Pure hydrogen is heavy greenwashing - after many years talking about green generation, still over 90% is created from natural gas, by the usual fossil fuel companies; they are also the ones promising to build the green hydrogen factories, by the way. It is indeed barely suitable for (direct) consumer use and highly inefficient for electricity generation (like 10% efficiency iirc).
this post was submitted on 19 Apr 2024
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Long duration energy storage efficiency with hydrogen is closer to 40-45%. It is feasible and a good option in certain grid applications.
hydrogen blends [...] compared to gas
I get the jitters reading that. They're both gases. Is it so hard to write "methane"?
I mean if someone says they have gas central heating I wouldn't question which gas it is. In context I think it makes perfect sense. Feels a little pedantic tbh.
It might be propane. Indeed very unlikely for central heating. But pretty likely if they're cooking with "gas".
I'm very confused. About a year ago I saw a YouTube video describing the use of hydrogen as a replacement for fossil fuels.
It went into great detail about the effectiveness and impracticable restrictions on distribution of pure hydrogen, mainly because its extremely small molecules leak through pretty much everything and compression is required to carry any useful quantities around, not to mention storage temperature and refuelling issues.
This was contrasted with using ammonia as a hydrogen delivery mechanism instead. We distribute and transport ammonia around the planet in great quantities already. The chemical process is green, uses significantly less energy, and we already know how to do this.
What I don't understand is why we're still talking about pure hydrogen, doing studies about cooking and still trying to promote this as a great fuel, when better, more effective ways exist.
Anyone?
More information here: https://news.northwestern.edu/stories/2020/11/ammonia-to-green-hydrogen/
This article is specifically talking about the use of hydrogen blended into natural gas pipelines as a way to reduce dependence on fossil fuels for heating and cooking. Ammonia as a transport mechanism has no place here.
The current consensus in the industry is that you can replace up to 20% of the natural gas with hydrogen in a pipeline with no adverse affects. This article is indicating that there may in fact be some adverse affects.
Edited to fix some stupid autocorrects. At least it was mainly verb tense this time.
Youtube videos often gloss over the details for the sake of uninhibited futurism.
Large-scale hydrogen electrolysis has a cost of around 55kWh/kg, and when you combust the H2 directly you get about 39kWh/kg back. Without compression/transport, using H2 as a heating fuel is 71% efficient.
H2 is usually compressed for transport. Compression of 1 kg of H2 to 700 bar costs about 5kWh of additional electricity. I'll spare you the calcs, but truck transport is under 1kWh/kg H2. This reduces our efficiency to 39kWh/61kWh or 64%.
Converting H2 to ammonia takes the place of the compressor and truck. 2 mols of ammonia burn for 162kcal, less than the 204kcal you'd get from 3 mols of H2. The Haber-Bosch process reduces output to 31kWh per kg of H2 put in. This reduces out efficiency to 31kWh/55kWh or 56%.
With currently-proven cracking technology, it costs around 23kcal/mol of ammonia, reducing overall efficiency to about 55%. It is more effective to burn ammonia directly than to convert it into H2 and burn the H2.
Using ammonia as a transport medium removes a bunch of technical problems, but it introduces new ones. It's corrosive, it's toxic, it burns eyes/lungs/skin, and it wastes more energy than you'd think.
Ammonia is an environmental hazard, in addition, the chemical processes, however green they may be, need extra energy compared to production of hydrogen. And that is already a very lossy process, energy-wise. You also need infrastructure for it. Afaik, only Japan is really interested in building such infrastructure.
The study hasn't been peer reviewed, so shame on the authors for talking about it like it's already decided, but the skeptical part of me can't rule out that this whole thing was destined to fail on purpose.
Big Oil: "See? Hydrogen doesn't work ~~in unmodified systems~~! Shucks, guess we'll have to keep using natural gas..."
And maybe it's less nefarious, like additional proof that we can't just retrofit existing systems by changing the gas mixture, but it's at least suspicious that it benefits fossil fuel producers so neatly.
Big oil has been the primary force pushing hydrogen, because they make most of it, from cracking fossil fuels products. It's complete green washing.
One possible reason is that ammonia is a fairly dangerous substance with both acute and chronic exposure risks.
Hydrogen leaks more than gas
Hydrogen is a gas. Gotta be more specific.