Hydrogen as a renewable energy source

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  • Dave2002
    Full Member
    • Dec 2010
    • 18052

    Hydrogen as a renewable energy source

    Yesterday I went on the RV1 bus, and perhaps for the first time went on a hydrogen bus.

    See http://www.google.co.uk/imgres?imgur...=1733#imgdii=_

    Elsewhere comments have been made about the difficulties of incorporating renewable electricity generation into the National Grid, and how it might reduce the efficiency of the system because of the need for stand-by plants.

    One possible use for such renewable generation (e.g PV and wind) could be to generate electricity for electrolysis to produce hydrogen. This might not be very efficient, but would if adopted presumably allow cleaner operation of some vehicles.

    I'm not sure how the London buses which run on hydrogen actually work. I suspect they simply use internal combustion engines. An alternative method would be to use fuel cell technology, in which case electric motors could be used. There is at least one fuel cell car now available, though it's very expensive. See recent news items and reviews for this - http://www.hyundai.co.uk/about-us/en...l%20cell%20car

    I think the use of hydrogen is discussed in Mackay's book, and I don't think he's very encouraging. As I've said, it may not be at all efficient, but on the other hand it does allow energy storage which is one of the major problems for renewable energy generation. However, storage for vehicles could also be done by charging up batteries, and having a battery swap system, and just possibly that could work, but would require very large scaling up to be viable. If Formula 1 teams can change a tyre in 4 seconds it might be possible to change a complete battery set in a minute at appropriate service stations.
  • Dave2002
    Full Member
    • Dec 2010
    • 18052

    #2
    Originally posted by Dave2002 View Post
    I'm not sure how the London buses which run on hydrogen actually work. I suspect they simply use internal combustion engines. An alternative method would be to use fuel cell technology, in which case electric motors could be used. There is at least one fuel cell car now available, though it's very expensive. See recent news items and reviews for this - http://www.hyundai.co.uk/about-us/en...l%20cell%20car
    Some, possibly all, of the London bus hydrogen fleet do work using fuel cell technology apparently -


    and



    I do believe it is possible to use hydrogen in more conventional engines. The RV1 I went on yesterday seemed quiet, but didn't feel like an electric bus, which led me to think it might have been using a conventional engine. Almost certainly it was a fuel cell vehicle driven by electric motors.

    Comment

    • Gordon
      Full Member
      • Nov 2010
      • 1425

      #3
      The "hydrogen" busses are indeed fuel cell driven. Hydrogen and oxygen combined to make water and some electricity which is then used to drive electric motors [on a cold day you can see the steam exhaust, enough to make an old steam engine enthsusiast glow!]. One danger is that they are so quiet one can come up behind without being heard as I learned almost to my cost on Waterloo bridge.

      The "hybrid" busses also to be seen on the streets are conventional diesel engines driving electric generators/motors just like a railway locomotive. Like cars, eg Prius, those engines use a modified valve timing cycle [Miller] to make them more efficient.

      Diesel [cetanes] and petrol [octanes] are dense molecules so a small volume contains lots of energy. As to storing and dispensing hydrogen like diesel/petrol, that is one of the issues - it's a very light gas and is flammable and you'd need lots of it under pressure, perhaps liquified but that means v v cold. Space vehicle launchers use liquified gas - H and O - engines of course and there must be a good reason for that, probably energy storage density at v low temperatures and a short burn with jetissoned tanks after use.

      It could, as has been suggested, however be derived from renewables and elecrolysis or the like.

      Comment

      • hedgehog

        #4
        Gets my vote as a relatively clean energy source.

        Comment

        • Dave2002
          Full Member
          • Dec 2010
          • 18052

          #5
          Originally posted by hedgehog View Post
          Gets my vote as a relatively clean energy source.
          There's hydrogen and then there's hydrogen .... http://www.rebresearch.com/blog/hydr...battery-power/
          Seems one can still bring fossil fuels back into the equation - see the last few lines -
          Not including the fuel cell, the cost of energy made this way is somewhat lower than the cost of gasoline, about 25¢/kWhr; since methanol is cheaper than gasoline on a per-energy basis. Methanol is made from natural gas, coal, or trees — non-imported, low cost sources. And, best yet, trees are renewable.
          I doubt very much that relying on trees is going to be effective for large scale operations though.
          Note also the carbon dioxide emissions - also quoted in the article

          CH3OH + H2O –> 3H2 + CO2, with the hydrogen extracted through a membrane within the reactor.
          An interesting article, nevertheless.

          Comment

          • Eine Alpensinfonie
            Host
            • Nov 2010
            • 20576

            #6
            I know there was some talk of using wind power to generate hydrogen and then using the fuel for highly efficient external combustion engines (steam).
            Sounds good to me.

            Comment

            • Dave2002
              Full Member
              • Dec 2010
              • 18052

              #7
              This article reports on another by Bossel, and appears to doubt the usefulness of hydrogen as an energy carrier - http://phys.org/news85074285.html

              Comment

              • umslopogaas
                Full Member
                • Nov 2010
                • 1977

                #8
                Hydrogen has its merits, but a major downside is that it is EXTREMELY explosive. OK, so is petrol, up to a point, but hydrogen is much more dangerous. I would be very nervous about driving around with a cylinder of the stuff in the boot.
                Last edited by Eine Alpensinfonie; 01-08-13, 16:20.

                Comment

                • ferneyhoughgeliebte
                  Gone fishin'
                  • Sep 2011
                  • 30163

                  #9
                  I know someone who speaks very highly of Helium.
                  [FONT=Comic Sans MS][I][B]Numquam Satis![/B][/I][/FONT]

                  Comment

                  • Nick Armstrong
                    Host
                    • Nov 2010
                    • 26575

                    #10
                    Originally posted by ferneyhoughgeliebte View Post
                    I know someone who speaks very highly of Helium.
                    "...the isle is full of noises,
                    Sounds and sweet airs, that give delight and hurt not.
                    Sometimes a thousand twangling instruments
                    Will hum about mine ears, and sometime voices..."

                    Comment

                    • Gordon
                      Full Member
                      • Nov 2010
                      • 1425

                      #11
                      Originally posted by ferneyhoughgeliebte View Post
                      I know someone who speaks very highly of Helium.
                      Raising the tone on these boards for once.

                      Well Hydrogen reduces to Helium in the sun but it's going to run out in a few billion years so we'd better get onto something else.

                      I know that science is tedium
                      But progress is made through that medium
                      Hydrogen plays
                      In Nuclear ways
                      To make the gas known as Helium

                      Since the Sun has come to the boil
                      It has never paused in its toil
                      Two atoms of gas
                      Lose some of their Mass
                      All explained by a fella called Hoyle
                      Last edited by Gordon; 01-08-13, 12:50.

                      Comment

                      • Eine Alpensinfonie
                        Host
                        • Nov 2010
                        • 20576

                        #12
                        Originally posted by umslopogaas View Post
                        Hydrogen has its merits, but a major downside is that it is EXTREMELY explosive. OK, so is petrol, up to a point, but hydrogen is much more dangerous. I would be very nervous about driving around with a cylinder of the stuff in the boot.
                        Actually hydrogen is less volatile than petrol. It burns extremely rapidly, but petrol explodes on ignition. There would have been no survivors from the Hindenburg disaster if hydrogen was as volatile as petroleum (the latter being the probable cause of the disaster).

                        Comment

                        • umslopogaas
                          Full Member
                          • Nov 2010
                          • 1977

                          #13
                          EA, are you sure? Hydrogen is a gas at room temperature and pressure, whereas petrol is a liquid, though admittedly a vapour-forming one. Surely a gas is more volatile than a liquid (correct me if I'm talking nonsense, I'm a biologist and was always hopeless at physics)?

                          Comment

                          • Eine Alpensinfonie
                            Host
                            • Nov 2010
                            • 20576

                            #14
                            There was an interesting TV documentary on the subject a few years ago, though a quick web-search didn't reveal any results. However, I did find this.

                            Comment

                            • umslopogaas
                              Full Member
                              • Nov 2010
                              • 1977

                              #15
                              Interesting stuff. I accept that the Hindenburg conflagration involved more than just its hydrogen content: the structure of the airship was also highly flammable. But I dont buy the "hydrogen was not to blame because it burns upward and the Hindenburg burned downwards" argument. Of course it burned "downwards", the structure was heavier than air. In the photo you can clearly see a ball of flame heading skywards (the escaping hydrogen) while the carcass plunges downwards. And of course, hydrogen can be controlled and used safely, just the same as petrol: but that doesnt avoid the fact that both are highly dangerous materials and capable of causing serious damage.

                              Incidentally, I dont know if there are gas-powered cars in the UK, but there are in Australia. I was once driving deep in the outback when we ran out of petrol. My mate trudged off to look for help and I stayed behind to flag down passing motorists. There werent many, but eventually one stopped. I asked if he had any spare petrol, but he said sorry mate, mine runs on gas. He showed me the steel tank in the boot, but I dont know whether the gas was hydrogen. (The second car that stopped ran on diesel, and my mate returned with a spare can donated by a local farmer before there was a third).

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