Factorio Forums

Hi there. First time poster here, I'm not usually very active on any forums at all. Decided to post today to share some random thoughts I had about the game that I wanted to share. Someone else may have done this before so if so sorry.

Anyway. I was thinking about it and was wondering just how much Iron and Copper is going around our factories. Now yes before we start I know things aren't to scale but this was all for fun anyway. So to numbers! with a little research its shown that Iron has a specific heat capcity of .45 J/g and copper has .385 J/g so that's 450 J/kg and 385 J/kg respectively. now its stated in game that one unit of coal has a value of 8 MJ (which by the way means that one unit of coal is roughly 1/3 of a kilo as on average coal has an energy density of 24 MJ/kg) so for Iron one MJ will smelt roughly 1 metric ton and copper will get you slightly more than that. (2222.22 kg and 2597.4 kg respectively) Multiply that by 8 gives you 17.8 tons and 20.8 tons of finished product per one single 8 MJ unit of coal. In game one unit of coal will smelt 12.75 units of raw ore, copper or iron the same either way. meaning that one unit of raw ore would weigh roughly 1.5 tons (slightly more for iron, slightly less for copper) which proves that the player is an absolute beast when it comes to pulling things around. this also works for oil drums too. one standard US barrel for oil is 42 gallons. one gallon is 8.34 lbs or 3.78 kg. so one barrel is 158.76 kg and one full stack of ten is 1587.6 kg or for comparison, roughly the same as one unit of raw ore.

Now of course this is all in good fun as of course the units aren't to scale and one would hope to get more than two single copper wires out of one 1.5 ton ingot of copper. and i will admit its not perfect as those values presume pure iron and copper and don't account for the 'dirtiness' of real raw ore. but it was a fun thought exercise I wanted to do since we were given a fuel value of coal and the others could be extrapolated from there. Hope this was educational and fun for all!

Caedrus wrote:a little research its shown that Iron has a specific heat capcity of .45 J/g and copper has .385 J/g so that's 450 J/kg and 385 J/kg respectively.

A little research is a dangerous thing.

The specific heat capacity of iron is 0.45 J/g°C. Note the temperature unit. The smelting temperature of iron is around 1200°C, which means you need 540 J/g or 0.54 MJ/kg to smelt it. 8 MJ only smelts 14.8 kg of iron ore.

In the game, 8 MJ can smelt 12.7 units of ore in a stone furnace, or 25.4 units of ore in a steel/electric furnace. This implies the stone furnace is wasting a bunch of energy, but we don't know how efficient the upgraded furnaces are either. If they are 100% efficient, 25.4 units of iron ore = 14.8 kg, or 1 unit = 0.58 kg.

You are of course right. This is what I get for trying to do this when I'm more than 24 hours on no sleep.

A little more research is even more dangerous. If iron ore is between 50% and 70% iron, and the specific heat of (whatever the rest of the ore is that isn't iron) is similar to iron, you only get 50-70% yield from your smelting energy. Which puts your lump of iron pretty close to the ballpark of 1/3kg you had for coal.

It also makes you wonder where the slag goes...?

Fun fact - if a tile is 1m^2, and a plate is 0.25m^s, 1/3kg of iron (7850kg/m^3) is roughly 0.17mm (0.007 inches) thick. I didn't do the calculation on your two copper cables, but my guess is you're getting really, really good deal when you make them.

DaveMcW wrote:This implies the stone furnace is wasting a bunch of energy, but we don't know how efficient the upgraded furnaces are either. If they are 100% efficient, 25.4 units of iron ore = 14.8 kg, or 1 unit = 0.58 kg.

Actually, we have another data point. Electric furnaces with efficiency modules use 80% less energy, which means un-moduled furnaces are at most 20% efficient. So 1 unit of iron ore is at most 0.12 kg, and 1 unit of iron plate is less than that.

DaveMcW wrote:

DaveMcW wrote:This implies the stone furnace is wasting a bunch of energy, but we don't know how efficient the upgraded furnaces are either. If they are 100% efficient, 25.4 units of iron ore = 14.8 kg, or 1 unit = 0.58 kg.

Actually, we have another data point. Electric furnaces with efficiency modules use 80% less energy, which means un-moduled furnaces are at most 20% efficient. So 1 unit of iron ore is at most 0.12 kg, and 1 unit of iron plate is less than that.

Nah, I find it more likely that adding efficiency modules increases the efficiency past 100%

If you don't accept Conservation of Energy, you can't use physics formulas.

I think a more reasonable thing is to assume that time is sped up. If time is being sped up 200x for gameplay purposes (1 day = 7 minutes instead of 1440 minutes), we can multiply mass by 200 to get more realistic results.

DaveMcW wrote:I think a more reasonable thing is to assume that time is sped up. If time is being sped up 200x for gameplay purposes (1 day = 7 minutes instead of 1440 minutes), we can multiply mass by 200 to get more realistic results.

Not quite sure I follow - the calculations are all based on energy, which is not time dependent. IE it takes the same number of Joules to heat the iron to smelting temperature, regardless of whether you do it over 10 seconds or 2000 seconds.

DaveMcW wrote:If you don't accept Conservation of Energy, you can't use physics formulas.

Yeah I can. Watch me!

DaveMcW wrote:If you don't accept Conservation of Energy, you can't use physics formulas.

1 raw wood = 4 MJ
1 raw wood -> 2 wood
1 copper plate -> 2 copper cable
2 wood + 2 copper cable -> 2 small power pole
2 small power pole = 8 MJ



I'll also like to point out that the amount of raw wood harvested from a tree is way off (1.2 kg trees?).

DaveMcW wrote:If you don't accept Conservation of Energy, you can't use physics formulas.

Its entirely possible that the efficiency boost comes from recycling the heat from the hot slag and putting it into fresh ore. Additional efficiency is possible by heat pumping from slag to ore, such that the same smelting heat gets reused over and over again.

In the end the total energy use would come from entropy and any chemical changes in the ore.

12 ice cubes come from 1 ice tray in real life but conservation of energy still applies. You can also make a mile of wire with 1 lb of copper or 5280 1 foot wires. You can not simply compare apples to oranges.

Who's violating what here? There's nothing fancy about it. Put a ball of cold ore in a room with hot slag. That gets you warm ore and warm slag and already saves a good chunk of energy. More energy can be saved by making it a multi step process, and it is more efficient to forcefully move heat with a heat pump than it is to run electric heater coils. Put it all together and you can basically run a furnace off its initial heat for a long time and have to put very little new energy into the system.

bobucles wrote:Who's violating what here? There's nothing fancy about it. Put a ball of cold ore in a room with hot slag. That gets you warm ore and warm slag and already saves a good chunk of energy. More energy can be saved by making it a multi step process, and it is more efficient to forcefully move heat with a heat pump than it is to run electric heater coils. Put it all together and you can basically run a furnace off its initial heat for a long time and have to put very little new energy into the system.

Producing iron from ore is endothermic, meaning that the reaction lowers the temperature. Usually the process is made exothermic (generating heat) by letting it react with carbon/carbon monoxide, but electric furnaces don' t use no carbon/coal