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ozone layer (thelemmy.club)
submitted 1 day ago by to c/microblogmemes@lemmy.world
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[–] 5 points 14 hours ago* (3 children)

Hey Chemist. Tell me about methane. We're about to get a lot of that.

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  • [–] 4 points 14 hours ago (1 child)

    Not a chemist but if you're comparing methane to refrigerants it doesn't even come close. Methane has a GWP of 27. That means it's 27 times worse than CO2. However, even the "environmentally friendly" HFO refrigerants like R-454a being used now have GWPs in the hundreds. If you look at the last gen of refrigerants like R-404a and R-410a which are still in use in most equipment you're looking at GWPs in the thousands and sometimes over ten thousand. Hell, just a few weeks ago I was working with R-508b which has a GWP of 13,396 and an atmospheric lifetime of 5,524 years.

    The only common refrigerants you'll find which have a GWP near methane are the hydrocarbon refrigerants like R-290 aka propane. However those can only be used in small appliances due to the flamability concerns. It probably wouldn't be a great idea to have several hundred pounds of liquid propane coursing through the walls of a grocery store for example (especially with how bad many grocery stores leak). The gold standard though for environmentally friendly refrigeration is R-744 aka carbon dioxide. It has a GWP of 1 making it the most environmentally friendly common refrigerant out there. However right now it is only used in heavy commercial and industrial refrigeration due to the cost of equipment designed to operate at the pressures required to use it. Also CO2 has a nasty habit of going supercritical at temps most places regularly reach during the summer so R-744 systems need to be designed to operate as transcritical systems which also adds a ton of complexity and cost.

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  • [–] 2 points 13 hours ago* (last edited 13 hours ago) (1 child)

    propane/butane/isobutane (gwp much lower than 0.1) is weaker ghg than methane because it decomposes faster, and i thought that for large installations the best choice, by far, is ammonia (0 gwp). you don't have to circulate ammonia around, there's glycol loop for that. carbon dioxide is really good if you need -80C, at common AC/freezer/whatever temperatures it loses efficiency and has way too high pressure. (wouldn't high pressure systems also leak, even more than regular ones?)

    there's also Ikon A, ancient (patent-free) refrigerant mix that is R-152a and CF3I aka R-13I1 that also has gwp around 20-30 but also it's not flammable, in fact it's a pretty good fire suppressant because of iodine content. it would comply with all restrictions but it's expensive tho

    worst offenders are perfluorinated gases. CF4 is 5300x as bad as CO2 and lasts 50000 years, SF6 is 17500x as bad and lasts 3200 years. some of the oldest refrigerants were also rather bad, R12 is 10800x worse and lasts 100 years. phasing them out was accidentally a good choice for two reasons

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  • [–] 2 points 10 hours ago (2 children)

    Ammonia is great but it's also kind of religated to being it's own thing in the refrigeration industry because of its incompatible with copper/brass which makes it incompatible with almost all standard refrigeration tools and equipment. Basically anyplace that runs an ammonia system will have their own techs because nobody else will work on it. It's pretty common for heavy industrial refrigeration but not much outside of that. It is also deadly in case of large leaks which makes people shy away from it.

    CO2 though is already in use for grocery store rack refrigeration systems. Aldi is a big user of them. You also can't actually go below -40C with on a CO2 system without risking forming dry ice in the pipes. As far as efficiency goes, the big impact is from transcritical operation but even then it really doesn't make a big enough impact to negate the benefits. Rack refrigeration systems can already be hilariously efficient with high end equipment and CO2 equipment is always high end. CO2 also has a remarkably high coefficient of expansion compared to most refrigerants which gives you some pretty big efficiency gains in that regard which ballances out most of the losses. As far as leaks go I haven't noticed that they leak any more or less than conventional systems, however when they do leak, CO2 is dirt cheap. The only real downside I've seen about these systems are, transcritical complexity, sheer cost, and for some reason they seem to plug oil filters more often.

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  • [–] 2 points 10 hours ago*

    I have just read and learned more about refrigeration, gasses/compounds and R values in the last 10 minutes than I ever thought I would in a lifetime.
    shit sure is interesting though, as someone who grew up with the whole ozone hole thing.
    thank you scientists and fellow lemmings.
    TiL.. a lot!

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  • [–] 1 point 14 hours ago

    we probably don't have to worry about clathrates too hard, permafrost is a different thing. i'm not a biologist, but i can tell you that in regular soil in many places there are bacteria that both produce and consume methane (and also hydrogen). i don't know how well this topic is studied

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