Seawater as Fuel?

[BrotherBenny]

I'm looking into writing a short story centered around this technology but I need to know if it is currently scientifically plausible.

I've read around the subject a little and there seems to be very little of substance, so I was wondering if anyone could help me.

 

[Trekker4747]

The only way I can see it being used for "fuel" is to use electricity to seprate the oxygen and hydrogen molecules and then you burn the hydrogen. But, it'd cost more to sepeate the H2 and O2 than you'd get out of it.

 

[Lindley]

http://en.wikipedia.org/wiki/Fischer-Tropsch

From my very limited understanding, it seems that the main problem is that for now the process produces too much methane and too little usable fuel. They're trying to change that.

 

[Robert Maxwell]

Isn't methane combustible?

 

[RobertScorpio]

Use the water off the east coast near the BP oilspill.

Rob

 

[Myasishchev]

Well, the best place to find deuterium is in the ocean.

 

[JustAFriend]

I've read around the subject a little and there seems to be very little of substance....

Yeah, the real-life laws of physics are a real pain that way...

 

[scotpens]

According to the Wikipedia article, the Fischer–Tropsch process "produces a petroleum substitute, typically from coal, natural gas, or biomass for use as synthetic lubrication oil and as synthetic fuel." Doesn't say anything about fuel from seawater.

The water-as-fuel idea sounds a lot like the "joe cell," which is really nothing more than old-fashioned electrolysis -- using an electric current to separate water into hydrogen and oxygen. As already pointed out, it takes more energy to split the water molecule than you'd get from burning the hydrogen. It's just the latest version of the perpetual-motion scam.

Bottom line: There Ain't No Free Lunch.

 

[Lindley]

According to the Wikipedia article, the Fischer–Tropsch process "produces a petroleum substitute, typically from coal, natural gas, or biomass for use as synthetic lubrication oil and as synthetic fuel." Doesn't say anything about fuel from seawater.

Well, I got the reference from here:
http://www.newscientist.com/article/dn17632-how-to-turn-seawater-into-jet-fuel.html

 

[darkwing_duck1]

According to the Wikipedia article, the Fischer–Tropsch process "produces a petroleum substitute, typically from coal, natural gas, or biomass for use as synthetic lubrication oil and as synthetic fuel." Doesn't say anything about fuel from seawater.

The water-as-fuel idea sounds a lot like the "joe cell," which is really nothing more than old-fashioned electrolysis -- using an electric current to separate water into hydrogen and oxygen. As already pointed out, it takes more energy to split the water molecule than you'd get from burning the hydrogen. It's just the latest version of the perpetual-motion scam.

Bottom line: There Ain't No Free Lunch.

It's not a "scam" (it acutally works), but it IS horribly inefficient.

It's utility depends on the user's objective. Is it to find a more EFFICIENT fuel? Hydrogen cracking isn't going to do that. Is the objective to find a CLEANER burning fuel? If so, and you're willing to pay the price for the inefficient conversion, then cracking is a viable option.

 

[Iasius]

Economic uranium resources will last for over 100 years at 2006 consumption rates, while it is expected there is twice that amount awaiting discovery. With reprocessing and recycling, the reserves are good for thousands of years.[48] It is estimated that 5.5 million tonnes of uranium ore reserves are economically viable at US$59/lb,[48] while 35 million tonnes are classed as mineral resources (reasonable prospects for eventual economic extraction).[49] An additional 4.6 billion tonnes of uranium are estimated to be in sea water (Japanese scientists in the 1980s showed that extraction of uranium from sea water using ion exchangers was technically feasible).[50][51]

We're probably not going to need to extract uranium from sea water for a while though. It's also not really using sea water as fuel, more like a "liquid ore".

 

[farmkid]

According to the Wikipedia article, the Fischer–Tropsch process "produces a petroleum substitute, typically from coal, natural gas, or biomass for use as synthetic lubrication oil and as synthetic fuel." Doesn't say anything about fuel from seawater.

The water-as-fuel idea sounds a lot like the "joe cell," which is really nothing more than old-fashioned electrolysis -- using an electric current to separate water into hydrogen and oxygen. As already pointed out, it takes more energy to split the water molecule than you'd get from burning the hydrogen. It's just the latest version of the perpetual-motion scam.

Bottom line: There Ain't No Free Lunch.

It's not a "scam" (it acutally works), but it IS horribly inefficient.

It's utility depends on the user's objective. Is it to find a more EFFICIENT fuel? Hydrogen cracking isn't going to do that. Is the objective to find a CLEANER burning fuel? If so, and you're willing to pay the price for the inefficient conversion, then cracking is a viable option.

It's not really an efficiency issue. You put energy into the system to split the hydrogen and oxygen, then you get energy back out when you oxidize the hydrogen (which is simply reversing the first process). You can't get more energy out of the second process than what goes into the first process. Hydrogen (or water, depending on how you look at it) is not the energy source or fuel, it's just an energy transmission medium. It's more like a wire or a battery than coal or a solar panel or nuclear reactor.

 

[darkwing_duck1]

According to the Wikipedia article, the Fischer–Tropsch process "produces a petroleum substitute, typically from coal, natural gas, or biomass for use as synthetic lubrication oil and as synthetic fuel." Doesn't say anything about fuel from seawater.

The water-as-fuel idea sounds a lot like the "joe cell," which is really nothing more than old-fashioned electrolysis -- using an electric current to separate water into hydrogen and oxygen. As already pointed out, it takes more energy to split the water molecule than you'd get from burning the hydrogen. It's just the latest version of the perpetual-motion scam.

Bottom line: There Ain't No Free Lunch.

It's not a "scam" (it acutally works), but it IS horribly inefficient.

It's utility depends on the user's objective. Is it to find a more EFFICIENT fuel? Hydrogen cracking isn't going to do that. Is the objective to find a CLEANER burning fuel? If so, and you're willing to pay the price for the inefficient conversion, then cracking is a viable option.

It's not really an efficiency issue. You put energy into the system to split the hydrogen and oxygen, then you get energy back out when you oxidize the hydrogen (which is simply reversing the first process). You can't get more energy out of the second process than what goes into the first process. Hydrogen (or water, depending on how you look at it) is not the energy source or fuel, it's just an energy transmission medium. It's more like a wire or a battery than coal or a solar panel or nuclear reactor.

My point to scotpens was that hydrogen cracking is NOT the same as a "perpetual motion" scam. The process does work and will produce burnable hydrogen fuel, but at a substantial NET loss of energy transfer when the inputs for the cracking are factored in.

 

[Jadzia]

The modern idea is to use microwaves to split the water molecule, and it does look quite impressive to have a 10cm flame roaring out of a test tube of water.

But the power consumption of the big white box sitting 30cm away from it is easily ignored by those who want to believe the process yields free energy.

 

[darkwing_duck1]

^Which I never claimed, for the record.

 

[farmkid]

My point to scotpens was that hydrogen cracking is NOT the same as a "perpetual motion" scam. The process does work and will produce burnable hydrogen fuel, but at a substantial NET loss of energy transfer when the inputs for the cracking are factored in.

Sorry if I misunderstood. The way your post reads, it sounds like you're saying that it requires lots of energy but there is a very small net gain. A "fuel" is something that can be consumed to generate energy--an energy source. In this case, hydrogen is not the energy source, the source is coal or natural gas or the sun (via solar panels or wind turbines) or uranium, etc. Hydrogen is simply a method to store the energy or transport it from one place to another.

 

[darkwing_duck1]

My point to scotpens was that hydrogen cracking is NOT the same as a "perpetual motion" scam. The process does work and will produce burnable hydrogen fuel, but at a substantial NET loss of energy transfer when the inputs for the cracking are factored in.

Sorry if I misunderstood. The way your post reads, it sounds like you're saying that it requires lots of energy but there is a very small net gain. A "fuel" is something that can be consumed to generate energy--an energy source. In this case, hydrogen is not the energy source, the source is coal or natural gas or the sun (via solar panels or wind turbines) or uranium, etc. Hydrogen is simply a method to store the energy or transport it from one place to another.

That can be said of any fuel. You CAN burn hydrogen in an appropriate engine and use that engine to do work, so it is a fuel, and a pretty flammable one.

The trick is to generate the hydrogen using a method that is efficient, or otherwise negates the energy cost for converting the hydrogen from water.

If your conversion power source is petrochemicals or coal, to name two, then arguably the end result is not worth the effort since there is a significant net loss of energy, and you're still spewing out pollutants.

But if you were to use solar, wind, or hydro power (or even nuclear) to fuel your "cracking" plant, hydrogen becomes more attractive.

 

[CuttingEdge100]

Well, hydrogen and oxygen can interact chemically to produce a sizeable amount of energy. The problem is to separate the hydrogen from the oxygen takes more energy than merging them together.

 

[PurpleBuddha]

It's utility depends on the user's objective. Is it to find a more EFFICIENT fuel? Hydrogen cracking isn't going to do that. Is the objective to find a CLEANER burning fuel? If so, and you're willing to pay the price for the inefficient conversion, then cracking is a viable option.

I never understand it when people say that it would be cleaner to add the conversion. Why not use the energy you are expending on the conversion as the primary energy source?

 

[RobertVA]

It's utility depends on the user's objective. Is it to find a more EFFICIENT fuel? Hydrogen cracking isn't going to do that. Is the objective to find a CLEANER burning fuel? If so, and you're willing to pay the price for the inefficient conversion, then cracking is a viable option.

I never understand it when people say that it would be cleaner to add the conversion. Why not use the energy you are expending on the conversion as the primary energy source?

Because when you're commuting ten or fifteen miles each way to work or school that's an awfully long extension cord. That would also apply to a street bus.

A pressure tank full of hydrogen would probably be lighter than batteries capable of producing the same energy and wouldn't contain the toxic chemicals that are a consideration when many types of batteries are disposed of.

The problems are flammability if the hydrogen storage is damaged in an collision (I suspect either liquid hydrogen or gas would create an explosive cloud much easier than with gasoline) and the expense of the fuel cell if you want an electric car/bus.