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I hope this is more focused D:

Setup; Hela is a exoplanet in the fictional Eurydice system, about 4 Ly from Earth. The exoplanet is significantly younger than Earth, and life on her is in a late carboniferous stage of development. Due to the star being larger than the sun and the exoplanets atmospheric composition, the average temperature is at ~30 C, and sea level pressure 40% higher than on Earth. EDIT; The Atmospheric composition contains a lot of Co2 and volcanic gases (and what they react to with water vapor) making it so Humans cannot breath it. In some places, the co2 concentration gets high enough that "death pits" develop, where if you breathed the air you would be dead before hitting the ground. A full face respirator is really all it takes to walk outside though.

Leavenworth is the main base for Humans on Hela. The complex is designed to facilitate the export of a valuable resource. Its basically a refinery. Roughly 4000 people live and work there. They live in a small town, Little Summer, which is inside a "Dome" Habitat.

enter image description here

Little Summer is where the big "You are Here" arrow points, the soft edged rectangles show the outline of the Hab Dome. The structure is nothing more than several strong and light transparent polymer sheets. This roof covers Little Summer and is held afloat by slight positive interior pressure. Anker cables hold it all in place. At least for now the roof is ~200 meters tall in the middle strip. The entire structure is roughly 3000x1800 meters.

The goal of the Hab Dome, and Little Summer, is to be as Earth like as possible. They got trees, normal Houses, wide open spaces, the whole 9 yards. The inside temperature is ~10 degrees colder than the outside.

Question; Given all of the above, a problem develops. This is a greenhouse. I might be overestimating this problem, but from what i see it seems this habitat would have serious heat problems as the interior air cant get out. The entire thing is isolated from the outside, as it has to be. This is made worse by the higher W/m² of solar energy on Hela and temperatures. I dont think using big fans on the inside would cut it either.

The question is, given this situation how could i realistically deal with the issue of the hab dome becoming a sauna ?

Solution ?; I gave this a solid think before asking here. My solution would look a bit like this;

enter image description here

There are already at least 2 layers to the roof, so i figure maybe they can move cold air quickly through this "interlayer" to pick up heat from the in- and outside. Thermodynamically, i think this works because the interlayer is much colder than both the outside and inside. It will absorb most heat which can then be dumped into water. This could potentially also be a sort of "active support" mechanism for the roof as a whole.

However, i am not sure this is a, let alone, the best solution to this problem. One issue i can see is the cold air having to be at a higher pressure than the outside, which given its high speed, might put to much weight on the roof, which is only held up by pressure.

Conclusion; Scale wise, i am aiming for "Hard" Sci Fi. I didnt put it in the tags because thats nerd stuff and this is a fairly minor element. I just want to make sure whatever solution i present is functional. For story purposes, or at least visuals, this might also be interesting. It rains a lot on Hela and depending on what the solution is there might be visible side effects. Which is always nice to write about.

I hope i explained the issue and, potential, solution in enough detail without making another question which needs a book to be answered.

Thanks for reading !

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  • $\begingroup$ "Humans naturally cannot breath this atmosphere." Not clear if this is given or author assumed. Because 30C and higher pressure is by itself not a limit to humans breathing it. "Given: Humans cannot breath this atmosphere." would be much clearer $\endgroup$ Commented Nov 22, 2023 at 23:30
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    $\begingroup$ Why wouldn't heat pumps/refrigeration combined with insulating dome be applicable? $\endgroup$ Commented Nov 22, 2023 at 23:34
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    $\begingroup$ To be clear when I say heat pumps/refrigeration I would expect all that to be sitting on the ground along with all the other heavy machinery that exists. An Insulted dome can dramatically reduce refrigeration cost depending on how much insulation, type of insulation etc $\endgroup$ Commented Nov 23, 2023 at 0:04
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    $\begingroup$ Note also that there are some honking big buildings here on Earth with temperature-controlled interiors including the kilometer-high Jeddah Tower in Saudi Arabia, which can be expected to have its own heating problems. In other words, we've likely solved this problem already on Earth and all you need is to adapt that solution, which likely involves industrial heat pumps. $\endgroup$
    – JBH
    Commented Nov 23, 2023 at 0:06
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    $\begingroup$ I don't think having the cooling system between the dome layers makes much sense. The problem is that it will pick up heat from the outside as well as the inside, making it inefficient. This can be mitigated by having a third dome layer outside that - but it would seem much easier to just have the cooling system somewhere else. $\endgroup$
    – N. Virgo
    Commented Nov 24, 2023 at 13:35

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The structure is nothing more than several strong and light transparent polymer sheets.

If you don't want a greenhouse, reduce the transparency. Cut down on the amount of light coming in, and the amount of in-dome heating will go down. If you had fancy future material tech, you could have variable opacity or reflectivity, to keep the sun out during the day, but keep things dark and enhance radiative cooling at night.

If you want the inside of the dome to be cooler than the outside, you're going to need some insulation in order to avoid your A/C bills becoming apocalyptic. Instead of having a plain dome shell, go for something a little more like bubblewrap. For a real world example, consider the Eden Project:

Eden project domes

(image credit: A1personage/wikimedia)

The Eden domes are held up by a space frame underneath, rather than air pressure, but the basic principle is the same. One of the internal volumes is held at a higher temperature and humidity than the outside to let rainforest flora thrive, and the cells in the dome structure help reduce heat loss.

I would suggest not following the advice of Monty Wild when it comes to using water mist for cooling, however. It is quite an effective and economical approach, however on the scale of something as large as your domes the risk is that the humidity of the air inside the habitat rises to the point where it make cooling of people more difficult (due to a reduction in the efficiency of sweating) and increases problems like mold and fungus growth that represent sources of damage to infrastructure, reduction of output in agriculture and health risks for humans and other animals living in the dome.

The dome air should be kept clean and relatively dry. Cooling via water mists and swamp coolers and the like could be done inside buildings, but probably doesn't belong in the dome itself.

A potentially good source of cooling would be geothermal, depending on what the local geothermal gradient looks like. If the ground deep enough beneath the surface of your habitat is cool, you can use it as a heatsink... circulating cooling fluid from the hot parts of your dome and the buildings within to cooler underground heat-exchanging regions like a city-scale ground-source heat pump. On Earth, a 20 m deep pit will reach far enough that you don't get sun and weather-induced seasonal variation. Your world might be different, of course, but even if the ground were weirdly hot a heatpump can cope with that, given sufficient power.

This might require significant excavation, but honestly: if you want to stay cool in a hot place, hiding in a deep hole isn't a terrible idea. You'll probably want to have some underground stuff anyway... emergency shelters to be used in the event of dome failure or compromise.

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  • $\begingroup$ I think, with all the comments, a certain solutions develops. On the one hand, the dome itself should be reflective to all the light we dont need. The interlay cooling should stay there as well. On the inside, we circulate the air using big fans along the middle, this circulated air gets sucked into a subterranean heat exchanger which could use rainwater and geothermal to get rid of the heat in the hot air. Visually, this might manifest itself as big steam plumbs being emitted near the dome. All the surface infrastructure might also double serve as emergency shelters. $\endgroup$
    – ErikHall
    Commented Nov 23, 2023 at 13:19
  • $\begingroup$ You don't necessarily need fancy future tech to vary the opacity - a Venetian blind type system with movable panels would do the trick. $\endgroup$
    – N. Virgo
    Commented Nov 24, 2023 at 13:31
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    $\begingroup$ So i am gonna mark yours as the correct answer, because it lead me down a way to deep rabbit hole on how large scale cooling systems work, how its basically a big fridge and how the energy bill is going to be "yes". Basically all of your suggestions, and those from the various other (all good) comments are also included. Thanks a lot ! $\endgroup$
    – ErikHall
    Commented Nov 24, 2023 at 14:32
  • $\begingroup$ @N.Virgo difficult to keep them reliable, lightweight and easily cleaned on a large freestanding dome, though. $\endgroup$ Commented Nov 27, 2023 at 19:33
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The trouble with the double-walled dome setup is that air doesn't have a particularly high heat capacity, and in a dome, the interior air won't be moving all that quickly. The inner surface of the dome would be cooler, and would remove some of the heat from the air, but I can see solar radiative heating contributing more to the temperature inside the dome than this cooling.

Air cooling is always going to be a problem. Whenever heat needs to be managed, water cooling is more effective given the very much higher heat capacity of water.

I'm not saying that you'd get rid of the double-layered dome, that's probably a good safety backup to isolate the inside air from the outside air, as well as an insulator, especially if the outer layer was partially silvered, but you'd need a number of other cooling methods.

Firstly, I'd make the roofs of the buildings from white or silver surfaces, to reflect as much solar energy as possible and minimise solar heating. I'd also water-cool them. Secondly, I'd set up water sprayers and fans to circulate water mist through the domes. The evaporation of water will remove a lot of heat from the air, and will also help with growing any plants kept in the dome. With a flow of humid air through the dome, it can be passed over refrigeratively cooled condensers to recover the water so that it can be misted again.

The air could be circulated by placing vents near ground level, mostly along the centre-lines of the dome, and forcing water-misted air upwards toward the top of the dome, where the largest body of hot air would otherwise tend to accumulate. By drawing air from the edges of the dome and passing it underground through condensers to cool and dry it, the air would circulate throughout the dome, mixing with air warmed by hot surfaces within the dome. By forcing the misted air upwards at speed, friction within the body of air within the dome would cause movement of the whole body of air inside the dome.

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  • $\begingroup$ Now that you mention it, the logic i have is a bit backwards. The Cooling system relies on hot air rising, which implies a noticeable temperature gradient inside the dome. Which is exactly not the situation we have. dang it. But i like the suggestions you gave a lot. The one follow up i would have is how you would circulate the air ? $\endgroup$
    – ErikHall
    Commented Nov 23, 2023 at 0:31
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    $\begingroup$ @ErikHall Have a look at my edit. $\endgroup$
    – Monty Wild
    Commented Nov 23, 2023 at 1:12
  • $\begingroup$ thanks for the clarification. The ideas you had are quiet visual which is nice, big towers along the middle, vents on the ground probably hidden in the forests. It feels very "yeah thats how you´d do that". Ill leave the question open for the night, but this has been really helpful :D $\endgroup$
    – ErikHall
    Commented Nov 23, 2023 at 1:39
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    $\begingroup$ @ErikHall Not big towers, probably only a meter high so people don't fall into them. $\endgroup$
    – Monty Wild
    Commented Nov 23, 2023 at 1:48
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    $\begingroup$ If you're venting air upwards in the middle and extracting it at the edges, you're going to get air circulation. It only needs to be big and fast enough, but it needn't be so dangerous that people need to be separated from the vents. The closer to the ground, the better the ground-level cooling. $\endgroup$
    – Monty Wild
    Commented Nov 23, 2023 at 2:01
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The main problem of your Little Summer is that the inside is designed to be colder than the outside, so the residents of your hab dome are living in a literal fridge. Therefore your proposed air cooling system would work with less effectivity than you expect, as the air flow would take off energy from the outer layer which has more to take than from the inner layer. Still it would be needed.

You should make the outer layer of the dome reflective and transparent, a thin reflective foil would do on top of the relatively thick but transparent structure layer; this way the energy income into the dome would be lessened, and you are able to control the amount of reflection at least at design time so that the interior insolation is comparable to earthly conditions when the local sun is in zenith, or at midday. Still, as earthly habitats are cooled by emitting radiation into open space, and your hab dome is closed, you would need a great air cooling system to instead cause this energy to be radiated from outside the hab dome; you would need a radiator field or a cooling tower that uses evaporating water as a means of energy sink that should be located somewhere uncovered.

Air cooling could be done the conventional way within the dome, however the entire A/C system should be pretty large. Develop several air tubes within the dome that would reach the top layers of air, above the levels where humans operate, place sucking pumps at their bases, provide a heat exchange with water and lead that water underground outside to the radiators to form the second heat exchange circle there, as well as produce a smaller water heating structure for the hab dome's internal use, because spending extra energy to heat it would be heating the dome and putting more load on the cooling systems.

Alternatively, check for water, if there's an above-ground or underground river somewhere close to the hab dome, you might position your heat exchangers in there, so your hab some would work like a modern power plant works with rivers in here, heating the waters of it with excess heat generated by the plant. If the river would overheat, and it's above-ground one, engineer a dam to increase the water volume available for heating and radiiating it away, as well as employ waterless radiators as either a backup or redundant heat sink.

PS: am I reading it so that you've put entire manufacture plants, including antimatter one, under the dome? Heavy industry is a serious heat source, so your industry is best to develop their own A/C systems each that would have heat sinks outside the dome, as the residential part would already be producing enough heat to justify a large scale air cooling of the dome's atmosphere.

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  • $\begingroup$ So the base consensus seems to be, the "interlayer" cooling is one part of a much greater AC system. Another is to make most surfaces, including the outer layer, partially reflective. Big fans are used to circulate air, the fans on the ground push heat into a external radiator setup. Probably something that evaporates water to get rid of the heat. As for the other plants, nah they are all just on the outside. Only Little Summer is in the dome $\endgroup$
    – ErikHall
    Commented Nov 23, 2023 at 12:56
  • $\begingroup$ @ErikHall oh whew, that block IS the dome, I read it as a bigger map with smaller scale that has the arrow pointing to where is the rest of the pic located. So it's roughly square and the inside is all residential. Then I say you would need only the interlayer and interior A/C, no extra water spraying would be necessary unless your installation also hits humidity issues. $\endgroup$
    – Vesper
    Commented Nov 23, 2023 at 13:03
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Gut feeling, solar radiation and air temperature are not your real problems.

Your dome interior is supposed to average 20°C and your planet has an average temperature of 30°C. So the ground, a couple of meters down, should have pretty constant temperature year-round which is close to that average.

  • Put an insulating layer between the ground and the 'topsoil' of your habitat.
  • Even so, you will need active cooling (a fridge), which means that by putting energy into the system you make it colder in some places (the dome interior) and even hotter elsewere (cooling towers? a river?).
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Large scale solar cooling system like this one in Singapore. You could manage it fairly cheaply. You could cover the entire dome in solar collectors.

Then use the power to run refrigeration using water as one of the coolants. As a byproduct you have plenty of hot water for daily use. Better still run a lot of your infrastructure on steam power and vent it outside.

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You have 3 approaches I see to cooling here:

1.) Reduce the energy input. A lot of your heat will actually be coming from the sun, not the hot air around your dome. Make your domes provide shade by making them only semi-transparent, or you can have a grid or checkerboard pattern of sun-shades (or even mirrors) interspersed with transparent sections, (the checkerboard pattern might be cheaper to produce as it could come from support struts and it would introduce a more alien feel, without making everything uniformly dim.) In real life this has been used in the Sahara dessert to make habitable areas through large sun-shades (Although they were not fully enclosed.) It has also been proposed as a way of terraforming Venus, (placing a lot of mirrors in orbit to reduce the heat reaching the surface.)

2.) Active cooling. You are creating a fridge or AC cooled-room on a huge scale. This is incredibly expensive. Look into real life heat pumps, AC systems, and refrigeration. I don't recommend this as the costs would be enormous and any power failure could result in cooking your residents.

3.) Passive cooling. Your atmosphere is hotter than your settlement so you can't passively transfer heat to the atmosphere, and the ground is probably too hot because it takes on the average temperature of the air... but space is incredibly cold and you CAN transfer heat to that if your atmosphere is transparent to the right light frequencies. On earth we have developed passive cooling white paint from BaSO4 that turns heat energy on the surface into infrared light that passes through our atmosphere. (Currently the paint works, but is extremely fragile and relies on a light spectrum that glass is NOT transparent to, so we can't protect it from the elements.) Your planet's atmosphere is different so it might have a different spectrum of light that works for this effect, (possibly one that can be made with a less fragile paint, or a spectrum that glass is transparent to.) It's also possible your dome will adequately protect the BaSO4 and is made from a material that is transparent to the relevant spectrum of light.

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  • $\begingroup$ All three suggestions are quiet nice, especially the pattern idea. I think adding your reflective IR paint is a nice touch, though probably not enough for the whole dome. $\endgroup$
    – ErikHall
    Commented Nov 24, 2023 at 10:47
  • $\begingroup$ IR paint has been proven in the lab to be 19°F (aprox 10°C) cooler than the air around it in current tests, but the technology is still new. So it actually might be enough by itself to handle your cooling issues, but a combination approach might be more interesting from a story perspective. $\endgroup$ Commented Nov 25, 2023 at 15:51

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