Electrical Fuel from Sand?

[Eumelia]

Originally Posted by minaret

Entertains me that all these luddites keep saying it'll never happen and to "stop thinking" when I posted a number of links to the actual product, which is on the market now, quite a ways back.

Entertains me when someone makes up silly names for people whose perspective they don't understand. I considered fuel cells very carefully but decided they were expensive and inconvenient to operate. Photovoltaic makes a lot more sense to me.

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[Simonsays]

Originally Posted by Eumelia

Entertains me when someone makes up silly names for people whose perspective they don't understand.

hmm, you might want to check you dictionary.
nothing made up there.

[StuM]

Maybe you should look it up. As Inigo Montoya said. I don't think it means what you think it means

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[Eumelia]

Is it really so important to double-down on a silly gratuitous insult? I was hoping we could get back on topic

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[denverd0n]

Haven't seen any "Luddites" in this thread. Have seen quite a few people who understand high-school physics, and as such know that sand is not a fuel and that there is no currently available technology that comes anywhere close to making sand a fuel.

Alcohol as a fuel? Well, sure. That's a whole different matter. No one has said that that is not possible, or even that it doesn't already exist (as it obviously does).

So, for me, it is kind of entertaining that someone would think that a basic understanding of remedial physics makes one a "Luddite." I guess you would have to take that as a compliment. Having studied a little bit of physics at the college level, God only knows what sort of name-calling I would qualify for!

[newhaul]

Well Don I suppose we could call you the pindar or some other arcane name

[Sailor_Hutch]

Originally Posted by MarkSF

The image shows hydrogen and oxygen inputs. BTW, that was the real reason for the Hindenberg disaster - leaks which allowed oxygen to build up in the hydrogen. And I'm supposed to have tanks of both on the boat? Hold me back!

Think I'll stick with diesel, thank you very much.

The combined thrust of the second stage's five (liquid hydrogen + liquid oxygen) engines is just over a million pounds, or five times that of the third stage's single J-2 engine. Development of the original hydrogen tanks was difficult because the low boiling point of hydrogen (-253 °C) required insulation sufficient to prevent transfer of heat from the outside and the comparatively warm (-183 °C) liquid oxygen.


From: Government archives ref Saturn Rocket:

http://history.nasa.gov/SP-350/ch-3-2.html

[TxThundr]

Understanding that Fuel Cells are a net negative energy source, it seems they come into play if you have a Wind/Solar setup that produces more energy than you can store in your current battery bank.

If stored Hydrogen has a greater density of Energy storage (or potential energy storage) than a battery, then I would think it would make sense to store your excess Solar/Wind energy in stored Hydrogen then just throwing it away.

From a Tesla forum discussing fuel cells:
Compressed hydrogen has an energy density of 142 MJ/kg.
Lithium ion batteries have an energy density of 0.6 MJ/kg.
That's 236 times as much energy per kg for hydrogen.

So if I have a choice between throwing out the excess generated electricity from Solar/Wind, or use the electricity to generate Hydrogen to store for later use in a Fuel Cell, then I think it's worth considering.

- James

[StuM]

Originally Posted by TxThundr

Understanding that Fuel Cells are a net negative energy source, it seems they come into play if you have a Wind/Solar setup that produces more energy than you can store in your current battery bank.

If stored Hydrogen has a greater density of Energy storage (or potential energy storage) than a battery, then I would think it would make sense to store your excess Solar/Wind energy in stored Hydrogen then just throwing it away.

From a Tesla forum discussing fuel cells:
Compressed hydrogen has an energy density of 142 MJ/kg.
Lithium ion batteries have an energy density of 0.6 MJ/kg.
That's 236 times as much energy per kg for hydrogen.

So if I have a choice between throwing out the excess generated electricity from Solar/Wind, or use the electricity to generate Hydrogen to store for later use in a Fuel Cell, then I think it's worth considering.

- James

It's not the energy density that counts in this case. It's the cost of storage. To keep a decent amount of H you need to compress it and that takes a lot of energy . If you are looking at storing lots you need to get it down to very low temperature and keep it there. That is even more energy expensive.

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[Adelie]

Originally Posted by TxThundr

Understanding that Fuel Cells are a net negative energy source, it seems they come into play if you have a Wind/Solar setup that produces more energy than you can store in your current battery bank.

If stored Hydrogen has a greater density of Energy storage (or potential energy storage) than a battery, then I would think it would make sense to store your excess Solar/Wind energy in stored Hydrogen then just throwing it away.

From a Tesla forum discussing fuel cells:
Compressed hydrogen has an energy density of 142 MJ/kg.
Lithium ion batteries have an energy density of 0.6 MJ/kg.
That's 236 times as much energy per kg for hydrogen.

So if I have a choice between throwing out the excess generated electricity from Solar/Wind, or use the electricity to generate Hydrogen to store for later use in a Fuel Cell, then I think it's worth considering.

- James

First you are quoting values for energy density that are actually specific energy, energy density is energy per volume, MJ/l or similar units.

Second, your argument fails to to take into account 3 things:

1) The total weight of the installation. The specific energy of the fuel (hydrogen) looks great, that that doesn't take into account the rest of the system. The total weight of the fuel cell system would include the weight of the hydrogen, the fuel cells, the storage containers for the hydrogen, the hydrogen generator and the hydrogen compressor. The weight of the battery system would just be the batteries. The weight of wiring, solar panels and controller would be the same either way. The specific energy of the system as a whole will be somewhat capacity dependent, but for a sailboat scale system I doubt the fuels cells will have much of an advantage if any.
Let's say that 1kg of H can be stored at 200bar in a 13l aluminum tank which weighs about 17kg (See link below). Let's assume the generator weighs the same, and the compressor and let's assume the fuel cell weighs half that. So 3.5 x 17kg +1kg = 60.5kg plus misc for the system. Let's call it an even 60kg. Tesla forum folks say 142MJ/kg fuel, Sandia Labs says 120 MJ/kg (see pg 8 of link below). Let's call it 142 MJ from 1kg of H but 60kg of total system so about 2.4 MJ/kg.

2) The complexity of the system. The fuel cell system has a lot more subsystems which is a disadvantage. Some of them have moving parts which is a very serious disadvantage compared to the battery option.

3) The energy density of hydrogen in compressed gas form at 200bar (scuba tank pressures) is 1.5MJ/l (see pg 13 of Sandia link below) vs Lithium ion which ranges from .9 to 2.4 MJ/l (see other link below). This would be a wash if you were just considering the fuels but you also need to consider the volume demands of the other parts of the system, the hydrogen generator, the fuel cell, the compressor and the plumbing.

https://www1.eere.energy.gov/hydroge...res_sandia.pdf
https://en.wikipedia.org/wiki/Lithium-ion_battery
https://en.wikipedia.org/wiki/Diving...nium_cylinders

[Cap Erict3]

I watch the small steps being made in alternative energy vehicles with hope for the future.

The fact that Southern California is the first place that has hydrogen fueling stations in the U.S. isn't a big surprise.

It will be some decades before it trickles down to the average sailboat IMHO.




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[Ironman162]

How sad to have stooped to urine! Time to leave I think and join a forum with less clowns!


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[Adelie]

Bye bye. But good luck with that quest, seems kind of holy grailish.


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[botanybay]

Originally Posted by Ironman162

I'm all for the technology too.
My boat has 3 X 250 litre fuel tanks with premium petrol - Not a bad second to a bomb either!
If the fuel don't go stale it max out my credit card at the pump!
The use of solar power to produce Brown gas from sea water has potential.
It produces Hydrogen and Oxygen out of salt water by circulating current through it. The gas then used as it is being produced. No storage required.
The idea is to have a dual fuel system: Start the engine on petrol and when on temp then change over to the gas producer. The Dual fuel approach is also a good backup for dull days.
The circulating current should be from solar or eind wind and not the engine itself as it will defeat the purpose. It cant feed itself in other words. Altermatively a seperate generator can do it in an emergency.
Any ideas welcome the more we think laterally the sooner a bright invention will happen!

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Why not just use the solar power directly without the additional losses?

[Ironman162]

I would use it directly if I could but it would mean repowering with electric motors.
One can but dream!
For now I need to marry new solar technology to old Chev 350 petrol engines somehow.

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