# Hydrogen Power Production: Where To Make It? **URL:** \ **Category:** Factual Questions\ **Created:** [November 20, 2002, 11:48pm UTC](https://boards.straightdope.com/t/hydrogen-power-production-where-to-make-it/137825 "2002-11-20T23:48:06Z")\ **Posts on this page:** 15\ **Page:** 3
**Author:** ![Harmonix](https://avatars.discourse-cdn.com/v4/letter/h/3ec8ea/32.png) [@Harmonix](https://boards.straightdope.com/u/Harmonix)\ **Post date:** [November 24, 2002, 3:44pm UTC](https://boards.straightdope.com/t/hydrogen-power-production-where-to-make-it/137825/41 "2002-11-24T15:44:08Z")
> [@](#): > > For every gallon of water electrolyzed, you will get ~64 cubic feet of pure O2 (4X4X4 feet at stp). That’s a lot of oxygen. When you combine that volume with O2’s reactivity and the fact that it is heavier than air and likes to pool in low spots, you end up with a massive disposal problem. If everyone in a good size town were to power their cars with electrolytic hydrogen, you’d likely have to contend with clouds of waste oxygen flowing down the streets and incinerating the low lying areas. - bear with me, I have a point… I think. it’s 7 am with no sleep after all. =) Hrm ok again someone correct me if i’m way off base. As I recall it a fuel cell takes hydrogen jacks the electrons to make electricity and the byproduct H+ combines with oxygen to form water. The car will get oxygen from the air and transform it into water. as I see it there is no circulation of oxygen in any way to the environment. therefore shouldn’t it be a REQUIREMENT to release that oxygen back into the environment?(in order to maintain air mixture balance) I would think the cathode(or was it anode, totally forgot my electrochemistry) end could be placed outside with a giant fan or something blowing regular air over it so there won’t be ever be a great concentration of pure oxygen. But them that brings up the problem of increased oxygen concentration around the areas where the hydrogen production is centralized. ---
**Author:** ![andy\_fl](https://avatars.discourse-cdn.com/v4/letter/a/49beb7/32.png) [@andy\_fl](https://boards.straightdope.com/u/andy_fl)\ **Post date:** [November 24, 2002, 4:05pm UTC](https://boards.straightdope.com/t/hydrogen-power-production-where-to-make-it/137825/42 "2002-11-24T16:05:23Z")
> [@](#): > > \*Originally posted by Harmonix \* > \*\*bear with me, I have a point… I think. it’s 7 am with no sleep after all. =) > > Hrm ok again someone correct me if i’m way off base. > As I recall it a fuel cell takes hydrogen jacks the electrons to make electricity and the byproduct H+ combines with oxygen to form water. \*\* Quite correct. > [@](#): > > \*\* > The car will get oxygen from the air and transform it into water. as I see it there is no circulation of oxygen in any way to the environment. \*\* Very correct again. But so does your car right now, when you burn any hydrocarbon fuel CxHy + (x + y/4) O2 —\> xCO2 + (y/2)H2O. So say you burn propane (C3H8), you’ll consume 5 moles of O2 per mole of propane. \*\* therefore shouldn’t it be a REQUIREMENT to release that oxygen back into the environment? (in order to maintain air mixture balance)\*\* Sure, if you can find a way to generate Oxygen. As far as I know, there’s none. Also, the air quality does’nt change much wrt oxygen content. \*\*I would think the cathode(or was it anode, totally forgot my electrochemistry) end could be placed outside with a giant fan or something blowing regular air over it so there won’t be ever be a great concentration of pure oxygen. But them that brings up the problem of increased oxygen concentration around the areas where the hydrogen production is centralized. \*\* You totally lost me there. Donno what you are trying to say. ---
**Author:** ![Harmonix](https://avatars.discourse-cdn.com/v4/letter/h/3ec8ea/32.png) [@Harmonix](https://boards.straightdope.com/u/Harmonix)\ **Post date:** [November 25, 2002, 12:33am UTC](https://boards.straightdope.com/t/hydrogen-power-production-where-to-make-it/137825/43 "2002-11-25T00:33:06Z")
> [@](#): > > Very correct again. But so does your car right now, when you > burn any hydrocarbon fuel > > CxHy + (x + y/4) O2 —\> xCO2 + (y/2)H2O. So say you burn propane (C3H8), you’ll consume 5 moles of O2 per mole of propane. I was assuming in the LONG run that we’ll be producing hydrogen via electrolysis of water. My question was that Hydrogen cars ONLY produce H2O as a byproduct no? I don’t know of any natural cycle that converts water into H2 and O. Meaning overtime the hydrogen cars will deplete the oxygen in the air. Now, if for every 2 moles of hydrogen we use we also use 2 moles of oxygen, doesn’t that perfectly correlate with the oxygen by product in electrolysis of water? Seems to be a perfect cycle to me. The problem I see however is that if hydrogen production is centralized then so is oxygen **production** whereas oxygen **consumption** is worldwide. I just can’t seem to imagine that oxygen diffusing about the world in a manner quick enough to replace the oxygen used. > [@](#): > > You totally lost me there. Donno what you are trying to say. Forgive me it was 7 am. wasn’t quite thinking straight. Anyway, I was under the impression that for the electrolysis of water you could have 2 giant vats each with electrodes in them. One would produce oxygen, the other would produce hydrogen. The one with oxygen would be placed exposed to the open air with a giant fan blowing over it so that all oxygen was automatically diluted into the air. But now that I think about it, I can’t seem to figure out a way for each vat to produce ONLY hydrogen or ONLY oxygen. So… I guess that was a moot point. correct me if i’m being double stupid this time. =) ---
**Author:** ![Harmonix](https://avatars.discourse-cdn.com/v4/letter/h/3ec8ea/32.png) [@Harmonix](https://boards.straightdope.com/u/Harmonix)\ **Post date:** [November 25, 2002, 12:34am UTC](https://boards.straightdope.com/t/hydrogen-power-production-where-to-make-it/137825/44 "2002-11-25T00:34:34Z")
> [@](#): > > \*Originally posted by Harmonix \* > \*\* > Now, if for every 2 moles of hydrogen we use we also use 2 moles of oxygen, doesn’t that perfectly correlate with the oxygen by product in electrolysis of water? Seems to be a perfect cycle to me. > \*\* :smack: 2 moles of hydogen we use 1 mole of oxygen. :smack: ---
**Author:** ![andy\_fl](https://avatars.discourse-cdn.com/v4/letter/a/49beb7/32.png) [@andy\_fl](https://boards.straightdope.com/u/andy_fl)\ **Post date:** [November 25, 2002, 4:18pm UTC](https://boards.straightdope.com/t/hydrogen-power-production-where-to-make-it/137825/45 "2002-11-25T16:18:19Z")
> [@](#): > > \*Originally posted by Harmonix \* > \*\*I was assuming in the LONG run that we’ll be producing hydrogen via electrolysis of water. \*\* Very unlikely, unless electrical power becomes very cheap. Electrical energy is the best quality of energy you can get, thermodynamically because 100% of this enrergy can be theoritically converted to work. Converting it into any other form of energy will make it inefficient - so you are better off using electricity as such. > [@](#): > > \*\*My question was that Hydrogen cars ONLY produce H2O as a byproduct no? I don’t know of any natural cycle that converts water into H2 and O. Meaning overtime the hydrogen cars will deplete the oxygen in the air. \*\* Yes they will deplete the Oxygen in the air if you don’t consider Photosynthesis converting the CO2 that is produced during the manufacture of H2 back to O2. > [@](#): > > **Now, if for every 2 moles of hydrogen we use we also use 2 (1) moles of oxygen, doesn’t that perfectly correlate with the oxygen by product in electrolysis of water? Seems to be a perfect cycle to me.** Yeap - if the H2 was made by electrolyzing water. [QUOTE] \*\* The problem I see however is that if hydrogen production is centralized then so is oxygen **production** whereas oxygen **consumption** is worldwide. I just can’t seem to imagine that oxygen diffusing about the world in a manner quick enough to replace the oxygen used. [QUOTE] \*\* Again a misconception. There are localized places where they consume Oxygen and localized places where they consume Hydrogen from even today. I’ve not seen anything in the literature saying the air oxygen content was effected by it. Localized Current Consumption of Oxygen : Purifying Steel - also known as the Bessemer’s converter. After raw molten steel is taken out of the blast furnace, it is taken to a Bessemer’s converter where - high speed jets (often even approaching supersonic speeds) of Oxygen are introduced through a lance into the molten steel. The oxygen reacts with residual Carbon and removes it as SLAG. Localized Current Consumption of Hydrogen : Prominent use lies in making NH3 (ammonia) for the fertilizer industry. A considerable portion (extimated around 50%) goes towards pollution control in coal based power plants. Hydrogen gas is also used for making Sponge Iron (You reduce Iron Oxide straight to Iron), in Hydrodesulfurization ( prevalent way of removing Sulfur at Petroleum Refineries), in Hydrogenated Vegetable Oil ( Americans don’t use it that much, but other countries do), Hydrotreaters (Used for alkylazation aromatization and a variety of such reactions in the industry to change hydrocarbon molecules for use as fuel, for making plastics. for making clothes, etc, etc.). > [@](#): > > \*\* Anyway, I was under the impression that for the electrolysis of water you could have 2 giant vats each with electrodes in them. One would produce oxygen, the other would produce hydrogen. The one with oxygen would be placed exposed to the open air with a giant fan blowing over it so that all oxygen was automatically diluted into the air. \*\* Why lose all that good oxygen. It can be used as a feedstock. You can reduce NOx emissions at power plants using that good O2 ---
**Author:** ![Una\_Persson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/una_persson/32/346_2.png) [@Una\_Persson](https://boards.straightdope.com/u/Una_Persson)\ **Post date:** [November 25, 2002, 5:57pm UTC](https://boards.straightdope.com/t/hydrogen-power-production-where-to-make-it/137825/46 "2002-11-25T17:57:40Z")
> [@](#): > > \*Originally posted by andy\_fl \* > \*\*Why lose all that good oxygen. It can be used as a feedstock. You can reduce NOx emissions at power plants using that good O2 \*\* Ummm…you certain about that? You may be talking about reducing the overall nitrogen content of the combustion air, but increasing the oxygen content may also increase the peak flame temperatures as well, and then you’ll just slide right on up that Gibbs Free Energy curve, and make more NOx…? Plus - you may not realize just how much oxygen a power plant needs. A 680MW coal plant might need as much as 561 tons of stoichiometric oxygen per hour, 102 tons of excess oxygen per hour, and 75 tons of leakage oxygen per hour. Now, if you are raising the overall oxygen content, the excess will drop. And if you can somehow directly inject the oxygen into the windbox (I don’t think you want to put it into the burners) you would not have additional leakage…but we’re talking some huge amounts of oxygen here anyways. ---
**Author:** ![andy\_fl](https://avatars.discourse-cdn.com/v4/letter/a/49beb7/32.png) [@andy\_fl](https://boards.straightdope.com/u/andy_fl)\ **Post date:** [November 25, 2002, 6:34pm UTC](https://boards.straightdope.com/t/hydrogen-power-production-where-to-make-it/137825/47 "2002-11-25T18:34:02Z")
> [@](#): > > \*Originally posted by Anthracite \* > **Ummm…you certain about that? You may be talking about reducing the overall nitrogen content of the combustion air, but increasing the oxygen content may also increase the peak flame temperatures as well, and then you’ll just slide right on up that Gibbs Free Energy curve, and make more NOx…?** You’re right Anthracite. Did’nt think about that. NOx production may go up with increased flame temperatures - not too sure about that either becuase N2 concentration would be low. But using richer oxygen air, you’ll be able to burn lower grade coals (semi-bituminous and lignite for example) far more efficiently even in Fluidized Bed Boilers. And Combined Cycle power plants will surely see a big difference, because as I recall much power used to get wasted in the air compression in the Gas Turbines. NOx production may still go up - may require more dosing there. \*\* Plus - you may not realize just how much oxygen a power plant needs.\*\* I happen to be aware of that although those figures were a great help. Excess air (over stoichiometry) is added to ensure complete combustion (although modern Low Nox Burners fron AirOil Flaregas/JohnZink sports some sophisticated burners). Another point maybe the exit temperature of the flue gases, higher NOx content will mean higher Dew Temperature and hence the air preheater will have to let go of the air at a higher temperature. So, frankly, I’ll wait for someone else to comment if it is so. ---
**Author:** ![andy\_fl](https://avatars.discourse-cdn.com/v4/letter/a/49beb7/32.png) [@andy\_fl](https://boards.straightdope.com/u/andy_fl)\ **Post date:** [November 25, 2002, 7:35pm UTC](https://boards.straightdope.com/t/hydrogen-power-production-where-to-make-it/137825/48 "2002-11-25T19:35:42Z")
Anthracite, your Oxygen figures made me think, here is a quick calculation : \*\* Gasoline O2 Consumption in US (neglecting Dieisel !) \*\* 1\> US consumes [360 million gallons (1.36 billion liters) of gasoline every day](http://www.howstuffworks.com/question417.htm). Density of gasoline is around 3kg/gal (I use kg because your figures were in tons which I believe is the metric ton). That makes a daily consumption of 1.1 million tons of gasoline. 2\> Air/Gas ratio in the mixture used in cars is around [15 by weight](http://courses.washington.edu/me341/oct22v2.htm). And this is the stoichiometric ratio maintained in the car. Considering air is 21% Oxygen, the Oxygen/Gas Ratio drops to 3.2 3\> So the Oxygen consumed by gasoline = 3.2\*1.1 = 3.5 million Tons per day. \*\* Power Plant O2 Consumption in US \*\* From [the DOE figures](http://www.eia.doe.gov/cneaf/electricity/ipp/ipp_sum.html) for 2000 fossil fuel power generation in the US: 1\> coal-fired capacity represented 260,990 megawatts. 2\> Gas-fired capacity accounted for 117,845 megawatts. 3\> Petroleum, 41,017 megawatts. The total is 419,852MW. And going by your figures on Oxygen Consumption (Assuming Gas and Petroleum power plants consume the same) the power plants will consume - (561/681)_419,852_24 = 8.3 Million Tons per day. So the Oxygen produced in the hypothetical case we were discussing before can still be used up by the power plants. ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [November 25, 2002, 8:26pm UTC](https://boards.straightdope.com/t/hydrogen-power-production-where-to-make-it/137825/49 "2002-11-25T20:26:21Z")
I am really surprised as to how this thread is turning out. Almost every report on recent (non-NASA) fuel cell advances I have read is about _methane_ fueled cells. The methane is converted into hydrogen _within the cell_. [Cite 1](http://www.epa.gov/lmop/products/fuelcell.htm), [cite 2](http://www.nwenergy.org/publications/activist/99_summer/99_summer_5.html). Hence, it’s all about collecting, storing, transporting good old methane. A substance we are quite familiar with in such regards. No electrolysis, no “where does the oxygen go”, etc. So the answer to the OP (remember the OP?) is: Inside the fuel cells. ---
**Author:** ![andy\_fl](https://avatars.discourse-cdn.com/v4/letter/a/49beb7/32.png) [@andy\_fl](https://boards.straightdope.com/u/andy_fl)\ **Post date:** [November 25, 2002, 8:38pm UTC](https://boards.straightdope.com/t/hydrogen-power-production-where-to-make-it/137825/50 "2002-11-25T20:38:07Z")
Thanks ftg. Something I pointed out in my very first post. FTG - but incidentally, have you wondered why they keep calling it Methane and not good old natural gas ? Its because most Natural Gas is sour and the sulfur poisons the fuel cell catalyst in no time. ---
**Author:** ![Una\_Persson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/una_persson/32/346_2.png) [@Una\_Persson](https://boards.straightdope.com/u/Una_Persson)\ **Post date:** [November 25, 2002, 8:58pm UTC](https://boards.straightdope.com/t/hydrogen-power-production-where-to-make-it/137825/51 "2002-11-25T20:58:42Z")
> [@](#): > > \*Originally posted by andy\_fl \* > \*\*But using richer oxygen air, you’ll be able to burn lower grade coals (semi-bituminous and lignite for example) far more efficiently even in Fluidized Bed Boilers. > > And Combined Cycle power plants will surely see a big difference, because as I recall much power used to get wasted in the air compression in the Gas Turbines. NOx production may still go up - may require more dosing there.\*\* Is that really an issue with FBCs? I mean, they are designed to burn all sorts of low-rank fuels, such as waste coals, mine tailings, boney coal, biomass and RDF/MDF/TDF fuels. I mean, I’m not sure I understand what you might be saying here. Agree with you on GTs. And they already have such high flame temperatures on them already that you just need to put an SCR on them and forget about worrying about combustion NOx any more than the low-NOx burners are already designed for. > [@](#): > > \*\*I happen to be aware of that although those figures were a great help. Excess air (over stoichiometry) is added to ensure complete combustion (although modern Low Nox Burners fron AirOil Flaregas/JohnZink sports some sophisticated burners). > > Another point maybe the exit temperature of the flue gases, higher NOx content will mean higher Dew Temperature and hence the air preheater will have to let go of the air at a higher temperature. So, frankly, I’ll wait for someone else to comment if it is so. \*\* I wasn’t trying to talk down to you with my “you may not be aware” comment. It was just a phrasing issue. My comment earlier about how excess air may not go up is that one of the reasons excess air is needed is because of the large amount of inert gases in the combustion air, coupled with mixing/distribution/other issues. In fossil power plants, I have never heard of NOx going to nitric acid being a problem in the ductwork or near the air heater. Typically, the only dew point temperature you need to worry about is the SO2/sulfuric acid dewpoint. And I’ve been to and analyzed units with the enormous NOx emission rate of more than 2.5 lbm/MBtu, which had no trouble with nitric acid formation. Now…I do not know if having a higher exess oxygen overall might lead to differential impacts on ammonium bisulfate deposition in the air heater - but hey, just use ceramic coatings and wash them down, right? Also - higher oxygen contents in the boiler can lead to other issues. Boiler tubing can see accelerated corrosion in more oxidizing atmosperes, sometimes greatly accelerated at key points due to mixing problems and possible “dead air” regions, especially in the ash hopper knuckle zone. Another issue is boiler waterwall slagging, which can sometimes be very sensitive to the oxygen content of the furnace. You may see an increase with some high-alkaline coals in boiler waterwall slagging, which would require either increased sootblowing (at a much higher O&M cost, due to energy requirements and tube wastage), or you may see an increase in high-temperature suspended tube fouling (due to reaction with sodium in the upper furnace region). In addition, if you have any level of vanadium in your fuel (because you are burning oil orimulsion, or some sort of opportunity fuel), you may end up with hideous amounts of vanadium pentoxide, and end up fouling and/or corroding your high-temperature radiant suspended tubes. Maybe. ---
**Author:** ![Una\_Persson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/una_persson/32/346_2.png) [@Una\_Persson](https://boards.straightdope.com/u/Una_Persson)\ **Post date:** [November 25, 2002, 9:00pm UTC](https://boards.straightdope.com/t/hydrogen-power-production-where-to-make-it/137825/52 "2002-11-25T21:00:58Z")
> [@](#): > > \*Originally posted by andy\_fl \* > \*\*Thanks ftg. Something I pointed out in my very first post. FTG - but incidentally, have you wondered why they keep calling it Methane and not good old natural gas ? Its because most Natural Gas is sour and the sulfur poisons the fuel cell catalyst in no time. \*\* To add to what you are saying - regardless of its hydrogen sulfide component, natural gas is not really equivalent to methane. It has a large methane component, and for some Eastern US gases it can make up 95% of the natural gas composition (volumetric basis). But if you look at Western or Rocky Mountain natural gas, the methane component can be as low as 83%, according to the Gas Research Institute. ---
**Author:** ![Tuckerfan](https://avatars.discourse-cdn.com/v4/letter/t/eada6e/32.png) [@Tuckerfan](https://boards.straightdope.com/u/Tuckerfan)\ **Post date:** [November 25, 2002, 9:36pm UTC](https://boards.straightdope.com/t/hydrogen-power-production-where-to-make-it/137825/53 "2002-11-25T21:36:07Z")
> [@](#): > > \*Originally posted by Squink \* > \*\*I expect that hydrogen embrittlement of the pipeline would complicate the design. ( [alloy hydrogen brittle diffuse](http://www.google.com/search?hl=en&lr=&ie=ISO-8859-1&safe=off&as_qdr=all&q=alloy+hydrogen+brittle+diffuse&btnG=Google+Search) ) H[sub]2[/sub] molecles are small enough that they like to quantum-tunnel out of containers, or at least into the walls. That’s not good for the material properties of the containers. \*\* Anybody know if nanotubes would be affected by this? I realize that we’re not at a point where construction of pipelines with them is feasible, but sooner or later we will be. ---
**Author:** ![andy\_fl](https://avatars.discourse-cdn.com/v4/letter/a/49beb7/32.png) [@andy\_fl](https://boards.straightdope.com/u/andy_fl)\ **Post date:** [November 25, 2002, 10:42pm UTC](https://boards.straightdope.com/t/hydrogen-power-production-where-to-make-it/137825/54 "2002-11-25T22:42:36Z")
> [@](#): > > \*Originally posted by Anthracite \* > **In fossil power plants, I have never heard of NOx going to nitric acid being a problem in the ductwork or near the air heater.** You are absolutely correct. Did’nt think of all those aspects. For the NOx though, I was referring to the Ammonia or Urea dosing in the SCR or SNCR in the GT. GTs are also also fossil power plants, I guess. > [@](#): > > \*Originally posted by Anthracite \* > \*\*regardless of its hydrogen sulfide component, natural gas is not really equivalent to methane … \*\* Of course not. I was trying to point out that although fuel cells work with methane from “recent” bio sources they fail miserably with good old methane sources such as natural gas. Actually, it is desirable to have higher MW compounds in Natural Gas because they have somewhat of a petrochemical value. A combustion process is not very sensitive to the presence of Sulfur, but a fuel cell is very sensitive. ---
**Author:** ![Harmonix](https://avatars.discourse-cdn.com/v4/letter/h/3ec8ea/32.png) [@Harmonix](https://boards.straightdope.com/u/Harmonix)\ **Post date:** [November 26, 2002, 4:39am UTC](https://boards.straightdope.com/t/hydrogen-power-production-where-to-make-it/137825/55 "2002-11-26T04:39:34Z")
> [@](#): > > Very unlikely, unless electrical power becomes very cheap. Electrical energy is the best quality of energy you can get, thermodynamically because 100% of this enrergy can be theoritically converted to work. Converting it into any other form of energy will make it inefficient - so you are better off using electricity as such. Well, I was thinking a hundred years down the line when nuclear(perhaps fusion?, I have a friend at princetontheir tokohma(Sp?) reactor is finally at the level of producing as much power as the put in. Last time i talked to her was last year though.)power is the norm and fossil fuels will need to be conserved for things that actually \* absolutely \* require it. Of course Hydrogen would be absolutely negated should there be a revolution in battery technology. > [@](#): > > Yes they will deplete the Oxygen in the air if you don’t consider Photosynthesis converting the CO2 that is produced during the manufacture of H2 back to O2. Huh? Although I must smack myself at the mention of photosynthesis, didn’t even realize that the hydrolysis of water would generate Oxygen! [Previous page](https://boards.straightdope.com/t/hydrogen-power-production-where-to-make-it/137825.md?page=2)