I used polluted water until I got super coolant. What gave me the idea was the slush geyser. The water coming out of there was -6 C (or about). So it was a great initial flush into the radiant pipes to give instant cooling. Then like you I ended up looking at the properties and had the same realization you did.
Oxygen Not Included: The Kerbal Space Program of base building & what Fallout Shelter should've been
I’m using polluted water as coolant, with some automation to prevent it from reaching -20. It hasn’t gotten there yet; the aquatuner is still running full-time. And the aquatuner is steel.
I wonder, could it be that I put too much water in the aquatuner chamber? Looking at these pics of other people’s bases, I wondered why everyone puts such little water in there, so I put in enough water to cover the entire bottom row (i.e., 1000kg per tile) then another 200kg per tile or so. I thought what would happen is that because of the pressure, not all of it would convert to steam, and I’d be left with a water bath along the bottom row. Instead, what happens is that it all gets vaporized to steam at ridiculously high pressures (450kg per tile or so.) I wouldn’t think that would make a difference, I’d just have more heat capacity, so it would take longer for the steam to get above 125 C, but also take longer to get back below 125. But once it gets above 125, the turbine only runs for about 15 seconds before the 95 C water coming out cools the remaining steam below 125 and it stops running, then it’s about 90 seconds before it gets above 125 again and the turbine kicks in.
If you have too much water, it definitely hurts efficiency. It takes a looooooooong time to get it up to 125 C (so much higher initialization cost), and it is harder to maintain.
I use about 40-60 kg of water, and even then I sometimes think it might be too much.
Yep. For better or worse, ONI doesn’t model latent heat of vaporization. That’s what allows water and steam to coexist in the real world–even at the same temperature, you have to add additional energy to make the phase transition between liquid and gas. Instead, ONI just changes phases at a certain temperature threshold, so if there’s good thermal conductivity in a system, it’ll either be all gas or all liquid.
In principle, this is true. It’s certainly supposed to be true, given ONI’s version of the laws of physics. However, I know there are weird quirks in the engine that allow heat to be deleted even outside of their strange machines (turbines, nullifiers, etc.), and it may well be that extremely high pressures are one of them. I’d try lowering the pressure to the 10-20 kg/tile range.
I did run into a similar issue when I made a very small steam chamber. I normally have a 3-high chamber, with the aquatuner in the bottom 2 rows and the top row left open. But I once tried a 2-high chamber, and it had similar behavior to what you describe–the turbine wasn’t running as long as I’d expect. So now I always stick with 3-high chambers.
Well, this is it. Time to make some liquid hydrogen. This should be fun. 
It is funny to watch my old living space fall to ruin. Carbon dioxide and other gases are taking over. I’m taking things apart. Other things have such little value they aren’t worth deconstructing. Power systems are going offline. Heating units are being turned off. What was once abuzz with dupes now has a few farmers and ranchers coming to pick up food that continues to grow there. Ranches will eventually be moved. But it is just so cool to see. It is like I can see how other places have become ruins. The people move out and little bits and pieces are all that is left behind.
Good luck! I still haven’t found a design I’m truly happy with, though I have some ideas about the next one.
One thing that I discovered late: super coolant can’t freeze, even if it’s at the minimum temperature and run through an aquatuner. I think they changed this at some point since I pretty distinctly remember having some pipes break, but in any case it’s not a concern now.
My current oxygen liquifier can make LOX just about as quick as I can pump it in, but I’ve never hit the same rates with LH2. I’m hoping the same basic design will work for LH2, but we’ll see.
Found this and thought some of the posters might enjoy it too: Subsurface Ocean Vs Magma Biome : Oxygen not included - YouTube
That moment when you find a Shove Vole in the middle of your base.
How the frak did he get there???
I finally finished exploring the last little corner of the map. And I found a THIRD natural gas geyser! OMG, it has been sitting there this whole time just barely out of sight!!! ARGH!
So this is what I ended up with as my hydrogen liquifier version 1. I know I can make a much better version, but it does work, albeit slowly.
Regolith Turbine version 3! I could have made this better but I had intended to put two turbines. For some reason I thought they were four tiles wides not 5 (5 inputs, duh). It actually powers one turbine really well.
Huh! I was thinking you were going to have problems with the LH2 expanding in your pipes, since it pumps it as soon as it condenses. But it looks like you’re using a flow valve, which if you set to 1 kg/s will mean the liquid won’t break your pipes. So if that’s what you’re doing, you shouldn’t have a problem.
I like to have big storage tanks so that I can refuel a rocket immediately, which means I don’t want to have a flow valve. So for me it’s important that the tank is as far below the condensation point as I can manage, though it’s tricky because there’s such a small difference between the condensation and freezing points with hydrogen. But I think I can make it work.
I see that you like to use pumpless designs. They always seemed a tad too exploity for my tastes, though clearly they have a power and compactness savings.
I have a pump. I’m not sure what you mean.
I definitely want to add a liquid canister to the setup. This was just to get a rough idea on the issues surrounding making LH2. Finding good temperatures, cooling the thermo aquatuner, etc. Proof of concept. Now I’ll build the real thing. 
I mean for the circulation of the coolant. You used the same technique for the standalone coolers, where the aquatuner just connects to itself in a loop. Circulates endlessly without a pump. Obviously the game allows it, but in the spirit of role play I don’t use those designs. Basically, any fluid flow should be traceable back to an origin point with a pump, though it may pass through several machines after that.
Ahh. See I figure for 1200 metal (400 for a pump) the aquatuner includes a rudimentary pump. I.e. it would cost 800 metal if it didn’t have a pumping effect.
I think I may start on a new, harder world. I think this base is as good as it will get it. Now that I have LH2 and LOX, I can trivially make a rocket to go to the temporal tear. It is simply a question of building the ship and making the fuel. Maybe I should do that before I start a new game. Just get it done and then start over.
I’m building and fueling a ship to do the temporal tear before I start a new world. It is interesting, but the regolith turbine produces more consistent power than a solar panel. The regolith turbine produces between 400-650W. 24 hours a cycle, every cycle. This is superior to the solar panel which maxes out at 380W, and it off quite often (during the night and storms). The only issue is heat, but cooling turbines is trivial. I may never build solar panels again. 
Hmmm so if you get a bit unlucky with the way meteors fall for a couple of storms in a row, your turbines can end up with no heat to convert.
I’ll need to solve that problem to make it more consistent.
It doesn’t help that most of my regolith has been eaten by shove voles. If I were doing this from the start, I would be keeping all that sweet sweet regolith around to power the turbines.
Yeah, the problem with renewable energy, just like on Earth, is that it’s inconsistent. Fortunately I keep big stores of hydrogen, natural gas, petroleum, and ethanol around. Plenty of combustible materials to cover the slack. Most days, solar+turbines covers well over half my production, but some days I get unlucky with the meteor storms.
Anyhoo, launch that rocket! You may be mildly surprised at one aspect of the flight, but I’ll let you discover that for yourself.
I’m sorta thinking of going for the gassy moo achievement. But I may go back to my old base since I already have a chlorine liquifier there. The gassy moos would be fantastic (they can turn a chlorine geyser into a 10x natural gas geyser), but the fact that they can’t reproduce makes them incredibly annoying. So I think I’ll just go for the achievement instead of really using them as an energy source.