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Re: Solar-hydrogen home power system?

Discussion in 'Photovoltaics' started by Don Lancaster, Oct 17, 2004.

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  1. Solar pv electricity is ridiculously too valuable to waste on hydrogen
    generation.
    The system would be a net energy sink and a net destroyer of gasoline.

    See http://www.tinaja.com/glib/energfun.pdf

    --
    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
     
  2. Glenn Martin

    Glenn Martin Guest

    Don, I'm confused here. Surely a method of storing excess power
    generation makes more sense than letting the daylight go to waste. Most PV
    battery systems lose charge in relatively short order. A properly sealed
    hydrogen tank should hold its' contents for months if not years. This would
    allow you to 'store sunlight' as it were in the long days of the summer to
    fill out the short days of the winter.
    ....and it could fuel leaf blowers!

    Glenn Martin
     
  3. Not when most of the value of the excess power is instantly destroyed,
    as irrevocably happens during electrolysis.

    Most PV
    Such a tank would cost far more than the energy value of the hydrogen it
    was holding.
    A net energy sink is guaranteed.

    Energy density of STP hydrogen is 2.7 watthours per liter.
    Energy density of gasoline is 9000 watthours per liter.
    The value of a kilowatt hour of electicity is ridiculously higher than
    the value of a kilowatt hour of unstored hydrogen gas. Because of a
    fundamental thermodynamic property called "exergy", most of the value of
    the electricity is instantly and irrevocably destroyed during
    electrolysis.

    Electrolysis is exactly the same as 1:1 exchanging US dollars for
    Mexican pesos. It is wildly and laughingly unsuitable for high value
    electrical sources such as grid or pv solar.

    Electricity NEVER gets cheap enough for electrolysis to make sense for
    bulk hydrogen energy aps.
    There ALWAYS will be more intelligent uses for the electricity.

    Synchronous grid storage is by far the most cost effective pv method
    today.

    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
     
  4. Gunnar

    Gunnar Guest

    Hi Don,

    I have never seen any calculations on energy usage for hydrogen production.

    When you say most of the energy is destroyed, I may assume that for every
    energy unit used to produce hydrogen, less than half is recoverable? Is the
    lost energy simply converted to heat during the electrolysis?

    Gunnar.
     
  5. The problem is not with the electrolyses, that can be done at up to
    85-90% efficiency expensively, 75% is more typical for commercial
    installations. Using 80% for production, it is what you produce that
    lacks value. With very expensive PEM you will get back less than 25% of
    the energy as far as transportation mechanical energy. If the input is
    coal at 30%, displacement means wind is strawman and coal is the source,
    maybe 5% of the heating value gets to the wheels of a vehicle.

    It makes no sense, whatsoever, to use hydrogen in terrestrial apps, the
    < 42% 'recovered' energy of a combined plant can't can't touch the cost
    and > 70% efficiency of pumped storage.
    Best, Dan.
     
  6. Exergy is a measure of the thermodynamically reversibly recoverable
    energy fraction.
    An unstruck match has very high exergy, a slightly warmer has very
    little.

    Electricial energy has very high exergy. Unstored hydrogen gas energy
    has very low exergy.

    If you go electricity ---> hydrogen ---> electricity you get less than
    none of it back, because of inefficiencies and fully burdened
    amortizations.

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

    --
    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
     
  7. Or, you can pump a bunch of water uphill, and use an old-fashioned
    waterwheel to get the energy back at night. That method, while it lacks
    portability, can be reasonably efficient.

    I briefly looked through energyforfun.pdf, and it looked interesting --
    but I didn't find the actual efficiency of electrolysis. In any case,
    multiply that by about 0.65 (the efficiency of a decent fuel cell), and
    factor in the energy needed to store the hydrogen (sneaky stuff), and
    any losses, and you end up with a system that will require several KWH
    of work to yield one KWH of output. There has to be a better way than
    that. In fact, off the top of my head, I can think of a few.
    Compressed air tanks and hydraulic accumulators can be used. The
    technology is mature and the efficiency of each step is in the 90%+
    range.

    Don't get me wrong -- I like hydrogen enough to have studied it a bit.
    It has many advantages, but also many disadvantages. It has lousy
    energy density (volume wise), is difficult to store, and likes to leak
    right through the walls of pipes. As far as danger -- well, it's about
    as dangerous as propane or methane. It has a lower energy density and
    tends to float away. On the other hand, you can't see the flame, so
    it's really easy to be in trouble before you know it.

    If it can be produced cheaply (off-shore nuke plants splitting water,
    for instance), and we develop some decent plumbing that'll contain the
    stuff, it wouldn't be a bad replacement for home heating and the like.
    Using it to power a car makes slightly more sense than putting batteries
    in an electric car. I haven't run the numbers, but I suspect that you
    can get more than the fifty or 100 miles per 'thankful that the best
    electric cars enjoy -- and you can fill it up in minutes instead of
    charging it for hours. Still, gasoline, propane, or methane work
    better.

    Want cheap fuel? Shovel a bunch of organic sludge into an air-tight
    container, keep it warm, and let the bacteria make methane for you.
    There are some engineering details to work out, but not as many as for
    hydrogen storage and transport.


    Ray Drouillard
     
  8. Earl

    Earl Guest

    I have worked with hydrogen, both as a chemist and as a
    submarine officer.

    Let me assure you, the one material you do not want in the hands
    of the general public is hydrogen. It would be safer to give
    everyone a big chunk of C4 -- at least that needs a detonator.

    The explosive range is 4% to 96%. The hydrocarbons have a very
    narrow explosive range -- somewhat wider flamable range.

    Look up the history of hydrogen explosions in subs. I have seen
    the results of just a little accumulation in the corner. Lives
    lost and mangled steel. Most of these were from battery
    charge/discharge. There is a second group of accidents from
    operating a O2 generater. Frequent explosions from mixing H2 and
    O2 at 3000 psi.

    Yes, I know that Hindenburg was a problem with the ultra
    flamable cover being ignited by a spark, I refer to real world
    damage actually done by hydrogen explosions.

    With trained crews problems can usually be avoided (the sub
    crews were also trained). But put the stuff in the hands of the
    general public and you have a disaster in the making.
     
  9. Jim Logajan

    Jim Logajan Guest

    I was not aware that the general public commuted in submarines.
     
  10. To quote an old farmer I once knew "Such thinking comes from long hours
    in the outhouse alone".

    --
    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
     
  11. A previous SEH poster created that large hole in the map between
    Colorado and California where Northern Nevada used to be. They tried for
    both the X prize and a Darwin award at the same time. The garage did not
    quite go suborbital and the second trip would have been problematic.

    Hydrogen even remotely near the general public is profoundly and
    fundamentally insane.

    http://www.tinaja.com/glib/energfun.pdf

    --
    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
     
  12. I feel your figures are overly optimistic.

    Here are mine from careful independent analysis:

    Significantly expanding photovoltaics -------------- 50 cents per
    peak watt
    Grid Parity photovoltaics -------------------------- 15 cents per
    peak watt
    Becoming a net energy source rather than a sink ---- 12 cents per
    peak watt
    Practical for smelting, refining, etc etc ---------- 8 cents per
    peak watt
    Practical for hydrogen electrolysis ---------------- 2 cents per
    peak watt

    I predict that there ALWAYS will be better things to do with electricity
    than waste most of its value during electrolysis by wantonly destroying
    its exergy.

    At present, the process of electricity ---> hydrogen ---> electricity
    returns LESS THAN ZERO output owing to equipment, efficiency, and
    amortization. I feel it is highly unlikely in any reasonable time span
    for it to even remotely approach, say, aluminum smelting or copper
    refining economics.

    More at http://www.tinaja.com/glib/energfun.pdf and
    http://www.tinaja.com/h2gas01.asp

    --
    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
     



  13. First of all, I'm not claiming that hydrogen is harmless. I never
    claimed that. My claim is that it isn't any more dangerous than
    methane, propane, gasoline, or diesel fuel -- all fuels that are in very
    common use around the world.

    I will concede the fact that hydrogen is more touchy due to its wide
    range of flammability. The fact that the flame front travels very fast
    might also cause problems. Still, it's less energetic than the heavier
    fuels, and a mixture that is not close to stoichiometric is going to be
    even less energetic. That doesn't make it safe, but I'll take a
    hydrogen explosion over a propane explosion any day.

    You gave an example of the damage caused by mixing H2 and O2 at 3000
    PSI. Yes, that would be very bad news -- but not as bad as a
    stoichiometric mixture of O2 and methane at the same pressure. It's not
    the hydrogen that makes it so damaging; it's the pressure.

    How dangerous is motor oil? Drop some liquid oxygen on a grease splot
    on the pavement, and you have trouble. Concentrated fuels and oxidizers
    need to be handled with care.

    I don't doubt that H2 is dangerous. My thesis is that it isn't any more
    dangerous than other stuff that we are already using. The main problem
    with it is that we (the general public) lacks experience with it.


    Ray Drouillard
     
  14. I know of no large holes in the landscape. Would you care to be more
    specific?
    That unsupported statement is currently under discussion. Simply
    repeating it doesn't add support.


    Ray Drouillard
     
  15. Glenn Martin

    Glenn Martin Guest

    Don, the key here is the phrase "most of". The system described with
    hydrogen yields more total energy than the system without. Obviously, some
    form of storing extra generation capacity is more beneficial. I'm not
    saying hydrogen generation is the best way to do it. The use of the term
    "destroyed" is odd as the word "lost" is much more accurate.

    In this case, are you discussing the financial cost of the storage tank
    versus the financial cost of the hydrogen it holds? Or are you comparing
    the amount of energy that went into making and shipping the tank to that of
    its' contents? The thing is, the tank will be refilled mnay times over a
    period of years. Thus 'the energy that it holds' is orders of magnitude
    more than its' capacity at any one time. I don't see that this has been
    factored into your analysis.


    I don't see how energy density enters the picture here. The original post
    discussed a case where the hydrogen was used in the same place as it was
    generated. Provided the resulting tank isn't so big as to leave no room for
    a house, density is not a concern. It is probably safe to assume that the
    size of domestic hydrogen storage would be on the order of domestic propane
    tanks or thereabouts.

    The value of unstored hydrogen is precisely equal to the value of unstored
    gasoline or ungenerated electricity; ie: zero!
    Here you mention the concept of "exergy". This is a concept based on the
    second law of thermodynamics which is stated many ways but can be described
    as not being able to get as much energy out of a closed system as what you
    put into it. The result is that a watt of gas does not equal a watt of
    coal. Energy that can be used in many different systems can be considered
    more valuable than energy forms with less adaptability. Once energy is
    used to do work, it mostly ends up as unreusable heat. In this sense it's
    more practical to use a watt of electricity to move four watts of heat
    through a heat pump than to directly convert four watts of electricity into
    heat. The same amount of heat is obtained but you have more stores of
    adaptable enrgy in the first case than in the second. Water at the top of a
    falls has great potential energy which could be used to run turbines to
    produce highly adaptable electricity. At the bottom of the cliff, this
    energy has been converted into sound, vibration and a minute increase in
    average water temperature; none of which is recoverable for practical
    purposes.
    Of course, the only closed system known in nature is the ENTIRE FRICKIN'
    UNIVERSE! Put water in a dark container in the window and it's temperature
    rises; an energy gain far outweighing that used to put the water into the
    container and set it on the windowsill. This is because it's not a closed
    system. There's that shiny thing in the sky that's been playing a part.
    There are more practical, localised applications of the concept. An
    engineer can easily ignore the environmental source of sound, heat and
    vibrational energy in studying an engine as this energy is practically
    irrelevant for the purpose of analysis. You could study various internal
    combustion engines to see which had the most efficient use of gasoline but
    their exergic value would be equally nil if they weren't hooked up to
    anything!
    This is key. Exergic value is NOT a constant! It varies with
    circumstance. Here's a good quote...
    "A second law approach to energy analysis indicates that,
    Energy is efficiently used when the quality of the source is matched to the
    quality demanded by the task. Thus, electricity is a thermodynamically sound
    way to drive the motor that agitates the clothes in the washing machine. It
    is not a thermodynamically sound way to heat up the washing machine's water.
    By thermodynamically matching sources to tasks, we can avoid the enormous
    waste of using high quality energy for low quality tasks, and minimize the
    growing social and economic costs of energy production."

    http://www.fes.uwaterloo.ca/u/jjkay/pubs/exergy/

    Excess PV generation is most efficiently put back into an electrical grid
    a house is tied to. Your electricity metre would roll back watts on an
    almost precisely one to one basis to what you put in. If you AREN'T tied to
    a grid and it's cost-prohibitive to link to one then some form of excess
    power storage will almost always increase the value of the generation
    system; even hydrogen generation. I mentioned an example in my previous
    post of a remote community using wind power and storing excess power
    generation as hydrogen. The regeneration of power from hydrogen coul be a
    source of clean, distilled water to supplement the communities supply.
    Also, the hydrogen could be used to power small, efficient run-about
    vehicles (should they ever come on the market) more suited to the
    communities' needs than conventional vehicles. These applications increase
    the capacity of the original power generator to do work and thus its'
    exergy. Perhaps more-so than a more efficient but less adaptable storage
    method.


    I want bring up another aspect of your writings that I've had
    difficulty with. You don't seem to make reference to change ovr time or in
    scale. The last 20 years has seen a steady drop in the price of PV
    electricity and a steady rise in that produced by fossil fuels. It is
    pretty much a given that PV electricity will be cheaper than fossil fuel
    generation within the next 20 years; sooner rather than later. Fossil fuels
    may be economical to harvest until as late as 2050 but will probably be out
    of the running as a viable general source of energy well before that time.
    Obviously the practical thing to do is to explore alternatives well before
    the crunch time comes to avoid the massive economic dislocation that could
    occur. To examine the problem from the scale of an individual is,
    at this precise moment, to decide that PV is not worth investing in. The
    result of this would be to destroy the residential PV industry and lose the
    experience and talent that have been built up so far. This would mean that
    closer to the crunch time, the government would have to initiate a hugely
    expensive crash program to recreate an industry. From a national scale,
    this would be the height of folly. A far better admonition would be to
    suggest a scaled investment. People should start with a backbone and a
    small PV array and expand as economies improved. If the backbone is
    properly designed, it would increase the options for a homeowner with regard
    to heat and power. A new electricity metre would not only be reversable but
    signal a display inside as to how much power is being used at the moment.
    Many regions are adopting different rates for different times of the day to
    encourage spreading use and reducing peak load. The backbone should also be
    designed to easily allow the powering of heat exchange systems and other
    suitable technologies.
    Again, context is everything.

    Glenn Martin
     
  16. Not even wrong.

    Electricity ---> hydrogen ---> electricity currently recovers LESS THAN
    ZERO of the initial electricity because of equipment, inefficiency, and
    amortization.

    It is exceptionally unlikely to EVER be able to compete with more
    intelligent electricity uses.

    If you have electricity and want hydrogen, sell the electricity, buy
    some methane, and reform the methane. It is far cheaper and destroys far
    less exergy. You also should be able to get MANY kilowatt hours of
    hydrogen for each input kilowatt hour of electricity this way.

    See http://www.tinaja.com/glib/energfun.pdf


    --
    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
     
  17. Does not matter in the least.

    The energy density of the stored hydrogen is so low that you will have a
    net energy sink regardless of the storage method you use.

    No effective storage method is known today.
    Thus, they are all bad.
    Some worse than others, but all bad.

    The contained energy density by weight of hydrogen is much lower than
    gasoline.
    The energy density by volume of hydrogen is ridiculously lower than
    gasoline.

    There is more hydrogen in a gallon of gasoline than there is in a gallon
    of liquid hydrogen.
    And, of course, far more energy in a gallon of gasoline than in a gallon
    of liquid hydrogen. About 6X or so.

    Figures in http://www.tinaja.com/glib/energfun.pdf

    --
    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
     
  18. Don W.

    Don W. Guest

    Hydrogen is more dangerous than methane, propane, gasoline and diesel fuel
    not only because it easily ignites within an extremely broad range of
    mixtures, but also because it must be made real cold or compressed to
    outrageous pressures in order to get enough of it to do anything into a
    reasonable-size container.

    Don W.
     
  19. October 18, 2004
    [nonsense snipped]

    And physics and progress itself is real dangerous, so we should all just
    quit doing it.

    Luddite.

    Thomas Lee Elifritz
    http://elifritz.members.atlantic.net
     
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