Guide/Base Cooling

Base cooling is a pressing issue at all times. Difficult to manage, temperature might be the biggest challenge you will be facing in Oxygen Not Included.

The main reasons for high temperatures are geyser water and machine heat, as you will need both through your game to keep your dupes alive.

## Rule 0: Don't Heat Up In The First Place

The first rule of base cooling is to not heat your base in the first place. Heat-sensitive objects like Duplicant living quarters, Plants, and Critter ranches should be built far away from high-temperature machines like the Glass Forge or Metal Refinery. Avoid digging through Abyssalite veins blocking off high-temperature biomes from cooler regions.

### Insulation

Insulated Tiles can be used to slow heat transfer between two areas. Mafic Rock is the best early-game material for temperatures below its melting point, while Igneous Rock and Obsidian can handle higher temperatures at the cost of faster heat transfer. Ceramic and Insulation should be used in the mid- and late-game as available.

Vacuum is the most effective insulator in the game - heat will not transfer over a vacuum at all. A "box base" surrounded by a layer of vacuum can be completely insulated from surrounding heat, meaning cooling is only necessary for handling heat produced inside. To preserve a vacuum along a high-traffic area in minimal space, Liquid Airlocks can be built with a shared Airflow Tile between them, which prevents heat moving from one airlock to the other as long as the rest of the chamber remains a vacuum.

### Specific Heat Deletion

Most machines, including plants and critters, don't actually care about the temperature of their inputs - output temperatures, plants wilting, and critter death is instead determined by the temperature of the entity itself, which exchanges heat with its surroundings. This means that cooling materials which are about to be consumed is often highly counterproductive - in order to minimise base heating, it's generally better to have machine and plant inputs as hot as possible.

A Sleet Wheat plant, for instance, can survive just as well on 95 °C water as 5 °C water - the plant's body temperature is determined by the temperature of its surroundings, not the temperature of the water it consumes. Pre-cooling water before sending it to your farms would require moving

90

∘

C

×
20

kg

×
# 4.184
7531200

DTU

{\displaystyle 90 {}^{\circ}\mbox{C} \times 20\mbox{kg} \times 4.184 = 7531200 \mbox{DTU}}

 per plant per cycle; but if the 95 °C water is kept in an Insulated Liquid Pipe made of Igneous Rock, only

90

∘

C

×
0.03125
×
1.000
×
50
×
# 600
84375

DTU

{\displaystyle 90 {}^{\circ}\mbox{C} \times 0.03125 \times 1.000 \times 50 \times 600 = 84375 \mbox{DTU}}

 are transferred from the liquid to the pipe (and then to the environment) each cycle. The rest of the heat is deleted as the water is consumed. In this simplified case, the same amount of cooling can support almost ninety times as many plants when applied to the environment rather than the liquid input; in practice, the change is not nearly this dramatic, as the small internal buffer of a Hydroponic Tile still causes a large amount of heat to leak into the environment - however, the smaller amounts involved still mean less heat needs to be moved compared to pre-cooling inputs.

## Heat Pumps

The primary means of heat transfer is through the use of heat pumps - the Thermo Regulator and Thermo Aquatuner. Both machines reduce the temperature of an input packet by a fixed 14 °C, and transfer the corresponding amount of heat to the machine itself. The Regulator uses less power and processes smaller packets with generally lower SHC; while this is a downside for large-scale cooling, it also means that storing the output heat is easier - as is running it

### Starting Out: Heat Sinks and Radiators

The basic core of a heat pump-based cooling system is a heat sink and a radiator, connected by a system of pipes containing a working fluid (or coolant). The radiator exchanges heat with its surroundings, which is transferred through the working fluid to a heat pump and pushed into a heat sink. The working fluid, cooled by the heat pump, then returns to the radiator to exchange more heat, until some equilibrium is reached.

A **heat sink** is a structure designed to store heat, either for deletion or just to keep it away from the rest of the base. Heat sinks are usually built as a room of some medium, usually Hydrogen or Water/Steam but sometimes Petroleum, containing a Thermo Aquatuner or Thermo Regulator to "load" the sink, and surrounded by Insulated Tiles and/or a vacuum layer. Heat is transferred into the sink by the Aquatuner or Regulator, stored in the medium, and kept isolated by the insulation/vacuum.

A Thermo Regulator made of Gold Amalgam in a room full of Hydrogen serves as a functional early-game heat sink. With access to Steel, a Thermo Aquatuner placed in Water that is later boiled to Steam is the primary heat sink design through endgame; once these are developed and Renewable Energy is researched, a colony has moved properly into the midgame of heat management.

   **Radiators** are designed to have pipes exchange heat with the environment passively. Due to how Thermal Conductivity works, these are usually comprised of Radiant Gas Pipes or Radiant Liquid Pipes (or both) snaking through a mass of solid tiles - ideally Metal Tiles or Window Tiles made of Diamond, but even regular Tile can suffice (with Granite being the best option). The tiles may themselves be adjacent to Tempshift Plates with high thermal conductivity, if faster exchange over an area is desired - Diamond is again an ideal material. Vacuum can also be used to control which cells the radiator exchanges heat with.

Early radiators can simply run radiant pipes through gas - while slower than using solid tiles, it also allows for Duplicant movement and building construction. For cooling some structures such as generators, Heavi-Watt Conductive Joint Plate can also be used as part of a radiator. Buildings can be placed on top of a radiator, but will normally not exchange heat with the blocks below them. A thin layer of Water or Petroleum can rapidly increase heat transfer, as long as it remains under the amount needed to flood the building.

It is also possible to build "smart" radiators by using Mechanized Airlocks in a sealed chamber. While the airlock is closed, it is a solid block and exchanges heat with the pipe passing through it; when it is open, it becomes replaced by Vacuum and no heat is transferred. This can be connected to e.g. a Thermo Sensor to precisely control the temperature of the environment.

### Midgame: Turbines

The Steam Turbine converts heat energy to electrical energy by converting Steam to Water. Building a turbine on top of a steam-based heat sink converts it into a powerful heat deletion device - though the turbine itself leaks some heat and must be cooled.

A turbine can handle steam temperatures of up to around 135 °C (in theory 140 °C, but this is unreliable in practice) by simply being placed in a Hydrogen atmosphere, and snaking a Radiant Liquid Pipe containing its own output back and forth across it. These "self-cooling" turbines are the most efficient way of converting heat into energy, but are beaten out by actively cooled turbines (linked to an aquatuner, usually the one in the heat sink beneath it) to maximise per-second heat deletion and energy output.

The Steam Turbine page covers turbine constructions in significant detail and will not be repeated here.

### Endgame: Super Cooling

Super Coolant is frankly overkill for cooling a well-designed base, and the first few batches should instead go towards Liquid Oxygen and Liquid Hydrogen production (or even condensation of Sour Gas). Once a large reserve is produced, and other industrial uses well in hand, it is substantially more energy-efficient than water when used with turbines; per the Steam Turbine page's calculations, a super coolant-based heat pump system optimised for heat deletion is 23 times as efficient as a water-based equivalent.

## Alternatives

### Anti Entropy Thermo-Nullifier (AETN)

The Thermo Nullifier is a structure which is found in some Ruins, and can be used as an early-game alternative to turbine-based heat sinks. The AETN takes in 10g/s of Hydrogen gas to remove 80kDTU/s of heat from itself. As 10g/s of Hydrogen is equivalent to 80W in a Hydrogen Generator, this has an effective energy efficiency of 1000 DTU/J - superior to the ~923.78 DTU/J achieved by a Thermo Aquatuner with Water as coolant, and by extension most other pre-endgame coolant options.

It is not recommended to produce hydrogen specifically for an AETN, and instead use byproduct hydrogen from Electrolyzer-based Oxygen production, or even a Hydrogen Vent. If including the costs of a dedicated electrolyzer, the energy value of 10g/s of hydrogen increases by ~10.71W, which makes the efficiency of the AETN drop to 881.93 DTU/J - at which point a water-based aquatuner/turbine system is superior, while also not consuming valuable Water.

### Passive Heat Sinks and Steam Batteries

Temperatures which are above 125 °C can be connected directly to a Steam-based heat sink without use of an Aquatuner, running a turbine and bringing the temperature down to below 125 °C by a standard self-cooling turbine. The primary source of these temperatures naturally is from Geysers - particularly Metal Volcanoes.

Buildings which do not require duplicant maintenance, such as Batteries and Power Transformers, can also be built out of Steel and placed inside heat sink steam rooms, essentially eliminating the need to cool them in a base. Auto-Sweepers and Conveyor Rail systems expand this to a large number of low-maintenance industrial machines.

Steam can also be kept at higher temperatures (usually 200 °C) - while this requires an actively cooled turbine, it has its advantages. Heat stored in Steam loses energy far more slowly than any type of battery, especially with well-insulated walls. Coupled with appropriate automation (a Smart Battery to keep the lights on, and a Thermo Sensor to establish an upper limit on temperature), this allows the steam to essentially act as a massive battery, powering nearby machines as needed. Various geyser tamers and Metal Refinery designs can use this method to become essentially indefinitely self-powering, ensuring that interruptions to grid power do not stop production.

### Low-Temperature Geysers

Several types of Geyser produce materials at low temperatures, allowing their output to serve as a rate-limited heat sink.

The Carbon Dioxide Geyser is largely useless for cooling due to the low SHC and thermal conductivity of Carbon Dioxide in both liquid and gaseous states. Heating the averaged output of 150g/s of CO2 from -55.15 °C to 30 °C only takes ~10806 DTU - which would cool a 10kg packet of water by about 0.26 °C. It would take 54 geysers to match the throughput of a single water-based Aquatuner. That said, this geyser can be useful for Food storage, as it combines a low temperature with the Sterile Atmosphere trait.

The Cool Salt Slush Geyser and Cool Slush Geyser have greater cooling potential, as Brine and Polluted Water have relatively high specific heat for low-temperature fluids.

Start by insulating your geyser and putting in some extra storage for when the geyser goes dormant.

   Then attach the output pipe from that into the cooling loop you build into your base. this should be done with a liquid bridge similar to those that you would use to fill a cooling loop for an aquatuner.

   And you're pretty much done. Using very cold water like this may have some risks but as long as heat is being produced by your base or being absorbed from the rest of the map this method will last you for your playthrough. Some points to note is that you should make the pipes out of granite and use normal pipes and not radiant ones. Regular granite or igneous pipes will release the 'chill' slowly enough into your base as to not cause hypothermia. If an area is particularly hot, then use radiant pipes or pipes made with thermally conductive material to remove more heat from that area.

    Overall pipe work (it's a mess, it was actually meant to be temporary but i needed to keep it in to remove heat as well as expanded it overtime as my base cooling needs grew. It can be used to restore nature reserves)

    Cooling machinery spaces with the cold water.

    I used reed fiber killing several birds with one stone as the excess fiber they produce is always good for later on in the game, this same fiber bed is the dump for my germy polluted water from the bathrooms.

    To remove the warm water use a liquid bridge that feeds into a liquid shutoff. A pipe thermal sensor is used to activate the switch this signal should be feed though a filter gate and set the filter gate to 10 seconds, this is done to prevent the switch from cycling too much. Using a liquid bridge like this will make the fluid "prefer" to flow off the loop because of how the game mechanics work until that backs up. (see bridge tricks for more information) In addition another liquid bridge should be used to feed onto the pipe that will go to the reed bed. this is done to give preference to the polluted water coming from the bathrooms and keep them from backing up.

    The cooling pipes can also be installed into the floor and roof of rooms instead of in the middle of them. Bathrooms are especially problematic to cool this way since they typically already have pipes running in the floor and roof of the room as well as the interior. These spaces can be cooled by changing the tiles to metal and the temperature will eventually equalize out. Granite tiles also have a decent enough thermal conductivity for this application.

### Partial Passive Cooling

Passive cooling means the system is independent and doesn't need additional power/cooling. This method is partial because it is not confirmed practically if it CAN be made fully independent.(in theory it should be able to) In Oxygen Not Included are a few substances which have different SHC and the change is reversible. The difference between 2 substance states to adds/deletes heat from the system. The amount of heat you want to remove depends on the difference in Specific Heat capacity(lower energy state(colder) should have a higher SHC than the higher energy state).

((DTU/g)/°C Removed)
State Border
 Glass
 Ethanol
 Steel
 Liquid Oxygen

NOTE: Nuclear Fallout condensation point is lower(66.9 °C) than Nuclear waste vaporization point(526.9 °C), so even if the substance deletes a very large amount of heat it requires some additional cooling.