hydride is 7.7% of H2. Energy density by volume is 13.3 MJ/L, about 40% that of gasoline. The fuel cell should be more efficient than an internal combustion engine, however, so you probably make back the difference.
Sodium is very easy to handle. There is no need for large pressure or any bonding elements. The hydroxide can be turned into sodium again by well known processes that were used on industrial scale more than 100 years ago already. This process and the "burn" of sodium with water both release hydrogen as a by-product. This could solve the winter energy storage issue. Also you could quite likely safely transport sodium in former oil tankers or by pipe if heated to a bit more than 100 °C/ or in the form of concentrated hydroxide (the "waste")... so the infrastructure is mostly there.
As you all well know, original sodium can be extracted from regular NaCl salt that we have plenty of in sea water and salt mines.
Best of all, sodium reacts so rapidly, it could under minor adjustments replace diesel in +- regular engines too. (That is also the contents of one of the patents.) That is of course not so efficient, but there is a large installed base.
It only blows up when it touches water.
Sodium is not remotely in that class.
More numbers on the mass of the crust in .
For many applications, using magnesium hydride should be much better than using compressed or liquefied hydrogen, but it remains far worse than gasoline despite the misleading statement from the article "POWERPASTE offers a range comparable to – or even greater than – gasoline".
This statement is false. Magnesium has twice the atomic weight of carbon and the hydrogen from magnesium dihydride provides only 2 electrons per magnesium atom, instead of 6 electrons per carbon atom, as in gasoline.
Because of that, a fuel cell using hydrocarbons (those exist, but the current prototypes do not have an acceptable lifetime) would have a 6-times higher energy capacity per fuel weight.
While the energy per weight of magnesium dihydride is very poor, the energy per volume is more decent, because gasoline has low density.
Nevertheless MgH2 has only twice the density of gasoline, which means that the hydrogen content per volume is about the same as for gasoline. Because when used in a fuel cell gasoline would provide 3 times more current per volume, magnesium hydride remains uncompetitive regardless how the storage cost is computed.
Pure dihydrogen would provide a voltage around 20% higher than hydrocarbons in a fuel cell. That is much too little to make a difference compared to factors of 6 and 3 in current per weight and current per volume.
Instead of wasting time and money to search for impossible ways of storing hydrogen, the energy research should be directed to improving the (already existing) technologies for making hydrocarbons from carbon dioxide and for making hydrocarbon-using fuel cells with better characteristics.
Seriously, man. There is no future where this is going to happen. We are not going to replace waste primary energy generated by fossil fuels by wasting our low carbon energy. We are going to reduce the amount of waste energy and thus lower the overall demand for primary energy. The energy density of gasoline is worthless if the efficiency is garbage.
A transition from ICEs to EVs works just fine without expanding power generation significantly precisely because we get rid of the inefficiency.
It is likely that the efficiency can be improved a lot but it is improbable that the efficiency of the complete cycle could reach much above 50% any time soon.
So you are right, for the best efficiency rechargeable batteries are the best.
Nevertheless, there are many cases when a maximum autonomy time is more important than the efficiency, together with the possibility of storing the energy for an indefinite time without any losses (e.g. due to self-discharge). In those cases hydrocarbons are optimal.
So both technologies are necessary and each has uses for which it is the best.
For example, a healthy human can live about one month without eating, due to the stored hydrocarbons, i.e. fat.
No future robot using lithium batteries will be able to do that, while performing a similar activity level and having the size of a human.
What makes you think that? I thought internal combustion engine efficiency is widely believed to have hit its reasonable limits?
And a hydrocarbon cycle doesn't necessarily have to be all that efficient to be practical, if the primary energy input is renewable, and the cycle is largely closed (IE, a plant somewhere consumes the same stuff the vehicle produces). The portability, safety, ease of handling, and rapid simple refill of hydrocarbons outweighs a lot of other factors at the point of use for some jobs, mainly vehicles.
Most other energy-consuming jobs can use a wide variety of other forms of energy, so this is mostly about vehicles, not energy usage in general. This is why your furnace doesn't burn gasoline.
Anyway what they're saying is that entire cycle can probably be improved a lot from what we can manage today.
We can surely continue discovering new and better ways to make a fuel cell that consumes a hydrocarbon.
And we are definitely still discovering a variety of different ways to synthesize hydrocarbons. Some have a lot of overhead like planting corn and eventually getting a small quantity of a low-density hydrocarbon (alcohol).
Some are more direct bulk inustrial processes that are fairly cyclic and lower overhead than farming.
We already have a variety of examples of both the consumer and generator parts of the cycle and we are definitely not done discovering all the possibilities.
Lithium battery tech typically trades off power rating and energydensity (Earlier - how much acceleration and range, nowadays with better batteries - how fast you can fill up) for other benefits.
This tech prioritises safety and power rating at some production cost and supply chain.
Gasoline gives emissions and engine complexity vs other conveniences
Rockets prioritize both power and energy density over everything else and uses LH2 and LOX dealing with cryo complexity
Keep in mind that both rockets and ion engines actually have fairly low realized energy density, because they can't just rely on atmospheric oxygen.
The racket it made, with a loud kerchunk splitting the balls, and the hissing immediately following, was just slightly terrifying.
This paste seems a good deal saner in comparison.
“The speed of the reaction is what distinguishes an explosive reaction from an ordinary combustion reaction.” - Wikipedia on explosion.
“An internal combustion engine nominally operates on a controlled rapid burn.” - WP on combustion.
Effective explosives have the exact same chemical goals and nearly the same thermodynamic goals.
If that isn’t a carefully controlled explosion I don’t know what is. I mean, come on, a piston moving up and down thousands of times per minute isn’t explosive enough for ya?
The alternative is a detonation, i.e. engine knocking. This causes a spike in cylinder pressure and will quickly destroy an engine. It is for this reason that engines are absolutely not trying to burn fuel as quickly as possible.
This is a difference of detonation vs. deflagration. Whether you consider both of these to be forms of explosions is a semantic issue.
No, the speed of burn in an internal combustion engine is not explosive:
“Knocking (also knock, detonation, spark knock, pinging or pinking) in spark ignition internal combustion engines occurs when combustion of some of the air/fuel mixture in the cylinder does not result from propagation of the flame front ignited by the spark plug, but one or more pockets of air/fuel mixture explode outside the envelope of the normal combustion front.” - WP on engine knocking, which is undesirable and may damage the engine.
If it ignites earlier, the pressures are far higher than normal. If it doesn't trigger, it won't for the complete cycle, as the piston expands and the temperature drops.
Free-piston engines have an advantage there, as they don't force the compression ratio with a crankshaft.
They would decelerate the piston somewhat earlier and harder than necessary, but there are no bearings that have to handle this load.
Their issue has more to do with extracting energy from the oscillation, and keeping a stable operating point that's neither prone to stalling nor prone to runaway.
It's both, no? Aren't all chemical-based explosions considered combustion?
If "explosion" means "a violent release of energy", that seems a reasonable word to describe what happens in a cylinder in about ~5 ms.
Indeed, it seems it's an hybrid of your fellow's tech, using magnesium both as a substrate for H2 and as a reducing agent for water: Mg + 2H2O -> Mg(OH)2(aq) + H2(g)
Less explosive than Na, hopefully :)
Now there are other groups trying to figure out if they can increase the power capacity of batteries by replacing the electrolyte. Which sounds like a fuel cell/battery hybrid to me.
University of New South Wales. (2020) 
Lawerence Livermore Lab (2018) 
University of Salford (2006) 
Older approaches involved lithium hydride chips. Not ICs, just chips of metal. The University of New South Wales system used titanium and other secret ingredients. That one is being offered as a product for stationary storage, Real Soon Now. Original article said it would ship by the end of 2020, but it has slipped to June 2021. You can pre-order the "launch edition" now. It's not a Kickstarter, but it's close.
Unclear if this is a good idea, or the next Bloom Energy Server.
OK sounds great! so this stuff is more sensitive to moisture than LiPo batteries and yet has to be dispensed somehow; that's going to be fun.
I'd like to see the reaction, here... We talking a little steam or dropping sodium chunks into a pond?
Seriously, though, this sounds like a horrible technology. Synthesize fancy goo that is unstable when wet. React with water to make hydrogen (itself moderately dangerous). Produce some kind of slush containing magnesium hydroxide (presumably) and miscellaneous organic crud as waste. What, exactly, happens with the waste?
At least magnesium hydroxide is not as nasty as sodium or potassium hydroxide, but you still don’t want to get it on your skin if you can avoid it.
In any case, what a substance does when rained on is not very relevant for a fuel that is kept in a fuel tank at all times. By the time it's exposed to the weather, the vehicle must have crashed and in such a circumstance most safety guarantees are out of the window anyway.
There are a number of projects planning to create green ammonia at scale, e.g. this: https://asianrehub.com/
Ammonia is already made from hydrogen today, making that green is pretty straightforward, you just need enough clean electricity. Just get the hydrogen from electrolysis, the ammonia synthesis process itself is well established technology.
The main theoretical point of hydrogen is very high specific energy per mass but it is essentially purest acidic gas and a pain. Bonding it to something else mitigates it so why 3 H per N instead of 4 H per C? Both are toxic gases at this point leaving ammonia's main advantage in the context being its own oderant.
You get that from CO2. But then you need to get the CO2. Where do you get it from? From a fossil-based plant? Well, ideally you'd want to get rid of those, not exactly smart to create incentives to keep them running. The alternative is either biomass (problematic) or direct air capture (expensive and inefficient). (Some insightful discussion on green methanol: https://www.youtube.com/watch?v=jXACyUxxBts )
With non-carbon based fuels like hydrogen or ammonia you skip that problem (air is 78% nitrogen, much easier to extract).
The big question in my mind is whether direct air capture is inherently expensive and inefficient...or if this is just a chicken/egg problem where we haven't invested time and money in making it cheaper because it's expensive, and it's expensive because we haven't invested time and money in making it cheaper.
I don't know enough about physics and chemistry to answer the question on what the theoretical lower bound on cost might be.
Regeneration is easy in another counter-flow packed bed reactor, this time reacting with a CaOH bed to exchange the carbonate ion. The output is mostly CaCO3, with some NaOH contamination. This can probably be washed for home-scale disposal (and recuperation of the NaOH), while the industrial scale process follows up with thermally decomposing the CaC03 into CaO and CO2. This can be very pure CO2 suitable for direct sequestration, if the thermal energy is provided electrically or by combusting a hydrocarbon with purified oxygen.
So the lower cost would seem to be that of calcinating the limestone (at 900~1050°C), and a trade-off between cap-ex and op-ex for the scrubbers. The lower the flow rate, the less energy is needed to force the solution and air through the packed bed.
But afaik freezing the CO2 out of the exhaust from fossil fuel power plants and industrial processes requires less energy than the calcination, and is therefore economically favored until all easy opportunities have been converted.
The calcination seems to require about 800 Wh/kg of CO2. At typical electricity rates in favorable locations of 10 ct/kWh, this makes 1 kg DAC-CO2 cost >~8 ct. If you want the carbon out of this, you're looking at 1.25 $/kg of DAC carbon. Assuming perfect electrolyzation of the CO2.
Even as a waste product from separating Nitrogen, Oxygen and Argon from the air, its still expensive (retail its ~$1/lb of liquid CO2).
Have a look at a tree...
I suppose it's possible that billon years of evolution has ended on a local optimum for low energy input (direct sunlight), and we might revolutionize it with high energy (eg: high voltage electricity, fusion etc) - but I doubt it.
Direct sunlight is actually quite powerful, around 1kW/m^2 at sea level.
Although I'd guess most trees aren't particularly efficient at absorbing CO2 vs the energy they consume, which makes sense, since they only have to be as efficient as necessary to survive.
But still, I'm not holding out that any such human created sunlight to chemical energy storage process is going to best the 20% conversion efficiency of solar panels * 95% round trip efficiency of modern batteries any time soon.
I know there are companies trying to make synthetic fuels from atmospheric C02 + renewable electricity for very specific use cases that are challenging for batteries (i.e aviation) but the jury is still out on whether that will work at scale.
The prices of extracted petroleum and CH4 will plummet as carbon taxes increase and demand decreases, until only the absolute cheapest extractors remain, and those products will be used only where the carbon tax can be afforded: mainly aircraft, and then only until the much more cost-effective LH2-powered airframes ground them. (Those will be fueled with LH2 generated on the spot at airports using regional solar.)
Solar-powered CO2 capture projects will bid for carbon tax credits. Only the cheapest processes will win bids, so will not produce fuel. Probably they will blow it underground, in places where the ground is porous, and let it react with rocks down there. Turning it into fuel and selling it will not qualify as reclaiming, because the carbon doesn't stay claimed.
That said: I'm all for investing in DAC technology. We will definitely need it for some sectors. But you need to consider the costs and if there are alternatives they will in many cases make more sense.
Not sure why they are trying to brand in all caps, but highly recommend adding Dresden to your bucket list post Covid. Most beautiful city I have experienced.
Also, not every invention has to save the world. So this paste might become useful for drones or in spacecraft. Depending on the energy density it might even be very usable for electrified air travel.
Refueling something like this would be faster than recharging, but if "quick recharge" is part of your requirements then it's straightforward to make a scooter battery swappable and maybe even standardized across brands.
Power outlets are ubiquitous, and these things just don't use enough energy to be more than a rounding error on anyone's electric bill (100 (scooter) km worth of energy is roughly the difference between washing your hands in hot water instead of cold water for 30 seconds).
There might a weight savings but lithium ion is something like 60 grams per kilometer of range for a light, slow vehicle. So a reasonable range battery is not prohibitively heavy even for a vehicle that you have to carry.
I'm sure there's a use case for this stuff, and scooters are trendy right now, but I don't think the two are a good match.
That said, the operational infrastructure requirements for this seem to be much easier to satisfy with off the shelf technology than hydrogen storage which, frankly, is really really hard.
More info here: https://en.wikipedia.org/wiki/Magnesium
I suspect some variation of these processes could convert the spent fuel back to metal and then the hydride form or something like that.
Although, looks like much of this is done with hydroelectric processes (same with Aluminum production).
Seems like it would be easier to accomplish in batch processing where you could cool to a point where you were under the activation energy of the magnesium reaction with air.
But the really awesome thing is that one could set up fuel reprocessing facilities in unused areas with high solar flux (aka deserts) and transport the resulting magnesium back to be made into paste again.
And the reason that is cool, is because one of the challenges with solar power is that electrical transmission wastes energy and storage is finite. Storing energy in chemical bonds like plants do is a MUCH more effective way of harnessing solar energy for later use in the production of things.
- small vehicles will have small, quickly, easily, cheaply rechargeable batteries, likely easily recharged from even plain old wall sockets
- LFP batteries will probably get good/cheap/dense enough to handle almost all 50-100 mile small vehicle ranges, its doubtful a hydrogen engine will get cheap enough soon enough
- and again, LFP and EV/battery tech is in the mainline of economies of scale, buildout, production, and cost cutting, and will be for a decade more. This stuff will need to compete at a price point 50% lower or less than today's.
- and it still has the sourcing problems. green hydrogen still smacks of the "clean coal" whitewash with a different label
If we had unlimited, clean power (hello fusion!) it might be viable.