# Electrolyzer -- cool the water or the O2?

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So I've got a really nice scenario.  I've got a Water Geyser close to an AETN, which makes a great combination for an Oxygen factory.  But I'm scratching my head a bit about where to apply the cooling to the overall process.

The Electrolyzer's minimum output of 70 C means there's a limit to how much cooling I can do to the Water prior to the Electrolyzer.  But the 95 C output makes me think it's still a good idea to do what I can beforehand, probably using a Steam Turbine setup.  But the numbers on that aren't nice -- 1 pass wouldn't be enough, and 2 passes would be less than 70 C and thus wasted effort.

It's also been a really long time since I've done any math involving AETNs and their effective cooling, so I'm not entirely sure what the best way to assemble a cooling radiator is -- how big it needs to be, what materials to use, vertical vs horizontal....  It will need to cool the Oxygen from <95 or 81> C to ~23 C for my base supply.  I seem to remember a long time ago 1 AETN could about manage 2 Electrolyzers at 70 C output, but again, that was a long time ago, I don't know if that math holds up.

Seed is 1469931496 if anyone is interested.  It's a Terra asteroid.  The Caustic Steam exposed is straight above the AETN, incidentally, and straight down from the Printer Pod is a regular Volcano.

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The specific heat of water is 4x that of oxygen, so you'll need to sink that much more heat. So it's probably better to cool down the O2 rather than the H2o.

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If it has not changed, the electrolyzer always outputs hydrogen and oxygen at 70C. So cooling the water is totally ineffective.

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55 minutes ago, PhailRaptor said:

But I'm scratching my head a bit about where to apply the cooling to the overall process.

As stated above, the SHC of the water if 4 times that of the oxygen.  Pre space materials, the best you're going to get is using an aquatuner with water or polluted water to cool the oxygen.  Just send the 95C water into the electrolyzer, outputting 95C oxygen. Then use a completely different coolant loop (with the aquatner) to cool that oxygen down, where it's needed. Don't bother cooling it all down, as your dupes are very happy to breathe 95C O2 in their exosuits, for some reason.

Hope that made sense.  Happy ONI.

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32 minutes ago, mathmanican said:

As stated above, the SHC of the water if 4 times that of the oxygen.  Pre space materials, the best you're going to get is using an aquatuner with water or polluted water to cool the oxygen.  Just send the 95C water into the electrolyzer, outputting 95C oxygen. Then use a completely different coolant loop (with the aquatner) to cool that oxygen down, where it's needed. Don't bother cooling it all down, as your dupes are very happy to breathe 95C O2 in their exosuits, for some reason.

Hope that made sense.  Happy ONI.

Doesn't the oxygen exchange heat with the atmo suit dock and heat the area?

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51 minutes ago, Christophlette said:

If it has not changed, the electrolyzer always outputs hydrogen and oxygen at 70C. So cooling the water is totally ineffective.

This was part of the changes to remove the fixed outputs.  The Electrolyzer now has a minimum output of 70 C, not a fixed output.  So if you put in water that is hotter than 70 C, the O2 and H2 that is produced from that water will also be hotter than 70 C.  If you put in water that is less than 70 C, the O2 and H2 will always be at least 70 C.

38 minutes ago, mathmanican said:

Just send the 95C water into the electrolyzer, outputting 95C oxygen. Then use a completely different coolant loop (with the aquatner) to cool that oxygen down, where it's needed.

That would preclude using the AETN, though, wouldn't it?  Cooling the O2 with an Aquatuner loop would mean using a Steam Turbine system for all of the heat control.

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29 minutes ago, suxkar said:

Doesn't the oxygen exchange heat with the atmo suit dock and heat the area?

Yes it does, just played a base with 20 duplicants all using jet suits all the time. The oxygen I fed to my suits was >90°C.

=> I ended with some hotter areas inside my base but nothing to stiff a plant or hurt a duplicant.

[My base cooling dealt with spreading heat, so it´s easier to cool even the suit docks than the oxygen itself. Duplicants still delete mass and are good heat sinks in the regard.]

24 minutes ago, PhailRaptor said:

That would preclude using the AETN, though, wouldn't it?  Cooling the O2 with an Aquatuner loop would mean using a Steam Turbine system for all of the heat control.

Ok, I don´t like steam turbines just to get it out.

=> I would prefer to heat up the produced hydrogen and burn it in an steel generator, to cool my oxygen down.

A steam turbine would still be more power efficient. [The turbine wouldn´t just delete the heat^^]

But if you got an AETN close, why not just cool all oxygen you want to vent into your base with it. [Not the oxygen on the way to suit docks^^]

An AETN isn´t scalable and to cool down the 95°C oxygen of a full time running electrolyzer to 20°C you would already use 80% of the potential cooling power.

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As others have said, do not cool the water, at least not right before it comes into the electrolyzer, cause that baby will output at 70C even if you give it absolute 0 in.

As for radiators, the best pre-space material at "normal" temperatures (below 660 C) is aluminum for radiant pipes and steel for radiant gas pipes. Aluminum ore isn't as good as steel, but it'll do for the gas pipes, so if you find a forest biome, you've got good radiator metal (Klei seems to have made an oversight in implementing aluminum, they gave it real-world thermal conductivity when everything else in the game past niobium has thermal conductivity scaled way down).

Anyways, forget AETNs and steam turbines for a moment, if all you want to do is use your electrolyzer for cooling, then all you need to abuse is the fact that water's SHC is greater than the sum of the SHC of oxygen and hydrogen, meaning that if the oxygen and hydrogen come out the same temperature as the water, you're already deleting a large amount of heat, and then destroying hydrogen with the AETN and/or a hydrogen generator is icing on the cake. Since the minimum output temperature is 70 C, you need the water to be that hot at least to maximize heat deletion.

So to get the water finally coming in up to the temperature of the oxygen starting to come out, and the oxygen finally coming out down to the temperature of the water starting to come in, we want radiant piping for each, running counter to each other on the same tiles, inside aluminum metal tiles surrounded themselves by vacuum or really good insulation. This is a similar design to how penguins remove excess salt (opposite flowing with diffusion to concentrate the salinity on the outgoing flow to excrete), by the way.

This should result in oxygen leaving the system near to the temperature of the water coming in, giving some heat deletion even without an AETN or such (as a real funny sidenote, SHC is reduced so much by the electrolyzer that, to have the gases out have the same heat as the water in, the water in would need to be just under 4 C colder than the AETN can go).

However, the asymmetry of the SHC (the very thing giving us heat deletion) will make it rather inefficient without something to directly pull from the oxygen's temperature and put into the water's; a thermoregulator is an idea, but a bad one, cause heat-transfer machines in ONI do set temperature changes (so oxygen's low SHC makes it rather poor). Basically, you'd want an aquatuner on some loop of water that goes through a heat exchanger with the oxygen, then the aquatuner to touch the pipes the water you're electrolyzing is in. Ultimately, a steam turbine is a good idea cause then you at least get power refunded while you delete a worthwhile amount of heat.

Anyways, with the AETN, it can either be used to cool the water before it goes into the system and gets the oxygen's heat transferred into it, or it can be used to further cool the oxygen after it's left the system. Cooling the water will be much faster (and an AETN only has so much area), but of course, an AETN will happily reach -170 C if you let it, which freezes water...but not if the water in your pipes is only in 1kg packets. Conveniently, the electrolyzer uses only 1kg of water to run, so those 1kg packets will feed it. Put a valve before the water goes over the AETN in some big serpentine of radiant aluminum pipes and set it to 1000g. Just note you'll need a pretty long heat exchange setup as described above to deal with water coming in at freezing temperatures. However doing this might stretch the heat exchange to where it's impractical, so maybe instead use a loop of 1kg water packets in the AETN, and heat exchange with the oxygen leaving.

At the end of the day, oxygen cooling is an annoyance because of its low SHC, which is why I've never really bothered with it. Your base's air will just end up being mostly whatever temperature your tiles and water are, and tiles and water are much, much easier to cool, so just do that. I would just run piping with radiant pipes in the base and over the AETN with 1kg packets of polluted water, much easier.

For the record, I recently went back to one of my old saves from 2017, which had an AETN and a thermoregulator trying to cool oxygen down near it...I replaced that with a loop of hydrogen and it just wasn't cooling my electrolyzers, so then I tried polluted water in pipes and it did a much better job. Believe it or not, while hydrogen is great among gases for temperature diffusion, it's really terrible compared to water.

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Heating up the water takes a lot of effort. Cooling down the oxygen takes very little effort. The end result is heat deletion.

Always feed electrolyzers the hottest water possible.

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Using a AETN if one is on the map always worked great for me to cool oxygen.

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Don't cool either.  You WANT dupes breathing the hot air because that deletes the heat.  The hot O2 will make nasty orange blotches in the temperature screen, but it won't affect the temp of the stuff much because by definition your dupes are inhaling it as fast as you can pump.

Instead, run a coolant line from the AETN to your base directly, and wipe out heat generated there as well as residual heat from the O2.

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10 hours ago, PhailRaptor said:

That would preclude using the AETN, though, wouldn't it?  Cooling the O2 with an Aquatuner loop would mean using a Steam Turbine system for all of the heat control.

You don't need to use a steam turbine for heat control.  Yes, its the easiest method.  No, it isn't the only method.  For example, you can use the heat to boil crude into petrol.  A counter-current design can also cool the petrol back down to reasonable temperatures before storage and you'll still lose heat in the process.  You can also set up a water boiler for purifying polluted water.  Although this is a bit more tricky, you can still remove heat due to the hysteresis around materials changing phase.

There are also a number of ways that still remain to delete heat.  You can feed hot polluted water to pincha peppers, for example.  Your pepper room may be hot, but hot polluted water carries a LOT of heat energy.  You can also feed hot clean water into oil wells.  The difference in heat capacity between oil and water means that you'll lose heat energy even if the oil comes out at the same (or slightly warmer) temperature.

If you have a glacier on your map, you can feed heat into it for a very long time, giving you the opportunity to find other ways of removing the heat.  These are just some of the possibilities.

My point in all this: Be creative.  Try different ideas.  Some might work great, others might not.  You don't have to do something a particular way just because everyone else does.

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May cool both: cool water and use cold water for O2 passive cooling. Or, as say @Lurve, precisely supply hot O2 for heat deleting via dup's breath.

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So, to talk briefly about why we cool down air in the real world, but it's a dumb idea in ONI, here's why we use air in the real world:

• Heat sources are usually spread out, and very few occur in any given enclosed space, and most are well-insulated cooking machines or the heat pumps themselves, so all you really need to cool down is people
• People mainly exchange heat with the air
• Air gets into every nook and cranny; you can't run big fancy heat pipes from your wall onto your computer easily
• Between those encloses spaces is an absolute massive heatsink called the atmosphere, which is made of air, so it's easy to pump it in cold and pump some out hot
• The SHC of that air is slightly higher due to being mostly nitrogen
• Wider temperature ranges in industrial applications make lots of water in pipes usually a bad idea for industrial facility general cooling even when you can put pipes all over everything (however when you want to heat things up instead, steam is actually a great option and commonly used to disperse heat)

And here's why you don't want to use air in ONI:

• Heat sources tend to be very clustered, and the whole space is inclosed, with a lot of very non-insulated machines, so you need to cool a lot more than just dupes
• Dupes vs. people are more heat-tolerant and won't dehydrate
• Dupes delete large amounts of air mass without absorbing its heat, so it's actually quite viable to heat up your oxygen to cool other things, then let dupes get rid of the heat
• Heat exchange surface area with the air is way lowered since there are no nooks and crannies, and you can just run pipes over everything
• Outside tends to be really hot stuff you need to fight heating from
• Oxygen's SHC is much worse than other options
• Air can only be moved in up to 1kg packets, which is the same amount for liquid piping without state changes (meaning infinite temperature range), and liquids have higher SHCs than solids

Basically, ideally, you want to have one water loop cooling your base, cooled by an aquatuner that dumps heat into your electrolysis water in 1kg packets, and then when that turns into hot oxygen you have dupes breath it away before it can do much to your cooling loop. An AETN just trivializes things, but can't handle as much.

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12 hours ago, bobucles said:

Heating up the water takes a lot of effort. Cooling down the oxygen takes very little effort. The end result is heat deletion.

Always feed electrolyzers the hottest water possible.

Yes, this. Actually getting hot water on hand should be incredibly easy, just don't cool the stuff down that's coming from your vents and/or saltwater geyser. Or if you're lucky enough to have a tepid or cold water vent you could use this as the basis for an entire cooling plant.

Water (of all types) is the 2nd most power-efficient coolant in the game, though it has some other issues with state changes & temperature bounds.

Because water's SHC is about 4.2, oxygen's SHC is about 1.1 and you're probably burning most of the resulting hydrogen - you delete a little more than 3/4 of your heat just by making oxygen. (cool the oxygen, not the water)

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15 hours ago, Lurve said:

Don't cool either.  You WANT dupes breathing the hot air because that deletes the heat.  The hot O2 will make nasty orange blotches in the temperature screen, but it won't affect the temp of the stuff much because by definition your dupes are inhaling it as fast as you can pump.

The problem with this is food.  I'm still on Liceloaf and a smattering of Berries.  I will need to get the Oxygen factory up and running, before my Algae runs out, so I can focus on building some dedicated Farms and Ranches, instead of just a row of Farm Tiles 1 floor down from my Printer Pod from way back when on cycle 5.  So if I'm filling my base with 70 to 95 C Oxygen I'll end up starving myself out as my plants Stifle.

15 hours ago, Lurve said:

Instead, run a coolant line from the AETN to your base directly, and wipe out heat generated there as well as residual heat from the O2.

That's the long term plan, but to get there requires squaring away the Oxygen, setting up the Farms/Ranches, and getting a power grid stitched together.

21 hours ago, Nebbie said:

As others have said, do not cool the water, at least not right before it comes into the electrolyzer, cause that baby will output at 70C even if you give it absolute 0 in.

This kind of tells me you didn't actually read the OP (before making either of your posts) because I was quite specific about the minimum output temperature of the Electrolyzer.  I was also quite specific about the Water source being a Water Geyser, which has an output of 95 C.  1 pass through an Aquatuner is 81 C, not 0 K.

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If you don't want to "waste" the cool water you pump in AND wan't to use cooled oxy: you can run it through radiant pipes in metal tiles and then route the output oxygen also in radiant pipes through the same tiles.

That way you can easily bring down the temp of the output oxygen without (energy) cost.
Perfect place for the refined copper of the new patch

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For early game, i think dont bother to cool either oxygen or water, but don't blow the hot oxygen directly to your farming area.

For mid game when you can build turbine, build a small pool of water (about 3X5 tile) at your base entrance. Maintain the water at 20C by AQ / turbine setup. Then pass the hot oxygen with radiant duct at the small water pool, it will cool quickly to about 30C.

This is the most power effective and easy to cool the oxygen i can think of.

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4 hours ago, PhailRaptor said:

The problem with this is food.  I'm still on Liceloaf and a smattering of Berries.  I will need to get the Oxygen factory up and running, before my Algae runs out, so I can focus on building some dedicated Farms and Ranches, instead of just a row of Farm Tiles 1 floor down from my Printer Pod from way back when on cycle 5.  So if I'm filling my base with 70 to 95 C Oxygen I'll end up starving myself out as my plants Stifle.

If algae is your concern, switch to terrariums for cool oxygen.  They still use algae, but much less, so what you have will go a lot farther.  One terrarium and a deodorizer next to it will provide oxygen for one dupe if you let the waste polluted water offgas.  Its downside is additional dupe labor filling and emptying the darn things, and they will happily overpressurize your base given half a chance.  Electrolyzers are a mid-game building, for when you start to value automation more than heat or water efficiency.

Your farm is literally the only thing in your base you ever need to cool.  You can put it in an insulated box in that gap next to the AETN, and cycle cold H2 through if it gets too hot.  Once you get better automation, you can swap that for cool water or petroleum and only chill the coolant when the farm gets warm.  Everything else can be allowed to heat up, because who cares if your beds are 50C.  Dupes don't seem to.