Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Not Answered
  • Locked Locked
  • Replies 45 replies
  • Subscribers 14 subscribers
  • Views 3141 views
  • Users 0 members are here
Options
You may also be interested in
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

Hydrogen Dreams or are they ?

Helios
There is no doubt that Hydrogen grabs most headlines in clean energy promotion , seems all so simple the fuel cell can work with H2 gas and air and produce a decent amount of electrical energy .Things start getting a bit different for trying to move heavy loads or where large amounts of power are needed as what is termed the energy density starts to become important , Diesel has a very high energy density and liquid fuels in general give battery/fuel cells a good run for the money in power terms. 

Things are changing , but fuel cells remain at around 60% efficient and bit more for the very hot solid oxide ones.

There is also the development of Hydrogen to be blended in natural gas mixtures for use in Gas turbines at around 20% by volume which has been successful and now the 100% hydrogen gas turbine is being developed , given gas turbines have recently broken the barrier for heat engines with 64% efficiency ,then this could well replace the fuel cell.

The main problem with hydrogen and particularly liquid hydrogen is the energy used to get it to liquid , 95% of all the worlds hydrogen used in mainly ammonia production comes from the steam reforming/gas shift reaction of natural gas which creates CO2 , 1000kg of liquid Hydrogen produced by this method produces 9-12 tonnes of CO2 (CO2 is quite heavy) , efficiency of energy in ammonia plants has improved but 1000kg of Ammonia uses 27,000,000 KJ , But here's the strange thing there is actually more Hydrogen in 1000m3 of Ammonia than in 1000m3  of liquid Hydrogen (146 kg of H2 in 1000m3 of Ammonia vs 71kg of H2 in 1000m3 of H2) . To keep it liquid great pressures are required for Hydrogen as well as vessels needing low thermal loss properties . A typical H2 fuel tank will need to be able to handle 350 bar which isn't far off the sorts of pressures found at the sea bed where the Titanic now rests , in old money that's 5000 lbs per sq inch.

according to IEA stats

1.4 GT of CO2 comes from the chemical industry

2.3 GT of CO2 comes from cement making (where calcium carbonate is heated/sintered driving off the CO2)

2.1 GT of CO2 from steel making

However the IEA stats don't really delve into the CO2 of steam reforming of natural gas , if we add the CO2 from oil the unit of the Barrel (around 40 us gallons 159 litrs ) produces a minimum of 317kg of CO2 and we use 95,000,000  Barrels a day.

1 Giga Tonne of CO2 is around 505,000,000m3 of CO2 , coal fired power stations put out around 10GT of CO2 globally


So back to Hydrogen , how much Hydrogen is made annually … mmm this is a tricky figure to get hold of and hoping this is correct I found 164,000,000,000 KG of H2 are produced every year mostly (95%) by steam reforming of natural gas so I get that to (9-12 tonnes of CO2 per tonne of Hydrogen) to 261 to 348 million tonnes of CO2 for making the so called clean fuel Hydrogen (or 131-175 million M3 of CO2) 


Flares , no not my fashion statement from the 1970s but the flaring of CH4 from gas and oil wells as part of the extraction process world bank report today has 150,000,000,000 m3 of natural gas flared off annually , enough to meet the gas requirements of sub Saharan Africa , which is kinda wasteful even if pretty in the night sky.


If we move to electrolysis of water current PEM technology claims to convert 75% of the electrical input , the hot alkaline variant 85% , but 1kg of Hydrogen needing 60kwh of electrical energy to make , soo 1000kg of H2 would require 60,000 kwh , so 164,000,000 tonnes of hydrogen for Ammonia I get to 9,840,000,000,000 KWh and this produces CO2 unless from a renewable source . (unsure if figure quoted is inclusive of 25% electrical loss or not if so 1kg of H2 would be 80kwh and not 60kwh)


Its getting complicated which direction to take , more electricity to make green hydrogen , more electricity to power the electric car  , hows the world going to do this ???

Well perhaps a start is for Hydrogen from water electrolysis to make Hydrogen for Ammonia then at least that's the 261-348 million tonnes of CO2 from ammonia taken care of. 

mmm 2,300,000,000 tonnes CO2 from cement making , I mean wow gee if we could only do something with that ?
  • 0
    I do agree that lightening is natural electricity and that it was used as an energy source in' Back to the Future' and by Baron von Frankenstein. I do think that it is even less dispatchable than wind and sunlight and can probably be discounted. 


    Best regards


    Roger
  • 0
    Mmmmm lightening is an interesting one , as we certainly now can construct a capacitor that could theoretically capture the voltage or part , but I suspect the heat would cause continual damage collection point apparatus , neither is lightening a regular energy source , but it is possible.


    Hydrogen in natural gas or biomethane , has had a lot of promotion as an energy system , its usually accepted that 20% by volume is the maximum quantity .It was speculated that if you drew the hydrogen out , you could use this (via fuel cell) to charge a battery mmmm well that system has a few problems a m3 of CH4 has a KJ value of about 385000 KJ but a m3 of Hydrogen only 11400 KJ , so just over 3 m3 of Hydrogen  to equal 1 m3 of CH4 so the lower KJ value may cause a greater gas flow , there is also the [problem of energy conflict , if you are relying on Hydrogen to make your electricity, the CH4 is not required when your central heating is off .

    So hydrogen for domestic gas heating systems has a few problems .

    However where it could work is in making liquid Hydrogen fuel , by placing a separator on the point of the gas main into town and separate it out and liquify it , and return any CH4 to the grid , the main problem is of course as with domestic heating , if you are not using the CH4 you are not getting the hydrogen and gas flows in mains quite literally double between summer and winter , however if we say mix in the gas mains at 40% H2 then it could be used as mass transport system , so long as you have the hydrogen storage. It is a difficult balancing system to make , as demands in volume terms are so stark , if your town has a big industrial gas user , you would obviously be separating more H2 annually than a similar town without a big CH4 industrial demand .

    The other option is to use the separated Hydrogen (via a large fuel cell) to charge a large grid scale battery (pref a flow battery) .

    Whilst it is from an energy efficiency point of view  to keep hydrogen as a gas and transport it viia pipe , a pure Hydrogen system could require more pressure of transmission (due to its lower KJ per m3) and use more energy , it is an attractive system , but will require a high degree of gas quality management , using it mostly for Hydrogen in the lower demand periods , and careful management in the high use CH4 period .

    Given we can now build houses that do not need the high heat outputs , that gas boilers originally solved (due to poor housing insulation) then any trajectory to the future must consider that gas supplies to new homes will be stopped , and some houses may convert to electricity. Some buildings ,have poor energy efficiency and cannot be changed physically without great physical and aesthetical damage and will need the high heat outputs of gas heating/ wet systems .

    At 60% efficiency and the energy to make and liquify the hydrogen , it is hard to see (unless the fuel cell efficiency improves by a good margin) how hydrogen will work as small vehicle transport use , some success is possible with ships/boats in easy water crossings , and possibly the coach , may be the bus , but the car just looks too difficult to operate , when considering the nature of Hydrogen
  • 0

    Hi Helios,



    Happy to to see some discussion about hydrogen on the IET forums, especially with the research you put into quantifying the scale of the task that is faced. Part of my day job is to try and make these numbers work for fuel cells. Happy to answer specific questions (with data!) about fuel cells if curious, particularly their applicability to different applications (stationary, automotive, rail, maritime and others) as things currently stand.



    A couple of points to try and build on the discussion below. Forgive me if they are a bit clichéd (or wander off topic a little), they are all well trodden points to make.



    More or less regardless of scale and technology, skipping the thermal stage in going from fuel to electricity means better efficiency. Fuel cells are not beholden to the Carnot limit. 83% is our theoretical limit when reacting hydrogen with oxygen to produce water. In practice, we can match and exceed combined cycle turbines even at household scales and there is still room for improvement. Even “omnivorous” high temperature fuel cells operating off of fossil fuels reduce emissions from generation significantly, simply due to getting more electricity out of the same fuel, whilst also generating no particulate, NOx or SOx air pollutants. Speaking of which:



    "The estimated annual economic costs of the above health impacts for PM2.5 was £1.4 billion, up to £2.3 billion for NO2, and up to £3.7 billion for both pollutants.”. [Page 328, “Economic evidence base for London 2016” https://www.london.gov.uk/sites/default/files/chapter7-economic-evidence-base-2016.pdf, which is itself citing a study from Kings College London: Walton, H. et al, (2015) “Understanding the Health Impacts of Air Pollution in London”, King’s College London for GLA and TfL.]



    Quantifying these kinds of differences between incumbent technologies and “sustainable” replacements is difficult, and harder still to persuade people of their relevance to an economic discussion. Factoring in even just the ones we can quantify greatly strengthens the economic arguments for post-combustion technologies like fuel cells.



    There is plenty of ongoing work to try and do this in an accessible and consistent way, which is something that you might also be interested in. To me it seems you have a good eye for getting hold of the obscure data and presenting it clearly!



    My view is that the best thing to do with any renewable electricity generation right now is to avoid converting it into other forms and use it directly, with the aim of shutting off as many of the oldest polluting power plants for good as we can. We’ve got a very big task on our hands to get to the stage where we have enough renewable generation to store significant amounts in hydrogen because to electrolyse you need clean (ish) water.



    Unfortunately fresh water is in increasingly short supply in many parts of the world (including the aquifers which support London), which looks set to get worse in the coming decades. So we need to add desalination of sea water, presently another energy intensive process, before getting stuck into the numbers you posted about electrolysis, storage and fuel cells. So add the renewable energy for this on top too. Or should we use the water to drink, or for agriculture? It’s all together an urgent global conundrum.



    Encouragingly we are winning increasingly more customers from all over the world with the varied benefits of fuel cell technology. We see international collaboration as vital for the transition away from fossil fuels and are very active in promoting cooperation wherever we can.



    As a miniscule part of the bigger picture, I must end my piece here by showing my support for everyone generating as much renewable power as they can, whilst reducing our collective energy footprints as much as reasonably possible without unacceptable losses in quality of life (easier said than done!). In my opinion these are the most helpful things we can do in enabling a sustainable future and bringing hydrogen dreams to life, both yours and mine.



    Thanks for your time and for reading!



    All the best,



    Joe


  • Former Community Member
    0 Former Community Member
    Joe, great post thank you.
  • 0
    Hi Joe great post , but if its true that the water vapour emissions from a fuel cell car could re ice road surfaces in sub zero temperatures , where does that leave us in terms of using fuel cell vehicles for countries with winters ???

    the 83% theoretical fuel cell efficiency is interesting , but what sort of pressures or flows of H2 are required for that ???

    Just looking at figures and it takes 3.3kwh to liquify 1 kg (14,12 l)  of hydrogen in transition from gas to liquid at boiling point as temp is so low i.e more energy is required .

    Also some reports of longevity are not good as high pressures have problems with corrosion

    I think the fuel cell does have a future , but as an energy peak system ?? .


  • 0
    I think it's worth pointing put that burning hydrocarbon fuels produces a lot of steam as well, but nobody worries about that.
  • 0

     



    Hello Helios,



    Regarding water vapour leaving the exhaust and freezing on the road, I am with Simon Barker on this one. Toyota’s Mirai does feature a “H2O” button for the concerned driver. This enables a human to override the automated control system and choose when to dump the reaction water. In the videos it does look a bit of a silly gimmick to me, because personally and I can’t really take a world in which I need to think about taking my vehicle somewhere appropriate to ‘relieve’ itself seriously.



    ___________________________________________________________________________________________________________________________



    Good practice to question the conditions and definition of the 83% figure for efficiency. It's common to quote an ‘efficiency’ figure that makes the thing you are selling look better than competitors, after all. It's important for us all to have a good definition of what we want out of a system to be able to evaluate different technologies fairly.



    My source for this figure comes from a textbook chapter written by Professor Wolf Vielstich, a well-known German electrochemist who was awarded the Faraday medal by the Royal Society of Chemistry in 1998. The RSC acknowledging his contributions to Electrochemistry is good enough for me to believe he knows what he is talking about.


    The conditions for the 83% figure are:



    - the reactant gases are at unit pressure



    - the gases are at a constant temperature of 25 degrees centigrade



    - that the product water is entirely liquid (due to the constant temperature being 25 centigrade).



    If the reaction definition changes to say that the product water formed is entirely gaseous, this theoretical efficiency goes up, because there is no ‘work’ done to carry out the phase change. At 298 Kelvin, we get 94%, though (at least for low temperature fuel cells) the product is a mixture of the two phases and the humidity is something we have to control quite well for other reasons to do with the membranes.


    Curiously, this measure says that some electrochemical reactions give ‘efficiencies’ greater than 100%. Reacting formic acid with oxygen (HCOOH + 1/2 O2 —> CO2 + H2O) gives a theoretical efficiency of 105.6%. This tells us that at these conditions, the environment must do work to enable the reaction, rather than the reaction doing work to heat up the environment. In practice, we always need to be careful to understand what else has to be done to make the reaction work - beware claims of the perpetual motion machine!

    ___________________________________________________________________________________________________________________________



    This also partly explains why fuel cells, particularly high temperature types (the leading technology here presently being Solid Oxide Fuel Cells SOFC) are very keen on finding uses for their waste heat. If the waste heat is something you really want, then we start seeing ‘efficiencies’ up near 100% quoted for real practical systems, since then there is almost nothing ‘unwanted’ coming out of the fuel cell. Whether this heating power is always actually wanted though, is something which must be considered on a case-by-case basis:



    - The exhaust from a low temperature PEM fuel cell (approx. 60 degrees centigrade) is a good temperature for heating up the passenger area of a vehicle in the winter, but what do we do in the summer?

    - Similarly for high-temperature fuel cells, could they be linked to industrial processes which want 600+ centigrade waste heat?

    - It seems unlikely that one single technology choice will universally supersede all others.

    ___________________________________________________________________________________________________________________________



    Working pressures for hydrogen in fuel cells are on the order of a couple of bar at most (again at least for low temperature fuel cells), and much less than any kind of compressed storage which I am aware of. In this area I wonder if a technology platform like the one being developed in the UK with the support of the UK government for liquid air storage could be used to recover some of the energy when decompressing the hydrogen for use. Another interesting development is the use of membrane technologies to compress hydrogen electrochemically rather than mechanically, which offers benefits like no moving parts and the ability to run the whole process on renewable energy (if we have enough to spare).

    ___________________________________________________________________________________________________________________________



    Longevity is a problem for any new technology, especially in energy technologies. In the low-temperature world, corrosion is a limiting factor on lifespan for technologies using metallic bipolar plates in particular. Graphite based plates show superior long-term performance, but at the cost of more expensive manufacturing and thicker cells, meaning a less power dense fuel cell stack (important in some applications).


    As with everything there is a tradeoff, and plenty of work has been done and is being done to improve the long term performance of all hydrogen technologies. The typical use case for a passenger car is much less taxing than any other kind of vehicle (5000 to 6000 operating hours over the product’s life time), something which is achievable already. For almost any other application, we’re talking at least double this before we can be serious about being a long-term replacement, but if you look closely there are companies out there offering fuel cells with 20,000 operating hour expected lifespans already.



    High temperature fuel cells are can be made of tougher materials and don’t need polymer membranes, but heat cycling these units featuring metals and ceramics leads to thermal expansion problems which can cause the cell stack to become leaky and fatigue joints in the cell. Leaky hydrogen boxes aren’t anyone’s friend, but lots of clever design has been done here as well to overcome this issue, and there are plenty of examples of these in use and for sale around the world.___________________________________________________________________________________________________________________________



    If by 'peak energy system' you mean using fuel cells to replace the gas / diesel peaker plants currently used to shave off peak demand at short notice, then we're getting into the realms of frequency support and grid balancing. A combination of batteries and hydrogen energy storage could be used to replace these fossil generators, which are far more expensive and inefficient than a large CCG plant and only work out because frequency support and quickly dispatchable power is so valuable. Hydrogen is in part so interesting because HES (hydrogen energy storage) could fit into the grid both as baseload and as dispatchable peaker plant. Technically, hydrogen fits very well with a future energy grid.


    Compelling renewable generation and associated supporting (hydrogen) technologies fit the conventional centralised generation model doesn’t make the best use of what they can offer. Whether the world is too invested both economically and socially to support a change to the central generation model is something that is debated at great length. In the mean time developers of renewable generation and hydrogen technologies are working hard on making the alternative path as attractive as possible, whether we are allowed to factor in the benefits to our planet from reducing our impact on it or not.

    ___________________________________________________________________________________________________________________________


    Thanks for humouring me and for your interest in hydrogen and fuel cells!



    Cheers,



    Joe


  • Former Community Member
    0 Former Community Member
    The problem with both hydrogen and electricity is that are energy transfer mediums rather than energy sources. Neither exist in a natural form in nature.


    Funny, I thought Hydrogen was the most abundant element in the universe?  This is a very interesting debate, certainly for my sector, as there is a big debate about the future of energy.  From my perspective, the future is absolutely electric, but those who are traditionally fossil fuel based see Hydrogen as a viable alternative.  I happen to think that electricity is too well established and too far ahead of Hydrogen for this to be any real competition.  In time, perhaps the two can work side by side with specific applications using electricity and others using some form of Hydrogen fuel cell.  As for EVs (and I'm a driver of one) I think we're almost at the VHS vs Betamax vs V2000 stage with Tesla and others racing ahead and Hydrogen placing as the V2000 system that is actually better than the others, but is just a bit too "technical" for the lay person to grasp.  Fascinated to watch this develop and look forward to the next 50 years.


  • 0
    Hi Simon yes they emit water also , not very clean water either.
  • 0
    I think you are right about electricty , as so many renewable mechanical sources of power can turn an alternator or dynamo , and some like solar but in some areas its pretty obvious solar can lose out . I must admit for EV some of the early ones are always interesting , very few people appreciate how well thought the Nissan Leaf is in under the bonnet design or toyotas electrical drives , and its these leaps that have enabled the EV the Lion Battery just part of the journey . The main problem for EVs I think are weight and the battery , the battery is still very poor at cycling and recyclng , and I dont think the car companies can get away from the fact , that at the moment the battery is a big factor in residual values , the EV should need servcing less , but be more thorough and battery aside vehicle longevity should be good . they are quiet and this could be a problem for e.g. the sight disabled , or wildlife on the roads not being aware. in mountainous areas i am not so sure the EV or the HFC will be of much use and it may be , liquid fuel is still used in these areas . The EV has many oppertunities , but I dont think the technology will be such a success once over the 3.5 tonne transit , and that is where Hydrogen could work , and at the HGV i definitely think it will be LNG or a biofuel with the KJ/l .

Community Rules & Guidelines