High Pressure Hydrogen Generation

benjamin
benjamin Solar Expert Posts: 34 ✭
in General Solar Power Topics #1
I have a few questions regarding high pressure hydrogen generation. Apparently this is somewhat difficult, but it's in the pipeline as something I will be building. I read a Department of Energy report that stated that it was difficult to reach pressures above 200psi. It went on to say that some company was able to hit 5000psi by keeping the oxygen generating part of the system at regular atmospheric pressure and then let the hydrogen side pressure up.

My questions are:

1. Why would it matter if the oxygen side had less pressure? I can't imagine that the system would no longer generate gasses when the oxygen side reaches a certain pressure.
2. If it's better to keep the two sides at different pressures, A: Why B: How would one do so?
3. Is there an optimum plate number, voltage/amperage?
4. Do rough surfaces on the plates produce better output?
5. Does inducing a frequency of some sort into the voltage produce better output?
6. What is the best material to use that can withstand high pressures? Considering the generator chamber probably shouldn't be metal, would high strength acrylic be a good fit?
7. I understand the local gas supply company sells hydrogen in tanks at 2000psi. I also understand that hydrogen reacts with steel and causes it to weaken or become more brittle. Why then are these tanks not made out of a different material.

Thank you, I appreciate any answers.

PS: Don't tell me I can't do this. You are the same folks who told me I couldn't build a 12v, 2100AH battery bank capable of sustained 500 amp loads. It's been running almost a year now.
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Comments

  • Ralph Day
    Ralph Day Solar Expert Posts: 1,022 ✭✭✭✭
    #2
    Re: High Pressure Hydrogen Generation

    ''PS: Don't tell me I can't do this. You are the same folks who told me I couldn't build a 12v, 2100AH battery bank capable of sustained 500 amp loads. It's been running almost a year now. ''

    If no-one here is correct in their advice, why ask another question?
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  • russ
    russ Solar Expert Posts: 593 ✭✭
    #3
    Re: High Pressure Hydrogen Generation

    @ Benjamin - Hope you live out in the country where you at least won't blow up your neighbors!

    I worked with hydrogen for many years - perfectly safe if you follow the rules and have a gas safety culture concept in your mind.

    It is obvious you have no idea what you are getting in to from your questions.

    Killing yourself is a personal problem but if anyone else is close by they deserve a bit of respect.

    I could care less about your battery arrangement.

    Russ
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  • Peter_V
    Peter_V Solar Expert Posts: 226 ✭✭✭
    #4
    Re: High Pressure Hydrogen Generation
    benjamin wrote: »
    I have a few questions regarding high pressure hydrogen generation. Apparently this is somewhat difficult, but it's in the pipeline as something I will be building. I read a Department of Energy report that stated that it was difficult to reach pressures above 200psi. It went on to say that some company was able to hit 5000psi by keeping the oxygen generating part of the system at regular atmospheric pressure and then let the hydrogen side pressure up.
    .

    That is not possible. The H2, O2 and H2O are all connected and have to be at the same pressure.

    If you don't already understand this, then I think your first step has to be educating yourself on basic physics.
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  • benjamin
    benjamin Solar Expert Posts: 34 ✭
    #5
    Re: High Pressure Hydrogen Generation
    russ wrote: »
    It is obvious you have no idea what you are getting in to from your questions.

    I understand it's explosive only if the oxygen is allowed to seep into the storage tank, which will not be allowed to happen. If you have worked with hydrogen for years, can you please answer my questions? At least the questions you know the answers to.
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  • benjamin
    benjamin Solar Expert Posts: 34 ✭
    #6
    Re: High Pressure Hydrogen Generation
    Peter_V wrote: »
    That is not possible. The H2, O2 and H2O are all connected and have to be at the same pressure.

    If it is not possible, why is there a DOE report on this? Please see below:
    Electrolysis of water, particularly in conjunction
    with renewable energy sources, is a potentially cost-
    effective and environmentally-friendly method of
    producing hydrogen at dispersed sites. However,
    current electrolyzers have a high capital cost and are
    inefficient. In addition, the output hydrogen pressure
    from current electrolyzers based on either proton-
    exchange membrane (PEM) or alkaline electrolytes
    is generally limited to 200 psi. Therefore, a multi-
    stage mechanical compressor is required to increase
    the hydrogen pressure to the 5,000 psi or greater
    needed for storage and/or dispensing to fuel cell
    powered automobiles. Mechanical compressors are
    expensive and have high maintenance requirements
    and poor reliability. Elimination of mechanical
    compressors, or at a minimum reducing the number
    of compression stages required, would increase the
    efficiency and reliability of electrolysis systems.

    Giner Electrochemical Systems, LLC (GES) has
    developed technology for producing hydrogen
    directly in the electrolyzer stack at high-pressure.
    The GES technology uses high-differential pressure
    across the PEM, so the oxygen is evolved at near-
    atmospheric pressure while the hydrogen is produced
    at high-pressure. The goal of the present DOE
    project is to increase the pressure of hydrogen
    production in the electrolyzer stack to 5,000 psi,
    while reducing the cost of the stack and system. This
    will provide a cost-efficient reliable system for
    generating high-pressure hydrogen.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #7
    Re: High Pressure Hydrogen Generation

    benjamin;

    First of all, no one here told you you can't have a 2100 Amp hour 12 Volt battery bank. We said it wasn't a good idea. It isn't, due to the current balancing problems explained in your previous thread (and many others). Furthermore, by that same thread you are not drawing the 500 Amps continuous. You stated your loads would be "more like 1000 Watts" which is sustainable at 12 VDC as it's less than 100 Amps. A 2100 Amp hour bank will supply that for 10 hours without difficulty. Trying to draw 500 Amps off it will result in your battery bank becoming scrap metal in about four hours.

    Second, do not count on hydrogen as a viable fuel source under any circumstances. Companies with millions of dollars worth of R&D have yet to produce a single viable hydrogen-based fuel system. Hydrogen is explosive mainly when it seeps out of its containment, which it can do fairly easily as it is quite "small" in molecular terms. The difference in pressure you're concerned about is related to this, in that the oxygen is a larger molecule and can not be compressed as much.

    Third, this is a solar and wind power forum. We really do not go in to exotic alternative energy supplies. Especially as the emphasis here is on practical solutions and things like high-pressure hydrogen are far from practical.

    And to everyone; let's watch the attitudes. Sometimes remarks meant to be humourus or even plain honest can come across as snippy, sarcastic, and rude. Let's keep it happy. :D
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  • benjamin
    benjamin Solar Expert Posts: 34 ✭
    #8
    Re: High Pressure Hydrogen Generation

    I didn't really know where to ask these questions. I'll be routing excess power from solar panels and windmills to the hydrogen generator. I figured some of the guys here might know something about this. I'm only going to build it if I can get pressures of 1000 to 2000psi without a compressor.

    There is a concern yes, with the oxygen side having a lower pressure. There's really only two concerns I have at this point:

    1. Keeping the pressures balanced on both sides or at least keeping the water levels balanced on both sides. You said the oxygen can't be compressed as much. This would only matter if the pressure was different right? Or are you saying it can't be compressed above a certain psi. If so, what psi? I figured that technically speaking the oxygen tank would only need to be 50% of the size of the hydrogen tank in order to work properly.

    2. Finding material I can use to build the box for the plates and water that can withstand high pressures. I'm looking into using 1" thick acrylic or similar as I'm assuming it cannot be made of metal. If it can be made of metal then that is no problem as I have access to a fabrication facility so I could have one built in a matter of hours.

    As for the batteries, there are 20 so a 500AMP load ends up drawing about 50A per pair. There's about 25kwh in the bank, so there shouldn't be an issue drawing up 12.5kwh of power at 500A. The bus bars and wires don't even get warm, but you can certainly feel the energy flowing through them.

    Thanks.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #9
    Re: High Pressure Hydrogen Generation

    I see you've already noticed some of the inherent problems with HP hydrogen. The fact that the pressures used are beyond what is normal for CNG or propane or any other compressed gas.

    But I think you've missed the big problem on the practical side: the amount of energy needed for the electrolysis process exceeds the amount of energy available from the hydrogen produced. This is an inevitable function of physics and can not be overcome. The "big boys" don't care because they are tapping megawatts of hydro power for the process. In terms of running it off solar you'd need a fairly spectacular array size to produce enough H to be viable for any purpose except experimental. As for doing it from "surplus" solar & wind, it's a nice idea but have you go that much extra to spare?

    See if you can find some numbers on the amount of electricity used vs. the amount of hydrogen produced. This was the problem when we first experimented with "self produced" hydrogen in my physics class over 40 years ago, and so far as I know Sir Isaac Newton hasn't been proven wrong yet.

    Personally I think hydrogen research is a waste of time and money, and the physics isn't there to support the concept. Maybe they could make some effort towards improving the efficiency of batteries, or getting the price of Lithium-Ion units down. That and getting panel efficiency above 18% would seem better avenues to explore, in my opinion.

    As for your battery explanation ... Uh, 500 Amps divided among 20 batteries is 25 Amps per battery, not 50. And the process doesn't actually work that way if the batteries are wired as a bank, because they (should) perform as one really big battery not a whole lot of little ones that happen to be in use at the same time. You've also got the time factoring confused: drawing 500 Amps all at once is an enormous amount of current. There is no viable wire that can handle that (0000 is good for about 300). Having 25 kW hours in the bank is not the same as supplying 25 kW all in one go. In other words, at 50% DOD that bank could theoretically supply 500 Amps for 25 hours. (BTW, "25 kW hours" is more than ten times your original figure of 2100 Amp hours. Decimal points matter. :p )
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  • benjamin
    benjamin Solar Expert Posts: 34 ✭
    #10
    Re: High Pressure Hydrogen Generation

    It's true that it is not efficient. But I would rather waste the extra energy creating hydrogen instead of dumping it into a dummy load. I can use it for many things, such has heating, running a generator, maybe even running a vehicle.

    All I need to do is get the stuff stored in tanks under pressure.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #11
    Re: High Pressure Hydrogen Generation
    benjamin wrote: »
    It's true that it is not efficient. But I would rather waste the extra energy creating hydrogen instead of dumping it into a dummy load. I can use it for many things, such has heating, running a generator, maybe even running a vehicle.

    All I need to do is get the stuff stored in tanks under pressure.

    That is only slightly easier than creating cold fusion. :p
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  • benjamin
    benjamin Solar Expert Posts: 34 ✭
    #12
    Re: High Pressure Hydrogen Generation

    I'll figure it out. Thanks.
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  • jagec
    jagec Solar Expert Posts: 157 ✭✭
    #13
    Re: High Pressure Hydrogen Generation
    Peter_V wrote: »
    That is not possible. The H2, O2 and H2O are all connected and have to be at the same pressure.

    If you don't already understand this, then I think your first step has to be educating yourself on basic physics.

    Naw, they use a PEM...basically running a fuel cell in reverse. Stick water on both sides (only one side will consume water, but the membrane must stay moist), add some juice, and oxygen will bubble up on one side, hydrogen on the other. You can run the two sides at different pressures if you want, it's not impossible.

    benjamin, the reason why the pressure on one side matters to the other is simple thermodynamics. Keep in mind that all reactions must be driven by a negative ΔG (which = ΔH - TΔS). Well, we can look up the standard values for H (enthalpy) and S (entropy) for each component of the reaction at different pressures (let's run this at constant temperature). The overall reaction has a POSITIVE ΔG, which we make up for by adding electricity until it becomes thermodynamically favorable. If we want to perform the reaction under high pressure, H for liquid water doesn't really change, but H for both hydrogen and oxygen goes up significantly (and S decreases), therefore the overall ΔG is much more positive, requiring more electricity. However, if we leave the oxygen side under atmospheric pressure, then the enthalpy and entropy only change for hydrogen, which produces a smaller corresponding increase in ΔG. Therefore, less electricity is required than if you were running the whole system under pressure.

    However, there are all kinds of reasons why this isn't a practical DIY project. Setting aside the inherent dangers of compressed gases and explosions, you simply aren't going to produce any useful amount of hydrogen with "excess" production from solar and wind. Using numbers from a NREL study, a medium-size PEM electrolyzer uses around 70 kWh to produce each kg of hydrogen (at a pressure of around 200 psig). Suffice to say, a hobby-sized system will be less efficient, and a higher-pressure system will need more power. A hydrogen car uses about .5 kg of hydrogen a day (60 miles per kg). That's a dedicated 10 kW solar system just for the car...assuming that you can match the efficiency of a mid-sized commercial system, which you can't. Especially not if you want to use a higher pressure. Also, I did some fuel cell research in college, and those sheets of PEM were EXPENSIVE, even for a small one, and you have to boil them in hydrogen peroxide and then sulphuric acid to activate them. Nasty stuff. Then you have to print them with expensive platinum catalyst, IF you can keep them from wrinkling up.

    Look at the numbers. A hydrogen car uses 117 kWh of electricity (1.67 kg of hydrogen) to travel 100 miles, with a commercial electrolyzer and no fuel losses. The Chevy Volt uses 36 kWh for the same distance. Batteries > hydrogen for power storage.

    But hey, if you still want to try it, knock yourself out. Here's a store that sells the membrane you'll need, with the electrodes already printed. These have been pre-protonated and don't need to be boiled in acid. It's $100 for a 5 cm square. It runs at around 50 watts. That will climb significantly if you're keeping one side under pressure. Remember that you'll need a thick membrane and good engineering of the flow-field plate in order to sustain the 1000-2000 psi pressure differential without any tearing.
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  • benjamin
    benjamin Solar Expert Posts: 34 ✭
    #14
    Re: High Pressure Hydrogen Generation

    Awesome, that's the kind of stuff I need to know.

    So does what you're saying hold true with all methods of hydrogen creation? A stainless steel based plate system would require more power to create hydrogen as the pressure increases?

    If this is true, would this mean that perhaps the level of energy required to produce hydrogen would significantly decrease under vacuum? I have a large vacuum chamber I could rig up.
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  • jagec
    jagec Solar Expert Posts: 157 ✭✭
    #15
    Re: High Pressure Hydrogen Generation
    benjamin wrote: »
    Awesome, that's the kind of stuff I need to know.

    So does what you're saying hold true with all methods of hydrogen creation? A stainless steel based plate system would require more power to create hydrogen as the pressure increases?

    If this is true, would this mean that perhaps the level of energy required to produce hydrogen would significantly decrease under vacuum? I have a large vacuum chamber I could rig up.

    Yes, it's true for all methods of hydrogen creation.

    But keep in mind that we care about the energy requirements for compression simply because we're going up to a really high pressure. The energy requirements "per atmosphere" are fairly low...very little of the applied energy is used to work against atmospheric pressure if you're just letting your stand bubble away in the open. So, a vacuum pump wouldn't really save much, and keep in mind that you'd just have to expend more energy to compress the hydrogen again into a useful density once you've made it. There's no such thing as a free lunch.

    Here's a good page on the thermodynamics of electrolysis. By looking up H and S values for the components under different states and pressures, you can get an idea of what does and does not make a difference. Even compressing up to 100 atm only gives you a 10% hit on power usage.

    There are no "easy solutions" to cheap hydrolysis, the vast majority of the energy that you pump in to it is directly required to break those chemical bonds. Very little is used for PV work.
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  • benjamin
    benjamin Solar Expert Posts: 34 ✭
    #16
    Re: High Pressure Hydrogen Generation

    Ok that's fine. I won't be able to use it in vehicles and I will need larger tanks, but based on what you said I should still be able to generate pressures up 100psi, maybe 200psi.

    I can live with that. I will study the page you linked to and start putting some plans together.

    Thank you very much for your assistance.
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  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    #17
    Re: High Pressure Hydrogen Generation
    Cariboocoot wrote: »
    Having 25 kW hours in the bank is not the same as supplying 25 kW all in one go. In other words, at 50% DOD that bank could theoretically supply 500 Amps for 25 hours. (BTW, "25 kW hours" is more than ten times your original figure of 2100 Amp hours. Decimal points matter. :p )
    I've not been reading this thread in a great deal of detail, and I don't have a dog in this hunt, but 2100Ah @ 12VDC = 25.2kWh. Or did I miss something?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #18
    Re: High Pressure Hydrogen Generation
    ggunn wrote: »
    I've not been reading this thread in a great deal of detail, and I don't have a dog in this hunt, but 2100Ah @ 12VDC = 25.2kWh. Or did I miss something?

    Nope; just me getting confused pulling bits from two different threads. :blush: He actually has 12.6 kW hours available from the 2100 Amp hour 12 Volt bank.

    Which is still a bad idea for a system.
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  • raydias
    raydias Solar Expert Posts: 68 ✭✭✭✭
    #19
    Re: High Pressure Hydrogen Generation

    I cam across this video on a solar/hydrogen setup (you might have already found it). You might be able to contact the Road Journal for additional details.

    http://www.youtube.com/watch?v=xEdQRVQtffw

    good luck
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  • benjamin
    benjamin Solar Expert Posts: 34 ✭
    #20
    Re: High Pressure Hydrogen Generation

    The next one I build will certainly be higher voltage. I did a lot of research on everything, but somehow missed the fact that amperage increases as voltage decreases for the same load.

    In any case, there's a hell of a lot of 2/0 wire in it and huge bus bars, but it works fine.
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  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    #21
    Re: High Pressure Hydrogen Generation
    benjamin wrote: »
    The next one I build will certainly be higher voltage. I did a lot of research on everything, but somehow missed the fact that amperage increases as voltage decreases for the same load.
    It doesn't. A load is a resistance, and V=IR, so R=V/I. For a given load (resistance), as voltage decreases, current (amperage) decreases commensurately. Perhaps what has you confused is power. P=VI, so for a given amount of power, as voltage decreases, current increases proportionately.

    I don't mean to be snippy, but it seems to me that you should maybe get more acquainted with the fundamentals before launching into a major design project.
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  • Ralph Day
    Ralph Day Solar Expert Posts: 1,022 ✭✭✭✭
    #22
    Re: High Pressure Hydrogen Generation

    Please, bye bye Bennie, or is there a way I can avoid this thread, not have it show up when I sign in?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #23
    Re: High Pressure Hydrogen Generation

    5000 Watts is only 416 Amps when at 12 Volts. But 12 Volt systems do not run at 12 Volts all the time. The concern over current draw is that at the minimum operating Voltage of a 12 Volt system (10.5 Volts usually) the current level is closer to 500 Amps. In either case it is beyond what even 0000 wire is capable of safely handling. Paralleling current paths is not a safe option either, and if done each wire should have its own fuse capable of protecting that portion of the circuit.

    NOTE:

    I have deleted benjamin's last post for attitude, which is getting very snippy around here.

    Anyone "subscribed" to this thread can unsubscribe by following the appropriate link in the e-mail notice.

    Any more attitude in this thread and it gets lock, offending posts will be deleted, and offenders will get a brief "time out" from the forum.
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  • benjamin
    benjamin Solar Expert Posts: 34 ✭
    #24
    Re: High Pressure Hydrogen Generation

    I see this in every occupation I have worked in. Everyone has their own ideas about how things can be done better, people argue over how things should be done but at the end of the day hardly anything gets accomplished.

    I don't claim to know everything but instead of sitting around debating things or critiquing others I'm out in my shop building things. I don't tell people something can't be done or tell others why something shouldn't be built. Instead, I help them if I can.

    If I did know everything I wouldn't be here asking for help. Afterall, that is what this forum is for correct? You can look down on me for not knowing as much as you do regarding a particular subject. I'll tell you this though, I'll figure it out. I might not get it right the first time, but I will build something, get it working, and make the next one better.

    I've been incredibly patient with numerous comments with "attitude" from numerous members on this forum. If you have positive input to provide, I will accept it graciously. If you just want to insult me, I'll probably overlook it. But don't expect me to be nice all the time. Go back and read some of the stuff you guys have written.

    I also don't appreciate my comment being deleted, because the fact of the matter is that there was no more attitude in my comment than some of the other comments aimed towards me. It appears they all still exist.

    Maybe this is some sort of right of passage for newcomers, I don't know and I don't care, that's not my problem. I come here only asking for a little bit of your knowledge. If you would rather joke around and insult me I'll just go somewhere else.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #25
    Re: High Pressure Hydrogen Generation

    benjamin; reread the very first three posts. The attitude problem has been there since post #1 (yours), as pointed out in post #2. It's gotten worse.

    I do not agree with the way some of the others have expressed themselves here either. But their underlying concern for safety is real, and you seem to have a certain disregard for that reality. High current levels are not safe. Hydrogen is not safe. The suggestion about learning some of the fundamentals may be heavy-handed, but it is well-intended. You obviously are interested in many things and I can appreciate your desire to learn. But you seem to be looking for the short-cut to success. A lot of the book learning is boring, especially compared to hands-on experimentation. However it can keep you from getting your hands blown off. Literally. Even recharging FLA's has to come with the warning about the explosiveness of the minute amounts of hydrogen gas released and the very real possibility of welding a wrench to the terminals due to the high current capacity available.

    As far as the members, moderators, and owner's of this forum are concerned safety comes first. We are definitely not going to suggest you go ahead and try it and see what happens when we can see the very real potential for danger.

    If you ignore these cautions, no matter how they are expressed, the responsibility is yours alone.
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  • techntrek
    techntrek Solar Expert Posts: 1,372 ✭✭✭
    #26
    Re: High Pressure Hydrogen Generation

    Very true about the little bit of hydrogen in a battery doing big things. The genset I own is known to have a problem overcharging its starting battery. Many people have reported very big explosions, ruining stators, air intakes and finding pieces 10s of feet from the genset. The battery is enclosed in its own metal housing far from the stator and other parts, and the amount of hydrogen less than half the interior of a standard starting battery.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
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  • russ
    russ Solar Expert Posts: 593 ✭✭
    #27
    Re: High Pressure Hydrogen Generation

    Quote, 'I see this in every occupation I have worked in. Everyone has their own ideas about how things can be done better, people argue over how things should be done but at the end of the day hardly anything gets accomplished.'

    You should stop and think about that statement possibly.

    Things are accomplished with knowledge and experience. Not by the bull in the china shop approach.
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