The Final Word on Steam Boiler Efficiency

[Omicron]

My Thanks Go Out To:
- solidity, who wrote the original LUA script to simulate boiler heatup, which served as the base for mine
- MilConDoin, who provided me with a couple formulas I was missing and pointed me towards the script in the first place


!Attention! This article was written during the 1.4.x era. Due to changes implemented in later versions of Railcraft and/or other mods, some fuel value numbers, MJ production numbers and/or editorializing statements presented herein may not be correct anymore in all cases. However, the main analysis is calculated directly in Heat Units (HU), and the derived conclusions remain independent of changes up to Railcraft 8.2.0.0.

Due to a complete boiler rework in Railcraft 8.3.0.0, this analysis no longer applies to that version and beyond.


The Purpose Of This Post
I'm by far not the first one to tackle the subject of steam boiler math (especially since I've been procrastinating on writing this up for so long, lazy as I am). There's spreadsheets aplenty and even online calculators that tell you exactly how long any boiler will take to heat up, how much fuel it will consume during that period, and how much fuel it will continue to consume once at maximum heat. There is, however, one topic that is often overlooked, or even misunderstood and done wrong (particularly by those who are just looking to use boilers, not to do math on them). That topic is fuel efficiency.

Now, we live in an age of infinite fuel loops. Powering a max-size boiler 24/7 is trivial; many people have never built anything but max size boilers, even if these things are completely oversized for their needs and most of their output is quite often wasted unused. So what, it's gonna be running around the clock anyways, and all that matters is that the output is available when you need it. Why, then, would anyone even bother with the (actually quite complicated) issue of boiler fuel efficiency at all?

Because I'd like to clear up those misunderstands that are being handed about for truths. A lot of this really goes down to imprecision in language; a forum poster who once read somewhere that "high pressure boilers are just as efficient as low pressure boilers after heatup" will happily repeat this information to other users, without stopping a moment to ask himself what the person who originally made that statement actually meant to say, and whether the correct words were used. The truth of the matter is that after heatup, a high pressure boiler will create just as much steam per unit of fuel as a low pressure one; but it will never be as efficient overall as a low pressure boiler.

This might seem like a trivial distinction - and some might not even understand where the difference is in the first place - but that's just because it's so easy to make the mistake.

As I am going to show you below, the actual impact in gameplay is not trivial at all.

And while I'm at it, I am going to show you graphs that visualize precisely how every single possible boiler performs in terms of energy production, both over a certain time and with a certain amount of fuel. I'm also going to provide a spreadsheet that has all these graphs for you to play with, as well as a fuel value list, a MJ calculator, and some general performance metrics. And finally I'll throw in the LUA script I wrote to calculate all these things, so you can even experiment with it ingame.

Let's get started.


So You Want To Build A Steam Boiler

The first question is: how much energy do you need? That will decide the size and type, and therefore the power output, of your boiler. The second question, then, is: what kind of fuel options do you have? Based on that, you decide whether you want to build a solid or a liquid fueled boiler. Here is a table showing you all the different fuel options you have. (side note: blaze rods got un-nerfed slightly to 800 HU in the latest Railraft build, but no FTB pack includes it yet at the time of this posting.)

Now, if you were concerned with fuel efficiency, what fuel you have available - specifically, the amount of it - should also prompt you to think about what size and type of boiler you really need. Everyone understands that bigger boilers give you more MJ for your fuel... but by far not everyone understands that that's actually not always true. If your fuel supply is not infinite, but in fact limited, then you may very well run into a situation where the opposite is true. The reason for this lies in the most commonly ignored trait of these devices:

Steam boilers are catastrophically inefficient during heatup.


Visualizing Energy Output

Let's look at a couple of sample fuel profiles.

1 Million Heat Units - Just shy of 10 stacks of charcoal, or just over 10 buckets of fuel.
'Wow, I have 10 stacks of charcoal', the newbie player thinks. 'Maybe I should finally stop messing around with stirling engines and build something really powerful! I bet I could run a really big steam boiler with this!' ...Or can he?

The graph I am showing you here is a fuel-energy graph. The horizontal X-axis is labeled with millions of HU, and the vertical Y-axis is labeled with millions of MJ. The hallmarks of a good and efficient steam boiler, then, would be to be listed as high up as possible, as early as possible. The less heat units are required to reach a given amount of MJ, or the more MJ produced with a given amount of HU, the better. And what boilers gives us the most bang for our buck here? The 1 LP variant, the tiniest and most humble of them all. It managed to pull ten times more MJ out of the available fuel than a 36 LP boiler. The 27 HP and 36 HP variants don't even show up in this graph; they produce not a single MJ.


10 Million Heat Units - Three a half wooden chests full of charcoal, or six and a half tank blocks full of fuel
Okay, the previous example was a little extreme... let's give more than just the smallest four boilers an actual chance to finish heating up. The only ones that do not finish in this example are the 27 and 36 HP variants. Do note, though, that the amount of fuel used here already borders on ridiculous. Nobody builds up that kind of charcoal stash; you'd need a diamond chest just to store it. Only liquid fuels really make sense to keep in storage at this point, everything else better be supplied by a constant source. It should give you pause to realize that with only the second graph I'm showing you, we're already in "infinite fuel loop" territory. There's two more after this.

Here, we see the low pressure boilers, one after the other, execute an upwards turn as they come out of heatup and from then on burn fuel at maximum efficiency. And due to that, one after the other eventually passes the 1 LP boiler in total MJ generated (though it continues to lead up until about 2.75 million HU). At the end of this chart, all the low pressure boilers have ordered themselves into their expected ranking, with 36 LP leading and 1 LP at the bottom.

You know what didn't pass the 1 LP boiler, though? Any high pressure boilers. Those are still zigzagging about below, even though the 1, 8, 12 and 18 variants have all finished heatup in this graph. The 8 HP one does it as early as 1.8 million HU, but it still struggles to catch up. Even after well over a golden chest worth of charcoal, the 1 LP boiler still manages to produce more total MJ than any and all high pressure boilers available. So much for the supposed fuel efficiency of HPs, eh?


32 Million Heat Units - Almost three diamond chests full of charcoal, or about the entire contents of a small oil spout
Finally, just north of 22.3 million HU, the last of the boilers finishes heatup. The 1 LP boiler is soundly overtaken by everything except the hobbyist engine and its own HP counterpart (which is invisible here due to the sheer scale of the graph). The larger high pressure boilers attempt to hurry upwards and sort themselves into the fan spread of the low pressure ones, but despite pouring an entire oil well worth of fuel down their figurative gullets, they still can't quite manage it yet.

From an efficiency standpoint, a 12 LP boiler would still give you better fuel efficiency here than a 36 HP boiler. And obviously, the larger low pressure boilers are even better. There's a gap of more than 75 million MJ between the 36 LP and HP variants.


96 Million Heat Units - Ungodly amounts of just about anything
And there we are! After enough fuel input to power a death star for a field trip to Alderaan, everything finished ordering itself into its right and proper place.

And here is what people mean when they talk haphazardly about 'efficiency' being the same. Notice how all the high pressure boiler lines are exactly parallel to their low pressure counterparts; they produce MJ at exactly the same rate. However, since the lines are exactly parallel, that also means that the gap will remain forever constant. The 36 HP boiler is still about 75 million MJ below the 36 LP variant, and it will forever remain about 75 million MJ below. That is why using the correct words is important, because while energy output per fuel is indeed identical, overall efficiency is clearly not.

You can, of course, keep increasing the size of the graph. As you do, you will keep zooming out to larger and larger scales, and the gaps between the lines will eventually appear to vanish, as you can see happening here with the 8 LP and 8 HP boilers. The gap is still there, and it is forever constant, but if you zoom out far enough it will become negligible in the overall scale of things. Thus we approach infinity, and thus the careless simplification of "high pressure has the same efficiency as low pressure" begins to work. But it works only out there, at infinity. For anything below infinity, it is wrong.

How wrong - that depends entirely on your scale.

 

[Omicron]

Talking About Efficiency

Now, so far we have only talked about efficiency in a very roundabout way. The graphs I showed you before did not display efficiency directly, but rather its building blocks. Efficiency is defined as energy per heat unit:

Efficiency = MJ/HU

Meaning, the more MJ you get out of your fuel, the higher your efficiency rating will be. As a result, you can gauge efficiency from the fuel-energy graph (the highest ranking boilers obviously are more efficient than the lowest ranking ones), but you're not seeing the actual value unless you pull out a calculator and do some division. We can, of course, remedy that with a different kind of chart. But first, before we can draw them, we have to calculate the values.

To start off, it is easy to calculate each boiler's theoretical maximum efficiency out of of its basic fuel use per tick, via the formula provided by CovertJaguar on the Railcraft wiki. First you figure out how long a given amount of fuel lasts, and once you know the burn time, you can simply multiply it by the boiler's MJ output in order to figure out how much MJ the boiler produced during the burn time. If you then divide the MJ output by the HU input, you get efficiency.

The most easy way to do this is simply inserting 1 as the HU input, because then the amount of MJ produced will exactly equal our thereoretical maximum efficiency for each boiler.

And here we are at the point where many people stop looking. 'I have calculated the efficiency', they say, 'and now I know that high pressure boilers are just as efficient as low pressure boilers, and that building the 36 HP boiler is the best choice for anyone, in any situation.' ...umm yeah, no. Now that we've already seen the graphs in the first half of this post, we know that that's not even close to true.

So what's missing? Time is missing. The value calculated above is a snapshot, a single moment with no time elapsed, a perfect steady state. In reality, however, your efficiency will be a running average over the entire lifetime of your boiler. If you are thinking that you are getting peak efficiency right away when your boiler finishes heating up, think again - despite the fact that all new fuel burned from now on will be giving you maximum output, your real, average efficiency over runtime will usually be a mere 40% right after heatup. And it will take a long, long time to push that average up anywhere near the theoretical maximum (which it will never completely reach).

Since we're talking about a running average over all the life stages of a boiler, let's define these life stages that must be included. The heatup phase, for starters. Then, the time spent at maximum temperature. And finally, if we want to be complete, also the cooldown phase after all your fuel input has been consumed, because that's giving you bonus MJ without requiring any fuel at all. But we have to keep in mind that a boiler only generates steam if the water is above 100°C in temperature, so both the heatup phase and the cooldown phase are shorter than you measure them to be for the purposes of energy generation. All this is necessary to determine the actual amount of MJ produced over the boiler's lifetime, and only with that value you can compute the real efficiency. Of course, all that is still operating under the assumption that not a single bit of steam is wasted, ever. Any MJ you are not using are not allowed to be part of the efficiency calculation.

The LUA script I have included at the bottom does this for you. Give it a burn time in ticks, and the size and type of boiler you are using, and it will output you a whole host of performance metrics, including efficiency. Calculate enough data points like that, and you can draw a chart of how a boiler's real efficiency develops over time.

And, for those of you sharp enough to wonder: yes, the fuel-energy graphs in the first half do already take into account heatup and cooldown phases in the proper way. That is why they look slightly funny and have kinks in some places. Brace yourselves now, because you're going to see even weirder looking graphs next!


Visualizing Efficiency

I am going to present the time-efficiency graphs in the same way as the fuel-energy graphs from before: each use case will be linked and then briefly discussed. The X-axis is showing time, in hours; the Y-axis is showing efficiency as we have calculated it, in MJ/HU.

The First Half Hour - baby's first puff of steam
Well? Did I not promise you that I've got even weirder graphs coming up? Well here it is, and it looks completely bonkers. High pressure boilers more efficient than low pressure ones? Lines going up-down-up-down several times in a row? Other lines suddenly flopping to the side as if someone broke them? What in the world is going on?

What you are seeing here are the wonders of the heatup phase. And yes, this is exactly what happens ingame - that LUA script is reproducing actual Railcraft code published by CovertJaguar himself. The lines look like they do because of the peculiar way the speed of the rise and fall of temperature during heatup and cooldown is handled. During heatup, the gain of temperature is fast at low temperatures and slow at high temperatures; during cooldown, the loss of temperature is fast at high temperatures and slow at low temperatures.

In this snapshot, only three boilers, namely the size 1 pair and the hobbyist engine, even finish heatup; all the other boilers are still well below maximum heat. As a result, the high pressure boilers are catapulted well above the low pressure ones by virtue of gaining a lot of temperature very quickly during early heatup, then losing that temperature only very slowly during cooldown, thereby gaining a ton of free bonus MJ. However, at some point that math turns sour for them, and raising temperature becomes harder while cooldown happens faster. This actually gets so bad that efficiency goes down again a bit, and waffles about a near-flat line for the rest of the heatup phase.

Because of this, the 1 LP boiler (which is not affected as strongly by the weirdness because it only has half as much temperature to gain) eventually overtakes the 1 HP boiler again, and by the time the two come out of heatup at around 4 and 8 minutes respectively, the expected order is restored: the low pressure boiler is well on top.

The fan favorite, the 36 HP boiler, is actually not doing half bad: it is ranked third here after the first half hour, and it looks like it's about to capture rank two. But, are you getting efficiency 9.091 from it? Nope - at this point it is giving you less than 3.4 real efficiency. Even the top ranked boiler, the 1 LP, cannot yet pass efficiency 4. If you're burning Buildcraft fuel or biofuel, I have bad news for you: simply using a combustion engine would have given you 6.25 efficiency straight from the first tick...


Two Hours - an average gaming session
At this point, the graph gets really busy. Boilers are overtaking each other left and right, before getting overtaken back in turn. The 36 HP boiler even manages to reach rank 2 for a bit as predicted, but then takes a dip and flatlines, losing it again. All low pressure boilers except the size-36 one have finished heatup by now, as have the 8 HP and 12 HP boilers. The 1 LP boiler is still unchallenged efficiency leader by a big margin; this should remind you of what you saw in the fuel-energy graphs in the first half of this post.

However, despite running for two hours straight, no boiler is even anywhere close to breaking efficiency 5 yet. And the combustion engine would still be happily chugging along at 6.25, almost twice of what a 36 LP boiler can offer at this point.


Ten Hours - a casual gamer's weekend in singleplayer
All boilers have now finished heating up, even the big ones. The effect is dramatic - the theoretical efficiency champion from our fuel-energy graphs, the 36 LP boiler, is absolutely skyrocketing and leaves every other competitor in the dust. And lo and behold, it reaches and shatters the efficiency 6 line, ending up sitting just a little bit below where a combustion engine would be. So here it is, folks: If you are burning fuel or biofuel, the absolute minimum you need to do to beat a combustion engine is running a 36 LP boiler for about 11 hours straight, spending roughly 107 buckets of fuel or 321 buckets of biofuel. Any other kind of boiler, and you'll be waiting even longer and spending even more fuel.

The other low pressure boilers, in the meantime, are starting to sort themselves into their expected ranking as the effects of the heatup phase are starting to get marginalized by many hours of peak temperature operation. The high pressure ones are not quite there yet, even though they too have all finished heatup. Still, only 1 LP and hobbyist engine are approaching their theoretical maximums by now; the others are still a long way off.

 

[Omicron]

24 Hours - a full day on a persistent server with constantly 100% TPS rate (is that even possible?)
Yeah, the hobbyist engine, 1 LP and 1 HP boiler are no longer rising visibly. They are still below their theoretical maximum (and they will never truly reach it), but they are so close that for all practical purposes they are maxed out. For the 8 LP and 12 LP boilers, that point in time is approaching fast, as well.

The high pressure boilers have finished sorting themselves among each other by now, but the order between low and high pressure is still off.

At almost the same time, around 19 hours, the 27 LP boiler and the 36 HP boiler meet and pass the combustion engine, spending about 130 buckets of fuel (27 LP) or about 400 buckets of fuel (36 HP) to do so. Yes, that's an entire small oil well, just to get your 36 HP up to the same efficiency as a simple combustion engine. Fun, isn't it?

Oh, and by the way: running a boiler for 24 hours on a multiplayer server only gives you this efficiency if you actually consume every last MJ it generates, even while you are offline, sleeping through the night and going to work or school the next day. If your boiler ever generates wasted MJ that you are not consuming, its efficiency is going to plummet downwards. The same is true for singleplayer, of course; but there you have the advantage of the boiler only running while you are actively playing.


72 Hours - an entire month of casual singleplayer time
If this sounds like a long time to you, that's because it is. If you play for two hours every day, an entire month will pass before you get there. But surely then, at this point all the boilers are closely hugging their theoretical peak efficiency, right?

Unfortunately, no. None of the 3x3 ones are, although the lines are getting very very flat already, practically not rising anymore for some. That is due to the huge inefficiency introduced through the very long heatup times these big boys have. But, there is some good news: the size-36 boilers are getting really darn efficient at this point. Even the fan favorite 36 HP variant manages to hit efficiency 8, which is really good. Always provided that not a single second of idle time happened, of course.

For the first time represented in this graph is the theoretical maximum line, the 9.091 MJ/HU that is the ideal peak efficiency of a size-36 boiler. But 72 hours don't seem enough to get close to it yet... well, I have one more graph for you.


162 Hours - a very long time indeed
This is more or less an arbitrary time. The last data point for the 36 HP boiler just happened to be sitting here by chance, so I created extra data for all other boilers as well to fill up the chart. In practical application, 162 hours of constant operation without wasting a single MJ is so unrealistic, most players will have started a new map before reaching this point. And those playing on persistent servers will likely never reach this efficiency either, because it is almost impossible not to waste MJ while offline. Only steam turbines hooked up to constant UU-matter production would do it, if the rotors are religiously replaced every third day (and if there is always enough scrap for GregTech implementations).

Little changes compared to the previous chart, except that all boilers that can still edge a little bit upwards, do so. For your convenience, I've listed the efficiency values at this final data point for all the boilers, compared to their theoretical maximum:

          36 LP: 8.790 out of 9.091
          36 HP: 8.556 out of 9.091
          27 LP: 7.358 out of 7.547
          27 HP: 7.207 out of 7.547
          18 LP: 6.342 out of 6.452
          18 HP: 6.254 out of 6.452
          12 LP: 5.816 out of 5.882
          12 HP: 5.760 out of 5.882
          8 LP: 5.513 out of 5.556
          8 HP: 5.478 out of 5.556
          1 LP: 5.058 out of 5.063
          1 HP: 5.056 out of 5.063
Hobbyist engine: 4.047 out of 4.051

Of course, for this graph you can do the same as for the fuel-energy graph from before. Make the time axis long enough, and you zoom out far enough to make the differences between the low and high pressure variants vanish, as well as the difference between actual and peak efficiency. At t = infinity, every boiler gives you what is advertised as peak for its type. But the question is - do you really want to wait for an eternity?


Closing Words

Obviously, a 36 HP boiler supplied by an infinite fuel loop will always be the go-to solution for MJ mass production, as long as infinite fuel loops exist. But that's okay - it was not my intention to tell anyone how to play their game. Much rather, I hope I have been able to clear up a few misconceptions with this project, and maybe even entertained a few people with the interesting math of this particular problem.

The LUA script I have mentioned throughout this post is here: http://pastebin.com/RSAuswvn
You can run it on your computer with any free LUA interpreter from the internet, or you can import it into your game world with ComputerCraft. Note that I've not actually tested this, but I see no reason why it should not work.

The Excel sheet with all the graphs and data is here: https://dl.dropbox.com/u/44754370/Boilerscience2Public.xlsx
You can play with the graphs by right-clicking an axis and choosing 'format axis', and then adjusting the range of values you'd like to display. Note: you might have to resize the graphs a bit if your screen resolution is different from mine. If someone would like to convert the spreadsheet for compatibility with OpenOffice et al, please, feel free to do so.

Also, Forecaster has provided an excellent online calculator here: http://calculator.towerofawesome.org
(Based on his own work, not related to mine, but I thought it's cool enough to link to anyways)

 

[Dravarden]

holly crap, amazing wall of text! for sure reading it again when I'm setting up the boiler in my world, thanks!

 

[kunglaopt]

Very interesting and well written, thank you.

 

[lorgan3]

So.. My 8HP boiler fueled by biofuel is still less efficient at 1000° than a few combustion engines?

 

[Omicron]

So.. My 8HP boiler fueled by biofuel is still less efficient at 1000° than a few combustion engines?

That is correct, I'm afraid. People generally underestimate combustion engines because of the instant association of "it can blow up, therefore it is a terrible engine". But as a matter of fact, they are extremely efficient energy producers.

Not to mention that boilers, too, blow up if their water supply fails

 

[MagusUnion]

Ok, now my question is this:

If we are not outputting the steam into engines, but instead to attached turbines, what do the efficiency numbers say? I've slapped two-three turbines on a max size HP boiler in test runs, and for one turbine, have gotten a 100% Output, with a 2nd turbine 75% Output...

To me, it would seem that the boiler system is more of a complex MJ -> EU converter than anything else. Relying on Steam pressure to push engines leaves open the losses via pipes to generate MJ, and since Forestry has electrical engines, why not just use/upgrade them based on need in order to maximize engine output?

 

[Omicron]

You seem to be misunderstanding a few things

A boiler generates steam. With the steam, you have two different options: you can create either MJ, or you can create EU (and if you want to be technical, the turbine can even do Universal Electricity power). Since Railcraft is a mod in the Buildcraft ecosystem, people generally measure steam boiler output in MJ. That's purely by unspoken convention, though.

Output in MJ via engine: steam / 5
Output in EU via turbine: (steam / 5) * 1.5625

The best conversion factor you can get from Forestry electric engines is 2 MJ for 5 EU, therefore: (EU input / 5) * 2 = MJ Output

Let's assume you have a 8 HP boiler, for ease of numbers. It produces 160 steam per tick.

Output in MJ via engine: 160 / 5 = 32 MJ
Output in EU via turbine: (160 / 5) * 1.5625 = 50 EU
Forestry engine: (50 / 5) * 2 = 20 MJ

So if you use Railcraft's steam engines, you get 32 MJ; if you use a turbine feeding into Forestry's electric engines, you only get 20 MJ out of the same amount of steam. Clearly, using steam engines directly is the better choice.

 

[noskk]

Haha, my choice of using 8 combustion engines was correct

 

[zwahlm14]

on my last multiplayer world i had i used a 36 hp boiler being powered by 4 peat bogs ant it warmed up just fine and was sustained, i didn't waste any of it and was in fact considering making another one because i was running 4 max size quarrys and that was in the old version of ftb where quarries had a max of like 18, now one quarry can use up all the mj a 36 hp can produce and with the new energy tesseracts energy waste is not really an issue, at least for me. and if you have the iron and already are producing massive amounts of wood anyway i don't think it is a problem, but if you don't mind making several redstone energy cells and just making a small power system and just use it every so often for things like powered furnaces then I think that a large boiler would be a stupid idea like you said. Really nice post btw, really informative and helpful for people that aren't as familiar with this stuff.

 

[Zjarek_S]

Haha, my choice of using 8 combustion engines was correct

That's cute: http://i.imgur.com/1ptQHdN.png .

3*15 + 16 combustion engines, all running on fuel in on demand setup (build before TE gate condition fix). I really don't like to be bothered with turning off machines like thermionic fabricator or rock crusher . This is certainly overkill, but when when my initial 16 engines struggled with recharging energy cells, I decided to go with ultimate solution. Of course everything remote, like bee facility or quarry has its own set of engines, because I don't believe in teleportation and super efficient solar panels.

 

[djtlite138]

Seeing some of this makes me sad... Steam boilers are epic in concept but to be quite honest i think i will stick with either magmatics and a pump in the nether with tesseracts or electrical engines with solars for my mj power solutions... Maybe one day a use for steam aside from in the form of MJ or EU producer will appear that entices me. Until then i will save steam boilers for a more decorative purpose...

 

[noskk]

That's cute: http://i.imgur.com/1ptQHdN.png .

3*15 + 16 combustion engines, all running on fuel in on demand setup (build before TE gate condition fix). I really don't like to be bothered with turning off machines like thermionic fabricator or rock crusher . This is certainly overkill, but when when my initial 16 engines struggled with recharging energy cells, I decided to go with ultimate solution. Of course everything remote, like bee facility or quarry has its own set of engines, because I don't believe in teleportation and super efficient solar panels.

Yep, I thought that fuel+combustion engine was limited and less OP than lava(eu) and biomass(MJ), but I ended up finding a HUGE oil pool (I'm at 4000 buckets of fuel and it's still refining) and using it to power most of my GT hungry machines (with diesel gen) and XBee machines. I got all of my platinum, ruby and most metals from bees (thanks to the OP serum and frame housings ) so I'm not going to make matter fabricator, or quarry.

 

[GearSB]

Ok, so at about 5.2 hours or so, a 36 LP boiler wins the efficiency race, and then stays in the lead till infinity?

And at a bit over 8 hours, the 36 LP boiler makes more MJ per HU and keeps the lead on that as well till infinity?

 

[un worry]

Yep, I thought that fuel+combustion engine was limited and less OP than lava(eu) and biomass(MJ), but I ended up finding a HUGE oil pool (I'm at 4000 buckets of fuel and it's still refining) and using it to power most of my GT hungry machines (with diesel gen) and XBee machines. I got all of my platinum, ruby and most metals from bees (thanks to the OP serum and frame housings ) so I'm not going to make matter fabricator, or quarry.

found a huge (25 block high) oil spout a few weeks ago. Filled an 9x9x8 tank with oil and half again with refined fuel before it tapped out. About 16,000 buckets in total. Sweet Hope you experience the same.

 

[Syrinori]

Seeing some of this makes me sad... Steam boilers are epic in concept but to be quite honest i think i will stick with either magmatics and a pump in the nether with tesseracts or electrical engines with solars for my mj power solutions... Maybe one day a use for steam aside from in the form of MJ or EU producer will appear that entices me. Until then i will save steam boilers for a more decorative purpose...

Why? The argument only makes sense in the case that it isn't entirely feasible to just stock up then infinite sustain your way through a 36hp boiler. (even states as such) The fact we can have infinite amounts of charcoal or biofuel makes it so overpowered its ridiculous, especially with power converters in ultimate pack.

 

[Omicron]

Ok, so at about 5.2 hours or so, a 36 LP boiler wins the efficiency race, and then stays in the lead till infinity?

And at a bit over 8 hours, the 36 LP boiler makes more MJ per HU and keeps the lead on that as well till infinity?

Partially correct. The 36 LP boiler is indeed the most fuel efficient boiler you can have if you run it longer than five hours. However, the first graph set has millions of HU on the X-axis, not hours. The boiler wins the efficiency race at ca. 5.2 hours and ca. 8 million HU.

Basically, both graphs are different ways to display the same thing. The 8 million HU point in the first graph corresponds exactly to the 5.2 hours point in the second one. If you use the LUA script, you can get a few more details.

 

[Ray Herring]

36HP boiler with sold fueled fireboxes running off of coal provided by 1 tier 5 wither skeleton soul shard. Takes about 6hrs or so to heat up (at least mine did, i got bored and just watched it while watching vids on my comp and doing actual work work), and never runs out of coal. My friend and i had so much spare coal that we set up 12 IC2 generators for the extra, and still extra coal left over that i sent some to a macerator for diamond production.

It got to the point where i still had more coal coming in and i had to do something with all these bones that i void piped the rest of the coal.

Though we now have a new 36HP liquid fueled firebox running off of biofuel, since that is near infinite too with a steves carts tree farm.

 

[Hydra]

I don't really understand the part about efficiency. People don't really care about the efficiency of their fuel during startup because the fuel is typically infinite. What matters is A) are you going to get the boiler heated up with the stores of charcoal / biofuel you have and B) how much fuel do I need per second after it's heated up to sustain the boiler.

That's why I think the approach in integrating the efficiency during startup and after is wrong: you get nice curvy lines but no one cares about the curve since after about 4.4 hours or so even a 36 HP boiler is at max heat and once you get there you typically have a setup than can be sustained indefinately.[DOUBLEPOST=1362395700][/DOUBLEPOST]

Though we now have a new 36HP liquid fueled firebox running off of biofuel, since that is near infinite too with a steves carts tree farm.

It's not near infinite, it's infinite

I have two 36 HP boilers, 1 solid (charcoal) and 1 liquid. Both are supplied by SC and Forestry farms. This means that this system could in theory last eternally.