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Codex Energy Stirling Generator
The Stirling Generator window: 5 energy and tank bars, 6 value, status and redstone lines.
The Stirling Generator turns heat that is already there into electricity: hot blocks below it, a Heat Port of a plant, an 
Electric Heater or a Geothermal Heat Exchanger next to it. A hot head drives a piston engine with a flywheel; the colder its other side, the more energy it gets out of the heat. It is a tier I block.
- Heat comes in. Hot blocks in the 3×3 area directly below the generator and heat from neighbours on any side warm the hot head, together up to 240 HU/t.
- The head warms up. It needs 300 HU for every degree. Until it reaches 500 °C the engine stands still and the status says "Warming up".
- The engine runs. Above 500 °C the engine draws 2 HU/t of heat for every degree the head is hotter. So the head settles where intake and draw meet: with the full 240 HU/t at about 620 °C, with little heat just above 500 °C.
-
Heat becomes energy. The engine turns the heat it draws into energy with its efficiency (see below), up to
volt.stirlingMaxOutput(default 100, allowed 1–100000) E/t.
The engine only draws heat while its buffer has room. With a full buffer the head heats up further; at 700 °C it takes no more heat.
Every tick the generator gets heat from the blocks in the 3×3 area one layer below it (checked every 2 seconds):
| Block below | Heat |
|---|---|
Lava source, blocks in the tag qnet:thermoelectric/hot_strong
|
25 HU/t |
| Soul fire, lit soul campfire | 12 HU/t |
| Lit campfire | 10 HU/t |
| Fire | 8 HU/t |
Magma Block and other blocks in the tag qnet:thermoelectric/hot
|
6 HU/t |
Flowing lava and unlit campfires give nothing. Nine lava sources under one generator give nine times 25 HU/t, nearly the full intake. A hot block under the 3×3 areas of several Stirling Generators is shared evenly between them.
On every side the generator takes heat like a plant's Heat Port does: from a Heat Port of a neighbouring plant (for example the exhaust of a Gas Turbine or Gas Engine, or a Solar Receiver), from an Electric Heater or from a Geothermal Heat Exchanger. Heat from below and from neighbours together never exceed 240 HU/t. More about heat: Process heat.
The efficiency is 0.55 of the Carnot efficiency between the hot head and the cold side, both in kelvin: efficiency = 0.55 × (1 − cold / hot).
The cold side gets warm from the heat the engine rejects; cooling around the generator carries it away. Its temperature is 20 °C + 200 °C / (1 + cooling). The cooling is the sum of the four sides and the top (not the bottom):
| Neighbour | Cooling |
|---|---|
Packed Ice, Blue Ice (tag qnet:thermoelectric/cold_strong) |
3 |
Water (also flowing), Ice, Snow Block, Powder Snow, Frosted Ice (tag qnet:thermoelectric/cold) |
1 |
| Situation (full heat intake) | Cold side | Efficiency | Output (E/t, about) |
|---|---|---|---|
| No cooling | 220 °C | 24 % | 57 |
| Water on three sides | 70 °C | 34 % | 79 |
| Blue Ice on four sides and on top | 32.5 °C | 36 % | 85 |
With nine Magma Blocks below and good cooling it makes only about a fifth of the best value, because the head stays just above 500 °C. The server's volt.generatorOutputMultiplier (default 1.0, allowed 0.01–100.0) scales the output after the limit.
The generator pushes its energy into all six neighbours and can be pulled from on every side. Its buffer holds 20,000 E.
- Status: "Running", "Warming up" (heat comes in, the head is below 500 °C) or "No heat".
- Energy: the bar of the buffer.
- Hot head and Cold side: the two temperatures.
- Heat: all heat that came in during the last tick; Heat from below: the part of it from the blocks below.
- Cooling capacity: the summed cooling of the neighbours from the table above.
- Efficiency: the engine's efficiency in the last tick.
- Output: the energy made in the last tick.
- The diagram at the bottom shows the heat that runs through the engine and the energy that comes out.
| Iron Bars |  |
Iron Bars | ||
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Redstone Dust | |
→ Stirling Generator |
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When you break it, the generator keeps its stored energy and the temperature of its hot head.
The flywheel and the pistons turn while the engine runs, faster with more heat flowing through it. The hot head glows with the heat that runs through the engine.
Tip
Warm-up From cold, the head has to warm up by 480 degrees, 300 HU each, before it reaches 500 °C: with the full intake about 30 seconds, with nine Magma Blocks below more than two minutes. The head keeps its temperature when you break the block, so a hot generator starts again at once.
Tip
Pairing with a geothermal exchanger A Geothermal Heat Exchanger deep underground gives up to 500 HU/t, enough for two Stirling Generators at full intake. Put two of them next to it, each with water or ice on its free sides, and they run without any fuel.