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Na + H2O2 (50%) -> H2?

Discussion in 'Electronic Repair' started by ZHEN, Jul 18, 2004.

  1. Tony Bryer

    Tony Bryer Guest

    Yes, but that was my point. These things (in one form or another) were
    known when I was born. What has happened in my lifetime is them
    becoming universal.
     
  2. David Harper

    David Harper Guest

    (SNIP)

    If you're 51 years old, then when you were born, the highest and
    fastest a human had ever gone was about 15 miles up and about Mach 2.5
    (about 800 meters/sec).

    Now we have a spacecraft swinging around Saturn, probes outside the
    solar system (over 12.5 *BILLION* miles away), people that have swung
    around the moon and returned at over 11.1 km per second, spacecraft
    that have exceed 68 km/s, and thousands of satellites in every orbital
    plane you can imagine. And that's just advances in aerospace. You
    don't think that's significant?

    Also consider the advances made with the advent of computers,
    medicine, etc.

    Dave
     
  3. Thiophilus

    Thiophilus Guest

    Fifty years ago daily life was much as it was today -- they had cars,
    radio, TV, electric fridges, airplanes, comic books, and so on.

    One hundred years ago it was much different. No radio or TV, no
    airplanes (not even the Wright bros had an operable one then),
    virtually no cars. No comic books. Maybe ice boxes instead of fridges.

    That's not to say that there hasn't been tremendous advances in
    science and engineering in the last 50 years. Obviously there has
    been, and it's unprecedented. But daily life has not changed that much
    in the last half-century compared to a whole century ago.
     
  4. David Harper

    David Harper Guest

    In terms of orbital mechanics? Yes. Although, I wouldn't call them
    too simple. They're pretty complex differential equations. :)

    In terms of heat transfer, fluid mechanics, etc? Not so much. Alot
    of research to better understand these areas was conducted to actually
    figure out what was going on before we attempted spaceflight, much
    less a trip to the moon.
    Interesting you say that. Alot of formulas used in fluid dynamics and
    heat transfer are emperical, and not based on derivation alone. Two
    days ago I had to review a CFD drag analysis by Boeing that took
    something like 1000+ CPU hours (I believe they have several CPUs
    working in parallel though), and alot of those emperical equations can
    still be found in their software.
    Less uncertainty than there could have been, thanks to planes like the
    X-15, X-2, etc...

    Dave
     
  5. daestrom

    daestrom Guest

    Okay, so check my math here....

    For 90 kg of reactants (54kg of NaAlH4 and 36kg of H2O), you get 8kg of H2.
    For each 1kg of H2 you can expect about 141.9 MJ of energy. That works out
    to about 12.6 MJ per kg of reactants. If you don't carry the 2H2O, then it
    would be 21 MJ per kg of NaAlH4.

    And gasoline carries about 43.8 MJ/kg when reacted with air.

    So, explain again how 12.6 MJ per kg is so competitive with 43.8 MJ/kg????
    Re-working for LiAlH4, I get 38kg for every 8kg of H produced, not 23kg
    (7+27+4*1). But add on the 36kg of water and we have 74kg of reactants for
    8kg of H. That works out to about 15.3 MJ per kg of reactants. Excluding
    the water, we get about 29.87 MJ per kg of LiAlH4. Better, but not
    tremendously so.
    Hmm, the above shows that LiAlH4 carries *less* energy per kg than gasoline.

    And you seem to be forgetting about carrying the water needed. Gasoline at
    least has the advantage that the other reactant can be taken directly from
    the atmosphere. Getting these amounts of H2O directly from the atmosphere
    is *not* as simple.
    Unless I made an error in my calculations, the 'scientific fact' would be
    that hydrides still carry less energy per kg than gasoline.
    Oh? Please show me the error in my calculations that shows 38kg LiAlH4
    liberates 8kg of H for an energy of 8*141.9 = 1135.2 MJ from 38kg of 'fuel'.
    And that is 1135.2/38 = 29.87MJ/kg. While gasoline contains ~43.8MJ/kg.
    And that is *assuming* the water reactant doesn't have to be carried.

    daestrom
    P.S. Energy values for hydrogen and gasoline taken from...
    http://www.uvi.edu/Physics/SCI3xxWeb/Energy/GasolineFAQ.html
     
  6. daestrom

    daestrom Guest

    I think you'll find it isn't the news-reader that 'mangles' such threads.
    It is the posting thru different news-servers. Such as I, that post via a
    time-warner RR server. The messages don't get forwarded to all other
    news-servers instantly. So someone reading/posting on another news-server
    will see things out of order.

    Blame it on the speed of conversation and that not all news-servers are
    synchronized.

    daestrom
     
  7. pragmatist

    pragmatist Guest

    If energy from H2O2 is the goal, why not just use the O2 from
    catalytic decomposition of the peroxide, (there is also energy
    produced), combined with an easier to obtain reducing agent than
    alkalai metals?
    There are no free lunches.
    H2O2 is an oxygen source.
    As reducing agents Na or Ca are more expensive than other fuels.
    You have to use energy to split off the Hydrogen to act as a reducing
    agent so why not simply supply a reducing agent in a more economical
    way?

    The energy cost of H2O2 is high as are the energy costs of Na or Ca.
    What you propose makes little sense unless for a very special
    application.
    As others point out, the reactions are likely to be violent.
    What are you up to?

    As a side note, H2O2 was once used with alcohol as torpedo fuel, (WW
    I IIRC), but this was a special case where oxygen had to be provided
    to run a compact, isolated, high energy system with technology that
    was primitive compared to what is now available.

    Pragmatist -"Somedays it's just not worth chewing through the
    Restraints."
     
  8. ^^^ note the dangling 'understood' generated by outlook....
    You have the physics to understand that.
    Yes, you have the physics to understand that.
    This describes technological advancement that would have to be evolved.
    In 1965 we knew we would have pentium computers by now, but we couldn't
    build them in 1965. The only physical surprise we have seen since 65 in
    the field that I know of deals with magnetic domains. Lucky for us or we
    would not have such powerfully dense and cheap hard drives.

    Best, Dan.
     
  9. Hi,
    Please see the post where I point out the mangling of the position of
    the word 'understood'. This is what I was speaking of.
    Best, Dan.
     
  10. What kind of technological advance do you have in mind that doesn't
    require the precursor of a new physics?
    Sources of energy are now a non issue? Sure, in that case, hydrogen
    makes a wonderful fuel because now it is cheaper than fossils.

    I'll repeat:
    As hydrogen is not an energy source, the cost of the source is
    compounded by the losses in the hydrogen vector. The limitation is
    physical, and vision doesn't change that.

    I'll repeat:
    Probably science fiction for another 5 or 10 decades.
    I'll repeat:
    A new discovery in physics is rather unlikely and if/when it happens, it
    won't just make hydrogen practical. As far as advancements go, they have
    been very predictable. Look at Moore's Law for an example. Other than
    the likes of high temperature superconductors, there have been no
    surprises for going on a century.
    ---
    Technological advancement is predictable based on known physics...
    And all about evolving technology based on known physics. If they could
    not have developed > mach 1 travel, it would have implied a new physics.
    Best, Dan.
     
  11. If we are talking about providing hydrogen to a fuel cell, the above
    is already competitive from an overall energy density standpoint.
    Remember, 43.8 MJ of energy in the form of gasoline will give you far
    less energy than this in the form of hydrogen if a gasoline to
    hydrogen reformer is used.

    Hydrogen energy converted to electrical energy in a fuel cell is more
    efficient than gasoline energy converted to mechanical energy via
    pistons and a crankshaft. This efficiency greatly impacts the numbers
    for overall energy density of the system including the fuel.
    Likewise, if you are going to convert gasoline into hydrogen you need
    a gasoline reformer which takes up space and is in many cases a large
    component of the system. This must be factored into the energy
    density numbers as it is part of an overall system.


    It should be (7+11+4) (I could be wrong about the 11 for Boron, it
    could be 11.5 or something and I don't have this one memorized but 27
    is for Aluminum). There is a big weight savings by substituting Boron
    for Aluminum. However, when the entire system is considered, for a
    variety of reasons including that the aluminate is easier to recycle
    than the borate, my money is on Aluminum.

    For Lithium Borohydride it would be 1135/22 (I'm assuming you are
    correct on the 1135 number) This is 51.6 MJ/kg which is higher than
    the 43.8 MJ/kg you report for gasoline. And the energy density
    number for the lithium hydride is MUCH higher than gasoline than even
    the 51:44 ratio once you factor in the efficiency difference between a
    fuel cell and a combustion engine.

    About the water issue: Assuming that water doesn't have to be carried
    is reasonable since MORE water is produced by the fuel cell than what
    the hydrolysis would need:

    4 H2 + 2 O2 --> 4 H2O *FUEL CELL*

    LiAlH4 + 2 H2O --> LiAlO2 + 4 H2 *HYDROGEN TANK*

    (Note that 2 times more water is produced by the fuel cell than what
    is needed, meaning that water recovery from the fuel cell only has to
    be a sloppy 50%. The rest could be converted to pure drinking water.
    Not such a bad byproduct.

    Jed Checketts
    Searles Lake, CA
     
  12. David Harper

    David Harper Guest

    I liken this question to asking someone in 1950 "How in the world
    would a spacecraft re-enter the atmosphere without burning up?" Just
    because you can't see an immediately practical solution doesn't mean
    one doesn't exist or won't exist in the future.

    However, as discussed before, maybe nanotech... maybe just cheaper
    ways to bottle solar using hydrogen as a currency.
    Fossil fuels do not provide a source of unlimited, already flowing,
    almost-free energy. That's why you're so concerned with the "losses
    in the hydrogen vector".

    If you get hydrogen from a solar source, the losses in the hydrogen
    vector aren't really an issue because you're just tapping already
    released energy. As mentioned before, this is not the case with
    fossil. Sure, going 100 miles on a tank of hydrogen might require
    more energy than using current fossil fuels... but if it's coming from
    an already tapped, much-cheaper, unlimited source, then efficiency
    (assuming it's not ridiculously low) becomes a footnote.
    Yes, probably. And I'll repeat: probably, but *possible*. You said
    that hydrogen "would have to come from a nuclear driven thermochemical
    processes". Now you say "probably". I guess you're conceeding your
    original statement *might not* ultimately be correct?
    So you're stating that super/hypersonic flight was a "known physics"
    in 1950? Maybe you should re-read the above quote:

    "The U.S. rocket program hit a wall in the late 1940's due to a lack
    of understanding of supersonic physics."

    The physics of going to the moon was not a "known physics".
    Technological evolution alone could not have gotten us to the moon in
    1950. We had to learn more first via experiments, tests, etc.

    Dave
     
  13. There are three elements to an energy delivery system: (1) The cost of
    the feedstock, (2) the cost of the infrastructure, and (3) the
    amortization of the system.

    (2) and (3) almost always dominate.

    Hydrogen-anything is virtually certain to be noncompetitive with other
    options. Because of unmanagable (2) and (3).

    Especially if there is an electrical intermediary stage thus creating a
    staggering loss of exergy.

    See http://www.tinaja.com/glib/energfun.pdf for a detailed analysis.


    --
    Many thanks,

    Don Lancaster
    Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
    voice: (928)428-4073 email:

    Please visit my GURU's LAIR web site at http://www.tinaja.com
     
  14. You didn't answer the question.

    Instead, you seem to have created a 1950 question as if it were some
    fundamental truth.
    And predictably, at least 5 decades off. At that, you still won't beat
    back the physical limitation. With thermochemical processes running 60%
    efficient, I fail to see how nanotech will revolutionize the use of
    hydrogen.
    You are claiming my concern?
    This has been beat to death on these threads. If you don't displace
    fossil sources of energy with that solar, and produce hydrogen instead,
    it does nothing but make some folks feel fuzzy good. This hydrogen has
    the equivalent effect of getting 5 or 10 percent, (depending on the
    technology), of the heating value of coal to the wheels of a vehicle.

    The only way what you write can look good is to deny the real world
    accounting of energy.
    Do you know why I use the word 'probably'?
    --circle one: yes, no --

    And I'll repeat it again:
    "Hydrogen as a 'fuel' has serious physical limitation." Technological
    innovation does not defeat physical limitations.

    The limitations are:
    It is not an energy source.
    It has a very poor energy density.
    It suffers losses during handling at somewhat reasonable energy densities.

    You seem to be hanging your hopes for hydrogen on this journalist's
    words. Here is the timeline supersonic science:

    http://history.nasa.gov/SP-4219/Chapter3.html

    Notice that the fine tuning of Mach's work was done in the 30s. Now date
    Mach...
    If you are going to make this claim, please cite the unknown physics of
    going to the moon in 1950.
    Best, Dan.
     
  15. David Harper

    David Harper Guest

    Fine, further discussion of hydrogen as a fuel won't get us anywhere.
    However, I can't let the following comments slide.
    If you'd read the article, you'd realize he wasn't a journalist, but a
    *professor* in physics.

    Here is the timeline supersonic science:
    This is another outlandish statement. If Mach's work had been "fine
    tuned" in the 30's, the following would not have happened (by the way,
    this is from the source *YOU* cited):

    "The general aeronautics community was suddenly awakened to the
    realities of the unknown flight regime in November 1941, when Lockheed
    test pilot Ralph Virden could not pull the new, high-performance P-38
    out of a high-speed dive, and crashed."

    After this incident:
    "Indeed, it was time for real airplanes to be used to probe the
    mysteries of the unknown transonic gap. It was time for the high-speed
    research airplane to become a reality."

    (again, from your own source)

    Mach did some groundbreaking work, but showing shock waves on a bullet
    isn't all the info NASA needed on HYPERsonic flow to go to the moon.

    From *YOUR OWN* article:

    "John Stack nicely summarized the situation in 1938:

    The development of the knowledge of compressible-flow phenomena,
    particularly as related to aeronautical applications, has been
    attended by considerable difficulty. The complicated nature of the
    phenomena has resulted in little theoretical progress, and, in
    general, recourse to experiment has been necessary. Until recently the
    most important experimental results have been obtained in connection
    with the science of ballistics, but this information has been of
    little value in aeronautical problems because the range of speeds for
    which most ballistic experiments have been made extends from the speed
    of sound upward; whereas the important region in aeronautics at the
    present time extends from the speed of sound downward."

    Also (from your own article):

    "In order to learn about the aerodynamics of transonic flight, the
    only recourse appeared to be a real airplane that would fly in that
    regime."
    See above. I think your article just did for me.

    Dave
     
  16. Would you agree we should not put our hopes for energy solutions into
    hydrogen?
    I did not see the name of an author at the beginning or end of the
    article. So, I don't know why I should accept the quote blindly.
    The Bell X-1 broke the 'sound barrier' in 1947 and it wasn't an
    accident. It was not done with an unknown science.

    So, back to the point. In 1950 it was understood that a rocket could get
    a man to the moon. It was understood that there was no physical
    limitation to stand in the way. They knew perfectly well it was only a
    mater of developing the technology.

    Hydrogen has physical limitations. It is not a matter of developing some
    technology to make it a viable energy vector.
    Best, Dan.
     
  17. daestrom

    daestrom Guest

    Yea, my bad. I saw the LiAlH4 formula, and the 23Kg and completely missed
    where you switched to LiBH4.

    Now it's getting interesting. By eliminating the need to carry 36kg of H2O
    for every 22kg of 'fuel', it looks more promising.

    What are you assuming for fuel-cell, controller, motor losses. An often
    used number for gasoline to wheels is ~20%. Advanced electric motor can be
    +90% and controllers of VFD often run in the 85% to 90% range. But which of
    the *many* different numbers quoted efficiencies for fuel cells are you
    assuming?
    What is the heat of formation/reduction of this reaction? Is it exothermic
    or endothermic? If exo, is there any use for this energy on the vehicle or
    is it a 'loss'? Since this fuel is manufactured, I presume that any energy
    liberated in the above reaction must be supplied in the manufacture of the
    fuel. And unless it can be recovered on the vehicle, it would be an
    'infrastructure' loss. Not that gasoline doesn't have a lot of
    'manufacture/infrastructure' losses, but it would be good to have some
    comparitive information about this part of the fuel cycle.

    daestrom
     
  18. Brett

    Brett Guest

    Fellas, please forgive me, even though I find this subject extremely
    interesting, what does this have to do with electronics repair?
     
  19. David Harper

    David Harper Guest

    Yes. If I had to bet, I wouldn't put hydrogen as a front-runner of
    possible candidates to replace/supplement fossil (nor did I ever say I
    think it was). However, I would not discount it either. It's
    certainly possible. Only the future will tell.
    But you assumed he was a journalist?

    Go down a directory:
    http://zebu.uoregon.edu/~js/

    He's a professor.
    You're making one enormous assumption with this statement: that in
    order for something to be accomplished, *everything* about it has to
    be understood before hand. This is most certainly not true. If your
    statement is correct, then explain the following:

    1. Fact: the X-1's original contract called for it to be stable up to
    only 0.8 Mach. Why didn't they design it for 1.0 Mach if they
    understood supersonic flight? The fact is, they didn't know what kind
    of effects they'd encounter over 0.8 Mach. That's why they did many,
    many incremental flights slowly increasing in speed, and adjusting
    things based on knowledge gained.

    If they completely understood supersonic flight from the beginning,
    why didn't they just break the sound barrier on the first flight?

    2. The X-1 lost its elevator effectiveness when it first reached
    about .94 Mach. This was not unexpected by the designers. If
    supersonic flight was truely understood, then why was this allowed to
    happen? (note the word "discovery" in the following quote):

    "So important was this discovery that nearly every transonic and
    supersonic aircraft since that time has had an all-movable horizontal
    stabilizer..."

    http://www.dfrc.nasa.gov/History/HistoricAircraft/X-1/techdata.html

    3. The X-1 had straight wings. Look at every supersonic aircraft
    after that. They have swept wings. Why? Because engineers didn't
    fully understand the advantages of swept wings in terms of supersonic
    flight. Or do you have another suggestion?

    If you need some more quotes, here's a few:

    [of the x-planes]
    "Their sole purpose was to explore and document the unknown."

    "The unusual part was that these aircraft had no obvious purpose other
    than expanding our knowledge of aeronautics."

    http://oea.larc.nasa.gov/PAIS/Supersonic.html

    "Although the X-15 has provided much new knowledge about this
    once-feared region, its return journey from there has proved even more
    fruitful."

    "...reentry flight has been mastered, and many previous unknowns no
    longer remain."

    http://www.hq.nasa.gov/office/pao/History/SP-60/ch-1.html
    Actually, your original comment was:
    "In 1950 the physics of going to the moon was well understood."

    They knew it might be "possible". Saying we KNEW it could be done in
    1950 is false. What if solar radiation outside the Van Allen belts
    had been 100,000 times what it really is? What if the X-15 had
    experienced aerodynamic heating that heated the leading edges to 2200F
    at only Mach 3.5 instead of 6.7? Hindsight's 20/20, and these were
    unknowns in 1950.
    See above comments. You're saying people in 1950 could predict the
    future with 100% accuracy. Also, your forgetting an additional point
    of mine was that it only took 20 years from 1950. Sure, alot of
    people probably figured it might be possible to get to the moon (once
    the knowledge AND technology developed), but how many people would
    have thought it possible in only 20 years?

    Dave
     
  20. Hi Dave,
    I'll concede. In the light of the information you have provided, my
    original comment should be considered wrong.

    But at the least, they had a science to grind on. What I don't see is a
    hydrogen science with mysteries to solve. And I've been all over the
    hydrogen thing. So, at least without new information, I don't believe
    hydrogen can be made part of an energy solution. There may be some kind
    of material science breakthrough to conquer the storage problem, but
    that just a rather small 'if' from here.
    Thanks, Dan.
     
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