Can you explain in terms that are specific why it takes more energy than it creates to extract hydrogen from water?
If you can, would you, I will try to follow your logic. Give me enough information so I can research your logic. If you can be math specific, I would appreciate.
I am curious.
Because of inefficiencies at every step. It could be theoretically equal, if you could do everything with pure superconductors that have no resistance, every calorie of heat released or required had zero movement in or out of the system, all products and reactants could be moved in and out without energy being spent. But there is some inefficiency in every step of the process, consequently each step requires some additional energy from somewhere.
First, burn fuel to create steam and drive a turbine to create electricity. How much energy is lost in this process? Now push that electricity thru a wire to the site where you're creating the hydrogen fuel. How much energy lost thru electrical resistance? Convert the current from A/C to D/C, more loss. Now use the energy that's left to split hydrogen from water. More energy lost to heat.
Take the H2 and run it thru a fuel cell, more loss.
If you can be math specific, I would appreciate.
I might have a link with specific numbers. If I get a chance, I'll look around.
OK, I now recognize from reading more closely that several of us here on this thread are engineers, and several are not.
We engineers are making references to thermodynamics, but we're not doing well at explaining the thermo issues to the non-engineers here. Therefore, without the engineering/physics lingo, here are the three laws of thermodynamics which constrain all issues of energy creation, conversion and use, in the joking manner that engineers use to remember them.
1. "You can't win."
This is the law that states that you cannot pull out of a system more energy than you put into it. This is the law that is used to negate all sorts of various quack perpetual motion schemes, as well as claims for things like hydrogen that it is a "fuel" instead of an "energy transfer mechanism."
2. "You can't even break even!"
This is where engineering starts sounding like the Dismal Science of Economics. If "winning" is doing better than breaking even, then breaking even would be simply achieving 100% energy efficiency as we change the form of energy; eg, if we could break even, we could convert electricity to mechanical power without any loss due to heat in the conductors, or we could convert electricity into hydrogen into mechanical energy without the evaporative losses of liquid H2 going to gas and floating away.
Mind you, "you can't break even" doesn't mean that we shouldn't try. At all levels in the engineering game now, the quest is on to eliminate or minimize as many inefficiencies and losses as we possibly can. The hybrid car, or super-efficient electric motors, superconductors -- these are all ways we're trying to get closer to breaking even. But we all know that we will never, ever achieve a "no loss" situation in energy conversions. All we can do is minimize waste and loss.
There is one caveat: you can break even, if and only if you cool the universe down to absolute zero, ie, zero Kelvins. Since most things assume a rather solid, steady and uninteresting state of being at this (lack of) temperature, it is a rather academic break-even point.
3. "You can't quit the game."
This means that if you live in this universe, laws 1 and 2 apply, and without inventing a whole new universe with whole new physical laws, and then moving you and your invention there, you can't get around laws 1 and 2. Just ain't no way.
With respect to hydrogen:
Let's say we have some wonderful new way to create massive quantities of H2 cheaply. It is a given that there is no "free" pool of H2 just sitting around on earth. We all agree that hydrogen is plentiful on this planet, but it is all bound up into some other matter: water, hydrocarbons, organic matter, metal hydrates, etc, etc, etc. It does not exist in a free, unbound form.
OK, so we all agree on that. Now to get H2, this means we must unbind it from where ever/whatever is holding it - let's assume water.
So, let's assume (for the sake of argument) electrolysis of water, which gives us 2H2 + O2 as a result, yes?
We have to use some type of power to generate the electricity. We have "X" electricity we generate.
Now we must conduct that power to the plant where we do the electrolysis. We lose some there. We do the electrolysis. In the process, some H2 is going to be leaked away. More loss. Now we want to liquid H2 to make it dense for transportation. Now we're stuffing in an incredible amount of power into this process to compress/chill the H2, and we're bleeding off the waste as heat in the compressed gas, which is mostly lost.
Anyone who has been around an air compressor can tell you that when you compress a gas, it gets hot. That heat is power being wasted, which we then have to cool off. That's energy loss. And we have more energy loss in the motor(s) to run the compressors, we have losses in friction in pipelines for the gas to be put into the compressor, friction coming out of the compressor, etc.
Now comes the monster losses in an H2 system. SO we have liquid H2. It is a cryogenic liquid, with rather interesting properties. Let's put aside the interesting properties and just deal with the fact that liquid H2 is very, very cold and the surrounding environment on earth is much, much warmer, even if you're located in Siberia:
All cryo liquids absorb heat from the outside environment. As they do this, the pressures become untenable in the storage system, so you have to bleed off the excess pressure -- ie, release gaseous H2. Big losses right there. And you have to do this in every cryo tank along the distribution path, so you have a compound effect of losses.
Getting the picture yet? The first law of thermo tell us that H2, because it has to be extracted from some compound to liberate it, as opposed to just "mined" in a usable form the way we do with coal, oil, natural gas, etc, we'll never get above unity on power creation. We're putting energy into the process of breaking hydrogen away from something. We can never get more energy potential into H2 than we put into breaking the atomic bonds that allowed us to liberate the H2. Got that?
The second law of thermo tells us that we're going to be losing power all along the way from the point where we created H2 from an injection of outside power -- in effect, we're using a very lossy piece of wire to transmit the electrical power we used to liberate the H2 in the first place. We would be better off using conventional electrical vehicles and batteries than using liquid H2.
And the third law tells us that no matter how inflated their egos, the Congress, the POTUS and all the bureaucrats in the US will never be able to mandate that the situation ever becomes any better.
The answer is really simple.
Every process we have to break water results in excess heat/energy being lost to the environment rather than being stored in the Hydrogen. when the hydroge recombines with oxygen the energy given up will never make up for that original energy lost. That heat/energy can never be regained when that hydrogen is oxidized. That is entropy.
The second problem is the quality of energy used to create hydrogen. Electricity is high quality energy and very expensive. You can now make hydrogen from water with about 90% efficiency but if you have the electricity where you need energy, you don't need the hydrogen. If you have to move the hydrogen that adds more losses. If you make the electricity from coal, you loose about 60 percent of the energy, another 5% over tranmission lines, 5-15% compressing it and 50% when you run it through a fuel cell. It would be more efficient running a coal powered steam car and cut out all of the steps. It would be even more efficient to make coal gas in the car and burn it in a standard engine.
You could make the hydrogen with nuclear heat but you would loose half your energy trucking it around the country and then loose another half in the fuel cell. If you want to use nuclear power, I think it would probably be more efficient to put the power plants on the shores to run huge desalination plants to grow alge in the deserts. At least that can be turned into diesel and piped to the cities. As a bonus, you would have enough power to never have another Califoria brownout.