OMG you are both right. All fuels are energy carriers. Your definition is questionable "It takes more energy to create than it produces - so it is not a fuel." Does it really matter if the oil was made last week via bio-synthesis or 500 million years ago by natural decomposition. In both cases it took more energy to produce than we get back out of it. Give it a rest.
Fuel cell
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Pushmi-Pullyu
Well-Known Member
Again, you're confusing economics with physical reality. Germany produced and used a lot of synthetic fuel near the end of WW II, after the Allies cut off their supply of oil. That synthetic fuel -- just like hydrogen fuel -- had a negative EROI (Energy Return On Investment), but that didn't magically make it "not a fuel".
And the car doesn't care how much energy it took to get the fuel into the car. Once it's in the car, the important questions are just how much energy the fuel will provide when it's oxidized, and how efficient the power plant is at converting that energy into useful work. Unfortunately, the fuel cell stack itself is only ~50% efficient.
That 50% loss of energy in the fuel cell itself is just one of the thermodynamic limits which science denying Fool Cell fanboys keep trying to convince us will magically disappear with future improvements.
No, oxidizing fuel to produce energy is very unlike storing energy in rechargeable batteries. Batteries don't need oxygen for their chemical reaction; and once oxidized, the fuel is disposed of rather than being re-used like secondary batteries.
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NeilBlanchard
Active Member
If it took more energy to get gasoline from oil, than you got out of it - would it be a fuel? Because, that makes no sense. You would be wasting energy.
Fuel has to provide energy that you could not otherwise get. They have to be a net positive gain. Some batteries do oxidize - are aluminum air batteries fuel?
Fuel has to provide energy that you could not otherwise get. They have to be a net positive gain. Some batteries do oxidize - are aluminum air batteries fuel?
Domenick
Well-Known Member
The energy was locked up in coal, so to make it liquid required a lot of energy.
Whether or not to consider hydrogen a fuel is, to me, really not worth the effort to argue about. It is a feedstock for the fuel cell in a FCEV. We all can agree on that, I believe.
Pushmi-Pullyu
Well-Known Member
Where are you getting this idea that the word "fuel" implies a net positive energy gain? A fuel cell doesn't care if the fuel it uses is frackogen (hydrogen reformed from natural gas) or renewable hydrogen generated by electrolysis. It also doesn't care if the hydrogen is low-pressure and carried by a pipe directly from the emissions plant, or stored under high pressure in a gas tank in a vehicle. What makes something a "fuel" is that it contains chemical energy which can be released to power a heat engine; usually the release involves oxidation*. The energy accounting, positive or negative, has nothing to do with whether or not it's a fuel.
The idea that something that's a fuel is somehow transformed into "not a fuel" the moment the supply chain carrying that fuel consumes more energy than the fuel contains... that's just bizarre. The English language doesn't work that way!
I honestly don't see why you're trying to re-define the word "fuel". You can, like Humpty Dumpty, use a word to mean anything you like. But if you use it in a manner different from its generally accepted meaning, then -- just like Humpty Dumpty -- all you're going to accomplish is to create confusion.
That's a mis-use of the term "battery". What you're describing is properly termed an aluminum-air fuel cell, which unfortunately is all too often mis-labeled a "battery" in the popular press.
That is a good example of why we should try to use technical terms correctly; it only creates confusion when we don't.
*Usually but not always. For example, hydrogen peroxide can be used as a rocket fuel by a chemical process of decomposition rather than oxidation. Details here.
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NeilBlanchard
Active Member
If a fuel doesn't provide more energy than it takes to get it - then you are using it (hydrogen) as a (poor) energy storage system. Otherwise, what would be the point?
Would you bother heating your house with wood, if it took more energy to get the wood, than you got out of it?
If aluminum air batteries are not actually batteries, then what are alkaline batteries?
Would you bother heating your house with wood, if it took more energy to get the wood, than you got out of it?
If aluminum air batteries are not actually batteries, then what are alkaline batteries?
Pushmi-Pullyu
Well-Known Member
Whether or not some material has an EROI that is positive or negative when used as an "energy storage system", is an economic question, not a question for chemistry and physics.
When we have to resort to citing dictionary definitions, this is generally a strong indication that a discussion/debate has passed the point at which it's useful, but perhaps this is an exception to that rule.
fu·el
noun
material such as coal, gas, or oil that is burned to produce heat or power.
noun
material such as coal, gas, or oil that is burned to produce heat or power.
* * * * * *
There's nothing there at all about whether or not more energy has to be added during the generating process than is present in the fuel.
It depends on just how useful the energy is when it's released. If it's highly useful, then it might well be worth it.
For example, the first economically workable steam engine, the "Newcomen Atmospheric Engine", was only 0.5% efficient (one-half of one percent efficient!) at converting the energy in coal to useful power. It unquestionably took more energy to mine that coal and move it into the Newcomen Engine than the engine was able to harness when it was pumping water out of the coal mine.
Did that mean the coal burned in it was "not a fuel"? Of course not! It just meant it nearly all the energy was wasted. At least the well-to-wheel process of using hydrogen fuel to power a fool cell car, poor as it is, is more efficient than that!
Battery cells.
I think I should step aside and let you argue with the dictionary.
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