Melting oxygen out of ice is the quick way at the start. In the long run water is often the better source: the electrolyzer splits it into oxygen and hydrogen. That gives you breathing gas and fuel from one raw material – and a mixture you have to treat with respect.
Where the water comes from
| Source | What you get |
|---|---|
| Ice (Water) | 20 mol of water and 5 mol of nitrogen per piece, melts from 273.15 K |
| Pure Ice Water | 50 mol of pure water per piece |
| polluted water | treat it in the Water Purifier |
| burning hydrogen | 2 mol of hydrogen and 1 mol of oxygen give 3 mol of steam |
Water takes up 0.018 litres per mole. So one piece of water ice gives 0.36 litres, and one litre of water is about 55.6 mol.
The Ice Crusher takes in ice through a chute and has one gas output and one liquid output. That way water and nitrogen end up separately in their lines.
The electrolyzer
The Electrolyzer takes water from a liquid line and releases gas into a gas pipe. It has only one gas output – so oxygen and hydrogen come out together, both at 20 °C. Data and power have separate ports, plus a slot for a chip; it has no inner chamber of its own. It needs a frame below it.
Two points from the game code are easy to miss:
Onalone is not enough.Modemust be 1 (Active), otherwise it stays idle. Without water at the input it drops to idle by itself;Activatereports whether it is currently working.- Power: 3,600 W while splitting, 50 W idle. The 10 W in the fact sheet are only the prefab's starting value.
It is built like the filtration unit and the air conditioner: place the Kit (Atmospherics), insert two Kit (Pipe), fit two cable coils with the screwdriver.
How much comes out
The game treats electrolysis as the reverse of its hydrogen–oxygen combustion: there, 2 mol of hydrogen and 1 mol of oxygen become 3 mol of steam, so the electrolyzer turns 3 mol of water into 2 mol of hydrogen and 1 mol of oxygen. That is less than real chemistry would give. In the game one litre of water (55.6 mol) yields about 37 mol of hydrogen and 18.5 mol of oxygen.
How fast it goes is set by the power: with water at 20 °C it splits about 0.73 mol of water per tick, just under 1.5 mol per second. Warmer water goes slightly faster.
A calculation for a room of four cells: for 22 % oxygen at normal pressure you need about 293 mol. That is 3 · 293 = 879 mol of water, roughly 15.8 litres. The electrolyzer needs about 1,200 ticks for it, a good 10 minutes, and 3,600 W · 600 s ≈ 2.2 MJ of power. Along the way 586 mol of hydrogen are produced. For comparison: oxite ice gives 22.5 mol of oxygen per piece, so you would need 13 pieces.
Separating the gases
A Filtration belongs behind the electrolyzer. With a Filter (Oxygen) or a Filter (Hydrogen) it splits the mixture onto two lines. Whatever the filter catches arrives at the output (…Output), the rest at the waste output (…Output2): with an oxygen filter the output is therefore the oxygen line. Remember to set the filtration unit to Mode 1 as well.
After that you have:
- oxygen for breathing air, see Gases and mixtures: breathing air, gas mixer, partial pressure,
- hydrogen as fuel. Burned with oxygen it delivers 306 kJ per mole and only steam as exhaust – which can be condensed back into water.
Between electrolyzer and filtration unit, fuel and oxidiser sit in one pipe. A spark is enough. Above 573.15 K (300 °C) hydrogen even ignites by itself with more than 1 mol. Keep this line short and cool, put no pipe heater on it and no wall heater near it – the heater makes a spark every tick.
Water in lines
Water follows the rules for liquid lines:
- At most 6,079.5 kPa, and the pressure is no good as a fill gauge. Measure the fill level (
VolumeOfLiquid/Volume) with a Liquid Pipe Analyzer. - Below 273.15 K water freezes in the pipe into chunks of ice. On Mars (about −50 °C at night) and on Europa (below −139 °C) outdoor lines need insulation or a Pipe Heater (Liquid).
- At 100 kPa water only boils at about 384 K in the game.
IC10: running the electrolyzer safely
This program only lets the electrolyzer run when there is enough water in the supply line, the oxygen store still has room and the gas at the output does not get too hot.
# Electrolysis only with water, storage room and a cool output
define ELECTRO -1668992663 # Electrolyzer (StructureElectrolyzer)
define LANALYZER -2113838091 # Liquid Pipe Analyzer
define GANALYZER 435685051 # Pipe Analyzer (StructurePipeAnalysizer)
define NELECTRO HASH("Electrolysis")
define NWATER HASH("Water Analyzer")
define NSTORE HASH("O2 Store Analyzer")
define WATERMIN 0.1 # fill level of the supply, stop below
define STOREMAX 20000 # kPa in the oxygen store
define TMAX 373.15 # K, 100 C at the gas output
alias volume r0
alias liquid r1
alias pressure r2
alias temp r3
alias run r4
alias tmp r5
sbn ELECTRO NELECTRO Mode 1 # 1 = Active, otherwise it stays idle
start:
yield
lbn volume LANALYZER NWATER Volume 0
bnan volume start # water analyzer missing
lbn liquid LANALYZER NWATER VolumeOfLiquid 0
div tmp liquid volume # fill level 0 to 1
sgt run tmp WATERMIN # enough water
lbn pressure GANALYZER NSTORE Pressure 0
bnan pressure start # store analyzer missing
slt tmp pressure STOREMAX
and run run tmp # store has room
lbn temp ELECTRO NELECTRO TemperatureOutput 0
bnan temp start # electrolyzer missing
slt tmp temp TMAX
and run run tmp # output not too hot
sbn ELECTRO NELECTRO On run
j startThe analyzer “O2 Store Analyzer” sits on the oxygen network behind the filtration unit. The line before start: sets the mode to Active once; after that the program only switches On. The 100 °C limit leaves a wide margin to the 300 °C at which hydrogen ignites by itself; the electrolyzer itself releases its gas at 20 °C.
Where next
- Filtration: separating gases, changing filters, getting rid of waste gases – filters, filtration and waste gases
- Evaporating, condensing, freezing: using phases on purpose – turning steam back into water
- Pipes and lines: gas, liquid, insulated – filling liquid lines correctly
- Survival: the first minutes – oxygen from ice at the start