What do I not understand about fuel cells?

[Sisyphus]

In discussions about hydrogen fuel cell vehicles, it's frequently said that "the infrastructure" would have to be in place before they could be practical, and the infrastructure itself wouldn't be profitable unless vehicles were widespread. Ok, so my question is: what infrastructure?

 

I guess it boils down to me not really seeing why you couldn't treat a hydrogen fuel cell as a rechargeable battery. Instead of having water vapor as exhaust, why not keep the water in the system? Then plug in the car to supply electricity for separating it into hydrogen and oxygen. Keep the hydrogen, let the oxygen go. Sure, the car would get heavier as you go, but not by that much, and the only "infrastructure" you need is a power grid.

 

Also, if for some reason that's infeasible (as I assume it is for some reason, since nobody talks about it), then still, wouldn't a "filling station" just need a supply of electricity and a supply of water in order to manufacture hydrogen on site, using only machinery a high school science class could build? Aren't those components of infrastructure that already exist everywhere? Couldn't existing gas stations pretty easily do this at relatively little cost (and thus need few customers to make it profitable)? No "hydrogen pipes" or tanker trucks necessary. Right?

[insane_alien]

the infrastucture is all the plants and transport system required to distribute the hydrogen.

 

look at petrol just now, massive tankers, refineries, filling stations, pipelines and so on.

 

you'd need to replace pretty much all of that for hydrogen to be distributed effectively.

[Sisyphus]

But my question is about why you would need a "hydrogen distribution system" at all. Did you read beyond the first paragraph?

[DrP]

I guess it boils down to me not really seeing why you couldn't treat a hydrogen fuel cell as a rechargeable battery. Instead of having water vapor as exhaust, why not keep the water in the system? Then plug in the car to supply electricity for separating it into hydrogen and oxygen. Keep the hydrogen, let the oxygen go. Sure, the car would get heavier as you go, but not by that much, and the only "infrastructure" you need is a power grid.

 

Also, if for some reason that's infeasible (as I assume it is for some reason, since nobody talks about it), then still, wouldn't a "filling station" just need a supply of electricity and a supply of water in order to manufacture hydrogen on site, using only machinery a high school science class could build? Aren't those components of infrastructure that already exist everywhere? Couldn't existing gas stations pretty easily do this at relatively little cost (and thus need few customers to make it profitable)? No "hydrogen pipes" or tanker trucks necessary. Right?

 

 

errr.... sounds great!..... too good to be true even - what am I/we missing?

[CharonY]

Also, if for some reason that's infeasible (as I assume it is for some reason, since nobody talks about it), then still, wouldn't a "filling station" just need a supply of electricity and a supply of water in order to manufacture hydrogen on site, using only machinery a high school science class could build? ?

 

Actually they are around already. I read an article of a couple of those in northern Europe and Japan. They are not terribly cheap though. One needs to generate the hydrogen, compress it, etc.

Another problem is that in case of using electricity to generate hydrogen, one is again dependent on either fossil fuels or nuclear plants to satisfy the energy need.

According to one calculation such a station would need roughly 3-57 MW to serve 100-2000 cars per day. Given this data it is likely that there is hesitation to set up a net of such stations as it is not clear whether the system is sustainable or not.

Edited February 4, 2009 by CharonY

[SH3RL0CK]

Sounds like a good idea, but I have some questions as to why this might not be practical (I don't actually know the answer, I'm just speculating here).

 

How long will it take to "recharge" this by spliting the water into H2 and O2 components?

 

How efficient is this "recharge"?

 

How much electricity is required to "recharge"?

 

Are there any dangers associated with this? High pressure? Hydrogen embrittlement of the parts? Fire and Explosion hazards from the H2 and O2? High temperatures? Others?

 

How large are the tanks of H2, 02, and H20 are we talking about? Are they heavy? Would the fuel cell itself be heavy? Maybe the fact you can freely get 02 (the heavy part) from the air and throw away the water (also a heavy part) makes a fuel cell possible where the weight would otherwise be prohibitive?

[CharonY]

For the integration of electrolysis into the car thing I would assume that normal cars would simply be too small for a electrolysis plus compression system. At least none that would generate meaningful amounts.

[Xittenn]

Electrolysis is highly inefficient.............wiki electrolysis see electrolysis of water. Platinum is very expensive and can easilly sour. General cost present day is absurd................

 

Algae photosplitting of water is the new and expected means of achieving cost effective production of hydrogen.............I suspect with the use of modern optics it could actually be introduced into peoples homes. Ocean production facilities are being looked into as being the most cost effective means. Here's a couple of good links that I found...............

 

http://www.nrel.gov/hydrogen/proj_production_delivery.html

http://www1.eere.energy.gov/hydrogenandfuelcells/pdfs/merit03/42_nrel_maria_ghirardi.pdf'>http://www1.eere.energy.gov/hydrogenandfuelcells/pdfs/merit03/42_nrel_maria_ghirardi.pdf

http://www1.eere.energy.gov/

[ishmael]

I think it takes more energy to produce the hydrogen than you get from using the hydrogen as fuel. Same thing with ethanol from corn.

[insane_alien]

But my question is about why you would need a "hydrogen distribution system" at all. Did you read beyond the first paragraph?

 

okay, well for one hydrogen production is governed by the economies of scale. it would be better(cheaper) to have a few massive hydrogen production facilities than to havea few thousand smaller ones dotted about.

 

not only that but the strain on the grid carrying electricity to the filling stations would currently take it far over capacity, thus the infrastructure would need to be replaced. not only that but new power plants would need to be made, lots of them. while if you were building centralized hydrogen plants then you would just need one power plant per hydrogen plant.

 

and obviously these can't be fossil fuel plants. i'm a fan of nuclear for this.

[CaptainPanic]

In discussions about hydrogen fuel cell vehicles, it's frequently said that "the infrastructure" would have to be in place before they could be practical, and the infrastructure itself wouldn't be profitable unless vehicles were widespread. Ok, so my question is: what infrastructure?

 

I guess it boils down to me not really seeing why you couldn't treat a hydrogen fuel cell as a rechargeable battery. Instead of having water vapor as exhaust, why not keep the water in the system? Then plug in the car to supply electricity for separating it into hydrogen and oxygen. Keep the hydrogen, let the oxygen go. Sure, the car would get heavier as you go, but not by that much, and the only "infrastructure" you need is a power grid.

 

Also, if for some reason that's infeasible (as I assume it is for some reason, since nobody talks about it), then still, wouldn't a "filling station" just need a supply of electricity and a supply of water in order to manufacture hydrogen on site, using only machinery a high school science class could build? Aren't those components of infrastructure that already exist everywhere? Couldn't existing gas stations pretty easily do this at relatively little cost (and thus need few customers to make it profitable)? No "hydrogen pipes" or tanker trucks necessary. Right?

 

Answer to OP

You are right. A supply of electricity (about 50-100 megawatts of it for one gas station) and a bit of water (a few kg/s) would certainly be sufficient.

And of course a compressor. I'm not sure about the change in efficiency of hydrogen production by electrolysis if you keep the reactor pressurized. (Ideally, you'd want to make the hydrogen at high pressure, so you can skip the compressor).

 

You should realize that if you go to the gas station, you take 50 liters of diesel in about 1 minute. Let's calculate the power: 50 liters = 40 kg of diesel. The heat of combustion is about 44.8 MJ/kg (diesel). You get 1.79 GJ of energy in 60 seconds. That's 30 Megawatt.

 

I'm sure you do not want a 30 megawatt electrolysis reactor inside your car... it will be big. It will generate heat (from heat and mass transfer limitations, like diffusion problems - electrolysis is not 100% efficient, and just 1% loss is already 300 kW of heating (that's the same as your normal engine of 400 horsepowers)...

 

In addition, you need to make sure that the hydrogen is at sufficient pressure (it needs to fit in a small volume if you don't want to look like a weather balloon on wheels), and that compressor would consume some energy. Perhaps it can be done in the same electrolysis reactor though... I am not sure about that.

 

Anyway, regarding on-board electrolysis, the 50 kg or water are not the issue. It's the extra equipment you need to put in the car that bring up the weight too much.

---

Merged post follows:

Consecutive posts merged

 

I think it takes more energy to produce the hydrogen than you get from using the hydrogen as fuel. Same thing with ethanol from corn.

About this quote

In fact, that is true for everything in the universe.

 

It is 100% logical - if the statement above would not be true, then the perpetual motion device would have been possible. Every process consumes more energy than that it will give off in the form of useful energy.

 

Charging a battery takes more energy than you get from using it.

Energy in gasoline is (much) more than you get in the form of kinetic energy when driving.

etc.

etc.

 

The story about ethanol (although off topic) is also a popular misconception. The statement is right: plants (corn) are not producing more combustible biomass than that there is sunshine.

 

Ethanol from corn is produced with a net gain in energy (if you assume that the sun's energy is for free). I mean: you do not use more fuel to produce the ethanol than what you get as a product... Take the ethanol you produce, subtract all the energy you use, and you will have left over.

 

It's a popular misconception that it actually has a negative effect which comes from worst-case-scenario studies combined with the fact that bad applications of fertilizer can produce nitrous oxides that are also greenhouse gases.

 

http://www.americanfuels.info/2008/09/ethanol-production-more-energy.html

Edited February 5, 2009 by CaptainPanic
Consecutive posts merged.

[npts2020]

Sisyphus; Wouldn't it be more efficient to use the electricity needed to separate water to just power the car to begin with? If you are going to use hydrogen, there is no way currently of producing enough with any device approaching the size of a car that would provide enough to power the vehicle for more than a very short time, hence the talk about infrastructure.

[CaptainPanic]

You can transport the electricity to the gas station, and build a relatively small hydrogen factory on the spot. You don't need hydrogen pipes through the landscape, although you might want to pimp your electricity grid. But indeed, as I explained 2 posts above, you shouldn't make the hydrogen inside the car.

[Sisyphus]

Sisyphus; Wouldn't it be more efficient to use the electricity needed to separate water to just power the car to begin with? If you are going to use hydrogen, there is no way currently of producing enough with any device approaching the size of a car that would provide enough to power the vehicle for more than a very short time, hence the talk about infrastructure.

 

Well, that's pretty much what you're doing. A fuel cell car is an electric car, just one that uses a fuel cell instead of a battery to supply the current. The actual motor would be the same. The question is not electric vs. fuel cell, it's battery vs. fuel cell. Clearly there are pros and cons to each, and research seems to be progressing rapidly on both fronts.

[Xittenn]

Car could carry an algae tank:-p...............................I know this point was made already but...............why would you have an onboard cell power an onboard electrolysis reactor to produce electricity to power a car? Just don't understand how that ever came into play. You could at the very least have used the hydrogen to power a hydrogen cumbustion engine(which are very much so in existence.) 25% to 50% standard heat loss in converting through electrolysis in the current range of reactors.................10% is hoped to be obtained...........seriously check out the links I posted it's like all the info from a formal American Government funded institute............or not.......no emoticon rrrrrrrrrrrr.........

 

It's also got to be salt water....................

Edited February 6, 2009 by buttacup

[CaptainPanic]

buttacup, I apologise for the following remark, but could you attempt to write in normal English sentences? With that I mean sentences that follow the grammar and spelling rules that you learned at school? It is difficult to read your posts, and I don't understand much of the last post you made.

 

Also, could you try to write down your ideas in a logical way? I get the feeling that you (and here I apologize again) just get stoned, and write any thought that pops up in your head.

 

Please read your own post before pressing "submit reply".

[Xittenn]

Well, I don't do drugs although I am currently on a fair amount of pain killers. As for your inability to understand what I have to say......well that's not something I'm going to be capable of correcting any time soon! Maybe it's a lack of interest in understanding what I have said that is preventing you from achieving just that. Feel free to not understand what I have said, I'm pretty used to it so you won't hurt my feelings. I wish I could more effectively share what I have to share, a lot of it is actually pretty good stuff ........... ummmmmmmmmm ....... wow you called me a stoner......

 

p.s. that last post was written with point form in mind, just like this statement..............

 

editing post

I can and have used quarter million dollar machinery to make parts for tanks...............I've repaired the quarter million dollar machinery...............hundreds of people have put their faith in my ability to do what I do and do it well.................they literally trust me with their lives.............I teach people how to do a broad variety of tasks..............I supervise and manage their time and efforts.........my time and efforts make rich individuals even richer...............I do all this and then I take the time to learn more...............I've been through a couple forums and I've been essentially riped apart every time..........I don't understand why I can't fit in...........I was really just hoping to get in on some cool conversations, some heated debates and some tasteful arguements...........I know my spelling and grammar aren't the best, they never where...................I'm young and eager so..............I make mistakes so....................I may even be at times judgemental of others, I still don't say what you just did.................I'm sorry I wrote this, please just nod and pass it off as something you didn't understand..............

Edited February 7, 2009 by buttacup

[Mr Skeptic]

Ok, so my question is: what infrastructure?

 

One is hydrogen transportation and generation. IMO you want to use a nuclear reactor; both the waste heat and the electricity generated can be used in-situ to make hydrogen making this fairly efficient. Alternately, the hydrogen could be used as load balancing for a green grid -- have the grid produce an excess, and generate hydrogen when not all is being used.

 

The trouble with your idea to generate hydrogen at each gas station is that it would be impractical at a large scale and at a small scale. At a small scale, there would not be enough customers. At the large scale, you would need to upgrade the power grid to power our transportation, and the local production would not be as efficient as could be. In any case, if we haven't managed to generate our electricity without fossil fuels, burning fossil fuels to generate hydrogen just doesn't make sense. After all, we can turn coal into liquid fuels that are easier to manage. At this point, a hydrogen car would serve mostly as a transition, a transition that we are not making yet.

 

Also, problems with fuel cells are storing the hydrogen (there's been some progress but its not impressive), and I think the fuel cells are still expensive. It would however make sense for electric cars to be built so that their battery can be replaced with a fuel cell system.

 

Overall, we should focus on getting our grid off fossil fuels before we worry about green cars.

[Xittenn]

 

Also, problems with fuel cells are storing the hydrogen (there's been some progress but its not impressive), and I think the fuel cells are still expensive. It would however make sense for electric cars to be built so that their battery can be replaced with a fuel cell system.

 

Overall, we should focus on getting our grid off fossil fuels before we worry about green cars.

 

As far as I've understood Titanium Sponge is the currently available tank material. Slow refueling and a poor discharge(amount of hydrogen actually released from a full tank) are the problems. This one link says it's for Tritium and Hydrogen Isotopes but I distinctly remember Titanium Sponge and Hydrogen storage for Hydrogen Combustion purposes.

 

http://www.cheric.org/PDF/JIEC/IE10/IE10-4-0539.pdf

http://books.google.ca/books?id=LfFIEQg1iioC&pg=PA100&lpg=PA100&dq=titanium+sponge+hydrogen+tank&source=web&ots=Zy5K05JL2n&sig=QoV78BnPu_25QNNxGRUuP7O_ri0&hl=en&ei=0TONSczNGJ3gsAOmk9CWCQ&sa=X&oi=book_result&resnum=6&ct=result