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Powerpaste, a hydrogen technology for small vehicles

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Re: Powerpaste, a hydrogen technology for small vehicles

#91

Post by s0rce »

ChuckMcM wrote: post #88
s0rce wrote: post #86

Earlier quoted context omitted.

There are a few industrial processes used to convert magnesium oxide to metal, for example the Pidgeon process ( https://en.wikipedia.org/wiki/Pidgeon_process ) which I still remember learning about in my Materials Science undergrad in Toronto. 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 som…

Thank you. That is excellent information. I wonder if anyone has looked into concentrated solar as the heat source for small batch magnesium production using that method.

Appears so: https://www.sciencedirect.com/science/article/abs/pii/S09596...

Although, looks like much of this is done with hydroelectric processes (same with Aluminum production).

Re: Powerpaste, a hydrogen technology for small vehicles

#92

Post by Reason077 »

usrusr wrote: post #27
tomas789 wrote: post #8

Solving hydrogen storage has great implications. Hydrogen has high gravimetric energy density (1 kWh worth of H2 is light) but very low volumetric density (1 kWh takes up a large volume). Easy solutions are compressed hydrogen (H2 is a small molecule and easily escapes even through a material, steel embrittlement and energy for compression are big issues), cryogenic cooling (energy intensive and cryocoolers have sign…

> One thing they didn’t mention is energy used for round trip per unit of H2 and cost of the material itself. 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 apparentl…

> "The claimed energy density is absolutely amazing!"

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.

Re: Powerpaste, a hydrogen technology for small vehicles

#93

Post by ChuckMcM »

s0rce wrote: post #91
ChuckMcM wrote: post #88

Earlier quoted context omitted.

Thank you. That is excellent information. I wonder if anyone has looked into concentrated solar as the heat source for small batch magnesium production using that method.

Appears so: https://www.sciencedirect.com/science/article/abs/pii/S09596... Although, looks like much of this is done with hydroelectric processes (same with Aluminum production).

Nice! And yikes! "Mg recovery in the outlet products was identified as one of the most critical process challenges because of the pyrophoric property of the produced nanopowder and its strong oxidation reactivity with air."

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.

Re: Powerpaste, a hydrogen technology for small vehicles

#94

Post by s0rce »

alexchamberlain wrote: post #89
s0rce wrote: post #85

Earlier quoted context omitted.

Doesn't most of what you said also apply to magnesium? Seems like we'll never run out (2.5% of earth's crust), there are well established methods to refine it and you just react the hydride with water to generate hydrogen.

Hehe never run out. Like we never ran out of IPv4 addresses or crude oil... I think any solution needs to be cyclic.

Looks like there is ~10^−8 earth masses of oil and coal [1]. I can't seem to find the mass of magneisum on earth but its 2.5% of the earth's crust, which is apparently More numbers on the mass of the crust in [3].

[1] https://osf.io/dkmwy/download [2] https://en.wikipedia.org/wiki/Earth%27s_crust [3] ttps://ui.adsabs.harvard.edu/abs/2007AGUFM.V33A1161P/abstract

Re: Powerpaste, a hydrogen technology for small vehicles

#95

Post by RealityVoid »

jonsen wrote: post #38
jackyinger wrote: post #33

Earlier quoted context omitted.

Internal combustion engines do in fact attempt to burn fuel and oxidizer at maximum stoichiometric efficiency, and they also are trying to burn it as quickly as possible to capture all of the heat rather than exhausting a partially burnt mixture and wasting fuel. 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…

> ...trying to burn it as quickly as possible... 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/fue…

Sounds to me that the problem is not the speed of the explosion that happens when engine knocking, but the timing of it.

Re: Powerpaste, a hydrogen technology for small vehicles

#96

Post by Brian_K_White »

eru wrote: post #65
petre wrote: post #62

Earlier quoted context omitted.

> Sodium is very easy to handle. It only blows up when it touches water.

From an engineering point of view, that might still count as easy. Especially compared to hydrogen.

You can carry gasoline in an open pail, spill it all over yourself, and even throw a lit cigarette right in the pail, all without harm, all while having very high energy density.

Sodium is not remotely in that class.

Re: Powerpaste, a hydrogen technology for small vehicles

#97

Post by Brian_K_White »

gspr wrote: post #84
adrian_b wrote: post #78

Earlier quoted context omitted.

You are right that the main disadvantage of storing energy in hydrocarbons is the low efficiency of the complete cycle, which is indeed around 20% today. 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 man…

> It is likely that the efficiency can be improved a lot What makes you think that? I thought internal combustion engine efficiency is widely believed to have hit its reasonable limits?

Internal combustion, or any form of combustion, is only one way to get energy back out of a hydrocarbon.

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.

Re: Powerpaste, a hydrogen technology for small vehicles

#98

Post by ngcc_hk »

ma-int wrote: post #69
oh_sigh wrote: post #61

Why don't we "just" synthesize hydrocarbons similar to what are present in gasoline/diesel/etc? We already have all the infrastructure for using, handling and distributing it.

Because the well-to-wheel efficiency of internal combustion engines isn't that good to begin with. Add lossy synthesation and it gets even worse. If we had unlimited, clean power (hello fusion!) it might be viable.

It is called solar. Wonder it is not allowed er Sahara or other desert.
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