Can Dry Ice be used as a fuel source?

[Patrick2568422]

I am not sure how much this is to do with astronomy but I was wondering whether dry ice could be used as a fuel source some how.  Just part of an idea I was thinking up. 

I am only 13 so this is probably a stupid question.

Thanks.

[andrew s]

You can use the evaporating CO2 to do work if you have a heat source to warm it up. However, you will have to do more work than you would get out to solidify it in the first place. 

Hope this helps Andrew

[Peter Drew]

Sorry it wasn't the breakthrough that the World has been waiting for but it will be someone like you that will eventually do so. Keep asking the questions.  

[Ravenous]

Good question actually.

You could put it in a sealed box, with just one outlet pipe.  A small turbine/propeller/paddle in the pipe would generate electricity. It would be fantastically slow though - the carbon dioxide gas would probably only be formed at a pretty slow rate, so it wouldn't spin the turbine very quickly.  You'd need a large amount of dry ice in a large box to get any output.

Another possibility is to sit a block of it on some sort of thermoelectric material. You would need one side of the material to be warm (in contact with normal surroundings) and the other side would be cold, in contact with the dry ice.  This is a bit like an RTG running backwards.  It would be very inefficient though I guess...

There are probably other methods someone will dream up.  You'll never get more than a fraction of the energy required to make the ice in the first place though, sadly  

[Stub Mandrel]

Some might say you can't because heating up the dry ice requires energy...

BUT a class of engines called 'heat engines' function by taking energy from a hot place to a cold place and making it do something useful on the way.

These 'Stirling engines' on ebay: http://www.ebay.co.uk/itm/Low-Temperature-Stirling-Engine-Motor-Model-Steam-Heat-Education-Toys

are usually used by placing them on something hot like a cup of coffee by taking heat from the coffee and putting it into the cooler air.

They would work just as well (perhaps better) sat on a container of dry ice - but they would run backwards because the heat would be flowing from the warmer air to the colder CO2!

 

So yes, dry ice will work as a fuel, if you have the right type of engine.

[Patrick2568422]

55 minutes ago, Stub Mandrel said:

Some might say you can't because heating up the dry ice requires energy...

BUT a class of engines called 'heat engines' function by taking energy from a hot place to a cold place and making it do something useful on the way.

These 'Stirling engines' on ebay: http://www.ebay.co.uk/itm/Low-Temperature-Stirling-Engine-Motor-Model-Steam-Heat-Education-Toys

are usually used by placing them on something hot like a cup of coffee by taking heat from the coffee and putting it into the cooler air.

They would work just as well (perhaps better) sat on a container of dry ice - but they would run backwards because the heat would be flowing from the warmer air to the colder CO2!

 

So yes, dry ice will work as a fuel, if you have the right type of engine.

I have heard of them before, they utilise changing air pressure they are really cool. 

If you have a pressurized container with carbon dioxide, it would form dry ice, would it then be able to keep the stirling engine running for ever?

My idea is that if you pressurize the carbon dioxide coming from cars, instead of releasing it into the air, then you can use it to power the car. So you put fuel in it one time and then the pressurized carbon dioxide just runs the car for ever. 

[Stub Mandrel]

23 minutes ago, Patrick2568422 said:

My idea is that if you pressurize the carbon dioxide coming from cars, instead of releasing it into the air, then you can use it to power the car. So you put fuel in it one time and then the pressurized carbon dioxide just runs the car for ever. 

Sorry, a law of physics is that "there's no such thing as a free lunch".

Any engine has an efficiency of less than 100%. For a heat engine it depends on the temperature difference it works off, but enough to say that the energy required to compress the CO2 is more than you can get out by letting it become a gas again. That means you can't even run the compression./expansion cycle for ever, let alone take out extra energy to run the car.

Check out 'perpetual motion machine' on Wikipedia for a longer explanation.

But well done for at least trying to find a solution to CO2 emissions!

[Patrick2568422]

21 minutes ago, Stub Mandrel said:

Sorry, a law of physics is that "there's no such thing as a free lunch".

Any engine has an efficiency of less than 100%. For a heat engine it depends on the temperature difference it works off, but enough to say that the energy required to compress the CO2 is more than you can get out by letting it become a gas again. That means you can't even run the compression./expansion cycle for ever, let alone take out extra energy to run the car.

Check out 'perpetual motion machine' on Wikipedia for a longer explanation.

But well done for at least trying to find a solution to CO2 emissions!

well I tried. 

[Patrick2568422]

22 minutes ago, Stub Mandrel said:

Sorry, a law of physics is that "there's no such thing as a free lunch".

Any engine has an efficiency of less than 100%. For a heat engine it depends on the temperature difference it works off, but enough to say that the energy required to compress the CO2 is more than you can get out by letting it become a gas again. That means you can't even run the compression./expansion cycle for ever, let alone take out extra energy to run the car.

Check out 'perpetual motion machine' on Wikipedia for a longer explanation.

But well done for at least trying to find a solution to CO2 emissions!

what if you somehow separate the carbon from the oxygen. I heard some scientist have been zapping CO2 with a laser and separating the two elements. The carbon can then be used again and again as a fuel source. 

[Stub Mandrel]

All the ideas you are suggesting are not really any different from a rechargeable battery, but just as you need to put about a third more energy into a battery than you can get back out, the same with any other way of 'recycling' fuel - you can't get more energy out of a system than you put in.

So yes you can re-use the carbon, but you need to make more energy to split it than you get back by burning it again.

[SilverAstro]

great questions

Ah ! the 'somehow' word, just like the 'what if' when speaking of the speed of light limit !!

there are many ways of splitting carbon from off of the oxygen in the CO2 molecule, ( doesnt even need lasers, nor even QM, just simple Victorian chemistry )  but they all require more energy than you will regain when you recombine them (by burning etc/other)

It is all down to the laws of thermodynamics and entropy - no free lunch.

(diversion = laws of entropy also seem to preclude a bouncing or recycling end-of-universe scenario )

PS ,,but dont ever give up thinking/asking  about it all, you     may  will come with something us oldies never ever dreamed of   

 

[Dave In Vermont]

There's an old saying, which is quite true in my viewpoint - "The only stupid question is the one you don't ask."

Keep up your research. It is, after all, what a scientist must do to be a scientist.

Starry Skies -

Dave

[Patrick2568422]

21 minutes ago, Dave In Vermont said:

There's an old saying, which is quite true in my viewpoint - "The only stupid question is the one you don't ask."

Keep up your research. It is, after all, what a scientist must do to be a scientist.

Starry Skies -

Dave

Thanks. I do want to be a theoretical physicist when I am older. 

5 hours ago, SilverAstro said:

great questions

Ah ! the 'somehow' word, just like the 'what if' when speaking of the speed of light limit !!

there are many ways of splitting carbon from off of the oxygen in the CO2 molecule, ( doesnt even need lasers, nor even QM, just simple Victorian chemistry )  but they all require more energy than you will regain when you recombine them (by burning etc/other)

It is all down to the laws of thermodynamics and entropy - no free lunch.

(diversion = laws of entropy also seem to preclude a bouncing or recycling end-of-universe scenario )

PS ,,but dont ever give up thinking/asking  about it all, you     may  will come with something us oldies never ever dreamed of   

 

Newton, who was in my opinion probably the smartest man in history, was wrong about time time being absolute.  Rudolf Clausius and William Thomson could be wrong too. There may be some way to create a perpetual motion machine.

I think the dry ice idea may still be possible. If you get a metal container you can condense C02 to turn the Stirling engine. It would almost the C02 fire extinguishers, and could be in liquid form like they are. Would then the dry ice eventually run out of cold? idk. I can see how it might turn back into C02 and then you can just circle it back to the start to condense again.

Condensing won't really take much energy. You can keep ic02 in a container and then when it reaches a certain capacity shoot in out a small pipe, so it would be more concentrated, and then into a cloth, that would turn it solid.  

[andrew s]

2 hours ago, Patrick2568422 said:

Condensing won't really take much energy.

How much energy do you think it will take compared to what you can get out? In the end physics (especially theoretical physics) is about the numbers

2 hours ago, Patrick2568422 said:

There may be some way to create a perpetual motion machine.

"If your theory is found to be against the Second Law of Thermodynamics I give you no hope..." Arthur Eddington. It would be nice if we could but we have found no hint of this possibility even with the rise of Quantum Theory and Relativity and all the technical innovations they have brought. The second Law of Thermodynamics developed from efforts to improve the steam engine still reigns supreme even in the era of gravitational waves, smart phones and GPS.

Regards Andrew

[Patrick2568422]

33 minutes ago, andrew s said:

How much energy do you think it will take compared to what you can get out? In the end physics (especially theoretical physics) is about the numbers

 

were talking about moving a little hutch up to let the C02 compress into some sort of material. So like 5 - 10 joules, 100% under 50

[ronin]

You could split CO2 but the energy to split it would be more then the energy released later when it recombines back to CO2.

What you have is: CO2 +E1 -> C +2O -> CO2 +E2.

The catch is that E2 is less then E1. That is the situation with the laser you mention.

However if the E1 source is something "free" then you have a system that is possibly viable in monetary terms if not the term of thermodynamics. The obvious free source being a solar panel and electricity. I suppose that a power station that splits water by solar electrolysis is feasible as the sun would provide the splitting of water to H+O (low cost to us) and then store these to burn later and reform H2O. Will say I hope they never do it as eventually the balance would be disrupted and we would be in deep do-do again.

[Dave In Vermont]

It would be an invaluable trick if we (humans) could find a way to tip the line of CO2 breaking even cost-wise (or better) regards being separated into the carbon and oxygen and recombined releasing energy at the same time. At least breaking even cost-wise. Or even a profit.

Now that the United Snakes has abandoned climate-change treaties and denying there even is such a thing as global-warming, we Humans must scramble to do everything we can to offset the damages forecast as a result of ever greater amounts of CO2 being released into the Earth's bio-sphere.

An ambition such as has been expressed by Patrick2568422 is to be encouraged with all expediency. In the face of the fast-approaching global-crisis - anything that we Humans can do to find an offset is an urgent task.

Forget about moving to another planet. Such a notion is about as viable as a matador singing nursery-rhymes to a charging Bull while waving his red-cape.

Dave

 

[andrew s]

22 hours ago, Patrick2568422 said:

were talking about moving a little hutch up to let the C02 compress into some sort of material. So like 5 - 10 joules, 100% under 50

and

On 5/27/2017 at 06:47, Patrick2568422 said:

If you get a metal container you can condense C02...

I think I see better what you are trying to do. If you have a cylinder of compressed CO2 and release it through a nozzle you can make solid CO2. You could evaporate this to drive a turbine to re compress the gas etc and so make a form of heat engine. However, you would find you needed energy from the environment to keep it running.

Regards Andrew

[andrew s]

7 hours ago, Dave In Vermont said:

It would be an invaluable trick if we (humans) could find a way to tip the line of CO2 breaking even cost-wise (or better) regards being separated into the carbon and oxygen and recombined releasing energy at the same time. At least breaking even cost-wise. Or even a profit.

This trick (without the economics) has been performed by green plants for some time. We exploit it via agriculture and bio fuels.

I agree Trump's stance poses a challenge but we were not stepping up to the issue any way (just deluding ourselves we were) so it may force us to.

Interestingly I attended a talk by a climate scientist at my local astro soc and he maintained we would be n an ice age now without the CO2 produced by the industrial revolution. 

It's an ill wind...

Regards Andrew

[Patrick2568422]

18 minutes ago, andrew s said:

However, you would find you needed energy from the environment to keep it running.

Regards Andrew

But why?

[andrew s]

Just now, Patrick2568422 said:

But why?

Simply because of the second law of Thermodynamics. It basically encapsulates the theory that you can't build a perpetual motion machine. If you google these concepts you may find good examples.

I am sorry just don't know how to explain it too you without concepts and mathematics you will not have studied yet. It involves not just energy but a measure of the quality of the energy (i.e. it's ability to do useful work) called entropy. I did not get to these ideas until I did university physics.

Regards Andrew

[Patrick2568422]

1 minute ago, andrew s said:

Simply because of the second law of Thermodynamics. It basically encapsulates the theory that you can't build a perpetual motion machine. If you google these concepts you may find good examples.

I am sorry just don't know how to explain it too you without concepts and mathematics you will not have studied yet. It involves not just energy but a measure of the quality of the energy (i.e. it's ability to do useful work) called entropy. I did not get to these ideas until I did university physics.

Regards Andrew

I wish we could do more complicated physics at school. All we do is stuff like moment = distance x force and stuff like that. 

What if whilst a wheel is turning in the car it is also generating electricity, like a big win turbine. So it is a hybrid between the dry ice energy and kinetic energy.

 

[andrew s]

Typing the last reply reminded me of the common misunderstanding about us and the Sun. It is commonly stated that we get our energy from the Sun (which is true) but we also loose as much energy back out into space. If we did not then the earth would continually heat up. Give or take some global warming we are in thermodynamic equilibrium as a planet.

What we get from the Sun is high quality energy in the form of visible and UV light with a lower entropy than IR radiation we radiate back out to the rest of the universe. The sun gives us negative entropy!

Regards Andrew

[Patrick2568422]

3 minutes ago, andrew s said:

Typing the last reply reminded me of the common misunderstanding about us and the Sun. It is commonly stated that we get our energy from the Sun (which is true) but we also loose as much energy back out into space. If we did not then the earth would continually heat up. Give or take some global warming we are in thermodynamic equilibrium as a planet.

What we get from the Sun is high quality energy in the form of visible and UV light with a lower entropy than IR radiation we radiate back out to the rest of the universe. The sun gives us negative entropy!

Regards Andrew

I have heard about that before 

[andrew s]

2 minutes ago, Patrick2568422 said:

I wish we could do more complicated physics at school.

When I was you age I read every book I could lay my hands on about science today you have the internet as well. Seek out some good quality sites and see what you can discover. Avoid those where one individual peddles there own pet theories.

Good luck Andrew