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I barely got through the introduction before giving up. The opening line - "Hydrogen is the ultimate clean energy." - is a vague, meaningless, scientifically v

• u320 4y ago
  For fixed infrastructure, nothing beats power lines. For mobile applications, hydrogen has numerous problems. There are other options, like batteries, ammonia, synthetic hydrocarbons etc that should be explored further. Hydrogen doesn't even come close to deserving the title "the ultimate clean energy".
  • ncmncm 4y ago
    That wholly misses the point. We need hydrogen production in unlimited amounts for myriad processes. Want synthetic ammonia? Need hydrogen. Methane? Hydrogen. Kerosene? Hydrogen. Green steel production? Hydrogen. Furthermore, liquified hydrogen is the future of aviation. So a tech that produces hydrogen efficiently anywhere there is air is intrinsically important.
    • eru 4y ago
      > Furthermore, liquified hydrogen is the future of aviation. What makes you think so? Why not eg methane? Or other synthetic carbohydrates?
      • ncmncm 4y ago
        LH2's extreme mass-energy density will make other aircraft unable to compete, because the weight savings may be sold as additional paying cargo capacity. That presumes a joule of LH2 is the same price as of kerosene. But LH2 may end up much cheaper, increasing the gap.
        • eru 4y ago
          One would suppose mass energy density is even more important for rockets. In practice, only some rockets use LH2. Many rockets use souped up kerosene (RP1) or, more recently, methane. Compare https://en.wikipedia.org/wiki/Liquid_rocket_propellant#Hydrogen https://en.wikipedia.org/wiki/Liquid_rocket_propellant#Hydro... and https://en.wikipedia.org/wiki/Hydrogen-powered_aircraft https://en.wikipedia.org/wiki/Hydrogen-powered_aircraft Also: > With materials available in the 2020s, the mass of tanks strong enough to withstand this kind of high pressure will greatly outweigh the hydrogen fuel itself, largely negating the weight to energy advantage of hydrogen fuel over hydrocarbon fuels. Hydrogen has a severe volumetric disadvantage relative to hydrocarbon fuels, but future blended wing body aircraft designs might be able to accommodate this extra volume without greatly expanding the wetted area. From https://en.wikipedia.org/wiki/Aviation_fuel https://en.wikipedia.org/wiki/Aviation_fuel
          • ncmncm 4y ago
            The need for higher mass density exhaust to provide enough absolute thrust to get off the ground overwhelms H2's energetic efficiency. Thus, SLS, like STS before it, depends on solid-fuel rockets until well clear of the pad, and then jettisons them. Aircraft operation involves nothing analogous.
          • semi-extrinsic 4y ago
  • ZeroGravitas 4y ago
    Ammonia and synthetic hydrocarbons will be built from green hydrogen though.
  • adrianN 4y ago
    Hydrogen is pretty neat as a storage medium. It's easier to store a few terawatthours in gas than in batteries.
    • usrusr 4y ago
      Most of all it's an intermediate for even neater chemical storage mediums. The entire range of non-biological regenerative fuels (or non-biological, period, if we include fossils in the biological group), including reduced Fe dust cycles, ammonia or plain old "e-fuel" hydrocarbons, they all start with hydrogen as the first stage. It's the natural short term storage medium that will be used as an input buffer for downstream processes so that they don't have to follow supply peaks as closely as they would have to without that buffer.
• aydyn 4y ago
  Those are just buzzwords thrown in to make their article sound more impactful and progressive. Every author does this (yes, literally every author). Who cares. What about their tech?
  • ncmncm 4y ago
    Yes. The tech seems very interesting. The key observation seems to be that atmospheric water vapor is massively purer than any terrestrial water source. And, production directly from vapor avoids efficiency and fouling problems seen when working in liquid. I don't know what they mean by "faradaic efficiency".
• csdvrx 4y ago
  > Hydrogen leaked into the atmosphere is 6-16 times more potent than CO2 as a greenhouse gas Which is a problem considering how small the H2 molecule is: we can't reuse our existing LNG pipelines. Personally, I believe aerochemistry will "work out" in the long term by generating short to medium length aliphatic compounds from CO2 and H2O: we'll eventually figure out the catalyzation from sunlight. We can then have access to lots of energy, with a negative carbon balance, using always sunny surfaces like the Sahara desert - which sits conveniently close to Europe! This could help with the European energy problems if only France would stop thinking short term and try to protect and extend the commercial life of its ailing nuclear energy business (50% of which is currently closed down to being unsafe/uncoolable etc) by shooting down initiatives to build LNG pipelines from North Africa to Europe. Yes, they are doing that, even now that they (and Germany, and the rest of Europe...) are facing a winter without Russian gas: https://www.archyde.com/gas-spain-criticizes-frances-opposition-to-the-midcat-gas-pipeline-project/ https://www.archyde.com/gas-spain-criticizes-frances-opposit... Unfortunately, France stands in the way between the shortest route from North Africa to continental Europe through Gibraltar. If a pipeline can't be build from Spain to Germany by going through France, the next best would be from Italy.
  • ncmncm 4y ago
    It is vastly more cost effective to build electric transmission lines instead of gas pipelines, and crack hydrogen at the point of use. Furthermore, the desert is a lousy place to put solar panels. They get hot and dusty, making them inefficient and shortening their life. The best places are floating on water, and sharing pasture and crop land. Spain, Italy, and Greece have plenty of room for such solar. Portugal, too, and former Yugoslavia, Albania and Bulgaria. Nukes will shortly be unable to produce competitive power, and will be mothballed except where taxpayers are forced to subsidize them.
    • csdvrx 4y ago
      > It is vastly more cost effective to build electric transmission lines instead of gas pipelines, and crack hydrogen at the point of use No it's not. You are building in your assumption that I talk about solar panels for electricity generation. I don't. I'm talking about direct aerochemistry, without separate solar panels, to avoid tackling up the conversion rate of solar to electricty on top of the conversion rate of the chemical reaction that would create the hydrocarbons. There is gas in North Africa. This gas can be directly burnt to generate heat. It can also be used to generate electricity. That's short term. In the long term, we'll be able to make similar compounds from energy (sunlight or heat) + CO2 + H2O. Inbetween, there's a window of opportunity for nuclear and solar, but both are extremely polluting due to the metals used: we should avoid getting locked in this bad situation. Also, I think the lack of nuclear accident in Western Europe so far has just been luck. With the dense population, it's a catastrophe waiting to happen. > Furthermore, the desert is a lousy place to put solar panels I don't think you understand, as I don't suggest at all the use of solar panels. Using solar panels to generate energy is nice, but it's at best carbon neutral. I'm talking about the future: being carbon negative: extracting CO2 from the atmosphere and generating a usable from of energy.
• harg 4y ago
  H2 may well be a more potent GHG when compared to CO2, but it's tendency to remain in the atmosphere for a long time is a factor than shouldn't be ignored and doesn't seem to be mentioned by your first citation. I.e. H2 may be 16x more potent than CO2 but if it reacts away within hours/days/[<16th of the time that CO2 stays around] then its overall contribution to warming will be less than CO2. (I don't know what this figure is, but I believe Hydrogen is pretty reactive so doesn't tend to stick around that long) From your second citation: > The evidence base relating to non-GHG emissions from end-use in heating applications is almost non-existent It then says that a single study: > suggests there is potential for up to six times higher point NOx emissions compared with natural gas". and that it could be significantly reduced with catalytic converters. The points you raise are not nearly as unequivocal as you make them out to be. I also don't feel like Hydrogen is going to solve all of our problems - it has many problems that needs to be overcome. But it could well play a role in certain areas when it comes to getting off fossil fuels, so studies into more efficient production of it will surely be valuable.
  • CorrectHorseBat 4y ago
    >H2 may well be a more potent GHG when compared to CO2, but it's tendency to remain in the atmosphere for a long time is a factor than shouldn't be ignored and doesn't seem to be mentioned by your first citation. I.e. H2 may be 16x more potent than CO2 but if it reacts away within hours/days/[<16th of the time that CO2 stays around] then its overall contribution to warming will be less than CO2. (I don't know what this figure is, but I believe Hydrogen is pretty reactive so doesn't tend to stick around that long) Usually these numbers take that in consideration and the two are compared over a certain number of years, i.e. 100 years. A quick Google seems to confirm this, H2 is ~10 more potent than CO2 over 100 years.
    • audunw 4y ago
      Good point Still.. we're talking about unintentional leaks here. With the alternatives, CO2-emissions is an unavoidable by-product (in theory it can be managed with CCS, but not for transportation) We should use batteries whenever we can, but seems to me like hydrogen is an essential component of a green, fully carbon neutral economy. Though I agree with the comment above that it's a bit... misleading.. to call hydrogen the ultimate clean energy. Green hydrogen (do differentiate from hydrogen made from natural gas) is a very good clean energy carrier. That'd be more precise to say.
• ZeroGravitas 4y ago
  Green Hydrogen is going to be big. You are correct that if you are burning it then you have taken a wrong turn, or at least haven't got to the final destination. Mostly it will be a sink of energy and a chemical feedstock. That is still massive, size of the oil industry scale big.
  • rvbissell 4y ago
    The prioritization that you propose will make the oceans saltier. Whereas, burning H2 is water-neutral.
• jbu 4y ago
  Were you thinking of methane instead of hydrogen? But the paper does seem hypy. H2 will have its place, but wire transfers electrons better than hydrogen.
  • ncmncm 4y ago
    You miss the meat of the article. Highly efficient production not subject to fouling makes hydrogen generated at point of use practical. H2 has myriad uses, and is gaining more at breakneck pace.
• ajnin 4y ago
  > "Hydrogen is the ultimate clean energy." This is a lie pushed by oil companies. First it is incorrect because hydrogen is not a natural energy source, it is a way to store energy. But above all, currently the vast majority of hydrogen is made by steam cracking methane or other hydrocarbons, which is a process that releases CO2. You can think of hydrogen production + hydrogen use as a combustion with additional steps. And since the hydrogen supply chain is very inefficient (hydrogen is very light so you need to compress it a lot to store it, it is a very small molecule so it leaks very easily, and when you use it you need to decompress it so you get more losses due to thermodynamic effects) it turns out as quite bad from the point of view of CO2 emissions. It is just a way to sell more oil.
  • ncmncm 4y ago
    You seem to have read only the introductory paragraphs. There is little need to store or transport hydrogen that may be produced right where and when it is needed.
    • wongarsu 4y ago
      If I read the abstract correct it's doing electrolysis of moisture in the air. That's a process that inherently uses more energy then you get back out of the hydrogen. After all burning hydrogen just turns it back into water, and we can't have more than 100% round-trip efficiency. I could imagine it as a viable storage technology, e.g. if you want to install a solar farm in a remote location you could have it produce hydrogen from the air and sell that.
      • ncmncm 4y ago
        Obviously all conversions involve losses. If you have electric power but need hydrogen, you have to make the hydrogen, whatever the loss. This method has lower loss than others. Probably ammonia will be a better transport medium than hydrogen, but you need hydrogen to make ammonia.
        • saalweachter 4y ago
• marcosdumay 4y ago
  With higher NOx emissions, come higher generator efficiency. Anyway, you can control both on your combustion chamber, so the claim for open fires does really not apply.