Liquid Oxygen as Fuel?

[PermaBanned]

Well in casually searching for a better way of powering the world's cars i started thinking - what would be the best substance for it? Obviously not the whole world has access to large quantities of this, but little old water. Distilled, that's Hydrogen and Oxygen. It would be easy to do away with the oxygen altogether, and use the Hydrogen to generate electricity which would eventually power car. But to exist in a liquid state Hydrogen would have to be cooled to −252.87°C and pressurised, something which on it's own it pretty hard to do from water. Besides, we all know what electric cars are like. So my proposition is this, separate the two elements from the water via electrolysis. This would leave you with Hydrogen and Oxygen gas. So to make them into liquids you need to cool them, as well as pressurise the Hydrogen, which would be done first to the Hydrogen using stored electricity in a battery (perhaps trickle charged by a solar panel elsewhere on the vehicle). Here arises the first problem - how do you cool it to −252.87°C? Well, (taking inspiration from CPU cooling here) some form of highly efficient phase change or vapour cooling might come in useful here. Going into specifics later, but Liquid Nitrogen would come in useful here. Can't have everything i suppose... then to pressurise it, which could be done with a piston (in a sort of syringe orientation) at regular intervals, with a certain amount of the cooled Hydrogen. Assuming this all worked correctly, you would then have Liquid Hydrogen. This could be used to power the cooling systems and piston, which would then (hopefully) be powerful enough and have a consistent supply to cool the Oxygen to the required temperate of −182.96 °C. This Liquid Oxygen would then be used (perhaps with a mixture of the Liquid Nitrogen, which is handy when you look at the compound H2O, as i shall explain below) as fuel in a modified Internal Combustion Engine. Since both of these elements in their liquid state can be and are used as main components of rocket fuel, they should have ample (of perhaps over, hence the modified engine) combustibility for our little old automobile.

Thanks for reading (if indeed you did), i just thought i'd run this by you before taking it on as a side project to work out all the specifics. Any problems you see or suggestions you have? So yes, i'm basically asking you to poke holes in it.

Cheers

 

[TaKeN]

Boom?

 

[PhillyDee]

You wouldnt need to cool it, compressing it does the same job.

Incredibly high volatility of the gasses in both forms.

 

[gurusan]

I don't get it. You are spending a crapload of energy to obtain pure liquid oxygen, and then going to do what with it?

 

[dekez]

I think, if I understand what you are saying correctly, this has already been done:

http://en.wikipedia.org/wiki/Hydrogen_vehicle

 

[PermaBanned]

You wouldnt need to cool it, compressing it does the same job.

Incredibly high volatility of the gasses in both forms.

Ah, that makes sense. Should make that step a fair bit easier too.

Fair point, but i assume the liquids are a 'bit' more stable? In which case they would have to be in a very secure, perhaps suspended environment. Sealed, of course.

Something i neglected to mention - Liquid Oxygen is Paramagnetic. Is there any way that this could be used as an advantage? Or will it simply not be a considerable factor, or indeed a negative one?

 

[PermaBanned]

I don't get it. You are spending a crapload of energy to obtain pure liquid oxygen, and then going to do what with it?

As i said i haven't gone into specifics yet, but basically... blow it up. That's essentially what happens to Petrol isn't it?

*acts innocent*

I think, if I understand what you are saying correctly, this has already been done:

http://en.wikipedia.org/wiki/Hydrogen_vehicle

In a way, but the only thing input into the car would be distilled water. That and that i'm utilising the liquid oxygen too. But thanks for that link, it does help answer the above question a bit...

http://en.wikipedia.org/wiki/Hydrogen_internal_combustion_engine_vehicle

 

[gurusan]

As i said i haven't gone into specifics yet, but basically... blow it up. That's essentially what happens to Petrol isn't it?

Yes but oxygen aids combustion of the petrol, you can't use oxygen as a fuel by itself.

 

[PermaBanned]

Surely the liquid oxygen has similar properties to liquid hydrogen, and as i posted above that can be used in internal combustion. Obviously it would require yet more modification...

 

[Burnsy2023]

Yes but oxygen aids combustion of the petrol, you can't use oxygen as a fuel by itself.

Indeed, some major physics fail here...

It's the fusion of O2 and fuel that releases energy.

 

[gurusan]

Liquid Hydrogen can be used in internal combustion with the addition of oxygen.

Oxygen is "free" so spending energy compressing it and storing it is where you've lost me.

 

[thepeganator]

It takes a lot of energy to separate water into H and O2, the energy from H is from is fusing it with O2, and considering you will lose some energy to other factors, you would have a net loss of energy.

 

[PermaBanned]

Okay, lets assume that there's nothing we can use the liquid oxygen for. What are the potential problems with simply using the water to get hydrogen, then compressing it to get liquid hydrogen which can be used on it's lonesome as a fuel in internal combustion. Obviously you'd get gas oxygen too, which could be used to make sure the only output is water (not mixed with any sort of nitrogen) as long as it's safely transported. Then how would you get the power to compress it into a liquid?

At above, i think you're exaggerating the amount of energy required for electrolysis, since you can do it yourself:

Which could be generated by some other 'green' means.

 

[Thomas. PLease.]

Basically whats the point. Hydrogen powered cars have already been developed. So surely if oxygen powered cars were even possible or at all viable it would have been thought of already.

Since it hasn't I think we can all agree thats its just not possible and or viable in comparison to hydrogen power.

 

[alex24]

Wow, there's a whole load of scientific misconceptions in your plan, and it's overly complicated.

Liquid oxygen is extremely explosive, and probably too dangerous to use in this fashion, as it reacts with almost any organic compound quite violently, so the implementation would be as difficult as making a rocket safe, and that's before mentioning it needs something to react with, and storage problems.

There is a great amount of research going into hydrogen storage for energy purposes, needless to say the theory can be complicated, and the fact no easy solution has been found probably suggests it's a bit more elusive than you may assume.

Hydrogen fuel cell technology is potentially promising, but for me, there is still a major issue with it: the electrolysis of water requires a lot of energy, which originates from power stations, typically coal and oil-fired, thus defeating the object and introducing more losses until we have a way of sustainably generating all our electricity.

With the invention of many new battery technologies in recent years, as well as some half-decent attempts surfacing, purely electric cars seem to be the best way forward, and would be more efficient overall I think, especially since there is no electrolysis or similar.

I think the only way of reasonably and sustainably powering our current transport infrastructure would be something like biofuels, but there are massive, massive problems with using those as I'm sure most people are aware.

 

[gurusan]

Well that's basically what hydrogen combustion cars are all about and it's already been done. The problem is basically about the power required for electrolysis....it's dirty and expensive so you might as well just burn petrol anyway.

IMO, I don't see hydrogen catching on until fusion power is underway...which if all goes to plan I think we'll be seeing fusion into the grid around 2050 (i'll be 65 )

 

[Burnsy2023]

Okay, lets assume that there's nothing we can use the liquid oxygen for. What are the potential problems with simply using the water to get hydrogen, then compressing it to get liquid hydrogen which can be used on it's lonesome as a fuel in internal combustion.

Which is how hydrogen cars work.

Obviously you'd get gas oxygen too, which could be used to make sure the only output is water (not mixed with any sort of nitrogen) as long as it's safely transported.

What? Burning hydrogen will only ever give you water as a product.

[QUOTE =Superewza;15436551] Then how would you get the power to compress it into a liquid?[/QUOTE]

I'm lost. Did you do GCSE Science?

 

[Burnsy2023]

IMO, I don't see hydrogen catching on until fusion power is underway...which if all goes to plan I think we'll be seeing fusion into the grid around 2050 (i'll be 66 )

Power for the electrolysis isn't the only issue. Storage is not trivial either.

 

[PermaBanned]

alex - I'm painfully aware of that, but i'll suffer through nonetheless

Yeah, we've already sorted that out. Just the liquid hydrogen would be used as fuel, the oxygen would then be used with that instead of being converted into a liquid.

It depends on the requirements of the reaction. I'm looking at ways to 'start if off' by generating electricity in other parts of the car. Then perhaps not all of the hydrogen would go to the engine, but be used to create electricity.

Burnsey - Hydrogen cars take liquid hydrogen at the pump. This would take water. Also, since the only output is water, could it then go round in a circuit to become the coveted self sufficient device?

I was simply thinking out loud - compression takes energy too. Assuming you don't have any yet as you don't have the liquid hydrogen you're going to need to generate it elsewhere. Since you ask i'm doing GCSE Triple Science, currently working at A* grade but i've so far just finished the Core modules (which i did a year early to save time). For various reasons i've missed a fair amount of lessons, so i'm doubtful if i will continue to work at that level.

Storage would be manageable, since the products are used in hydrogen cars currently.

 

[Ricochet J]

You can't take the two elements apart and expect a positive half Rankine Cycle unless you

Well in casually searching for a better way of powering the world's cars i started thinking - what would be the best substance for it?

Second generation bio-fuels that do not compete with the food chain seems to be what researchers are moving toward. They give a suitable Carnot Effeciency rating which is more feasible than liquid oxygen.

Distilled, that's Hydrogen and Oxygen. It would be easy to do away with the oxygen altogether, and use the Hydrogen to generate electricity which would eventually power car. But to exist in a liquid state Hydrogen would have to be cooled to −252.87°C and pressurised, something which on it's own it pretty hard to do from water. Besides, we all know what electric cars are like. So my proposition is this, separate the two elements from the water via electrolysis.

You see, there's your problem. You can't seperate hydrogen from oxygen using electrolysis adiabatically. It'll mean most of the energy will lead to an inbalance in your stoichiometric analysis when considering each element of oxygen and hydrogen. You're essentially solving a problem with a bigger problem. But going with your -252.87°C and high pressure dilemma - this is easily resolved if you model it as a perfect incompressible gas. You either sacrifice higher pressure for a lower temperature, or higher temperature for a lower pressure. Your choice.

This would leave you with Hydrogen and Oxygen gas. So to make them into liquids you need to cool them, as well as pressurise the Hydrogen, which would be done first to the Hydrogen using stored electricity in a battery (perhaps trickle charged by a solar panel elsewhere on the vehicle).

Read the first law of thermodynamics.

Here arises the first problem - how do you cool it to −252.87°C? Well, (taking inspiration from CPU cooling here) some form of highly efficient phase change or vapour cooling might come in useful here.

Read my above comment regarding low temperatures. Cooling of a liquid (inc gas), or a solid for that matter would be extremely difficult since your control volume is small. In this case a heat exchanger will not be practical. It'll require large surface areas to maintain the same vapour side temperature difference between your fluid and atmostpheric temperature.

Going into specifics later, but Liquid Nitrogen would come in useful here. Can't have everything i suppose... then to pressurise it, which could be done with a piston (in a sort of syringe orientation) at regular intervals, with a certain amount of the cooled Hydrogen. Assuming this all worked correctly, you would then have Liquid Hydrogen. This could be used to power the cooling systems and piston, which would then (hopefully) be powerful enough and have a consistent supply to cool the Oxygen to the required temperate of −182.96 °C. This Liquid Oxygen would then be used (perhaps with a mixture of the Liquid Nitrogen, which is handy when you look at the compound H2O, as i shall explain below) as fuel in a modified Internal Combustion Engine.

Sounds like a PMM2.

Since both of these elements in their liquid state can be and are used as main components of rocket fuel, they should have ample (of perhaps over, hence the modified engine) combustibility for our little old automobile.

Thanks for reading (if indeed you did), i just thought i'd run this by you before taking it on as a side project to work out all the specifics. Any problems you see or suggestions you have? So yes, i'm basically asking you to poke holes in it.

Cheers

I suggest you do A LOT of reading if you want to propose ideas. It's not a flame, but rather some criticism. From what I've read, you certainly need to read up on Thermodynamics and Heat & Mass Transfer. Them two alone without Fluid Mechanics will be pointless.

If you're going to persue this further, good luck.