Talk:Fuel cell/Archive 1

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First image incorrect

Electrons flow in the opposite direction to conventional current. The arrows with e- should be reversed. Could someone please correct this?

-- The direction of the flow is correct -- Electrons flow from the anode side(H2) to the cathode side(O2). The arrows would need to be reversed only if instead of indicating a flow of e-(electrons) it were labeled as i (current), which would flow from cathode to anode. What is incorrect in the image is the (+)label on the anode and the (-)label on the cathode. These two should be reversed. --fiera 19:36, 31 May 2006 (UTC) Done.Mion 02:40, 1 June 2006 (UTC)

-- The direction of flow of electrons is INCORRECT, somebody please change the diagram ---

Electrons flow from the anode(H2) to the cathode(O2) through the external circuit, as correctly stated above. At the anode oxidation of H2 takes place producing electrons and protons, making the anode negative due to excess electrons. Here, as with all electrochemical cells the anode is negative. As opposed to semiconductor or vacuum tube devices with polarity, where the anode is positive. At the cathode O2 is reduced to water by taking electrons from the cathode and protons from the electrolyte, making the cathode electron deficient and therefore positive. As with all electrochemical cells, here the cathode is positive, whereas in semiconductor or vacuum tube devices with polarity the cathode is negative.

When dealing with electrochemical cells (fuel or battery cells), the best way to determine which electrode is the cathode and which one is the anode, is to remember that negative ions, anions are always going towards the anode, and positive ions, cations are always going to the cathode. i.e. anions to anode, cations to cathode.

In the case of the hydrogen fuel cell example, the protons, positive ions, cations are heading to the cathode. They do so because they are diffusing down a concentration gradient, from a high concentration of protons to a low concentration of protons.

So, the only thing that is incorrect in the diagram is that the flow of electrons should be in the opposite direction to that shown, everything else is correct.

Oenus 16:59, 12 June 2006 (UTC)

The protons are not driven by diffusion. The concentration of protons is the same throughout the membrane, and equal to the concentration of negative ions. (Otherwise there would be an unbalanced charge in some parts of the membrane.) It is the electric potential that drives the protons. --PeR 07:26, 14 June 2006 (UTC)

Focus, please.

This article is currently more focused on fuel cell cars than on actual fuel cells. I would like to move a lot of the vehicle-related text to the hydrogen car or similar article, so that this one can focus more on the fuel cell itself.

For the record, I personally don't believe in fuel cell vehicles, but this is not the reason why I want to move the text. It is simply in the wrong place.

--PeR 08:26, 20 February 2006 (UTC)

Doesn't Make much sense

"about 80% of the world's carparks have the legal requirment that cars should be able to start in sub-zero temperatures."

???

Availability of Metals Used in Fuel Cells

Are there any metals used in the construction of a fuel cell for which there is not a large supply, or known reserves of?

---

Platinum is required for a PEM fuel cell. I think research is being done to try to find another catalyst because platinum is too expensive.

Brianjd

Platinum is not required, it is simply the most effective. They are trying things like Platinum Rubideum mixes which are better in some ways but worse in others - AlexS

To be precise, platinum is not especially expensive in the manifacture of fuel cells; however, if one were to change all internal-combustion engines in the world to fuel cells, there would be not enough platinum in the world (and the price would obviously skyrocket). --Orzetto 20:07, 22 July 2005 (UTC)

The International Platinum Association [1] claims that the supply of Pt should be enough to match the requirement of replacing existing car engines with fuel cells. Current use of Pt in fuel cells is reported at 1.1-1.4 g/kW, with the goal of reducing it to 0.2 g/kW, so that a 50 kW car would use 10 g of Pt, that is about twice what is currently used in the average catalytic converter (4-5 g).

As a person who works in the fuel cell manufaturing field, please note that Pt actually accounts for a very small part of the manufaturing cost. at an average of 5g/m2, using the price of Pt today ($1030/tr oz), we are only talking about $166/m2 of electrode, while base materials run at a much higher price; e.g. Nafion membrane ~$500/m2, Gas diffusion layer ~400/m2, Graphite bipolar plates ~$3000/m2. In comparison, the price of Pt is almost negligible, but definitely something to be worked on.

alternatives to precious metals in fuel cells

I found the biological agent working as a catalyst instead of platinum. It is an enzyme produced by desulfovibrio bacteria. The enzyme is called hydrogenase. More info on subject (or something very near it) here. The article I read it from originally was in Tieteen Kuvalehti, published by Bonnier Publication International. ISSN 0109-2456. The magazine is in Finnish. Khokkanen 00:53, 27 September 2005 (UTC)

"While higher current densities can be achieved in fuel cells using electrodes containing precious metals, the researchers found that good current densities can be generated using a simple carbon anode." -- http://www.spacedaily.com/news/energy-tech-04zzg.html

Precious metals are needed for low temperature activation of hydrogen and oxygen molecules, as catalysts. For a reaction to occur, chemical bonds need to be broken, either by temperature or by catalysts. Platinum that dissolves hydrogen can break hydrogen and oxygen into reactive atomic species. In absence of catalysts you can use high temperatures - 500-1000 °C, and then you can use any kind of electrode, carbon, copper, anything that conducts electricity, you don't need a catalyst-electrode. Sillybilly 04:00, 27 December 2005 (UTC)

In my experience, you can use plain carbon electrodes in PEMFCs and AFCs with little or no degradation in power, but electrode life is cut by about a factor of ten: instead of a few thousand hours of operation, you will only get a couple of hundred. -- Thopper 04:48, 8 January 2006 (UTC)

More generally, others on this site have pointed out that palladium and rhodium have been used with success in PEM. I have also seen some work with cobalt porphyrins, but the cobalt doesn't stand up well in the acidic environment of the membrane, even when encapsulated in the porphyrin molecule. AFCs, of course, do not have this problem, and operate quite happily with non-noble metals as catalysts. Nickel anodes and silver cathodes have been used for decades in terrestrial AFCs, cobalt porphyrin is quite stable, and other catalysts have been tested. -- Thopper 04:48, 8 January 2006 (UTC)

I'd be interested in a specific PEM example that uses only pure plain carbon electrodes that are non-platinized, palladized, etc. Usually the precious metals and catalysts are carried on a conductive but inert support material, which may happen to be carbon, but the key is not the support material, but the catalyst it supports. You can probably get away with using carbon or any kind of electrodes on the oxygen side of PEMFC's, as long as you do use catalysts at least on the other side, providing low activation energy on the hydrogen side, that generate the hyperactive atomic hydrogen/proton that's capable of reacting with unbroken, still molecularly intact oxygen. It's what's called a free radical chain: H* + O2 -> HO* + O*, HO*+H*->H2O, O*+H*->OH*, O*+O*->O2, the * signifying hyperactive, high energy state free radicals or atomic species. Only O2 and H2O are stable, and nonreactive, the rest are restless, they rummage around until they find something quench themselves with into a nonhyperactive, stable state. But any free radical chain reaction needs to be initiated somehow, either by heat, light, or catalysts, and PEMFC's being low temperature and and non-UV-irradiated but dark, they need catalysts at least on one side. Of course besides platinum, there are other metals capable of functioning as catalysts to a lesser degree, including almost all the precious metals such as palladium, rhodium, ruthenium, iridium, osmium, that are all very expensive, or even less expensive [[Rai]ney nickel]] that's used in vegetable oil hydrogenation to produce margarine, or nickel-titanium-vanadium-rare-earth based electrodes such as used in NiMH batteries (by the way NiMH batteries could use platinum too, they'd just be too expensive that way), or sophisticated organometallic compounds such as the cobalt compounds you mention. Life deals with molecular oxygen via hemoglobin, that contains heme, an iron centered organometallic compound, and the hydrogenase enzyme Khokkanen mentioned is iron-nickel-sulfur based. Life uses different catalysts than precious metals for all the internal dealings, for all the enzymes, because it cannot deal with platinum that's so unreactive when it comes to forming compounds that can be carried in a bloodstream. The point here is that at low temperatures there is a need for catalytic action and not just anything will do, but yes, there are different catalysts with different catalytic capabilities, and different stability/longevity issues, and platinum may not be the one that wins out in the long run, but for now it's one of the longest life materials due to being so inert/nonreactive/stable - it cleans itself of any tarnish because it prefers being in the unrusted metal state, so platinum rust/crud will jump back to shiny platinum metal at the slightest chance, while it's superhigh reactive when it comes to catalytic action of forming atomic species on its shiny/black surface. AFC's using a bit higher temperature can probably get away with weaker catalysts. Temperatures above 5-600°C don't need any catalysts, or room temperature systems that are UV irradiated also don't need catalysts, but you need some way to deal with the activation energy. Life uses enzymes, but enzymes aren't forever either, they degenerate and age, and they have to keep being replenished by life on a daily basis. What's cheaper, more effective? Keep replacing the aged electrodes in a fuel cell every hundred hours, or buy a very expensive platinized electrode that needs to be replaced only after a few thousand hours? Sillybilly 09:02, 8 January 2006 (UTC)

I should have been somewhat clearer: you can use plain carbon, but it is not desirable for the reasons you have so nicely summarized: the free radicals which attack the carbon and degrade the electrodes, leading to short life. I cannot think of any specific print references to this (other than the SpaceDaily news item previously referenced), but if I can find one, I'll pass it along. I certainly wouldn't expect anyone to try this for any real-world application. I have tried it myself with AFCs as a baseline for other investigations, and spoken to a few researchers who have done the same with PEMs. Most of this work was probably done between 40°C and 100°C. I'm not sure what would happen at lower temperatures; perhaps the catalyst would contribute more to higher powers. Under normal operating conditions, it's the high surface area carbon used in the electrocatalyst layer that supports the high current density, while the catalyst largely seems to prevent attack on the carbon (and, of course, boosts power slightly).

My point, though, was not to suggest that noble metals are not needed, especially in PEM, but to contribute to the discussion of "alternatives to precious metals." You can use others, but nothing works as well as platinum and some combinations of platinum with a few other noble metals, especially in PEM, as you have said. In AFCs using flowing electrolyte (and hence a relatively high ohmic impedance), though, DSK-style Raney Nickel anodes seem to work as well as Pt-carbon anodes, and at slightly lower cost. Incidentally, I have worked with metal hydrides containing small percentages of platinum (less than one percent), and the improvement in performance is substantial. Too bad Pt is so darned expensive. -- Thopper 14:55, 8 January 2006 (UTC)

I went and read that SpaceDaily article more in depth, and the gist of it is that they use polyoxometalate catalysts, that look something similar to what life would be using, it looks like electrolyte dissolved salts that could be carried in a bloodstream, or as nondissolved salts supported on the membrane/electrode. These catalysts function as oxygen activators, even atmospheric molecular oxygen, so in a fuel cell you'd have something roughly along the lines of O2->2O* (activation step, it's probably not this simple), O*+H2O->2 HO*, e^-+HO*->HO^-, high energy hydroxyl ions generated at the oxygen electrode, which wander over through the electrolyte to the hydrogen side and attack the otherwise inert molecular hydrogen H2 + HO*->H*+H2O, etc, if that works like that, without activation. That they can catalyze and activate atmospheric oxygen is a big deal, but you may still need hydrogen side activation too - they say "carbon anodes," what about the cathodes? They still need platinum fro cathodes? Usually PEMFC's use platinum to do the hydrogen activation, where platinum excels, but they also use platinum for oxygen activation too. They would probably have to look into coupling polyoxometalate for oxygen side reactions with the secrets stolen from life's above mentioned hydrogenase enzyme working on the hydrogen side, to completely eliminate precious metals for both electrodes, because platinum works on both sides as a catalyst/activator. Or you may just use polyoxometallates on the oxygen side, and titanium-nickel based NIMH battery electrodes on the hydrogen side.

One of the issues is that most polyoxometalate catalysis research is into selectivity, into incomplete oxidation[2] [3], when in case of a fuel cell you'd like full and complete oxydation of anything that gets thrown at it on the cathode side, be it molecular hydrogen that needs a hydrogenase catalyst to get activated, or methanol, wet undistilled(therefore cheap) ethanol, glucose, etc. In the latter cases you'd have to deal with figuring out how to catalyze the oxidation reactions all the way to CO2, then how to carry the carbon dioxide buildup away, just like life running on glucose does. Life figured it all out at room temperature, how to harness the chemical energy stored in glucose + atmospheric oxygen, why can't we make a good fuel cell doing the same thing, at room temperature? One of the issues with life is speed of reactions, power generation capacity because of the low temperatures - there can be sudden instantaneous loads, but sustainable levels of energy loads are relatively low - people get tired because of concentration buildup, reactions only happen so fast at low temperatures, more fuel and oxygen needs to diffuse to the reaction site that only diffuses so fast, and life can only work so hard for extended periods and not much harder, it gets tired. This might be an issue when we try to copy life, fuel cells would get tired, i.e. overloaded, but it's scalable, elephants are equivalent to some pretty heavy duty machinery, so there is a good outlook there, though hopefully a fuel cell based on life-like catalysis of equal power to an elephant, would be much smaller size than an elephant. Sillybilly 18:10, 8 January 2006 (UTC)

One idea here is just to use life on the cathode side - aerobic bacteria that are starved for oxygen and use up any amount they can find to process the sugarcane solution they are floating in. This would set up an oxygen concentration differential across a membrane driving an electric current, just like concentration-batteries do. Basically you'd have the polyoxometalate catalyze atmospheric absorption to convert O*+H2O+2e^-->2 OH^-, sucking electrons providing you with a positive electrode, then on the other side of the electrolyte-membrane the process reverses to 2OH^-->O*+H2O+2e^-, and the O* would be in a form that the bacteria could process. There are probably different kind of bacterias that can live under various kinds of oxygen starvations and still do fine, but I don't know ultimately what kind of efficiency you could derive from such a system, because life itself isn't that efficient in converting chemical energy, some always gets wasted at each step, in each reaction, and then there is a lot of energy needed to maintain order, decreased entropy, for life to function at all. There is also the ethical issue of "bacteria starvation" that animal rights, or bacteria rights activists might stand up against. Sillybilly 09:19, 9 January 2006 (UTC)

By the way, sugar, which is easily carried in a solid form, and unlike coal or aluminum, it's easily soluble in water to be available to catalysts, has an energy density of 17 MJ/kg, compared to 13 for aluminum and 23 for coal, as shown at the pumped storage article. Life was pretty good at coming up with an energy dense, water soluble, and easy to handle energy storage medium. The hard part, of course, is the low 0.03% concentration atmospheric CO2 extraction that we might have a hard time to efficiently duplicate in conjunction with solar panels, and still beat the 0.5-2% overall efficiency of photosynthesis with our 15% efficient solar panels. We may find it easier to just process sand or aluminum minerals instead, or even water into hydrogen/liquid ammonia, which are much more concentrated and plentiful on the planet with high turnovers unlike biomass which can only recover so fast after a harvest. Another idea is to use fuel cells and instead of releasing CO2 into the atmosphere where it dilutes away, we could capture it, either in a liquid CO2 state, or some chemical state, and ship it to the solar processing station to be "recharged." Sillybilly 11:24, 16 January 2006 (UTC)

Fuel cell as Battery

I think this section is unnecessary now. I will read through it properly when I get the time.

Brianjd 12:26, Nov 5, 2004 (UTC)

I have archived the old talk in Talk:Fuel cell/Battery? and summarised it below. Note that all the blockquotes are actually quotes. Brianjd 10:14, 2004 Nov 16 (UTC)

---

Jerzy argues that a fuel cell *is* a battery and not merely *like* a battery, that therefore all battery laws also apply to fuel cells, and that even if this is wrong, a clear explanation of the difference should be given.

Mkweise argues that a battery is an ESD (energy storage device) and a fuel cell as an ECD (energy conversion device).

Jerzy says that the lead-acid automotive battery and the pumped storage plant are both ECDs, agrees that a fuel cell "cannot be reasonably construed as an ESD" and provides the following thought experiment:

But a better approach is to think about a system with a primary battery that is is not storing energy, but only converting it from chemical to electrical form. It's tempting to say that just disconnecting the charging system doesn't change the function of the disconnected at any given moment, and periodically they change roles. You, or your robot battery restorer, is at work on the disconnected battery: the depleted electrolyte gets dumped in the road and replaced from your sulphuric acid tank, while the sulphated electrodes get pulled out and stuffed in the trunk (for trade in), and fresh lead-metal electrodes, delivered like belted machine-gun ammunition, get installed in their place, so that battery is rebuilt and ready to take its turn as active battery. The tank and electrode magazine are storing energy as the fuel-cell tank does, but the electrolyte and electrodes in the lead-acid ECD have an energy storage function no more than is does the fuel in the space between the electrodes of the fuel cell; this kind of storage is merely incidental to the ECD process. Thus i think we have an "open ended", ESD-free, lead-acid battery ECD.

(I haven't checked the battery (electricity) article to be sure whether you've been misinformed by it or misinterpreted it; if you want to point out specifics, i'd be willing to express an opinion as to which applies.)

Jerzy believes that the same physical laws apply to both batteries and fuel cells:

(We're not, for instance, talking about cold fusion here; if new principles in chemistry had been involved, i'm confident i'd have heard about that.)

Mkweise:

From the viewpoint of pure physics (which you seem to be taking), batteries and fuel cells would both be referred to as electrochemical cells. They are fundamentally the same, just as motors and generators are - but from a functional viewpoint they are completely different: One is a closed system that holds an exhaustible supply of energy, while the other depends on a continuous external fuel supply. Think of a syringe vs. an IV line. Or, to use your own analogy: you wouldn't think of saying that a blast furnace is a type of forge (or that a forge is a type of blast furnace)—would you? And yes, all ESDs except capacitors internally employ two-way energy conversion but that, again, is beside the point as these are also functionally (as opposed to fundamentally) defined terms.

Hankwang believes that the definition of a battery is too vague to resolve this debate and suggests:

So, choose either "a kind of battery" or "similar to a battery" in the description of a fuel cell. In both cases, describe the important features that distinguish a fuel cell from what is commonly called a battery, mainly the fact that the latter normally is a chemically closed system. But then, a zinc-air battery for hearing aids isn't closed either.

Summary of a post signed "bblakemo@ford.com 8/10/2004":

Unlike capacitors, complex and multiple chemical reactions happen in batteries so they are difficult to model, and they are really ECDs (energy conversion devices, as opposed to ESDs - energy storage devices). Also, in a hydrogen-oxygen fuel cell, hydrogen should be called the anode and oxygen should be called the cathode (rather than the membrane and catalyst being called the cathode and anode). "I understand that this is a somewhat simplified view that does offer some problems in practice but would ask the reader to consider the Nickel Hydrogen battery in which gaseous Hygrogen is truely considered the Anode."

First hydrogen station

The article states (in a US-centric view maybe) that the first public H2 station was opened in Washington, DC, in november 2004. I was in Reykjavik in november 2003 and I visited the local H2 station. Maybe it boils down to the word "public". What is meant by that? If it is providing only for 6 state-owned vehicles, it's less public than Reykjavik's, which supplies a couple of hydrogen buses (which are regularly used by the public, bus route number 2 I think). See this link. Orzetto 12:06, 10 Dec 2004 (UTC)

...Since no objections are raised, I'll substitute in the Reykjavik station instead of the Washington one.Orzetto 09:06, 14 Dec 2004 (UTC)

Breakthrough in fuel-cell technology (in german sadly)

If someone here is interested in the subject and speaks some german you can find in interesting article about a new form of fuel cell developed by the Fraunhofer Institute in Germany here: http://www.n-tv.de/5465399.html Cheers, --Jpkoester1 11:25, Dec 21, 2004 (UTC)

I'm a hydrogen reasearcher, I can tell you that people keep inventing new types of fuel cells all the time. There are many ways to build a cell, and the link you posted tells of a "secret composition", that by the public may sound like "very advanced", but to mine sounds like "vaporware". Unless something about this is found in peer-reviewed journals, this is not to be taken too seriously. --Orzetto 21:02, 22 July 2005 (UTC)

Not a relevant argument anyway

I always used to think this is a good reason against hydrogen economy until i came across the post i have linked at the end this talk. "The hydrogen typically used as a fuel is not a primary source of energy: it is only an energy carrier, and must be manufactured using energy from other sources. Some critics of the current stages of this technology argue that the energy needed to create the fuel in the first place may reduce the ultimate energy efficiency of the system to below that of the most efficient gasoline internal-combustion engines; this is especially true if the hydrogen has to be compressed to high pressures, as it does in automobile applications (the electrolysis of water is itself a fairly efficient process)." This is from the main page. The main argument is hydrogen is not a source of energy, but what the argument avoids to say is gasoline is not a source of energy also. Once you agree with the fact that gasoline(Also a store of energy) is not a source of energy, the above argument becomes mute. This post nicely summarize the whole argument. [4] Note, even if you don't believe the above, hydrogen would still be a better option in that it would allow centralization of the gasoline usage. This would mean easy control of emission. In short, that argument is hopelessly weak

Gasoline is not a store of energy because it doesn't take more energy to produce it than you get from burning it. If we didn't have energy sources, instead of stores of energy, we'd be violating the laws of thermodynamics. If hydrogen gas was available in the environment, it could be used as an energy source, but it isn't. -- Kjkolb 13:44, 2 January 2006 (UTC)

Neither does hydrogen. If you produce hydrogen from natural gas, the first reaction is (I lump together the reforming and water shift reactions, forgive me; data from NIST):

$CH_{4}+2H_{2}O\rightarrow 4H_{2}+CO_{2}$, which has a $\Delta G=113.13kJ/mol$ at standard conditions;

Then we burn hydrogen and we get:

$4H_{2}+2O_{2}\rightarrow 4H_{2}O$, with a $\Delta G=-912.25kJ/mol$ at standard conditions.

The result is that we use 28.2 kJ to produce a mole of hydrogen, that returns us about 228 kJ when we burn it.

In fact, there are indeed ways to produce gasoline that could require more energy that what you get. When Nazi Germany was out of fuel, they used the Fischer-Tropsch process to make fuel from coal. Given the efficiencies of the time, it is quite possible they used more energy in producing the fuel than what they got out of it in mechanical work. --Orzetto 16:24, 19 February 2006 (UTC)

The fact that it is not an energy source should not be taken as an argument against using hydrogen. It's just something that you should take into consideration. Many people talk about using hydrogen, but they are not aware of where it comes from. We can produce it from fossil fuels or using renewable energy, but it is not a source of energy. -- Kjkolb 13:47, 2 January 2006 (UTC)

Well, gasoline can be considered an energy carrier, it's carrying all that solar energy collected in the past. Hydrogen is a very efficient energy carrier, giving it future potential, especially when fossil fuels that have carried so much solar energy from the past, have run out. PeregrineAY 20:18, 2 January 2006 (UTC)

It depends on your definition of an energy carrier, and I was using one that defined them as fuels that take more energy to produce them than we get from burning them. Even with all of the work to find, transport and process oil, we still get more energy than we put into it. The same with nuclear, hydroelectricity and solar. Batteries, hydrogen and electricity are energy carriers under this definition. Hydrogen production requires other energy sources such as solar, nuclear or coal. It should not be viewed as a put down on hydrogen. It takes more energy to produce electricity than we get out of it, but we produce it anyway because it is a high value form of energy. The same might be true of hydrogen when there is widescale production. People need to understand that it's not an energy source because they often speak of hydrogen as if it were, like suggesting the conversion of all power plants and vehicles to hydrogen. They should also realize that whether using hydrogen reduces pollution depends on how it is made. -- Kjkolb 15:14, 7 January 2006 (UTC)

I hope you'll pardon me jumping into the conversation. The formulation that I believe I have seen more frequently is to refer to fossil fuels as hydrogen carriers, and make a distinction between primary and secondary energy sources. In this formulation, oil is a hydrogen carrier and a primary energy source. Batteries, compressed hydrogen tanks, or metal hydride would all be considered secondary energy sources. I have rarely seen "energy carrier" used in the literature. After all, from a fundamental perspective, everything is an "energy carrier." -- Thopper 23:11, 7 January 2006 (UTC)

Agree with Thopper, everything is an energy carrier. But, when we argue for or against hydrogen economy, whether H2 is a source of energy or a mere carrier is something completely irrelevant. Fuel cells are compared, and often opposed, to internal combustion engines, or should I say, H2 is opposed to gasoline, not because they are a source or a carrier, but because of the result of an equation that balances "cleanliness", efficiency and renewability (and other factors). Of course it would not make much sense if we were to burn gasoline to generate electricity, to then make H2 by electrolysis, but if the electricity came from i.e. solar power, we can then generate H2; therefore greatly justified, and definitely not inefficient, regardless of the high pressure storage or etc.--fiera 17:54, 31 May 2006 (UTC)

Carnot efficiency

What do you mean with Fuel cells are electrochemical devices, so they are not constrained by the maximum thermal (Carnot) efficiency? I thougth that second thermal law and Carnot's theorem should always stands. AnyFile 21:09, 30 Jan 2005 (UTC)

I agree that this is a somewhat confusing statement. Fuel cells, like any other device, have a maximum theoretic efficiency equal to delta-G divided by delta-H (almost 90% for hydrogen; over 98% if the lower heating value, LHV, is used instead of delta-H). However, fuel cells do not require high temperatures or pressures to reach high efficiency. The term Carnot efficiency normally applies to the efficiency at which the temperature difference between two heat reservoirs can be converted into work. Starting from a fuel is not the same thing, although it is possible to compute the maximum temperature of combustion, in which case the Carnot efficiency is equal to delta-G divided by delta-H. I guess what people mean when they say that an engine is limited by the Carnot efficiency is that the maximum temperature is limited (due to material constraints.) PeR 07:31, 4 Feb 2005 (UTC)

I would disagree about your definition of efficiency; it should rather be "energy extracted as work" divided by the Delta-G. This because there is no way to get the Delta-H anyway, and it makes sense to define the maximum theoretical efficiency as 100%.

It does make sense to define the maximum theoretical efficiency as 100%, but unfortunately that is not the definition that people use. (Hence the need to compare with the Carnot efficiency rather than then number 100%.) --PeR

Delta-G=Delta-H - T x Delta-S, or dG=dH-TdS. dH is fixed for a scenario, while dG depends on your reaction temperatures, so while dH is the same at room temperature, 1000°C or 2000°C, dG isn't. To complicate things more, Carnot-efficiency is a function of temperature too. Also, for water, for the reacton 2H₂+O₂-->2H₂O, 3 molecules generate 2, the entropy change dS is negative, so dG=dH-TdS gets less negative(less spontaneous), to the point that about 2500°C dG is 0, the free energy of the reaction is 0, no energy is extractable. See the reverse process, high temperature electrolysis. So Carnot requires high temperatures for high efficiency, but dG for hydrogen/water requires low temperatures for high Delta-G. The lower the temperature you react hydrogen, the more energy is freely available from it, i.e. the more negative the Delta-G change.

Carnot efficiency only relates to thermal engines, and it limits the maxium efficiency extractable, based on the temperatures you use in a thermal engine. As PeR noted, all the available energy could be extractable through cyclic thermal ways (assuming you get the same energy per mole at high temperatures too, which is not true) if you had no limit on your upper use temperature. The formula for Carnot efficiency is eff=1-T1/T2, T2 being the upper use temperature, temperatures in Kelvins. So if you had a heat engine operating on "heat falling between thermal heights" of 10,000°C and 0°C, you could extract 1-273.15K/(10000+273.15K)=1-.0266=.9734, or 97% of the energy, only 3% would be handed over as waste to your cold temperature reservoir at 0°C, at your low height. However, using a 100°C high temperature instead of 10,000°C, gives you only an efficiency of 1-273.15K/373.15K=1-.7320=.2680, or only 27% maxiumum theoretical limit, 73% wasted on heating the cold temperature reservoir (you'd essentially be heating the outside atmosphere, ocean, world, giving your energy away to non-useful purposes.) There is simply no way to have a cyclic thermal engine, one that recovers to inital state without the purging some heat out to the universe during the recovery process. Think of one if you can, then you can beat the Carnot limit that's pretty much a law set in stone for now. You can get 100% thermal to mechanical energy conversion efficiency easily, by going just one way in an engine, if you had engines that just go one way but the very need to complete a cycle makes you waste some energy, ruining your 100% numbers. So, for instance, if you have a gram of fuel to burn, and a cyclic thermal engine to extract the energy from it, and have the option, of say, to heat 1 ton of water by 1°C, or heat 1 gram drop of water to 1,000,000C, then run a Stirling engine with your 1°C and 0°C, or 1,000,000°C and 0°C reservoirs to extract the work, you should opt for the heating 1 gram water to 1,000,000°C, because that gives you a 99.97% theoretical maxium efficiency of converting heat energy to mechanical energy, that wastes only 0.03% heating the outside world, instead of the 1-273.15/274.15K=0.36% maxium efficient 1°C to 0°C thermal engine, that has to use 99.6% of the provided energy to heat the outside world during its recovery process in its cycle. However, finding a heat engine that won't evaporate at 1,000,000 °C is very hard. Practical temperatures in internal combustion engines are near 300-1200*C, and you can calculate how efficiently an internal combustion engine car can work, usually well below 40%, and over 60% of energy is vented through the exhaust pipe, heating the world. An analog scenario would be lifting a ton of water by 2 mm, or 1 gram to 2 km heights, and then letting each fall down, pulling a pulley, but unlike in this case, in thermal engines you have a minimum height you can drop to, say 1 mm, and then you have to let the water freely drop from there, on its own, without doing useful work, otherwise it will never flow out of your engine. So it's like 1 ton of water falling 1 mm doing useful work, then another millimeter without doing useful work, vs. a 1 gram drop of water falling 1 km doing useful work, then another millimeter as waste, before it gets lifted again. This "minimum required waste height" in cyclic thermal engines is fixed by the cold reservoir operating temperature, and if you had a cold reservoir with a 0K temperature, that unattainable absolute 0, then eff = 1-Tcold/Thot = 1-0/T2 = 1-0= 1 = 100%, you'd have your thermal engines operating with 100% efficiency. However, in the world we live in, the practical cold temperature reservoir is near 0-30°C=273.15-300.15K, and not absolute 0, however in outer space things are different, though the extreme vacuum there is very insulating and doesn't make a good heat transfer medium (so most thermal energy is exchanged through black body radiation, instead of thermal conduction.)

Therefore on this planet, in the practical world we live in, you should always avoid resorting to thermal ways of energy conversion, if you can. For instance, mechanical to electrical or electrical to mechanical energy conversion efficiency in electric generators, alternators is routinely above 95% at room temperature conditions, at very practical conditions. Imagine you had a weight tied to a pulley, and while this weight drops, you had the option for the pulley shaft to either directly drive the rotor of an alternator to harness the energy, or, to rub against something, to heat it via friction, then use the heat generated as the hot temperature reservoir for your thermal engine. Then, if you're smart, you will opt for directly driving the alternator, and you will avoid the thermal/friction way, unless you have a tiny bit of material that you can rub to 1,000,000°C via friction, in which case you'd be okay, only wasting 0.03% in your thermal engine, theoretically speaking. In practice, most likely you'd only be able to rub it to, say, a maximum of 100C, even wasting some energy on air/bearing friction. Dynamos and alternators are incredibly efficient devices at sucking mechanical energy into electrical one, provided they have strong magnets and huge amounts of thick low resistance copper, or better, superconductors, and relatively little is wasted in the bearing and air friction, or copper electrical resistance heating.

Fuel cells are devices intended to directly convert chemical stored energy to electricity, instead the conventional ways, going through thermal means, through free combustion in air to obtain high temperatures then harnessing the heat via a cyclic thermal engine. Converting any form of energy into thermal storage at temperatures well below 1,000,000C means it will be only 35% efficiently convertable into other forms of energy, such as mechanical energy through a carnot/stirling engine, or electrical energy, through direct heat-to-electric devices called Peltier elements. Mechanical/electrical forms of energy are up to 97% efficiently convertable into other each other (mechanical bearing friction and copper resistance losses being the culprit for losses), or into chemical energy, inside a battery, which, in the case of lead acid, is 90% recoverable into mechanical/electrical.

Note that you can always convert everything 100% efficiently into heat, because everything heats its external universe as a wasting mechanism, whether it's bearing friction, copper resistance, battery operation, they all heat up as a wasting mechanism, and you just add your 97% efficiency to that 3% waste heat and always get at least 100%. At least, because, in fact, even more than 100% heating efficiency is possible, from other forms of energy, by running a Carnot engine exactly backwards, in which case you "steal" warmth from your cold reservoir, as in heat pumps, the cold reservoir being at some higher temperature than absolute 0 K. So for electric heating, instead of a resistor heating element, that only gives 100% heating, you're better off running a heat-theft-device-heat pump, that gives you even more heat, it steals some heat from the outside cold weather. The lower the heat-to-mechanical efficiency of a carnot engine is, the higher its mechanical-to-heat efficiency, which is its mathematical inverse, heat-pump-effcy=1/carnot-effcy. So heat pumps work best when heating a room from 0°C to 1°C, being 1/(1-273.15/274.15)=1/.0036=27000% efficient, but they are less efficient at heating from -30°C to +30°C, 1/(1-243.15/300.15)=1/.018=500%. There isn't too much market for heating something by 1 degree or half a degree, and heat pumps are expensive to build compared to simple heating resistor elements, but still, a number above of 500% effiency is not too shabby. Unfortunately, electricity needed to run a heat pump is generated via a forward Carnot process, so the backwards way in theory only gets you back to the original available energy, "undoing" the waste at the power plant with your heat-stealing heat-pump. But this was not even considering delivery losses through the long-long copper or aluminum cable from the power plant, so you're back to square one, because it's more efficient to deliver the natural gas to you through a fat hollow pipe, than electricity through a heavy, solid conductor, so if heat is what you want, then use the fuel directly, instead of converting it to electricity in a power plant. But in fact, if you ran an efficient ideal carnot engine between 0°C and 1000°C in your home, then used its mechanical output to drive another, "less efficient" carnot engine operating between only 0°C and 30°C "thermal heights" in reverse mode, as a heat pump, the net effect of an efficient carnot engine driving an "inefficient" carnot engine in reverse mode is heat stolen, higher than 100% efficiency. However most practical engines are not ideal, the carnot engine numbers of 40% maximum efficiency being theoretical, and practical engines are much less efficient, say 25-30%, plus there is a huge capital cost and maintenance nightmare associated with this scheme, but it works, with natural gas delivered to your home, instead of burning it, use a dual-carnot engine setup that steals heat as a net effect from the cold weather outside. Still, a power plant can usually operate at much higher temperatures because of scale and size, thus thermal insulation, than a tiny device you need at home, plus maintenance costs of one big device are less than a million tiny generators, so the economies of scale dictate having power plants in general, at least for electricity. There are other reasons too, such as safety, especially if we start heavily relying on nuclear fuels, you wouldn't want everyone to run a nuclear based home generator, such as submarines do, with customers purchasing fuel rods in a lead case from a store, that's free-market with-zero-big-gov't-interference gone-wrong, you'd rather have it done in a government controlled/licensed, secured large-scale facility, and only deliver safer forms of energy, whether it's hard-to-store electricity, or easier to store liquid ammonia, magnesium or aluminium rods, green-house neutral hydrocarbons such as biomass+hydrogen converted to methane or liquid butane, or even ethanol/methanol, or hey, even that hard to tame/store hydrogen, in a fictional hydrogen economy. Ammonia you could even use as a fertilizer, and ethanol, if 100% pure, you could dilute 50% to brandy. :) Imagine an ethanol economy with everyone with an alcohol pipe in their home, they can use like tap water to cook, heat, clean, disinfect, drink, refill the car etc. :)I don't even want to think of what all wrong you can do with supercool liquid hydrogen. Magnesium rods are relatively safe, easy to handle - car wheels and engine blocks even made from it, but if powdered/grinded, the dust can catch on a very severe fire, even releasing blinding UV radiation while burning, but magnesium is easier to make or react than aluminum is.)

Returning back to the point of trying to avoid heat as an intermediate energy storage medium, of course if heat is what you want, the thermal intermediate is fine, such as for solar heaters, but to get electricity or mechanical motion from sunlight, you either need a super high temperature stirling engine solar concentrator to get reasonable Carnot efficiency numbers, or avoid thermal means by using direct photovoltaic light-to-electric conversion. Currently all nuclear, coal and natural gas electric power plants use conventional thermal engines and they cannot break the Carnot efficiency barrier, meaning they heat the outside world 65%, and only deliver 35% of the available energy to you. Fuel cells on the other hand directly harness the chemical energy to electricity, they directly harness "dropping through chemical heights" without "dropping through thermal heights", (through chemical potential energy gradients instead of thermal potential energy gradients), but because fuel cells are not 100% efficient, they still release some of the energy as waste heat, that you can still use in your thermal engine, so they give a 30-50% electric + 35% thermal means of harnessing the energy, instead of just 35% thermal means, wasting only 15% to heat the outside world, instead of 65%. Sillybilly 17:35, 11 December 2005 (UTC)

For Anyfile: the reason the Carnot limit does not apply in fuel cells is that the energy conversion does not pass through heat: the Carnot limit is normally understood (at least in the terminology I learnt at my university) as the limit of heat cycles, and the fuel cell is not one. Of course, the second principle stands.

For AnyFile: I've corrected the article text to read: Fuel cells are electrochemical devices, so they are not constrained by the maximum Carnot cycle efficiency as combustion engines are. This sentence could be worded much better, but atleast it isn't misleading now. Faraz Syed 06:44, 19 October 2005 (UTC)

Rerversible fuel cell - only a configuration

By definition a fuel cell can be operated in reverse. Reversible fuel cells should not be considered a separate type of fuel cell. I realize that the page for reversible fuel cells states:

"So while the reversibility is applicable in principle to any fuel cell device, a practical device may not be built with this intent. Hence the distinction between reversible fuel cells, and generic fuel cells."

However, this does not mean it is a different type of fuel cell. Operating a fuel cell in reverse is simply a matter of configuration/capability and has nothing to do with "types" of fuel cells, which should only distinguish between cells which utilize different fuels and/or different half-cell reactions.

My suggestion is that the page simply state:

All types of fuel cells can also be operated in reverse. However, most fuel cells are constructed for the purpose of generating electricity only and therefore may require alterations before a reversible process can be run. For more information, please see Reversible Fuel Cell.

Faraz Syed 02:04, 30 August 2005 (UTC)

Removal of external links

As per Wikipedia:External links, I've removed a large number of links. If there are any that really scream to be replaced, here's a good place to talk about it.
brenneman^(t)(c) 06:55, 26 September 2005 (UTC)

Thanks for doing that. This article has attracted an unusual amount of linkspam. -Willmcw 22:36, 26 September 2005 (UTC)

The list was building up again and I reduced the number of links. Only the best sites for the article should be kept. I say "the best for the article", because a site can be good, but not be useful for the purposes of an encyclopedia article. For example, a site with fuel cell components for sale, and no significant content about how fuel cells work and such, would not be helpful for most readers. Rather than removing the links immediately, it might be best to do it periodically, so that there is not a fight about the addition and removal of every link. Also, editors might be less likely to take the removal of a link they added personally. However, if an editor adds the same link to many web pages or if the site is a linkfarm, immediate removal might be better. -- Kjkolb 05:03, 21 April 2006 (UTC)

Research Development Links

Added a section for links on research development for fuel cells, as I think this is really needed, especially since fuel cells are still under researched and being continually developed.

The link I have placed is a huge break though in hydrogen fuel cells, allowing for cars to store hydrogen (for use in a fuel cell) without a potentially dangerous compressed hydrogen tank. So that is why I thought it would be important to add in.

If anyone has any other links for future or previous dates which reveal a breakthrough in research development into fuel cells, then please add them.

• What's preferable is if the information is summarised and added into the article. And please do sign you name with these, ~~~~, please.
  brenneman^(t)(c) 09:10, 4 October 2005 (UTC)

• The information will be severly disadvantaged if it is 'summarised'... perhaps a link and a summary?

Please understand that the purpose of this project is to amass information, so links to outside sources do us little good. Breakthroughs are important, but as an encyclopedia we're more interested in technologies that have already been proven one way or another. We can be the last to report an innovation. -Willmcw 16:37, 4 October 2005 (UTC)

Low Efficiency

"Fuel cells running on compressed hydrogen may have a power plant to wheel efficiency as low as 22%"

What is the purpose of stressing how low an efficiency a fuel cell may have? Aren't we more concerned with the current and theoretical maximum efficiencies of fuel cells? Anyone can make an engine with 1% efficiency, or lower.

The total efficiency (from coal or methane to hydrogen to fuel cell to vehicle motion) is important and should be included, but the theoretical maximum efficiency and the current efficiencies should also be given without taking that into account. It would be odd for an article on internal combustion engines to give only the efficiency after the energy used for oil exploration, drilling, transporting, refining and distribution are taken into account, and not give the efficiency you get just gassing up the car and driving. The efficiency given for a combined heat and power fuel cell is also incredibly low. -- Kjkolb 12:23, 2 January 2006 (UTC)

Types of Fuel Cells

A number of experts in fuel cells, including Karl Kordesch, have noted that the main advantages and disadvantages of a fuel cell stem from its electrolyte, and that this is why fuel cells are classified by their electrolyte. It seems that the Wikipedia article underemphasizes the importance of the electrolyte by placing the "Types of Fuel Cells" section at the bottom, and not providing any discussion or comparison at all of the various types.

I'd like to add a section either just before or just after the "Science" section that lists the types of fuel cells and their relative strengths and weaknesses, and perhaps some operating characteristics (such as temperature range). This would still leave the separate pages for each type to go in to details regarding how each type of fuel cell works. Any suggestions or comments? -- Thopper 00:30, 8 January 2006 (UTC)

Also, the diagram of the alkaline fuel cell, showing water flowing out with the excess hydrogen flow, is only correct for immobilized electrolyte designs such as those used in the Space Shuttle. Terrestrial AFCs typically have mobile electrolyte, allowing water management to be mediated through the electrolyte itself. I'm not quite sure how to capture this, and certainly haven't the artistic skill to update the diagram. -- Thopper 00:34, 8 January 2006 (UTC)

Hi! I just came to think whether it can be explained: is it possible to carry out virtually any oxidation thermal generation process to a fuel cell process via catalyzation? I mean, in theory it involves exchange of electrons, and essentially represents a reaction whose anergy could be trapped by a wise invented (or accidentally found) catalyst and membrane.

What I wanted to ask may be is this theoretically possible: to generate electricity by mere catalytic oxidation of natural oil or other fuel instead of simply burning it in air stream, to avoid Carnot process? -- mtodorov_69, 16 February 2006

Is it possible to build a nuclear device that will directly transform nuclear bond energy to electricity, without using intermediate thermal stage of energy conversion? Is it possible to covert directly from chemical and nuclear to mechanical, without intermediate thermal or electrical? This could be at least in "See Also", please, this is very intereseting. I hope it's not SF.

"Stranded" diagrams

Coming here to see how a fuel cell works, I eventually spotted the diagrams hiding at the bottom of the article. I understand that not all fuel cells work the same, but one or two of these diagrams, with appropriate explanation, would make the "Science" section a lot more useful to the unknowledgeable reader, if you ask me. - IMSoP 01:05, 28 January 2006 (UTC)

Efficiency of a standalone electrolyzer

As far as low efficiency as a standalone electrolyzer goes, we need to understand a bit about fuel cells. In particular, all fuel cells use a membrane to only allow only ionic species to flow into the reaction zone. That is, the reactants are forced to undergo an ionization process at the surface of the membrane, by either giving off or accepting electrons, before they are granted free passage into the reaction zone. Once ionized, the concentration gradient pulls the ionic species across the membrane, to the reaction zone, where the ionic species are consumed, thus keeping the concentration near 0 on the reaction side, and the gradient across the membrane active. Without the separation membrane the reactants could simply jump and react each other, without giving us the electrical way to tap the energy. With direct reaction we would only get heat, which, according to the principles of the Carnot Cycle, is an even more inefficient way to tap energy - most internal combustion engines are limited to 10-40% efficiency, while fuel cells can beat that easily, providing 40-70%, still falling short of batteries that can return over 65-90% of the available chemical energy as useful work.

The giving off or accepting electrons is the process that harvests the bulk of the available chemical energy. Still, like in any conversion process, not 100% energy becomes available, a lot is wasted. For example, some energy is consumed/wasted because there is electrical resistance by the membrane against the current flow carried by the ions - the ions bounce against the membrane atoms, and generate waste heat in the process, just like electricity passing through an incandescent bulb filament heats it up, consuming energy. The longer the path travelled by the current flow, the more energy is wasted. For this reason a good fuel cell membrane is as thin as possible, and as highly conductive ionically as possible. Also, a good fuel cell has as large a surface area as possible, because a large surface area lowers the overall membrane electrical resistance as well. There is always a balance in how big and thin you can physically stretch a membrane, without risking pinholes or large holes in the membrane, that would completely ruin your cell's efficiency, so the ionic conductivity of the membrane material remains a key player, limited by the available materials science technology at the time.

Low temperature fuel cells make very expensive electrolyzers, because of the special nature of the membrane surface, which needs a platinum coating. The reason for this platinum catalyst is to provide a low activation energy for the H₂ → 2H reaction, the breaking of the hydrogen molecules into atomic species. This reaction is an energy intensive process, but still, like all chemical reactions, in an equilibrium, and any equilibrium can be driven by concentration gradients in either direction. Such catalyst is not necessary for the backwards process, for electrolyzing water, because 2 nascent and reactive hydrogen atoms or oxgyen atoms freely recombine as pairs into a stable, lower energy molecules, which bubble up to the surface. That is, you can effectively electrolyze water with two metal rods, even copper or steel, and produce molecular oxygen and hydrogen gas from the nascent atoms that form at two electrodes, however, you could not use such two-metal rod electrolyzers backwards as a fuel cell, because, even if you bubble hydrogen or oxygen to their surface, they wouldn't be able to generate the needed atomic/ionic species, without either high temperature (600 to 1000 °C), or a low temperature catalytic activity that platinum has. The known catalysts, the metals that are highly active at gaseous molecule splitting at room temperature, are either very expensive precious metals — platinum, palladium — or sophisticated blends of lower cost, but still expensive metals, such as those used in NiMH (nickel-metal-hydride) cells. NiMH batteries blur this boundary between batteries and fuel cells somewhat, at least the hydrogen side of things — the atmospheric oxygen activation may still be an issue - hemoglobin anyone? True, that while almost any metal can be used to electrolyze water, there is the factor of electrode overpotential that limits the efficiency of electrolysis, and these low activation energy catalytic metals make the very best electrodes. Still, there is no need for a membrane for electrolysis, but only for the forward, fuel cell mode of operation. Ideally, the metal side of the membrane would be flooded with the highly conductive water electrolyte for electrolysis, the electrolyte being in direct contact with the metal without a separation membrane, but dry it off and keep the electrolyte on the other, nonplatinated side, during operation as a fuel cell, to force all ions to travel through the membrane.

High temperature fuel cells such as solid oxide membrane (e.g. zirconia) fuel cells have no catalyst-expense limitation, but they are similarly costly because of the very nature of high temperature operation, slow startups (up to 8 hours), bulky size and the need of thermal insulation. High temperature electrolysis is currently an area of active research because it can directly utilise cheap heat energy, partially replacing the expensive electric energy needed to split water. This is based on the thermodynamic entropic drive in the reaction 2H₂O → 2H₂+O₂, 2 moles reacting to for 3 moles of product, therefore increasing entropy, so forward reaction favored at higher temperatures, becoming spontaneous at the impractically high temperature 2500 °C. At temperatures below this point some electricity is required, but the closer the reaction is done to 2500 °C, the less extra 'nudge' needs to be supplied by electric energy. The highest practical temperatures are near 1000 °C, using a solid oxide fuel cell exactly in reverse mode. Even in view of the above cited thermodynamic advantages, this method has its own disadvantages, namely having to separate the reactant steam from the product hydrogen, by energy wasting cooling to liquid water, then having to reheat it back to the reaction temperature to complete the recycling step.

Mostly likely the most efficient large scale industrial water electrolysis method is, as described in the patent literature, via lower temperature steam injected into molten alkali metal hydroxide, near 200–400 °C, this molten electrolyte being hygroscopic enough so that not much steam evaporates with the product gases so no expensive separation step is needed. Molten alkali hydroxides have very high ionic conductivities, allowing very low resistive losses, and extremely high current densities.

nice text, is going to be integrated in Fuel Cell. Mion 10:19, 9 April 2006 (UTC) Coming from Reversible fuel cell Mion 23:19, 10 April 2006 (UTC)

Some images for free...

... here: http://www.anl.gov/Media_Center/Image_Library/engtrans.html about fuel cell.

These images from Argonne's research image library are available for your use with an Argonne acknowledgement.

-- Harp 07:39, 19 April 2006 (UTC)

Use in aircraft

I removed the following from the article:

"Critics of fuel cells have also pointed out that their proposed use in aircraft (in order to cut the use of kerosene, which contributes massively to global carbon emissions) would have little or no impact on mitigation of climate change, since water vapour, itself a greenhouse gas, would be emitted."

First, there needs to be a source for this statement. Second, it is incorrect. Water vapor is a greenhouse gas, but its concentration in the atmosphere is not changed much directly by human activities. Water vapor is important in that increased carbon dioxide levels, causing global warming, may increase evaporation and therefore the level of water vapor in the atmosphere, increasing the greenhouse effect even further. The warmer temperatures may cause more water to be evaporated, which would increase the greenhouse effect further, causing a runaway greenhouse effect. Also, the burning of kerosene produces water vapor and carbon dioxide, instead of just water vapor, so even if water vapor was a problem, at least carbon dioxide would not be released as well (it is released during some types of hydrogen production, however). -- Kjkolb 17:28, 24 April 2006 (UTC)

Fuel cells vs batteries

"Fuel cells differ from batteries in that they consume reactants, which must be replenished, while batteries store electrical energy chemically in a closed system."

This distinction seems a little weak. Both batteries and fuel cells consume reactants. Most modern batteries cannot be replenished, but archaic ones like gravity cells could (replacing the anode and the electrolyte was routine).

Can someone clarify the distinction?Kurzon 00:10, 21 January 2007 (UTC)

From an intrinsic point of view, fuel cells and batteries are exactly the same: both generate compound by means of a chemical reaction, where the side effect is electricity and heat. But in reality comparing them is almost like comparing apples and oranges. Any weak distinction made, is only arbitrarily come up with a definition for fuel cell Vs battery. Exceptions to the definitions will arise. --Fieraloca 04:00, 7 February 2007 (UTC)

The distinction may be arbitrary, but it is nevertheless important and valuable. All of the reactant in a battery is contained in the cells. If you want to increase capacity(Amp-hours), then you have to increase the size or number of cells. That is expensive. If you want to increase power output(kW), you also have to increase size of number of cells. This is not true with a fuell cell. Capacity is based on how big your reactant tanks are, and they are cheap compared the cost of battery cells. Power output determines the size and number of fuel cell stacks.

Also, storage batteries (not the ones that you throw away) are rechargable. This means that when the terminal voltage is raised above the cell voltage the reactants will chemically transition to their original states. Fuel cells cannot turn their products (water and heat for a H-O fuel cell) back into the original reactants. —The preceding unsigned comment was added by 149.37.200.150 (talk) 14:10, August 23, 2007 (UTC)

Electro-galvanic fuel cell

Electro-galvanic fuel cells have been used for decades for measuring oxygen concentration in a breathing mixture. Would a short description or a reference to the article / use be appropriate? Especially as to how the concentration of oxygen gives a difference in voltage, which is converted to a displayed oxygen concentration. --Seejyb 20:12, 20 May 2006 (UTC)

They have their own article Electro-galvanic fuel cell--DV8 2XL 20:26, 20 May 2006 (UTC)

Removed image

Who removed the image from commons ? its a GFDL licensed image from the French wiki. Fuelcell.en.jpg Reg .Mion 05:46, 16 June 2006 (UTC)

water fuel cell

1989 A so-called water fuel cell is an unrelated claim of a perpetual motion device, which in fact was not claimed to function the way a fuel cell does.

If the water fuel cell has its own article it could be referenced on, it makes people more critical about real inventions and hoaxes, //Enron/Tesla Motors.Mion 16:31, 19 June 2006 (UTC)

Wikipedia's job is not to make people critical of hoaxes. This belongs in the disambig page, which is why it was removed. Chris Cunningham 17:36, 11 August 2006 (UTC)

In which disambig page ? Mion 19:14, 11 August 2006 (UTC) , and read the first part of the sentence, If the water fuel cell has its own article it could be referenced on, the second part was my personal view. Mion 19:14, 11 August 2006 (UTC) thats why i put it back.

and another one, there are loads of patents given on the design, it has the design of a fuel cell, the fact that we didn't see one working , tja.Mion 19:14, 11 August 2006 (UTC)

It isn't a real fuel cell, the disambig tag at the top of the page links to the article in question, and you haven't given a justification which fits with the goals of the project. It's pretty disingenuous of you to ask "which article" without actually doing a search for "water fuel cell". Chris Cunningham 21:53, 11 August 2006 (UTC)

ok, i missed the top link to the disamb page, and which article, did i ask you  ? well , i think it still belongs in the history section of fuel cells, or are we making only an article about fuel cells that where succesfull ? in that case there is more to clean out. reg. Mion 23:24, 11 August 2006 (UTC)

This article is about fuel cells which fit the description given in the intro, i.e. which take hydrogen and oxygen as fuels. The water fuel cell works the other way around, so it isn't a "fuel cell" as per this article. It is mentioned, in the disambiguation tag. It isn't part of the history of fuel cells as per this article. Chris Cunningham 07:22, 12 August 2006 (UTC)

Yes, which takes hydrogen and oxygen as fuels to create a current. see Reversible fuel cell. reg. Mion 11:26, 12 August 2006 (UTC)

A speculative stub does not an argument make. Chris Cunningham 12:46, 13 August 2006 (UTC)

well, can the process be reversed in a fuel cell? Mion 13:45, 13 August 2006 (UTC)

First, the fact that the water fuel cell was granted a patent is absolutely irrelevant; in fact the patent was granted on the basis of construction of the invention, and not on whether the invention actually works.

Second, Nope, a fuel cell does not have to be used with H2 and O2 only, don't forget direct methanol fuel cells, solid oxide, etc etc etc. What characterizes the fuel cell is not the reactants it uses, but the exchange of protons between the cathode and the anode via dielectric media. --Fieraloca 04:15, 7 February 2007 (UTC)

DCFC

http://www.wired.com/news/planet/0,2782,69713,00.html Mion 13:12, 16 July 2006 (UTC)

Turning off vs. continuous operation

If the water is not evaporated quickly enough, it reduces efficiency, and if it is evaporated too fast, it can crack the fuel cell. So, if used in, say, an automobile, does it have to keep operating all the time even when the car is parked, or can it be shut down, unlike the ones used in the Apollo space missions? (Jim Lovell on Apollo 13 knew that if they shut down the fuel cells as Mission Control told them to, they could not be restarted.) GBC 17:21, 11 August 2006 (UTC)

Yes, they can be started, but it will take some time before they operate at full efficiency (depending on type: SOFC take a full 8 hours!). More than cracking, the dry-out causes an increase in internal resistance (it just does not work), but such PEMFC systems usually come with an humidifier. As for the Apollo, they used quite primitive alkaline FC technology... I do not know the details, but they were probably short-lifespan gizmos (after all they had to last for a few days only) assembled thinking more about saving weight than flexibility in usage. Come think of it, there is at least one type that must be operated continuously, the PAFC (phosphoric acid): below 41˚C the acid solidifies, and good luck warming it up again... but PAFC are almost ignored nowadays.

Once the membrane is hydrated within the break-in period of a new fuel cell, full performane can be achieved within minutes. Continuous operation is not necesary. Water is not evaporated from a fuel cell; the gas diffusion layer moves the water into the flow field of the current collectors.--Fieraloca 08:34, 12 November 2006 (UTC)

It should be noted that start up time depends heavily on type of FC, modern PEMFCs can start within a few seconds. The startup time of a fuel cell system usually depends on time required to get the ion conductivity layer to produce adequate conductivity for the current required. Nafion, a popular material for PEMFC ion conductivity layer (electrolyte) can operate lower than 0 C (32 F). SOFCs need to reach about 600-800 C to start conducting ions for efficient operation.

Fuel cell definition

Oxford dictionary: • noun:

• a cell producing an electric current direct from a chemical reaction.

[[5]]Mion 11:52, 11 September 2006 (UTC)

the indefinite article does not denote that any device matching that short description is a fuel cell, any more than a definition of a crow as a "black flying object" implies that cannonballs are crows. Consensus has been shown to be in favour of leaving this article only for devices matching the scientific definition of a fuel cell as a device which creates electricity through oxidation. Chris Cunningham 14:18, 11 September 2006 (UTC)

I cited a reference, the Oxford dictionary: can you give me an equal valuable reference on the scientific definition of a fuel cell ?

If consencus has been reached, ok , where can i find it ? if not the first part of the article has to be rewritten.

or the other way around, if i cant hold my argument i am going to revert it myself. Mion 14:29, 11 September 2006 (UTC)

Try some specific literature like "Fuel Cell System Explained" by Larminie and Dicks, it is a common textbook in the subject. You should find it in any university library.

The reasen why there was a discussion :[[6]]. result. stays as it is.. al thanks for the help. Mion 10:22, 29 September 2006 (UTC)

Need help in writing an article about Pure Hydrogen-Air Fuel Cell

Hi Mion or Anyone can help-- Please. . .

As ESL (English as second laguage) person I need help in writing an article on what I beleive it could be a break through in Fuel Cell research.

I have found in the setting of embrittled aluminum as anode, stainless steel as cathode and water as electrolyte one can build Hydrogen-Air fuel cells; I have it test run for hundreds of hours, no membrane or catalyst required; This will be:

The least expensive to build.

CO and CO2 Immune.

If you can help me in anyway please foreward me a note at ephitran at gmail.com

Many Thanks.

Phi

My advice is that you get in touch with the electrochemistry department at your local university. Write them (in your own language) a short abstract about your experimental setup and analysis, and I'm sure they will either help you or tell you why your invention doesn't work (My guess is the power density is too low). You will need to have a peer-reviewed publication elsewhere before you can post an article on Wikipedia, since original research is not allowed here. Good luck. --PeR 09:19, 2 October 2006 (UTC)

You are talking about a galvanic cell. Yes, you can get a galvanic potential when you place certain dissimilar metals together e.g. zinc and copper. There's no particular use for such as power source in real life.--Fieraloca 08:29, 12 November 2006 (UTC)

CHP efficiency

The paragraph about combined heat and power (CHP) appears to contain contradictory information. It states that fuel-to-electricity conversion is "typically 15-20%". Toward the bottom of the same paragraph, however, it states that PAFCs, which dominate the CHP market provide electric conversion efficiencies typically around 45-50%.

I don't know which range of numbers is more accurate, but it would seem that at least one of them is wrong. --jfinlayson 10:59, 18 October 2006 (UTC)

Proposed correction to Fuel cell issues

"Water management (in PEMFCs). In this type of fuel cell, the membrane must be hydrated, requiring water to be evaporated at precisely the same rate that it is produced. If water is evaporated too quickly, the membrane dries, resistance across it increases, and eventually it will crack, creating a gas "short circuit" where hydrogen and oxygen combine directly, generating heat that will damage the fuel cell. If the water is evaporated too slowly, the electrodes will flood, preventing the reactants from reaching the catalyst and stopping the reaction. Methods to dispose of the excess water are being developed by fuel cell companies."

Fuel cells virtually never run at an ideal condition, where "the same amount of water generated is PRECISELY evaporated". The gas diffusion layers (GDL) take care of the water management. If you have ever ran a fuel cell, you would know that the excess water is continuously discharged through the cathode side. --Fieraloca 08:17, 12 November 2006 (UTC)

This phrase: "In 2008 UTC Power has 400kw Fuel cells for $1,000,000 per 400kW installed costs." is confusing. If it is "per 400kW installed cost" it is redundant. The intersting data here will be the cost per kW. --Nachoj (talk) 15:58, 27 April 2008 (UTC)

Propose to modify chart

Propose to remove Metal Hydride Fuel Cell MHFC and Direct Boro-Hydride FC from the chart of different types of fuel cells.

Metal hydrides and Sodium-Borohydrides are HYDRIDES not fuel cells. They are H2 storage media. The H2 obtained from these two types of hydrides are usually fed into PEMFC.--Fieraloca 08:21, 12 November 2006 (UTC)

Oppose removal of Metal Hydride Fuel Cell (MHFC). MHFC is in fact a variant of the alkaline fuel cell; the metal hydride may be used as either a hydrogen oxidation catalyst or as a hydrogen storage medium that is integrated into the anode.

It is arguable that Direct Boro-Hydride FC should also remain on the list due to the unique technical challenges and operating points resulting from the use of a liquid fuel source, much as Direct Methanol Fuel Cells are often classified as a different type of fuel cell.

Perhaps it would be helpful to break the classification into a "major" and "minor" scheme, where the "major" categories are AFC, PEMFC, PAFC, MCFC, SOFC, and then variants like the MHFC, DBHFC and DMFC are "minor" categories.

Thopper 03:59, 7 November 2007 (UTC)

Correction to fuel cell efficiency

You got my vote to taking this paragraph out. If you write something like this in a freshmen physics exam on thermodynamics, you have to repeat the class. The Carnot limit is fundamental and follows immediately from the second law, which is nothing else than the definition of temperature. A fuel cell just like a solar cell (non-experts make exactly the same mistake with those) is subject to it like EVERYTHING else. When the temperature increases on a fuel cell or a solar cell, the max. achievable voltage goes down and so does the efficiency. Period. No discussion.

As long as this stays in, the whole article belongs into the garbage. Literally.

--- Anonymous --- (Sorry... got no account, yet. But I did read this article and it pisses me off big time. There are way better science articles on Wikipedia.) —Preceding unsigned comment added by 69.3.190.146 (talk) 23:20, 5 August 2008 (UTC)

Using cell voltage as an indicator of efficiency is the biggest non-sense that I have ever heard!!!

Example: Take a perfect fuel cell; at an open cell potential of 1.23V, the current is Zero, thus the amount of H2 consumed is also Zero. Which means that you have just invented a perpetual motion machine, no need to feed H2, just 1.23V of pure Potential?!?!?

The efficiency of a fuel cell has to be measured as a ratio between the amount of energy obtained Vs the total enthalpy differential. Or other methods would also be fine.

--Fiera 08:52, 12 November 2006 (UTC)

In calculus there is the idea of limits. The open cell potential is always an ideal approximation - you measure it with a multimeter that draws a few picoamps, never 0. Similarly, the amount of H2 consumed due to these picoamps is a few femtomoles, which is still quite a few atoms considering avogradro's number is about 6x10²³. When you talk about voltage, or potential energy in general (voltage in an electric forcefield, height/pressure/liquid head in a gravitational forcefield, pressure/spring constant in an electric forcefield between atoms), you always talk about rate of change, energy gained vs. distance traveled, motion. It's how much energy I would get per foot if I traveled north down this hillisde, there is an idealized answer to that, similarly like there is an idealized answer to an open cell potential, how much energy you would get per electron flowing through your wire, how many volts it carries. But you don't actually get any energy if you don't take a step, just sit still. Measuring the energy you have to move by a millimeter down the hillside, record the results to calculate how much you would get per meter. Similarly, if I have a pipe with 20 psi pressure of water meaning each cubic centimeter could give me such and such energy if I let it flow through my turbine/electric generator, the higher the pressure the more energy I'd get per cc of liquid. Staring at the pressure gauge on the pipe expressing to me the "pure potential" does not mean I have a perpetual motion machine because nothing is moving. In fact all pressure gauges obtain their reading by moving, whether a few millimeters against a spring load, or a few nanometers against a piezoelectric membrane. Sillybilly 13:12, 12 November 2006 (UTC)

Uhm... yea... i think i was being sarcastic when I said I invented the perpetual motion machine. What I am referring to is the following quote from the main fuel cell page, under "efficiency":

The efficiency of a fuel is very dependent on the current through the fuel cell: as a general rule, the more current drawn, the lower the efficiency. A cell running at 0.6V has an efficiency of about 50%, meaning that 50% of the available energy content of the hydrogen is converted into electrical energy; the remaining 50% will be converted into heat. For a hydrogen cell the second law efficiency is equal to cell voltage divided by 1.23, when operating at standard conditions. This voltage varies with fuel used, and quality and temperature of the cell. The difference between enthalpy and Gibbs free energy (that cannot be recovered) will also appear as heat.

What I'm saying is that this entire parragraph is pure non-sense. Whoever wrote this believes that the current stays constant with changing cell potential, that energy is measured in Volts, and that the open cell potential would yield a perpetual motion machine. Paragraph will be deleted unless objected by anyone. --Fieraloca 04:45, 7 February 2007 (UTC)

I would suggest to ask an electrochemist to clarify this point. The entry about fuel cell efficiency and thermodynamics ruins the quality of the whole article. I would suggest taking the whole section out until someone with a background in fuel cells can take a shot at it. My criticism as a reader, not an editor, would be as follows:

Fuel cells are just as much thermodynamic devices as anything else in the universe. The second law holds and the Carnot Cycle is indeed a hard limit for fuel cell efficiency, except that it is not obvious what temperatures to throw into the Carnot limit equation. If I had to wing it, I would say that the lower temperature has to be the temperature at which the cell operates, and the upper temperature is probably the theoretical combustion temperature of the ideal fuel/oxidizer mix (at the partial pressure equivalent to the concentrations of the fuel and oxidizer?). Since that temperature is very high compared to the cell temperature, the Carnot limit will be somewhere above 90%. Now, the reactions inside a fuel cell are not equivalent to a Carnot Cycle because there is interaction between the fuel, oxidizer, the solvant and the electrodes, therefor the theoretical efficiency has to be less than the prediction of the Carnot Cycle. Any real science argument would obviously start with the well known ways to calculate dynamics of ionic reactions in solvents in, not the basic equations of thermodynamics for beginners.

I am a physicist, not an electrochemist and I do not have the detailed knowledge of fuel cell chemistry required to explain this quantitatively or even qualitatively. Anything I could write would therefor not approach a scientific quality standard. All I can tell is that the way it is written right now leaves a very bad impression to those with even a minimum of physics literacy. --[J.L.]

To my understanding, the Carnot equation was derived under the assumption that the device in question works by taking in heat from a "hot" reservoir, and later rejecting that heat to a "cold" reservoir. The energy input to a fuel cell is not in the form of heat at all, but of chemical energy. Redefining terms in order to force the Carnot equation to apply does, as you have indicated, require lots of mental gymnastics involving the notional "temperature" of chemicals undergoing non-equilibrium processes.

In the same way, applying this equation to electric motors would require that a copper wire at exactly 300K with 10V applied vs. ground would be somehow much "colder" than an identical wire at exactly 300K with 110V applied to it (let's see...kΔT = 100eV...that's a huge ΔT!). This, even though negligible heat would flow across a diamond placed between the two wires.

In my experience, thermodynamics are applied in these instances by regarding structured energy as separate from heat, and applying the second law in ways more general than Carnot. This allows us to preserve our traditional notions of temperature.--Joel 20:54, 13 April 2007 (UTC)

I agree with JL and others who state that the following text is, at best, nonsense. I'm moving it here until someone can rewrite it to make sense. I'm moving it here because the issue was brought up over six months ago and hasn't been fixed. Mkultra72 21:55, 21 June 2007 (UTC)

The efficiency of a fuel is very dependent on the current through the fuel cell: as a general rule, the more current drawn, the lower the efficiency. A cell running at 0.6V has an efficiency of about 50%, meaning that 50% of the available energy content of the hydrogen is converted into electrical energy; the remaining 50% will be converted into heat. For a hydrogen cell the second law efficiency is equal to cell voltage divided by 1.23, when operating at standard conditions. This voltage varies with fuel used, and quality and temperature of the cell. The difference between the reaction's enthalpy and Gibbs free energy (that cannot be recovered in any case) will also appear as heat, along with any losses in electrical conversion efficiency.

The text that you removed is completely correct, so I'm going to put it back in. However, it's apparently misunderstood by many readers. The reason why efficiency is proportional to voltage is that the fuel consumption is proportional to current, and power output is proportional to voltage times current. The reason why voltage drops when current is increased is a combination of ohmic losses, reaction kinetics, and mass transport. --PeR 21:17, 23 June 2007 (UTC)

The text that I removed is not even wrong. If it is misunderstood by many readers then it is badly written. Current is proportional to voltage at a fixed resistance, your statement fails to explain at what current (or resistance) the given efficiency holds. Disputed unsourced statements stay out until a source is provided. There are several unsourced statements in the above text that are being disputed by me and by several other people on this talk page. Please provide a source which says _both_ that efficiency is dependent on current _and_ efficiency is 50% at 0.6V. Thank you. Mkultra72 13:12, 26 June 2007 (UTC)

I never said that voltage is proportional to current. Read my text again. Almost any textbook on fuel cells will serve as a reference. The one I refer to most often is "Electrochemistry" by C. H. Hamann et al. (See section 9.7: "Efficiencies of batteries and Fuel Cells".) --PeR 15:32, 27 June 2007 (UTC)

You're right, you didn't say V is proportional to current. In that case I'm completely missing your point. Are you telling me (before I go to the library and look up the reference you're providing) that the section you're citing supports every specific statement in the unsourced material you insist on reinserting? If so, provide an inline cite in the article. I will double check your reference so you should make sure you're right. (p.s. That text is currently checked out of the library, so it wil be a couple of weeks before I'll be able to double check your reference. When you include your cites in the article please provide page numbers because I don't want to have to read through a hundred pages just to verify that your cite supports your statements.) Mkultra72 20:01, 27 June 2007 (UTC)

I say the text is right. It's a consequence of the 2nd law of thermodynamics that only "quasi-equilibrium cyclic processes have a 0 entropy change". Anything else generates entropy. To have a quasiequilibrium process you need to proceed infinitely slowly, and it takes and infinite amount of time to harvest the energy. Basically, the farther away you are from equilibrium, the more energy is wasted to generating entropy and the less is harvested as useful work. Sillybilly 20:56, 26 June 2007 (UTC)

We're basically talking power supply efficiency. Any electric power supply (such as a wall socket, a fuel cell, etc) can be approximated by an idealized voltage and an internal resistance. The internal resistance is the big deal here. Assume you have a power supply with an open circuit voltage of 100V and an internal resistance of 5 ohms. If your load is 10 KOhm, that will draw a current of I=V/R=100/10000=.01 A = 10 mA. Actually it's less, because the total resistance through the circuit is 10000+5 Ohms, considering that internal resistance in the big picture, and the actual current drawn will be less than 10 mA, more exactly 9.995 mA. And the actual "in use", "non-open-circuit" voltage measured at the terminals will also be lowered because of the internal resistance, as in a resistor voltage divider 10000/(10000+5)*100V=99.95 V. You can simply measure this "in use" voltage to calculate that your power supply is wasting 0.05% energy and delivering 99.95% to the load, therefore the "efficiency of the power supply is 99.95%." The actual "useful" wattage through the load is 99.95V*9.995mA=0.99900025 Watt, a very slow drain. Now take another scenario - assume your load is 1 Ohm. In this case the 5 Ohm internal resistance of the power supply is no longer "negligible." In this case the idealized power supply would deliver 100 V/1 Ohm=100 Amps, but because of the internal resistance it only delivers 100 V/(1+5) Ohms=16.7 Amps, and that's a big difference. Also, the voltage you measure on your power supply rails is 1/(1+5)*100=16.7 Volts, as opposed to 100 V you're expecting. You can "say" your power supply is delivering 16.7% efficiency, and wasting the rest on its internal resistance as heat. In this case the power delivered through the load is 16.7V*16.7Amps= 278.89 W, a very large drain giving a low efficiency, compared to a very slow drain giving a very high efficiency in the previous case. The internally wasted heat is I²R=16.7²*5=278.89*5=1394.45 W, and the actual "energy efficiency" is 278.89W delivered/total (278.89 delivered +1394.45 wasted)=16.67%. The faster you're trying to milk juice out of any electric power supply will give you a correspondingly smaller "efficiency" and greater internal waste as heat. The way to combat the problem is to drop the internal resistance of the power supply. In case of a wall socket this would mean really fat copper wires and a short distance from the actual energy source (the power plant), and for fuel cells increased membrane area and decreased membrane thickness to drop the resistance, which also has the problem of increasing the chance of a puncture hole giving an internal short circuit. Once you sufficiently drop the membrane resistance, then mass transfer/diffusion could become the limiting factor, in which case you need to increase the agitation/turbulence inside the fuel cell. For a 1 ohm load you would probably choose a power supply with an internal resistance of say 0.01 ohm, while for a 10 KOhm load whether you're using a power supply with 0.01 Ohm or 5 Ohm internal resistance, it doesn't really matter. You can always check how well you're doing simply by measuring the "dynamic", in use voltage on the power supply terminals and compare it to the "static", open circuit voltage. If the two are close, you're doing well, if the voltage dropped significantly, you're wasting a lot of energy. Sillybilly 22:28, 29 June 2007 (UTC)

Mkultra, if that book was checked out, then just borrow any book on fuel cells, and read the chapter that discusses the efficiency. Since you're missing my point I'll try to make it more clear:

Efficiency = output power / reactant energy flow
Reactant energy flow = constant * current (We'll disregard leak currents and wasted reactant for now)
Output power = voltage * current

Combined, these three equations give:

Efficiency = voltage / constant

The section (9.7) that I referred to above actually discusses first law efficiency, and in that case efficiency is $V_{cell}/1.48$, not $V_{cell}/1.23$, so it's not an exact match. I could probably find an exact reference if I searched a bit, or rewrite the section to discuss first law efficiency instead (which is the most commonly used definition of efficiency anyways), but I can't be bothered right now.

If you don't now enough on the subject to say that the text is wrong, then you're better off letting the people who do know the subject decide on whether the text should be removed, referenced or not. I'll not revert you any more. I suspect somebody else will do it soon, and otherwise I hope you revert yourself once you've gotten that book from the library. --PeR 21:06, 27 June 2007 (UTC)

When you provide a reference for text that you insert, I'll check the content you insert against the reference you provide. What I know or don't know about the subject matter is actually immaterial. Knowledge of the subject matter is one skill required in writing content. Communicating the subject matter effectively is another important skill. Being able to back up what you say with references is another important skill. The explanation you've given above clearly demonstrates (to me) that Efficiency=voltage/constant. But the key point (that several people have brought up on this talk page) is that the statement that Efficiency is dependent on current (which strongly suggests that the author didn't understand the difference between current and voltage, whether or not this is true.) Which brings back the point that the content is (at best) poorly written. But if your source also states that efficiency is dependent on current then I'll at least leave it be (but I do hope you'll find someone to rewrite it to make it more clear to those of us who don't understand the subject.) Mkultra72 02:25, 28 June 2007 (UTC)

Here's a list of articles that all contain graphs showing that voltage decreases with increasing current [7]. Will you please restore the text now? --PeR 05:26, 28 June 2007 (UTC)

I've been fairly consistent with my message, but it still seems to me that you don't understand. This is the last time I'll explain it to you. The text I removed doesn't make sense: it needs to be rewritten, truth is irrelevant. The text I removed has no source: sources need to be provided, truth is irrelevant. I will not respond on the talk page again until these issues are addressed. Mkultra72 23:40, 28 June 2007 (UTC)

I've been fairly consistent with my message, but it still seems to me that you don't understand. (So we agree! :-) The text does make sense, but you don't have the background knowledge to get it. The text is useful to some people, therefore should not be removed. If you think the prose is bad, then make it better. If you can't improve it then you're better off editing articles where you do understand the subject. I have now edited the text to try to make it more accessible to people with no background in electrochemistry. --PeR 06:46, 29 June 2007 (UTC)

---

PeR, The statement is absolutely wrong and should be deleted!!!!! You are trying to explain a very complex thing (fuel cell efficiency) though Voltage only? You are completely disregarding the stoichiometric flow through each cell!! Are you saying that a cell running at 0.6V and a stoich of 5 has the same efficiency than a cell running at 0.6V and a stoich of 1.2???? You assume constant current? Oh wait, you are ALSO assuming constant stoich. ok.

How about O2 diffusion efficiency? air contains 20.9% O2, your statement does not address how the diffusion plays a role in efficiency and real Vs theoretical stoichiometric values at the reactions sites. Nor does the statement address catalyst utilization/ reactivity. And you do not address proton trasport resitance. And crossover? So that too? you are also assuming that these factors are constant?

Let me see if I understand your statement. If every single operating parameter of a fuel cell is kept constant. Then efficiency is measured with voltage.

Trying to explain efficiency by Voltage only, is a little bit of an oversimplification, dont you think?

--Fieraloca 23:32, 12 November 2007 (UTC)

I noticed the efficiency information on this article as well as its calculations are wrong. Fuel cells using hydrogen oxygen to water reaction can easily get 80% efficiency in the conversion from chemical hydrogen and 20% oxygen atmosphere in to electricity. potentially the 50% statement may be closer to correct if a reformer is required, IE converting fossil fuels in to hydrogen, but this is not the goal of most of the fuel cell industry as it negates the goal of eliminating fossil fuel usage
1 of my sources I had handy [8]
The statement about drawing current lowers voltage = less efficiency is totally false.
If you start at 1.5v at .5A and you add to the load pulling it down to .5V at 1.5A you still have .75W of energy.(these numbers are examples).
watts law amps*volts=watts watts = energy witch has direct conversions to horsepower, BTU, calories, and joules take your pick.
When I get some free time ile start cleaning up this article using verifiable sources. Eadthem (talk) 04:25, 5 December 2008 (UTC)

Please make sure you use reliable sources then. Unfortunately most of what's published on popular science websites is way overoptimistic about fuel cell efficiency. They typically get their information from press-releases by companies that want to attract venture capital, and they don't seem to care for or don't have the ability to read peer reviewed scientific journals. The figure of 80 % that you quote, is practically impossible, so whoever made that statement was either lying or ignorant. I know you find figures like that all over the internet, but you won't find them in any peer reviewed journal.

An efficiency of 80 % would require that the cell voltage be higher than one volt (it is never that high in an actual stack even at zero power), and that all the losses Fieraloca lists above are zero (they are not), and that no power is needed to circulate air through the cell (which is typically a significant loss).

Regarding your "example", you are confusing efficiency with power. It is true that you can draw the same (or even more) power by increasing current (amps) while the voltage decreases. However, since the fuel (hydrogen) consumption increases more than the power output, efficiency decreases. You can actually figure this one out using high-school physics only, if you think about it for a while. Hint: Look at the diagram that explains how the fuel cell works, or read my previous comments on this talk page.

--PeR (talk) 23:23, 5 December 2008 (UTC)

The Birth of the Fuel Cell - But Who is the Father?

One cited article [9] in the history section claims that the fuel cell was not invented by Groove in 1839, but by Schoenbein, and that Groove did not build a fuel cell until 1842.

Most fuel cell related articles, in the "background" or "history" section will cite Groove as the inventor and the year as 1839. (See, for example, [10] or [11])

Does anyone know the truth behind this? I think the article needs to be clarified.

--PeR 12:31, 29 November 2006 (UTC)

Vehicles

There is mention of cars and other vehicles that use fuel cells but not other vehicles. Perhaps there should also me mention of the first space craft. This submarine also uses Fuel Cells. I do not know if there were any before it. http://en.wikipedia.org/wiki/Type_212_submarine

Yewenyi 04:12, 6 December 2006 (UTC)

Current or Voltage

Consider the following section:

The efficiency of a fuel is very dependent on the current through the fuel cell: as a general rule, the more current drawn, the lower the efficiency. A cell running at 0.6V has an efficiency of about 50%, meaning that 50% of the available energy content of the hydrogen is converted into electrical energy; the remaining 50% will be converted into heat. For a hydrogen cell the second law efficiency is equal to cell voltage divided by 1.23, when operating at standard conditions. This voltage varies with fuel used, and quality and temperature of the cell. The difference between enthalpy and Gibbs free energy (that cannot be recovered) will also appear as heat.

This is confusing. Firstly, it says the efficiency is current dependent. Next, it gives an estimate of efficiency for a particular voltage. This needs to be clarified.

Ordinary Person 06:28, 6 December 2006 (UTC)

Paragraph should be deleted. Inaccuracies cited under discussion --- Correction to fuel cell efficiency ---

Fuel cell efficiency is dependent on several factors (stoichiometric flow of reactants, recirc vs non-recirc systems, parasitic loads, humidification of reactants, cell impedance and resistance, diffusion properties of the microporous layers, catalyst activity, etc etc etc. Voltage alone says nothing.--Fieraloca 04:54, 7 February 2007 (UTC)

New fuel cell developed

It is a simpler design and is more efficient. It is expected to first be incorporated in smaller engines like those found in lawn mowers. That should make in impact, since they are not regulated.[12] Brian Pearson 23:05, 16 January 2007 (UTC)

Micro fuel cell demonstrated by Japan Steel Works at FC Expo 2007

Take a look at [13]. DFH 20:31, 8 February 2007 (UTC)

Future technology?

New offshoreship with FC tech coming soon [14] --OddMartin 23:42, 22 February 2007 (UTC)

Question

User talk:80.123.226.133 asked about Fe + 2FeCl3 = 3FeCl2 + energy. I found one Google hit. Could someome discuss it with him/her? Simesa 13:42, 26 April 2007 (UTC)

GE provided 6kW SOFC to DoE

Anyone seen this? Efficiency of 49%. October, 2006: [15] Simesa 00:11, 30 April 2007 (UTC)

mechanism doubted

"In the archetypal example of a hydrogen/oxygen proton exchange membrane fuel cell (PEMFC), which used to be called solid polymer electrolyte fuel (SPEFC) around 1970 and now is polymer electrolyte membrane fuel cell (PEFC or PEMFC, same as the short writing of proton exchange membrane) while the proton exchange mechanism was doubted," I don't get this. What happened while the mechanism was doubted. Is this thing still happening or did the doubt stop? --Gbleem 12:17, 22 May 2007 (UTC)

H2O

so if we go H2 + O2 ---> 2H2O, aren't we trapping O2 (breathable oxygen) in H2O molecules? won't we eventually run out of O2? Sahuagin 01:39, 28 May 2007 (UTC)

Pending an expert dropping by to give us a proper answer, here's a quick and unnuanced overview: The idea is to give a clean-at-the-point-of-use and transportable form of energy. The energy could have been produced via electrolysis from a renewable or nuclear source, in which case the equivalent amount of oxygen is released in the process. (As wind, water and photovoltaic power are not constant, making hydrogen fuel as a form of energy storage is seen as a key application of the technology.) If fuels are to be used as the source, they would have been burnt anyhow! The oxygen cycle renews this oxygen via plants, a process which of course is closely linked to the carbon cycle.--Old Moonraker 06:57, 28 May 2007 (UTC)

ah thank you. i was unaware that H2O was broken down in photosynthesis as well as CO2. much thanks. Sahuagin 23:03, 6 June 2007 (UTC)

History part?

UTC's Power subsidiary was the first company to manufacture and commercialize a large, stationary fuel cell system for use as a co-generation power plant in hospitals, universities and large office buildings. UTC Power continues to market this fuel cell as the PureCell 200, a 200 kW system.[8] UTC Power continues to be the sole supplier of fuel cells to NASA for use in space vehicles, having supplied the Apollo missions and currently the Space Shuttle program, and is developing fuel cells for automobiles, buses, and cell phone towers; the company has demonstrated the first fuel cell capable of starting under freezing conditions with its proton exchange membrane automotive fuel cell.

In 2006 Staxon introduced an inexpensive OEM fuel cell module for system integration. In 2006 Angstrom Power, a British Columbia based company, began commercial sales of portable devices using proprietary hydrogen fuel cell technology, trademarked as "micro hydrogen."[9][10]

This needs to be moved or removed from the article. It has nothing to do with history that Staxon in 2006 put out a cheap FC...

The UTC part is even worse, it is manipulative, UTC might be the first to put out that specific type of backup power, but Japan have been using stationary power plants for many years. And most hitech firms have some sort of fuel cell production / development going on these days, with my limited knowledge, i do not recall having heard of one car firm using UTC cells in demonstration projects. No doubt UTC plays a major role in developing backup power systems, and due to the instability on the US power grid, there is a major demand for super reliable systems, that can also keep power flowing for many hours, maybe even days, but that should go in a separate article. Unless someone provides counter argument, i will move the staxon part to news, and remove the UTC thing. (Larkuur 14:20, 12 August 2007 (UTC))

Update: Moved Staxon part, since the wikibot considers me a newbie (true), it wont let me delete anything... I still believe any one with the powers should remove the UTC part from the article, maybe move it to the UTC main article. (Larkuur 16:35, 13 August 2007 (UTC))

Edited "Fuel cell design"; please check it

Hiya, I'm a really bold dumbass who feels qualified to rewrite and even create whole new paragraphs when all I know about the subject I learned from reading Wikipedia. In other words, I know very little about fuel cells, so would someone check my rewrite of the first two or three 'graphs of "Fuel cell design" to make sure I didn't get it completely wrong?

One thing, as noted by User:Gbleem above, is that reference to the "early 1970s" and the proton exchange mechanism not being understood. I moved this, and reworded it to make what sense I could out of it, but there's actually no cite for this claim, and I was tempted to remove it. I decided not to, on the theory that whoever added it probably knows more than me. If it doesn't make sense, tho, someone who knows that should remove it. In any case, I think my layman's introduction paragraph is an accurate overview of the mechanism. Am I right? Eaglizard 21:06, 19 September 2007 (UTC)

deleted non existent links

Just deleted links to non existent wiki articles Fuel cell system and Fuel cell module. Could someone who has a good idea of fuel cell systems , WGS and PROX start these articles? shampoo 05:59, 27 October 2007 (UTC)

Or translate de:PROX ? Mion (talk) 18:39, 7 September 2008 (UTC)

I can do that (in ~12 hrs), where were you thinking of creating the page? In PROX or in one article Fuel cell system. User A1 (talk) 00:13, 8 September 2008 (UTC)

I think in PROX, but's up to the translator. Cheers Mion (talk) 01:34, 8 September 2008 (UTC)

--outdent

Done. Please check content for sensibility. The original seemed to be written in a very stop-start style, which only makes it worse :). User A1 (talk) 14:27, 8 September 2008 (UTC)

--outdent2

I did, great work, maybe de:Kværner-Verfahren next ? :) Mion (talk) 15:28, 8 September 2008 (UTC)

I tried to implement PROX into Reformed methanol fuel cell, maybe someone has an better image with fuel processor schematics ? Mion (talk) 09:45, 10 September 2008 (UTC)

--outdent3

de:Gestufte Reformierung maybe next ? Mion (talk) 10:59, 10 September 2008 (UTC)

Maybe in a few days. Let's move further discussions to my talk page User A1 (talk)

Fuel Cell Markets

Fuel Cell Markets is one of the leading online resources for Fuel Cells and contains a depth of information on business opportunities, recruitment, products and information about fuel cell resources.

Fuel Cell Markets facilitate the introduction and development of strategic partnerships and joint ventures towards building the global fuel cell supply chain and assisting with the creation of the hydrogen and fuel cell economy.

Piyush.fcm.kumar (talk) 11:47, 12 December 2007 (UTC)

Water fuel cell

I've added an interesting link to Water fuel cell in the see also section. --CyclePat (talk) 21:42, 19 March 2008 (UTC)

a link to a dp? and a hint to a non verified technology ? Mion (talk) 21:05, 1 July 2008 (UTC)

HHo?

In introduction there is a sentence "Some HHo fuel cells convert water to Hydrogen and oxygen that is in an excited state and hold its electrical potential until it recombines on burning releasing the energy and reconverting to water." It sounds like perpetuum mobile of first kind. It probably should be removed from introduction or rewritten in much clear way. Plus no any reference in the whole article what that “HHo” means. Do I horribly miss something here? --- MxM (talk) 19:33, 1 July 2008 (UTC)

it is, hho spam, thanks for noticing, it's removed. Mion (talk) 20:57, 1 July 2008 (UTC)

Request Glossary of fuel cell terms

I added some of the terms like PROX and WGS on Glossary of fuel cell terms, if you think its usefull, please add more from the EERE public domain fuel cell glossary [16]. Thanks Mion (talk) 11:34, 17 September 2008 (UTC)

Objectivity - if interested in...

1.Design issue section:

Cost issue:

No definition of the term "cost" exists here - production cost? - shelf price? Also this part in the article lacks the fact that a manufactured product's cost generally depends on production numbers. In other words mass-production lowers the final product's cost. Hence this regards the final shelf-price for the end consumer, the material cost of the manufacturer as well as cost of manufacture.

This part of the article creates the idea that a fuel cell is too expensive, too cost-intensive, to be mass manufactured.

Do you think this is a neutral viewpoint?

2.Design History

Wilson, Mahlon S., Ph.D.,is not even being named here?

pfff

check out this:

http://www.lanl.gov/orgs/mpa/mpa11/bio-wilson.htm

and this:

http://www.freepatentsonline.com/6808838.html

and make you own assumption... —Preceding unsigned comment added by 77.185.223.145 (talk) 19:37, 26 September 2008 (UTC)

Design Issues - inconsistent use of monetary systems

In the Design Issues section, one point mentions the cost in US Dollars, while another mentions Euros. Since dollars are used in other sections, the Euros cost should be restated in dollars.

Smwechsler (talk) 16:24, 22 November 2008 (UTC)