Ethanol

[Embar Angylwrath]

Eidolon...

Small correction... the reverse osmosis used in desalination is filtration process (if memory serves they use some kind of membrane that works as an ion trap). Although Narith has absolutely no idea what he's talking about in his post, it is correct to say that water desalination is a filtering process.

[Eidolon Faer]

Actually, Relbeek, Narith's proposal violates the First Law of Thermodynamics. It's an Enthalpy thing, not an Entropy thing, to break the chemical bonds in water to liberate hydrogen. He's trying to get heat out without putting heat in.

Reverse Osmosis is a Second Law phenomenon, however.

[Eidolon Faer]

And Embar...

The answer to your point is "kinda".

The membrane doesn't "trap" the salt, it just allows water to pass and not the salt. The mathematical difference between the two processes is that "filtration" is separating a solid phase from either a liquid or a gas and the pressure drop across the filter is caused by fluid mechanics...basically friction. Reverse Osmosis is separating chemical species within a single liquid phase and the pressure drop across the membrane is driven by the Entropy term in the thermodynamic equations.

So any Chemical Engineer (like me) would point out that an analogy between the two processes is strictly limited.

[Relbeek Einre]

Oh, right, because he wanted to filter the elements out, not use the car's energy to break the bonds.

Without that little piece, he was proposing a perpetual motion engine, which does break the second law.

[Ddrak]

Well, pretty much anything that breaks the first law is going to break the second law as well. A perpeptual motion machine that delivers energy from nothing is a clear first law violation before you even get into second law effects.

Besides, the second law is really more of a guideline than a law, mainly because it's a statistical result and not an absolute one. You can violate the second law, but more by chance than by design. The first law on the other hand is far closer (if you include mass as energy) to involate until you get down to quantum theory where you can "borrow" energy for some time from nowhere.

Dd

[Narith]

Umm not to beat a dead horse, but you can break the bond between hydrogen and oxygen atoms with the simply positive and negative of a car battery. Of course that breaks them into the gas form.

[Narith]

As for removing the impurities from sea water I have no idea how they did that, I live in Michigan we only deal in fresh water so never had to look into how a desalinitation plant worked.

But seriously like I said above the only thing you need to break the bond between the hydrogen and oxygen atoms is a simple positive and negative charge (try it sometime and geuss where I learned that?). The oxygen I assumed would be waste product because I assumed it would create more oxygen than it consumed during the combustion process as I do not know the ratio of burned hydorgen to needed oxygen. For an internal combustion engine one can modifie it to run off anything that is combustable, even used french fry grease (yes there are people out there who have done it). So why not hydrogen?

[Eidolon Faer]

Ddrak:

You can reverse Entropy only by expending energy. That creates disorder somewhere else...the place where you GOT the energy. You cannot violate the Second Law any more than you can violate the first. You never get a free lunch.


Narith:

You're a dumbass. Where do you think the car battery gets the energy from?

For that matter, why not hook a big motor to the car battery and drive your car forever on it? Why bother with the Hydrogen?

If they ever invent cars fueled by pure stupidity, we've got it made. And I'll PERSONALLY ask for the privilege of clubbing you like a baby seal for that rich harvest of sheer idiocy.

[Ddrak]

You can reverse Entropy only by expending energy. That creates disorder somewhere else...the place where you GOT the energy. You cannot violate the Second Law any more than you can violate the first. You never get a free lunch.

That's simply not universally true. The system in question has to be statistically significant before the second law comes into effect. You'd have to be a chemist and not a physicist to say something like that. ;-)

When you can correlate "the place you GOT the energy" with Heisenberg's ΔE.Δt ~ h then you can come back and talk first/second laws being universally true to me.

Dd

[Ddrak]

Narith,

To break the bonds between the Oxygen and Hydrogen in water takes the exact same amount of energy from the battery that you get back when you burn Hydrogen + Oxygen to create water again (you knew that burning hydrogen gives water, right?)

When you split the bonds between Hydrogen and Oxygen you get 2 Hydrogen molecules per Oxygen molecule. When you burn Hydrogen, it takes 1 Oxygen molecule for each Hydrogen molecule. In other words, you are performing the exact same reaction in reverse.

In other words, you're starting with water and ending with water. How did you expect to get an energy gain from that reaction?

Dd

[Eidolon Faer]

And, umm, Relbeek...

Perpetual motion isn't exactly what the Second Law forbids. You could put a flywheel inside a glass sphere, evacuate the sphere, and have the wheel float, spinning forever, in zero gravity. It wouldn't touch anything. No friction. It'd spin forever. Perpetually moving, y'know.

What the second law forbids is converting energy from one form to another with 100% efficiency.

For that matter, a photon will fly forever until it runs into a piece of matter somewhere. Thermodynamics is a creature derived from statistics on the behavior of matter, similar to how the Ideal Gas Law was derived, and it doesn't directly apply to quantum-scale phenomena.

Sorry for being so nitpicky, but it's kinda what my degrees are all about. I'm sure if I started making overgeneralizations about PHPBB programming, you'd have just as much trouble explaining the fine points to me.

Anyway, this thread was about Ethanol, and not intended as a treatise on Thermodynamics. The Laws of Thermodynamics are only expressible accurately as equations, and the verbal phrases for the laws are sometimes imprecise or misleading. And going into the nitty-gritty details of the consequences of the mathematics was the subject of quite a few of my college courses.

[Eidolon Faer]

Ddrak,

Bingo. Chemist and Chemical Engineer.

If you're working with a system that's not statistically significant then yeah, you can sometimes beat the odds on a very tiny scale, for a short period of time.

Anything big enough to power the nation's automobiles is going to be statistically significant, trust me.

And yes, some of the more-bizarre quantum-mechanical effects the Physicists have started looking at COULD potentially generate a violation of the Laws.

[Ddrak]

Anything big enough to power the nation's automobiles is going to be statistically significant, trust me.

Absolutely, and sorry for the confusion if you thought I was implying you could extrapolate bizarre quantum effects to this scale.

Dd

[Arathena]

Okay, for those who can't be bothered to understand the implications of the laws for themselves, this is what they mean any time you're designing anything whatsoever that uses energy:

You can't win.
You can't break even.
You can't quit.

The problem, Narith, is that to pump water of any kind into your car, and expect to elecrolytically crack the water in an infinite cycle, is as follows.

To break one moles of water (18g) into one mole of oxygen(16g), and 2 moles of hydrogen(2g), requires 571.6 kJ of energy. Unfortunately, we're also going to lose a certain amount of heat to the current passing through the water, to expanding the gases away from the water, etc. It's.. around 7 kJ, research tells me. That's.. around 98% effiency, which ain't fucking shabby.

Now, burning 2 moles of H2 and 1 mole of O2 to make one mole of H20, is gonna produce ... you guess it yet? It's 571.6 kJ of energy. Now, someone elses thermogoddamits tell me I can only get about 474 kJ of electricity out of it.

We've now spent over 100 kJ of electricity... and we haven't even moved the car yet! Therefore, for hydrogen to be useful as a car fuel source, it must be catalyically refined somewhere, then trasported to points of sale. The infrastructure doesn't exist for it yet, is prohibtively expensive to create... and you can expect to get 5-7 miles per gallon of cryogenically stored hydrogen. Something like ethanol, or preferably, a blend of stuff like, say, n-heptanol, n-octanol, etc created through an organic or semi-organic process would be somewhat more feasible due to compatibility with current fuels / engines / infrastructure.

[Relbeek Einre]

Sorry for being so nitpicky

Quite all right. It's not like you're being rude about it.

[Ddrak]

It's 571.6 kJ of energy. Now, someone elses thermogoddamits tell me I can only get about 474 kJ of electricity out of it.

That's assuming a fuel cell operation. Narith was talking about an internal combustion engine wherefor a standard 4-stroke Otto cycle it's much more like 340 kJ back (60% efficiency).

Dd

[Arathena]

It's 571.6 kJ of energy. Now, someone elses thermogoddamits tell me I can only get about 474 kJ of electricity out of it.

That's assuming a fuel cell operation. Narith was talking about an internal combustion engine wherefor a standard 4-stroke Otto cycle it's much more like 340 kJ back (60% efficiency).

Dd

Point. Of course, going from one engine to the other is the energy equivalent of thowing away 80 Oreo cookies per gallon of liquid hydrogen burned. That's a lot of oreo cookies you're throwing away on the way to work, so for god's sake, use the fuel cell.

[Ddrak]

Deep fried Oreo cookies, or regular?

[Arathena]

Standard, single-stuffed Oreos. I don't /want/ to know the nutritional information of deep fried oreos, except that I'm fairly certain that we'd have to express the 'Calories from Fat' in terms of 'Megayears of Solar Production".

We need to go get some more.

[Embar Angylwrath]

For that matter, a photon will fly forever until it runs into a piece of matter somewhere. .

<cough> gravity wells <cough>