The Ultimate Geothermal Heat Pump

[ONI-addict]

1. INTRODUCTION / TLDR:

Hello, in this post I want to show you my Ultimate Geothermal Heat Pump. I call it Ultimate, because it sustainably producues the maximum of all the possible resources - including Fullerene and Niobium - the Geothermal Heat Pump can produce, which means each production cycle is 416 seconds long. It is fed with 30kg/s of around 2270°C hot Molten Glass. To heat the Molten Glass I am using four 4kg/s 2926°C Rock Gas Boiler, so 16kg/s in total. In its current configuration it also produces extra 0.97kg/s of Glass, so Dupes will never have to use a Glass Forge again.

2. BASICS to understand this machine:

Spoiler

First you need to know about the 2 most important mechanics that make this build work, without them it would be impossible:
- Surface Pumping,
- Preventing phase change in pipes.
Then it is also important to know about
- SHC and TC,
- as well as counter-flow-heat-exchangers.

Search for an explanation in the Compendium of Amazing Designs

Surface Pumping allows the pumping super hot liquids into pipes, that would normally breaks the liquid pumps.

Preventing phase change in pipes can be done, when the mass of the content in a pipe is =<10%, so for liquids it is not more than 1Kg in the pipe, or for gas 100g.
By preventing the phase change, the Molten Glass can be heated to 2926°C without becoming Rock Gas in the pipe and bursting.

Why am I using Molten Glass and not Magma or something else? Molten Glass is renewable and has a very low SHC of only 0.2 DTU/g/K. That means to heat one 1kg of Molten Glass by 1°C (or 1K) only 2kDTU are needed. Magma would need 5 times as much, because it has a SHC of 1. So by using Molten Glass I can save on a lot of heat energy.

For counter-flow-heat-exchangers you can read articles about it on Wikipedia or the Internet. But the tldr is that when two heat sources of different temperature meet it will create an equilibrium where the temperature evens out. So to efficiently bring a low temperature medium to high temperature lots of equilibriums are being created, so minimal heat energy is wasted. I'd be greatful if someone else wants to give a better tldr in the comments.

3. HOW THE MACHINE WORKS:

Spoiler

The Geothermal Heat Pump (GHP) requires an average liquid temperature of at least 2226.85°C to create Fullerene and Niobium. At that temperature the GHP will remove 150°C from the liquid before exiting from the Geo Vents. It also deletes 8% of the liquid, so for every Pumping Cycle (which is 416 seconds long) it deletes 960kg of the 12000kg Molten Glass. The Glass exits the Geo Vent tamers with an average temperature of about 1100°C, which means I need to heat 11044kg of 1100°C Glass to 2270°C. 4kg of the 11044kg are from GHP extra resources.

The average temperature of the Solid Glass mainly depends on game speed. Yes, you read that right. If it is speed 1, the average Solid Glass temperature can exceed 1200°C, on speed 2 it stays around 1100°C and on speed 3 it can fall below 1100 to around 1050°C average. I build the machine for playing on speed 2, my old i5 6600k can't handle more than that, so it works just fine for me. But I am curious how the machine works on other PCs, so if you are interested you can run it for a few hours and tell me the results.

3.1 Geo Vent Tamers

Spoiler

I am freezing the Glass in the Geo Vent Tamers because it is the easiest way to deal with all the liquids and gases. The Tamers are cooled to 260-300°C. That way only Hydrogen, Sour gas and Steam exist, Sulfur is turned to Liquid and everything else is turned to solids. That makes dealing with resources very easy.
As mentioned, depending on the game speed the Solid Glass absorbs a different amount of heat from the Molten Glass when it spawns.

The Gas filtering works with gas moving through diagonals trick. I don't really care about the filtering but the build works well like that, because it allows me to keep the desired gas pressures I want and keeps the sour gas in the bottom, which prevents the solid Glass from losing more heat, and seperates the steam into the upper middle. This tamer design is just a 9 months old relict when I had some different goals in mind, but it still works fine and don't want to change it.

Spoiler

I am using Super Coolant as Heat buffer, which is very much needed when super hot 2100°C Steam exits the Vents. The buffers are also cooled with Super Coolant that is then sent into the Steam-chamber.

Spoiler

The Robominer is needed, because rarely solid tiles form on the left tile of the Small Liquid Pump.

3.2 Glass Heat Exchanger

Spoiler

The Glass is then sent to the 8 lanes heat exchanger, that can handle 8*20/6=26.667 kg/s. Slightly more than the 11044/416=26.548 kg/s I produce every GHP-cycle (416 seconds for every GHP pumping animation).
As counterflow materials I use both Liquid Uranium and Super Coolant gas, 20kg/s and 2kg/s, so 2.5kg/s and 0.25kg/s respectively per lane. For this design I was constrained by available space, so I would recommend at least 12 lanes. This time the heat exchanger is not about saving heat energy, because the counterflow materials reheat at the same heat buffer as the glass, but just to increase the speed of how fast the Glass with its terrible TC of 1.11 heats up. Now that I think about it this design was probably a mistake and a simple big block would have been enough, so maybe I change it later.

The Glass-Buffer is heated mainly by another buffer, which draws it's heat from the Rock Gas Boiler (RGB), but more on that later. After exiting the Glass-Buffer the Glass is transported to the Glass Melter.

3.3 Glass Melter

Spoiler

The Glass Melter evenly melts Glass and Sand/Polluted Dirt into Molten Glass. It is heated by the 16kg/s Magma coming from RGB through the Molten Glass Heater. It consists of 10 chambers, each receiving 2.5 + 0.155 kg/s Glass packets and 20/11=1.82 or 2 kg/s Sand/PDirt Packets. In its current configuration it melts 4*20/11 + 6*2 = 19.273kg/s Sand/PDirt and  10*2.655 = 26.55kg/s Glass.

The Automation ensures that it never overflows on Molten Glass, prevents forming of too much cold debris (the bigger the debris the slower it heats up, slowing down the machine significantly), and turns of Magma Flow, in case the end of the Sand-Magma-heat-exchanger gets too hot, which could lead to the sand/pdirt melting too early.

A pipe priority logic ensures that the pipes that feed the RGB with Molten Glass are filled first.

3.4 Sand-Magma-Heat-Exchanger

Spoiler

This is a counterflow-heat-exchanger to exchange heat between hot Magma and cold Sand/PDirt. There are 10 lanes for sand to exchange heat with the Magma. You will notice not every lane has the same length/ same amount of heat-exchange blocks. The reason is not enough build space.
Since there is 16kg/s of Magma, it needs to be spilt to 1.6kg/s per lane. 1.6kg/s is more than 10% of the phase-change-limit, so that also needs to be split in to 0.8kg/s lines. That explains why the rail paths are alternating between the tiles and pipes. But why have 10 lanes and 1.6kg/s Magma in each and not something like 1kg/s?

PDirt Compatibility

PDirt can be used because off-gassing is completely prevented in this build. That comes with some annoying costs though: PDirt packets cannot be remerged, because if a Sweeper takes some PDirt the PDirt can off-gas and the high temperature will break the Sweeper. Another problem is heat management and the pumping capacity of the Glass Melter. If I would send in Sand/PDirt packets of different sizes, the required heat in each glass melter will be different. That makes the heating with Magma difficult. Also since conveyor packets cannot merge on rails, the flow of a conveyor line is limited to 20/n, where n is a natural number. For example if I sent in packets of size 3kg, the seventh packet is always going to be only 2kg big, so on average 20/7=2.857kg/s.

That means I cannot merge packets after splitting them for counterflow-heat-exchange with Magma.
And if I use larger and smaller Sand /PDirt packets, for example like 2.857kg/s or 20/16=1.25kg/s (which would exchange nicely with 1Kg/s Magma flow), then I would have to change solid Glass distribution in the Glass Melter (same conveyor flow limitations apply) and therefor also completely change how to distribute the heat from the Magma.

If the packets are the same size everywhere, then everything is easier.

3.5 Molten Glass-Magma/Super Coolant Gas-Heat-Exchanger
This one just heats the Molten Glass to the highest temperature of the system, which means between 2270 and 2275°C. For the first two blocks, that feed the RGB, it uses both 4kg Magma and 1kg Super Coolant Gas each from the two left RGBs. Since there is such a large SHC difference between 10kg/s of Molten Glass (total SHC of 2) and the Magma and SCG (4 + 8.44), the equilibriums are heavily shifted towards the high temperature, which makes the heat exchange much faster and results in a smaller loss of temperature for the Magma and SCG.
Note that the energy cost stays the same. Counterflowing with a high SHC difference is a nie trick to preserve temperature.

The Magma then flows into the Glass Melter to heat, while the SCG heats the RGB buffer, that feeds the Glass buffer. Heating the RGB buffer is necessary to prevent the RGBs from overheating.

3.6 ROCK GAS BOILER

Spoiler

This is my finest creation of ONI, and I am really proud of this design.
This boiler heats up 4kg/s of Molten Glass to 2926°C and turns that into Rock Gas. It creates 5 times as much heat as it costs, making this a wonderful source of renewable heat energy. In just 4 tiles of vertical heat exchange with the hot Rock Gas, the Molten Glass reaches a temperature just a few degrees short of the maximum safe temperature of 2926°C. Heating 4kg/s of Molten Glass by 5°C costs just 4kDTU/s, while a Kiln has an output of 20kDTU/s. So actually this whole Ultimate Geothermal Heat Pump is just powered by a few Kilns that provide less than 20kDTU/s of external heat energy.

The RGB has a bottom layer of Molten Aluminum for heat buffering and transmitting. The Magma prevents the Rock Gas from leaving the Boiler and stores the Heat. The Liquid Pump can pump up to 5kg/s of Magma, which prevent the RGB from clogging with Magma. The Kilns are partially submerged in Molten Steel for quick heat exchanging and are controlled by automation to never reach melting temperature of 2926.9°C (yes, the 3°C buffer doesn't apply to buildings). The other automations makes sure the RGBs never overpressure.

For the RGB to not break and to continue to produce magma, it needs to be cooled down. It is cooled by the SCG that heats the Molten Glass in the heat exchanger and the RGB buffer that heats the Glass buffer. All the necessary energy to reheat the solid Glass from the Geo Vents comes from the cooling Rock Gas in the RGB.

Basically the average 2270°C temperature of the Magma and the Aluminum buffer in the RGB comes from the energy drain of the Solid Glass Heating. It is the equilibrium between 16kg/s 2926°C Rock Gas (minus the 16kg/s Molten Glass heating cost inside the RGB) and the 1100°C Solid Glass average temperature.

3.7 Steam Chamber / Cooling Chamber

Spoiler

To cool down the Geo Vents I pump "cold" Super Coolant from the big pool towards the Geo Vents, and let the heated Super Coolant drop down into the pool. That way the heated Super Coolant instanly cools down when it merges with the Super Coolant in the pool. It works just like Nuclear Waste in the CLRR.
34 Steam Turbines are used here to create an average temperature of 190 to 195°C. The cooler the steam temperature, the more the Super Coolant in the Geo Vents can cool. Which means Adding a few more Steam Turbines can cool down the Geo Vents more.

4 FINALE

I planned this 10 months ago and after lots of breaks and low motivation I forced myself to finish it today.

I build this the way it is, because I want to rebuild it in my same seed Survival Map. It is supposed to work on speed 2 and not take too much space. That's why I had a lot of space constraints. If you have more space, you can make lots of improvements. This machine has been running 200 cycles without issue now, but to prevent breaking I would suggest to make sure you have a steady source of Sand/PDirt.

Building this in Survival will be a huge challenge for several reasons:
High cost of Insulite, I will probably replace lots of insulated pipes with radiant Tungsten pipes (lowest SHC), and replace lots of the Magma-Sand-Heat-Exchanger insulated Tiles with Ceramic Insulated Tiles.
This build requires a lot of careful preheating, pretty much all of >1000°C places require lots of preheating.

I will upload my spreadsheet as well, but it is quick and dirty, so don't expect much.

Feel free to ask me questions, point out mistakes and give constructive criticism on the build and the way I presented things.

 

ONI.ods

TEST CERES7,0.sav

Edited December 6, 2025 by ONI-addict

[6Havok9]

Hey, that's cool! Also hey, you beat me to it  I've been building a geothermal heat pump "thing" for some months now. Yours seems quite a bit more advanced than mine, I especially like that rock gas boiler and will try to experiment with something like it.

 

I was planning to post about it "soon", as soon as I finish building it in survival, but oh well. It's taking a long time. I don't use space materials, but I almost exhausted the asteroid's wolframite supply. It works by alternating one water cycle and one gold cycle, using meter valves and signal counters. It somewhat autofixes itself and only allows a gold cycle to start when everything is ready, and never runs two consecutive gold cycles.

I use molten gold, provided by regal bammoths. Extra heat is provided by the fossil quarry, while PEGGYs bring the materials out. Vents are fare from each other, so every vent gets its own section.

Some not very useful sandbox screenshots of work in progress.

Spoiler

Vents sit in their own chamber, three wolframite doors close off the chamber for some seconds while erupting solids in water mode, or as long as the eruption lasts while in gold mode. So the chamber becomes "insulated" thanks to the displacement pumps leaving 100mg of steam between the doors and the rest of the build. This allows to keep the heat in and vaporize lead, leaving gold as the heaviest liquid in the chamber. Gold sits into one tile pits, while other metals get shoved down by doors, along with sour gas.

 

When the eruption is over, 20 kg/sec of water cool down the chambers, so sand natural tiles can never form. Liquid gold is dropped down where a pitcher pump sends it back to the reservoirs, sour gas remains trapped at the bottom, hydrogen escapes to the top, remaining solid gold just sits there waiting to be remelted.

The quarry uses two super artist bionics, creating 23xx degrees C magma or 3400 C rock gas as needed. Can't go higher or tungsten conduction panels would melt and the cozy drywall behind would not survive, which is unacceptable. They don't mind the rock gas, even without atmo suits.

This is a actually a 5kg/sec rockgas volcano, the heroic bammoth made the ultimate sacrifice using its considerable size to plug the hole exposing the planet's raging core.

 

[ONI-addict]

Oh wow, I did not know about the Fossil Quarry heat multiplication. I have never even used the thing before in my 1845 cycle game, because it is on a different planet.

Your build also seems to be quite advanced, and quite a bit complicated as well. That is a lot of automation. Your Vent Tamer is very impressive and ingenious.

If you have lots of heat you can also try GreezyHammers Extreme Glass Boiler. You can achieve higher Molten Glass temperatures that way, up to Tungsten melting point. However when I experimented with it, I saw Magma replace a Molten Steel tile on a liquid vent, so be careful. At these super high temperatures there is no room for mistakes, because they would be very tedious to fix in survival games.

Spoiler

Initially I wanted to build my Ultimate GHP without space traveling and make Niobium and Fullerene without ever using a rocket. But at some point I realised that I should just go all out because I was spending so much time on it. I am glad to know I am not the only one who takes a lot of time to build/plan something  . I wanted to wait with posting until building it in survival, but that is going to take a few more weeks or months . 

I forgot to mention that I want my build to work 100% automatically, without any Dupe interaction. At first I will use 3 bionics to recycle the 16kg/s of Igneous Rock to make Sand, but eventually replace them with 120 domestic Arbor Trees feeding 60 Ethanol Distillers for 20kg/s PDirt. And the Dirt from automatic Pip Ranches with Critter Fountains.