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Cake day: March 31st, 2025

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  • (pref sea water)

    doesn’t matter because you have to purify it anyway

    direct hydrogen uses that make sense given hydrogen is cheap are ammonia, methanol (also from biomass), steel and generally speaking fine chemicals. methanol and ammonia can be used as fuels for cases where BEVs don’t work, like shipping. this also requires monstrous overbuild of power grid

    prerequisite for cheap hydrogen (cheap electricity) will also make further electrification make sense and that eats lunch of hydrogen use for power even before hydrogen infra buildout happens


  • for hydrogen propulsion to make sense prerequisite is to have lots of cheap green hydrogen, which mean very cheap renewable electricity, by which point there’s no need because electric cars are more direct replacement. but there are applications where hydrogen is used directly, as a reagent instead of as energy source and can be made from renewable electricity. Yara makes some of fertilizer this way and there’s a pilot plant for green steelmaking in sweden iirc. it just so happens that now cheapest hydrogen is made from gas

    this also pulls in different directions because people building renewable generation don’t want electricity price to be too low











  • the entire point of three phase circuit is that you can split it into single phase circuits without using too much wire. usually block will be wired so that 1/3 of flats is connected to one phase, but if you need to power big loads like ag tools or something like concrete mixer three phase supply can be done (415V these days, there’s upward shift in voltage)


  • in EU there are really only two standards. for single phase loads up to 3.8kW, regular 16A plug is sufficient. above that, 3-phase 5-pin 32A plug (most common of them) is used which can deliver up to 23kW. there are common variants of 3-phase 5-pin plugs rated up to 125A that can deliver up to 89kW and uncommon up to 800A variants that are also part of the standard, but it delivers up to 0.57MW and it’s a bit silly

    i’ve found 1999 version of iec 60309 standard and biggest connector defined there was 250A. actually i wasn’t able to find vendor for currents higher than 125A, but for 125A, standard expects 16 to 50mm^2 cable and for 250A 70 to 150mm^2. lower ends of these ranges would be insufficient for full load and would require limiting current appropriately. maybe higher currents were latter additon. either way 32A is almost-standard and anything above that is in some way custom job





  • you see, you can be as wrong as you want to be. i won’t be teaching you middle school level chemistry against your will in a comment section. in concrete Ca2+ remains Ca2+, be it as hydroxide or carbonate or silicate and it cannot become reduced in normal concrete conditions and definitely it can’t be oxidized.

    The Calcium Carbonate degrades into Calcium Oxide

    no it fucking doesn’t, this is what happens when cement is prepared in a kiln. near surface of curing concrete calcium hydroxide captures carbon dioxide from air, then this crust of precipitate blocks it from moving deeper. which is why the rest of calcium hydroxide reacts with silica forming calcium silicate, which takes more time and is responsible for late strengthening. before you lost plot i was talking about oxidation of steel rebar, and it depends on many things, but for regular carbon steel if there’s no oxygen then it’s much slower. and because concrete is not very permeable to oxygen, there are all these engineering requirements about how deep rebar has to be. anyway, a little bit of vinegar would be just neutralized by calcium hydroxide from concrete and won’t do anything, a little bit of salt would be diluted massively and also won’t do anything, hydrogen peroxide would decompose because anything will do that