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Powerpaste, a hydrogen technology for small vehicles

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Re: Powerpaste, a hydrogen technology for small vehicles

#71

Post by namibj »

NickM wrote: post #13
hannob wrote: post #11

Earlier quoted context omitted.

The problem with every hydrocarbon-based fuel is that you need the carbon. 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 o…

or direct air capture (expensive and inefficient) 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 t…

From some research into the feasibility of an indoor CO2 scrubber that targets pre-industrial concentrations (100~200 ppm), using a sodium hydroxide solution in a simple counter- or cross-flow packed-bed wet scrubber does a good job at scavenging CO2 from the air down to 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.

Re: Powerpaste, a hydrogen technology for small vehicles

#72

Post by plun9 »

Animats wrote: post #6

Storage of hydrogen in a solid has come around a few times already. University of New South Wales. (2020) [1] Lawerence Livermore Lab (2018) [2] University of Salford (2006) [3] 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.[…

What's wrong with Bloom Energy Servers?

Re: Powerpaste, a hydrogen technology for small vehicles

#73

Post by adrian_b »

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…

This magnesium hydride technology certainly does not solve the hydrogen storage problem in the sense of being better than using hydrocarbons for energy storage, as the living beings have been doing for billions of years.

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.

Re: Powerpaste, a hydrogen technology for small vehicles

#74

Post by usrusr »

choeger wrote: post #15

I know this sounds awfully complicated to handle (and recharge), but I think the market for practical applications of H fuel is existing, so these ideas can be evaluated in practice. 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.

If storage losses are sufficiently low and the converter hardware is small/cheap enough maybe the process could also find a market as a sealed system, a factory-recyclable single use battery. How about a 3HU rack form factor that if installed in groups automatically coordinates depletion to oldest-first? Main market would be what is currently served by rarely refueled backup generators but it could have a huge long tail of undiscovered use cases wherever power density of batteries is insufficient and diesel generators suffer from noise or bad maintenance, but where fuel price isn't the main concern. Pricing model could be as easy as implementing effectively fuel + rent with a deposit that shrinks over time (blockchain the device log if it makes you feel better somehow). Once established for server rooms, fishing cabins and whatever other niche it will find it might even end up mainstream with BEV that opt for just offering an RX rack over killing range anxiety with half a ton of extra rechargeable that is never really needed. Approaches like this are usually made impossible by chicken/egg problems, but if it starts in a niche both technology and distribution can grow organically. Remember how Tesla was "the laptop battery car" while incumbents insisted on starting all their BEV projects (they did exist) by reinventing the battery?

Re: Powerpaste, a hydrogen technology for small vehicles

#75

Post by adrian_b »

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…

Bound hydrogen is what is in gasoline and any other hydrocarbons. So it is nothing new, but a method for storing energy already used for a few billions of years, since free dioxygen appeared on Earth.

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.

Re: Powerpaste, a hydrogen technology for small vehicles

#76

Post by imtringued »

adrian_b wrote: post #73
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…

This magnesium hydride technology certainly does not solve the hydrogen storage problem in the sense of being better than using hydrocarbons for energy storage, as the living beings have been doing for billions of years. 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 arti…

Are you seriously suggesting we should waste our renewables and nuclear to capture CO2 from the atmosphere and then turn that stuff back into hydrocarbon fuels only to turn 80% of it to waste heat?

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.

Re: Powerpaste, a hydrogen technology for small vehicles

#77

Post by jcims »

imtringued wrote: post #76
adrian_b wrote: post #73

Earlier quoted context omitted.

This magnesium hydride technology certainly does not solve the hydrogen storage problem in the sense of being better than using hydrocarbons for energy storage, as the living beings have been doing for billions of years. 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 arti…

Are you seriously suggesting we should waste our renewables and nuclear to capture CO2 from the atmosphere and then turn that stuff back into hydrocarbon fuels only to turn 80% of it to waste heat? 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 ener…

It wouldn’t be a permanent solution but there are trillions of dollars worth of infrastructure built around petroleum fuels. Moving personal vehicles and metro transit to EVs is straightforward, but it’s less so for freight/marine/aircraft and doesn’t account at all for industrial uses of petroleum fuels.

Re: Powerpaste, a hydrogen technology for small vehicles

#78

Post by adrian_b »

imtringued wrote: post #76
adrian_b wrote: post #73

Earlier quoted context omitted.

This magnesium hydride technology certainly does not solve the hydrogen storage problem in the sense of being better than using hydrocarbons for energy storage, as the living beings have been doing for billions of years. 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 arti…

Are you seriously suggesting we should waste our renewables and nuclear to capture CO2 from the atmosphere and then turn that stuff back into hydrocarbon fuels only to turn 80% of it to waste heat? 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 ener…

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 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.

Re: Powerpaste, a hydrogen technology for small vehicles

#79

Post by danans »

ncmncm wrote: post #64
danans wrote: post #41

Earlier quoted context omitted.

> low energy input (direct sunlight) 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.

2% efficient, at best. 1000J in, 20J worth of wood and leaves out. Burning it, you get back only a fraction of that, with much of it carried away in the smoke.

That sounds about right. It takes a whole lot of energy to reverse entropy at the margins. Then again life exists basically at the margins of the massive energy output of the sun.

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.

Re: Powerpaste, a hydrogen technology for small vehicles

#80

Post by diggernet »

kaliszad wrote: post #59
corty wrote: post #9

Earlier quoted context omitted.

Ammonia is one of the less pleasant chemicals one could use. I'd rather have Hydrogen-exuding paste than Ammonia in an accident. The Hydrogen might explode. But the Ammonia definitely will hurt you.

Ammonia is quite ok. You can smell it :-) You can put it into water, where it is quite stable. We know how to handle it at industrial scale because of fertilizers.

Yes, you can smell it, when drastically diluted in water (which, as you say, is stable) such as for a household cleaner. But in a concentrated form such as that required for use as fuel, if you smell it, it will kill you. Quickly.
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