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The CO2 emmissions seem to be regarded as being rather high,which surprised me as I thought the burning of Hydorgen produced H2O and not CO2.
What ever we do in the development of technology the answers will never be totally green.
Consider the 7 Billion humans on this planet releasing CO2 continually and if all these humans want to stay fit and run marathons or ride their bicycles then they will release more CO2.
In response to “The future of hydrogen trains” by Peter Sheppard published 19/01/2021
It is very good for the effects and consequences of technologies to be carefully and thoroughly questioned right from the start and regularly thereafter; environmental aspects are no exception. Mr Sheppard does this in both the first and final sentences of his piece. Sincere debate of merits and flaws is essential for the development of new technology.
For transparency, I'm an engineer who develops commercial hydrogen fuel cell systems professionally for my company, a world leader in commercial fuel cell technology (not UK based). My writing represents my individual views only and is informed by my experience of this topic as we supply fuel cell systems for commercial rail vehicles presently.
My honest view is that the UK would be better off finishing off electrifying its rail network and then supplying it using wind energy. Any hydrogen fuel produced in the UK would be much better used for maritime and long-distance aviation purposes, which remain impractical to conduct without the use of fuel.
This turned into a longer form piece by accident, I appreciate Mr Sheppard did not have as many words to write with as I do - I may well be misinterpreting the intent of his writing at times. I reacted with more detail because it is important to me to represent what hydrogen has to offer in the technical community (as best I am able) and to be open about the risks and drawbacks. Please do question what I write if anything seems unclear, amiss or more sources would be appreciated - many thanks!
"Green" and inferring too much from a demonstrator
It was unfair of Mr Sheppard to acknowledge that the HydroFlex project’s vehicle is a demonstrator, then to admonish the practicability of commercial rail vehicles using on hydrogen fuel in general. The deliberate design choices for this demonstrator would make it obviously unsuitable for commercial service, but that doesn’t mean the concept shown would be unsuitable.
An example is Linsinger Maschinenbau G.m.b.H.’s new hydrogen powered MG11 rail milling machine, claimed to be “the only vehicle of its class that fits in the London Underground”. The hydrogen infrastructure is compactly installed above and below the vehicle, leaving plenty of room for the milling equipment: https://www.linsinger.com/portfolio/rail-milling-train-mg11-hydrogen/
To generally question how “green” a technology is in isolation is not an effective way to communicate the present or future quality and value of the technology. My suggestion of a more useful framing is:
- A “green” rail vehicle should provide the same or greater valuable benefits (safe, fast, reliable and efficient mobility on land) with the same or fewer drawbacks (noise and air pollution, low fuel-to-wheel energy efficiency) which the incumbent diesel-diesel or diesel-electric technology does.
- A “green” rail vehicle must also enable the decoupling of this technology from an inherent dependence on our current favourite (but limited) store of the sun’s energy, fossil fuels.
For me both hydrogen-fuelled and also directly electrified rail vehicles can tick both of these boxes, making them a “green” and sustainable options for future rail-vehicles.
CO2 emissions from hydrogen production
Mr Sheppard describes the CO2 emissions of contemporary hydrogen production correctly. “Grey” hydrogen presently represents the vast majority of global production, where hydrogen is reformed from natural gas. However it is not clearly stated that hydrogen can be produced in large volumes using methods which have no inherent CO2 emissions to the atmosphere, using “blue” or better yet “green” production methods.
I encourage caution regarding “blue” hydrogen: the easiest way to keep the emissions in the ground is to not extract the fossil fuel in the first place. Although a great deal of research and development has been conducted, regrettably a commercial carbon-capture and storage technology is yet to emerge (to the best of my knowledge).
For this reason I am observing projects such as HyNet North West (https://hynet.co.uk/) with great interest, because it is still unclear who is responsible for the CCAS or the capture method chosen.
Safety concerns: if risks are acceptably minimised for methane (CNG), why not with hydrogen?
It is responsible to openly acknowledge that molecular hydrogen has inherent properties which mean it can pose a danger, though these also make it useful fuel. Every serious provider of hydrogen fuelled systems makes its safe use the highest priority - accept nothing less from your hydrogen technology partners!
It was unhelpful of Mr Sheppard to describe the hazards of hydrogen vaguely, to then reference two very frightening failures which did not involve hydrogen fuel. Associations of this kind do not help to build confidence for future users of hydrogen technologies. Hydrogen was not a good choice for lighter-than-air flight 92 years ago, as Legh Richardson reminds us, yet this alone does not mean it is an unsafe fuel. I attempt to counteract this statement with the following explanations to offer some reassurance.
Fuels, once synthesised, typically are associated with the following types of hazard:(1) Environmental and toxicity hazards
(2) Transportation and storage hazards
(3) Flammability (or utilisation) hazards
(1) Hydrogen is not toxic and does not persist in the environment. It being the lightest element in the known universe means it disperses into the atmosphere very quickly and tricky to contain. Even very cold liquid hydrogen disperses very quickly when spilled, as shown in this video from testing conducted in 1960 (61 years ago!) by US Air Force researchers about the flammability of liquid H2: https://youtu.be/7bFJK5kU_UQ?t=146
(2) Compressing (including liquifying) then storing any gas creates a potential hazard should the storage vessel become compromised, irrespective of the flammability of the gas. This is demonstrated in this clip in which a composite type cylinder (similar to those used for storing hydrogen) filled with air to 300 bar experiences a containment failure: https://youtu.be/f-xmaPSZ6GM?t=128
Fortunately industrial gases stored at high pressure in cylinders are used safely every day all over the world, enabling us to make the most of the benefits of storing our gases at high pressure without unacceptably high risk.
Furthermore high pressure containers are inherently much more robust and resistant to external damage than the diesel tanks which fuelled the fire (and severe environmental pollution) in the case of the Llangennech derailment referenced by Mr Sheppard.
(3) Safely using potentially explosive gases is something many of us do daily, for example when using a gas heater, cooker, oven or vehicle with a combustion engine. The specific nature of the risks for hydrogen are well understood. To compare with methane, the majority molecule of compressed natural gas (CNG) and liquid natural gas (LNG) when mixed into atmospheric (STP) air: the minimum flammable mixture “UEG” is very similar for both fuels and a static discharge from clothing would be sufficient to provide the energy to ignite the gas-air mixture of both fuels.
There are more than 10 million CNG-fuelled vehicles in operation around the world, which are generally safely operated despite the inherent hazards. The example of the CNG bus in Stockholm being a rare and upsetting example of it going wrong, though the incident analysis revealed that the explosion should have been preventable.A test conducted in 2001 by Dr. Michael Swain with the University of Miami at Coral Gables comparing the behaviour during a fire of a conventional vehicle and a hydrogen vehicle. 20 years later, modern hydrogen vehicle design still plans for the eventuality of a fire internal or external to the vehicle, as in the demonstration 20 years ago: https://youtu.be/OA8dNFiVaF0?t=23
If the risks can be minimised acceptably for methane, why not with hydrogen?
Source for ignition energy: https://downloadcenter.bgrci.de/resource/downloadcenter/downloads/T033_Gesamtdokument.pdf Source for LEL/UEL: http://www.wermac.org/safety/safety_what_is_lel_and_uel.html
Thank you for your time and reading - have a nice day!
Much better to try and use ammonia NH3 or hydrogen peroxide H2O2 which are carbon free liquids but can produce heat quickly under the correct conditions I think.
Hydrazine N2H4 is more promising Nitrogen hydrogen compound for fuels, as it actually has a reasonably energy of combustion. The penalty is you have to put that energy in to make it in the first place.
H2O2 is a great oxidant, but really you need some kind of fuel to oxidise with it,. and unless you are in space, the oxygen is not normally the hard part.
Over along time H2O2 naturally decomposes into water and oxygen if it is not in dilute solution,and to use as the oxidant for rocket fuel you need it concentrated, so hard to store. You can make a mono-propellant for a rocket by adding a catalyst to speed the decomposition to create the oxygen and water vapour fast enough to create some thrust, but this is much weaker than using it as the oxidant with a conventional hydrocarbon fuel.
Re the ammonia the webinar last night considered that ammonia may be made safer if stored at low slush temperature in a sponge filled container.
H2O2 >> H2O + O
twice so really
2 (H2O2) >> 2 H2O +O2 is less stressed, so a bit exothermic, the bottle fizzes like lemonade and gets a bit warm.
If you warm it up, or add a catalyst (platinum nickel or others) then it goes off more like the icing sugar in your beer experiment and unlike the beer it gets really quite hot (try the sugar trick in in someone else's beer to make enemies quickly).
In a confined space this can generate enough heat to boil some of the water created to steam, and the steam and the oxygen give some propulsion. It is not that great.in terms of energy per volume of fuel.
But far better is to use the O of the
H2O2 >> H2O + O
to generate oxygen in the middle of a real fuel (petrol, methane, hydrogen) where the oxygen meets a carbon or another hydrogen and creates loads of heat in the process.
Unlike normal burning where the oxygen is only getting in at the outside surface of the fuel, properly mixed this can give an instant burn throughout, so lots of energy may be released more or less explosively - great for launching rockets, less of a good thing in engines, where rarely do you want it all to burn at once.
IET SEP Editorial:
Last year a hydrogen-powered train travelled on Britain’s rail network with the aim to start carrying passengers by the end of 2021. What are your thoughts on hydrogen technology, key considerations, or risks? Comment below to share your thoughts!
One thing to keep in mind in case of hydrogen fuel cell engine that it gets heated so in case of countries with cold climate hydrogen trains are good but if we consider hot climate regions i.e. countries near equator then it may cause heating problem in engine and gets explode and also the availability of hydrogen should be consistent and storage should be of lower cost for feasibility in greater extent
I just wanted to take a moment to respond to your comments, specifically about what happens to modern, liquid cooled, PEM-type hydrogen fuel cell engines when they operate in higher ambient temperatures, and in a similar way at altitudes significantly above sea level. I only mean to clarify on this point and to express that I agree with you that questions related to the availability and storage of the fuel are highly relevant to this discussion, in my view more that the technology to convert fuel to electricity (or another energy form for propulsion).
Operating a fuel cell engine in ambient temperatures commonly experienced in equatorial regions does not present an inherently increased hazard, such as the potential for a catastrophic failure like an explosion, than were the system to be deployed in temperate or polar regions.
There is an optimum temperature to run any given fuel cell at which enables steady and stable efficiency in generating electricity from the fuel (in this example hydrogen). The cooling system strives to keep the fuel cell very close to this temperature at all times. The capacity to do so, within the stated limits of the use (ambient temperatures and height above sea level) are guaranteed (or certainly should be!) by the manufacturer when they place the technology on the market.
Questions always welcome, thank you for your time, keep safe and have a nice day!