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13594Re: [renewable-energy] Reed Pellets Untapped Potential

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  • o1bigtenor
    Jul 9, 2014
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      Just to further (hopefully) the discussion. (I am a licensed pressure welder and also a licensed machinist.)

      On Tue, Jul 8, 2014 at 8:53 PM, Darryl McMahon darryl@... [renewable-energy] <renewable-energy@yahoogroups.com> wrote:
      A few additions to Jim's list.


      The pressurized hydrogen tanks for hydrogen vehicle use are typically
      5,000 to 10,000 psi, to obtain a range of 150 to 300 miles between
      fueling stops.

      These tanks are not easy to build and because of the pressures AND the contents the certification process is very very stringent (read very expensive!)

      There was research in hydride-based storage a few years/decades back,
      but this technology is not being used in the few H2 vehicles being
      produced now.


      If you get a leak in such a system, it can be self-igniting.  The static
      electricity built up from the gas friction against the vessel edge can
      generate a spark to ignite the gas.  H2 will ignite in very wide range
      of oxygen ratios (typically from 4% to 75% at atmospheric pressure -
      oxygen ratio in Earth's atmosphere is typically between 19% and 20%).

      This just means that the stuff is not just a little dangerous its quite dangerous.
      Insurance companies (auto insurance) will have a windfall situation until long term figures are in at I think that would take at least 10 years.
      My guess is that insurance costs on a hydrogen vehicle would be at least 4 if not 5 times (tried asking the insurance agent but they have no idea).


      H2 is odourless and colourless, so it is difficult for humans to tell
      when there is a leak.  Perfuming H2 tends to make it unfit for use in
      PEM fuel cells.


      The fueling infrastructure is essentially non-existent, and will have to
      be built from scratch.  No existing pipelines for NG, oil etc can be
      used for H2 due to leakage (as Jim noted, H2 is a very small molecule)
      and embrittlement issues.

      From what I have been told you wouldn't even be able to use pipelines too well.
      There are issues with pumping and leakage for at least two.
      Don't think you can make the pipeline from any kind of steel so no we are talking huge dollars.


      The flame from hydrogen is a very pale blue, invisible in room-lighting
      or daylight to most humans.  In labs where hydrogen fires are considered
      a threat, a common detection mechanism is to hold something flammable
      (e.g., a frayed sheet of paper) in front of you as you move.  If it
      ignites, you can see the flame from paper burning, and you have found a
      hydrogen fire.

      Something like you use a piece of wood (possibly cardboard) for hydraulic leaks.

      The round-trip efficiency for hydrogen as an energy store is not
      attractive (in a sustainable energy cycle) compared to other existing
      off-the-shelf options.  (Primary energy source to electricity to
      electrolyis, compression of the H2 produced, storage [losses generally
      1% per day due to venting, leakage], combustion in internal combustion
      engine or electricity generation via fuel cell.)


      Most commercial hydrogen production today comes from cracking natural
      gas (methane or CH4).  Generally not pure enough for use in PEM fuel
      cells.  I have not crunched these specific numbers, but if H2 fuel is
      coming from CH4 to be burned in an internal combustion engine (such as
      former Governator Arnold's PR Hydrogen Hummer), my initial guess is that
      the energy efficiency will be better if we just burn the CH4 directly in
      the engine, and over-all carbon emissions would be roughly equal either way.

      Over-all carbon emissions would be higher in that by adding another layer of complexity you have to account for the impact of those structures and processes. There are no processes that I know of that are 100% efficient.


      There are no hydrogen wells.  We obtain H2 by cleaving it out of
      something else.  There is always another real energy source involved to
      get H2.


      The upsides of hydrogen are few.


      1) The ash of hydrogen is water.


      2) Hydrogen can be produced as part of a sustainable / renewable energy
      cycle.


      3) By weight, hydrogen is an energy-dense fuel.

      The downsides list on the other hand is not at all this short.
      Most of the downsides are not easily overcome either.
      Experimentation is great but when the likelihood of serious economic success (at least 5% better than what we have right now IMO) is vanishingly small I would prefer to lend my energies to something else.

      Dee
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