Stirling Engine

Kit (Stirling Engine)

Creates a Stirling Engine

Properties
Stacks	Yes (10)
Autoignition	300°C
Flashpoint	100°C
Recipe
Created With	Electronics Printer
Cost	5 Gold, 20 Copper, 30 Steel
Logic
Item Hash	-1821571150
Item Name	ItemKitStirlingEngine

Stirling Engine

Front

Back

Operation
Power Usage	1W
Burst Pressure	11 MPa
Volume	54L+5L+5L
Thermal Convection	~1.248 m²
Thermal Radiation	~1.248 m²
Solar Heating	8.51
Prefab Hash	-260316435
Prefab Name	StructureStirlingEngine
Construction
Placed with	Kit (Stirling Engine)
Placed on	Small Grid
Requires Frame	Yes
Stage 1
Deconstruction
Deconstructed with	Hand Drill
Item received	2x Electronic Parts
Stage 2
Deconstruction
Deconstructed with	Wrench
Item received	2x Steel Sheets
Stage 3
Deconstruction
Deconstructed with	Hand Drill
Item received	Kit (Stirling Engine)

Overall Stirling Engine Cost/Requirements

Front

Recipe
Created With	Electronics Printer, Autolathe
Cost	6 Iron, 9 Gold, 26 Copper, 31 Steel

Description

Harnessing an ancient thermal exploit, the Recurso 'Libra' Stirling Engine generates power via the expansion and contraction of a working gas to drive pistons operating an electrical generator.

When high pressure hot gas is supplied into the input pipe, this gas will heat the hot side of the unit, then pass into the output pipe. The cooler side uses the room's ambient atmosphere, which must be kept at a lower temperature in order to create a differential. Add a working gas by inserting a Gas Canister. The unit must be deactivated when adding or removing canisters, or the working gas may leak into the surrounding atmosphere.

Gases with a low molecular mass make the most efficient working gases. Increasing the moles of working gas can result in a greater potential power output. However, overpressuring the unit may have... sub-optimal results.

-Stationpedia

Efficiency

The Stirling Engine has an efficiency curve that is dependent on three factors:

• Environment
• Working Gas
• Pressure Difference

The best a Stirling Engine can provide in power is 18% efficiency converting input heat to electric power, slightly more efficient than a Gas Fuel Generator's 17%. However, the gas fuel generator's exhaust can be passed into a stirling engine for a higher total combined efficiency.

Environment

The Stirling engine itself is best placed in a -10~50°C environment to provide the highest efficiency. The only planets where it cannot effectively be used outside are: Venus, Moon and Mimas. On Vulcan it can only be used outside during the night.

The operating temperature efficiency curve is measured at the cold side, which performs convection with the environment's atmosphere through a 3.5m² radiator.

• 
  Temperature efficiency curve

In World

• Moon (Vacuum): 0%
• Venus: 18% efficiency @ 464°C
• Vulcan (Night): 90.1% efficiency @ 126°C
• Mars: 99% @ -10°C
• Europa: 28% @ -147°C

These figures assume no load. In particular, Mars will not reflect these figures without forced air intake as the low atmospheric pressure will result in poor thermal conductance between the radiator and cold side. At 0.04atm, expect a thermal conductance of only 14 W/K.

In Room

The Stirling engine can be kept in a 1+ atm room to cool the cold side down at maximum efficiency (350W/K thermal conductance), but because all wasted heat needs to be removed, this requires an effective cooling system. At the maximum power output of 8 kW, a minimum cooling capacity of 8/0.18 ~= 44.4 kW is required to get rid of waste heat.

Working Gas

The working gas is a canister of gas that must be provided to the machine before it can be used. The gas itself is not lost, only used as a heat transfer gas.

It's shared between 3 chambers: a 54L regenerator chamber, a 5L hot piston chamber, and a 5L cold piston chamber. Only the 5L chambers are used for energy generation, with the regenerator acting as both a heat exchanger between them and as a secondary radiator (~1.275 m² convection/radiation area).

If the regenerator chamber ever reaches a difference of 11 MPa relative to environment atmosphere, the machine will have a chance of instantly exploding. This sets a limit on maximum safe operation temperature based on how many mols are present in the canister. At 60 mols, that's 1411 K assuming a loss-of-cooling scenario.

Different working gases achieve different efficiencies. Here are the efficiencies of several gasses:

• Steam: 5%
• Pollutants: 5%
• Carbon Dioxide: 8%
• Oxygen: 12%
• Nitrogen: 12%
• Nitrous Oxide: 12%
• Ozone: 12%
• Methane: 15%
• Helium: 18% (Best)
• Hydrogen: 18% (Best)

Mixed gases have their efficiencies weighed by their ratios in the mix. Liquids have a 0% working efficiency.

Pressure Difference

The Stirling Engine works best when the difference between hot side's pressure is at least 2500 kPa greater than the cold side. This can be achieved by increasing the amount of working gas, or by increasing the temperature range between hot and cold sides.

Besides controlling the cold side's temperature as suggested in the environment section, the hot side's temperature can be controlled in two different ways: Increasing the input's temperature, and, to a lesser extent, increasing the input's pressure (which works better at higher working gas thermal masses).

Unlike the cold side's heat exchanger, which has the entire cell the stirling engine is in to exchange heat with, the hot side's heat exchanger only exchanges heat with a single 10L pipe segment at a time (even though it has 2 m² of heat exchange area to work with). Because of the low volume being exchanged at a time, low input pressures may reach a hot side heat exchanger equilibrium temperature far below the actual input temperature, leading to a colder output but also a colder hot side temperature.

Power Generation

The difference in energy between hot and cold sides is calculated, with the result(after all efficiencies are multiplied) being converted into energy and removed from the hot side before hot and cold sides are mixed again into the regenerator for another cycle (being effectively wasted heat). A well-tuned Air Conditioner or phase change loop can make a stirling engine produce significantly more power than the supporting equipment required to run it in an isolated environment.

Because of the 8 kW power generation limit, additional energy is wasted as heat. As an optimally-efficient stirling engine needs to produce at least 5520 W, this makes for a fairly narrow full-efficiency operating range.

User Comments

The Stirling Generator has a maximum pressure differential of 11000 KPa (11 MPa): If the difference in pressure between the internal working gas and external atmosphere exceeds this, it will explode in a radius of 2-4m, destroying everything in its path and killing players.
The power output scales on how fast it can transfer heat from the input gas to the outside atmosphere, which depends on the pressure and heat transfer rate of the working gas, and the temperature difference between the input gas and the outside temperature. The cooled down input gas is transferred to the output pipe - you can connect the output to the input in order to extract heat energy from a pipe network.
To increase the pressure differential efficiency, you can increase the temperature delta between the input gas and the outside atmosphere, increase the input gas pressure, or increase the working gas pressure(if it doesn't pose enough of a danger to warrant lowering hot side temperatures).
Details
Max power: 8000W

Maximum internal-external pressure differential: 11000kPa

Environment operating efficiency: Around 285-300K for 100%
Minimum power for maximum internal pressure differential efficiency: 5520 W
Maximum working gas efficiency: 18% (0.18) with Helium or Hydrogen

Technical details

Ideal pressure differential: 2500
Internal volume: 54L
Piston volume: 5L
Heat exchanger volume: 10L
Hot side area: 2
Cold side area: 3.5
Convection factor: 0.15
Radiation factor: 0.15
Surface area: 8.499227

Vulcan

The Stirling Engine is a reasonable way to generate night time power on Vulcan when solar power is unavailable. Place it outside so it's in night time (400K) atmosphere, and capture mid-day (900 to 950K) atmosphere into a tank and run the Stirling Generator from that hot air at night, the generator can produce around 1.8 kW from the temperature difference. For the working gas, a good starting point is 70 moles of H2 in the canister. You can boost the power output to about 2.1kW by using an active vent to blow cold night air into the large grid that the Stirling Engine is in to cool it down.

Data Network Properties

These are all Data Network properties of this device.

Data Parameters

These are all parameters that can be written with a Logic Writer, Batch Writer, or Integrated Circuit (IC10), and can be read with a Logic Reader, Batch Reader, or Integrated Circuit (IC10).

Click here to see/hide all the data network properties

Parameter Name	Data Type	Access	Value	Description
On	Boolean	Read Write	0	Off	The current state of the Stirling Engine.
			1	On
Setting	Integer	Read Write			?.
Power	Boolean	Read	0	Unpowered	Can be read to return if the Stirling Engine is correctly powered or not, set via the power system, return 1 if powered and 0 if not
			1	Powered
Error	Boolean	Read	0		1 if device is in error state, otherwise 0
			1	Error
Pressure	Float	Read			In kPa
Temperature	Float	Read			In Kelvin
RatioOxygen	Float	Read			Ratio of gaseous Oxygen in the atmosphere
RatioCarbonDioxide	Float	Read			Ratio of gaseous Carbon Dioxide in the atmosphere
RatioNitrogen	Float	Read			Ratio of gaseous Nitrogen in the atmosphere
RatioPollutant	Float	Read			Ratio of gaseous Pollutant in the atmosphere
RatioVolatiles	Float	Read			Ratio of gaseous Volatiles in the atmosphere
RatioWater	Float	Read			Ratio of liquid Water in the atmosphere
Maximum	Integer	Read			?
Ratio	Float	Read			?
Quantity	Integer	Read			?
RequiredPower	Integer	Read			Idle operating power quantity, does not necessarily include extra demand power
PowerGeneration	Integer	Read			Returns how much power is being generated
TotalMoles	Float	Read
Volume	Integer	Read			In L
RatioNitrousOxide	Float	Read			Ratio of gaseous Nitrous Oxide in the atmosphere
Combustion	Boolean	Read			1 if the atmosphere is on fire, 0 otherwise
EnvironmentEfficiency	Float	Read			Environment Efficiency reported by the machine, as a float between 0 and 1
WorkingGasEfficiency	Float	Read			Working Gas Efficiency reported by the machine, as a float between 0 and 1
RatioLiquidNitrogen	Float	Read			Ratio of liquid Nitrogen in the atmosphere
RatioLiquidOxygen	Float	Read			Ratio of liquid Oxygen in the atmosphere
RatioLiquidVolatiles	Float	Read			Ratio of liquid Volatiles in the atmosphere
RatioSteam	Float	Read			Ratio of gaseous Water in the atmosphere
RatioLiquidCarbonDioxide	Float	Read			Ratio of liquid Carbon Dioxide in the atmosphere
RatioLiquidPollutant	Float	Read			Ratio of liquid Pollutant in the atmosphere
RatioLiquidNitrousOxide	Float	Read			Ratio of liquid Nitrous Oxide in the atmosphere
RatioHydrogen	Float	Read			Ratio of gaseous Hydrogen in the atmosphere (Hydrogen is deprecated and has been replaced by Volatiles)
RatioLiquidHydrogen	Float	Read			Ratio of liquid Hydrogen in the atmosphere (Hydrogen is deprecated and has been replaced by Volatiles)
RatioPollutedWater	Float	Read			Ratio of liquid Polluted Water in the atmosphere
PrefabHash	Integer	Read			The hash of the structure
ReferenceId	Integer	Read			Unique Reference Identifier for this object
NameHash	Integer	Read			Provides the hash value for the name of the object as a 32 bit integer.