Solar Panel return on investment

[DaveMcW]

Your first solar panels are very cost-effective, replacing inefficient boilers with clean energy while the sun is shining. Solar panels have a peak output of 60 kW, but average 42 kW over an entire day/night.

Solar Panel
+ 5 steel (furnace): 7.88 MJ
+ 67.5 iron/copper plates (furnace): 21.26 MJ
+ 15 electronic circuit (assembler 3): 1.26 MJ
+ 45 copper wire (assembler 3): 1.89 MJ
+ opportunity cost of mining 67.5 ore instead of coal: 67.5 * 50% boiler efficiency * 8MJ = 270 MJ

Divided by 42 kW: 2 hours to recoup investment


Switching to a coal-free factory is great in the very long term, but accumulators and electric furnaces increase the cost to break even. I am assuming one accumulator per solar panel here.

Accumulator
+ 14 iron/copper plates (furnace): 4.41 MJ
+ 5 batteries (chemical plant): 4.2 MJ
+ 10 sulfuric acid (chemical plant) 0.34 MJ
+ opportunity cost of producing 81.5 ore and 10 sulfur instead of coal/solid fuel: (81.5 * 8MJ + 10 * 25MJ) * 100% steel furnace efficiency = 902 MJ

Divided by 42 kW: 6.2 hours to recoup investment

[Thourion]

Well if you wanted to be perfect, you would want to include the cost in fuel while driving your car to go place the panel setup, the potential cost of repair packs while fixing your car that hited some trees along the way, the needed electrical poles to connect the thing together, along with the much prefered substations. But of course you must add the decrease in pollution if you switch to pure solar, and calculate how many attacks in your base they save you VS the steam engines you had, because during the steam era you probably had your walls attacked a bit more, wasting more repair packs, walls, bullets or laser power along the way.

Erm ..i should get my coat now

[Marconos]

Let's be honest .... what are you going to do with those resources otherwise

[DarkenDragon]

yea plus energy isnt some finite resource either, so spending so much energy to get it back makes no difference really.

if you really want to see if its worth building solar panels vs steam engines (which Im assuming is the question here since those are pretty much your only 2 sources of energy) then you should really be looking more at real-estate or land usage vs the amount of pollution being created.

thats really the only difference between using the 2 types of power source. The amount of fuel a boiler uses is so small and coal/solid fuels are so abundant that you should never have to worry about that being the problem.

the amount of energy compare to land usage will always be in favor of the steam engine, and the energy compared to the pollution will be in the favor of solar power.

and pollution only affects how often you get attacked if the enemy bases are within the pollution radius. so if you kill all the alien bases that are within the radius, then pollution becomes negligible. thats really the only thing you need to consider when deciding if you should go for solar or more steam engines.

[silenus]

This type of analysis is really good for figuring out speed run timings.

How would you take into account resource abundance? I ask because i like to play with really weird resource start up amounts to mix things up. In my current game Im bottlenecked on oil, which makes sulfur "expensive".

[DarkenDragon]

technically hes not even comparing resources, hes comparing energy cost.

which in fact is a bit useless since energy is an infinite resource. thats what we're trying to say.

though the analysis is nice. just not practical

[Marconos]

I do agree that energy is too easy at this time. Though if you don't start with enough coal in your starting zone you are kinda screwed. I have had some spawns with zero coal with the default ore generation settings.

As for pollution and spawns. Depending on your critter settings the pollution can be a big deal as you don't have the ability / resources to clear all them before the pollution starts having affect. With standard settings I find critters to basically be non existent the entire game. With higher settings it causes quite a few attacks that can greatly tax your resources (especially when your turrets randomly stop working).

[Khyron]

I find it kind of interesting to see this type of analysis. I'm a bit surprised about the 42kW average though. From looking at the day/night cycle on the energy graph I would have assumed it was much better than 70/30.

Of course, the important thing about switching to solar and electric furnaces is that it's the only way to reign in pollution as you expand production. If you don't contain pollution you stimulate more biter attacks and drive up the evolution factor much quicker. That in turn means you need to spend more resources on defenses, which creates more pollution. If you counter that by going out and killing biter bases that are in range of your pollution footprint, you drive up the evolution factor and after a while settlers will come and build new biter spawners anyway. Another alternative is to just not expand production but that runs pretty counter to the game's purpose.

Edit: On second glance, this analysis is pretty questionable. The "opportunity cost" is not measured properly and it accounts for 90+% of the energy used in the solar example, and more in the accumulator example.

[ssilk]

70/30 should be right: https://forums.factorio.com/wiki/inde ... =Units#Day

Edit: https://forums.factorio.com/wiki/inde ... e=Game-day

[Der_Doodle]

60/40 (Accus/Panels) works fine aswell and makes a nice loooking pattern

[DarkenDragon]

with the information given, 1 solar panel can fully charge 2 accumulators, assuming that the panel is running at half power while the other half is powering the factory.

though since the day cycle is a lot longer than the night cycle, you wont need that many accumulators to power the night.

and to know how many accumulators you need for your factory, just take your highest peak usage (cuz you want your accumulators to be able to run everything) divide it by 300kw and then multiply that by 8. that'll be how many accumulators you'll need to run your factory over night.

the way I got all this information is based on these formulas Accumulator capacity / charge/discharge rate = Duration

so accumulator capacity is 5mj or 5000 kj, or kw*s, charge per panel is 30 (assuming half is used for charging up, and the other half is for the factory), and discharge rate is 300kw, and duration is 291.66 seconds of day light, and 124.99 of night time (using only half the value for morning and evening)

so for charge the formula looks like 5000/30x = 291.66 where x is the amount of panels required to fully charge 1 accumulator.
and for discharge the formula looks like x(5000/300) = 124.99 where x is the amount of accumulator running at full discharge are required to last the night.

edit: though I forgot to add in that these are assuming your not using laser turrets. if you are you'll need even more accumulators because those bad boys will drain a ton of your power. but at least now you have the formulas to figure out exactly how much you need. but good rule of thumb, always have more accumulators than you need. since having too many will not hurt you in any way other than taking up space, but having too little can be a disaster cuz turrets might not shoot and thus biters can run rampant through your base (had this happen to me and ended my run)

[Loscil]

with the information given, 1 solar panel can fully charge 2 accumulators, assuming that the panel is running at half power while the other half is powering the factory.

though since the day cycle is a lot longer than the night cycle, you wont need that many accumulators to power the night.

and to know how many accumulators you need for your factory, just take your highest peak usage (cuz you want your accumulators to be able to run everything) divide it by 300kw and then multiply that by 8. that'll be how many accumulators you'll need to run your factory over night.

the way I got all this information is based on these formulas Accumulator capacity / charge/discharge rate = Duration

so accumulator capacity is 5mj or 5000 kj, or kw*s, charge per panel is 30 (assuming half is used for charging up, and the other half is for the factory), and discharge rate is 300kw, and duration is 291.66 seconds of day light, and 124.99 of night time (using only half the value for morning and evening)

so for charge the formula looks like 5000/30x = 291.66 where x is the amount of panels required to fully charge 1 accumulator.
and for discharge the formula looks like x(5000/300) = 124.99 where x is the amount of accumulator running at full discharge are required to last the night.

edit: though I forgot to add in that these are assuming your not using laser turrets. if you are you'll need even more accumulators because those bad boys will drain a ton of your power. but at least now you have the formulas to figure out exactly how much you need. but good rule of thumb, always have more accumulators than you need. since having too many will not hurt you in any way other than taking up space, but having too little can be a disaster cuz turrets might not shoot and thus biters can run rampant through your base (had this happen to me and ended my run)

Thanks for the info, brah.

[Gurba]

I thought I'd share my calculations here as well.
Someone else probably posted the same set somewhere but I didn't find them so far.

I might be wrong here, but it seems to work fine.
If you find an error, please let me know. I might even redo the calculations and update this post.
Mind that this is based on a constant load, you sould always have some extra solar panels and accumulators for peak loads (lasers firing for example)

Since this is about solar panels and accumulators it seems like a decent enough fit.

I'll be using 100 solar panels here to get a bit of scale.

Facts: (as far as I can find them)

• Nr of solar panels: 100
• Nominal output (as advertised on the tin): 100*60kW = 6000 kW
• Day/night cycle time: 416.66 s according to the wiki
• A solar panel spends 50% of its time producing 60kW (day)
• A solar panel spends 10% of its time producing 0 kW (night)
• A solar panel spends 20% of its time producing a increasing amout of power (dawn) for an avarage of 30 kW
• A solar panel spends 20% of its time producing a decreasing amout of power (dusk) for an avarage of 30 kW
• This means we can simplify this by saying a solar panel productes 60 kW 70% of the time and nothing during 30% of the time

Calculations

Lets start by calculating the effective power output.

Energy produced during full cycle (kJ):
nominal output * cycle time * 70% = 6000 kW * 416.66 s * 70% = 1749972 kJ

Effective output (kW):
produced energy / cycle time = 1749972 kJ / 416.66 s = 4200 kW

This means that we have 4200 kW available to play with, any more and the solar panels will not be able to keep up over a full day.
We obviously have to store some of the energy for the night cycle if we want to keep our factory going.

Lets go find out how many accumulators we need and what that does with the load on our solar panels, remember that we have a 30% night cycle.


Energy needed for storage (kJ):
effective output * cycle time * 30% = 4200 kW * 416.66 s * 30% = 524991.6 kJ

Energy available for work (kJ):
energy produced - stored energy = 1749972 kJ - 524991.6 kJ = 1224980,4 kJ

Maximum acceptable load (kW):
work energy / cycle time = 1224980,4 kJ / 416.66 s = 2940 kW

Accumulators needed to keep going:
energy stored / 5000 = 524991.6 kJ / 5000 = 104.998 accumulators needed

[eduran]

Energy available for work (kJ):
energy produced - stored energy = 1749972 kJ - 524991.6 kJ = 1224980,4 kJ

Maximum acceptable load (kW):
work energy / cycle time = 1224980,4 kJ / 416.66 s = 2940 kW

The stored energy isn't lost, it still does its share of the work during the night. The maximum acceptable load should be 4200kW, because that is what 100 solar panels manage to produce on average. The accumulators job is to store overproduction during the day to fill the gap at night. They do so without any loss of energy.

Energy needed for storage (kJ):
effective output * cycle time * 30% = 4200 kW * 416.66 s * 30% = 524991.6 kJ

You assume one has to store energy for 30% of a cycle, but that were only true if the accumulators kicked in the second the solar panels start to lose power. In reality, the accus start their work when the panels drop below their effective output of 4200kW and stop when the output exceeds this value.
So, after dawn begins, how long does it take until the accus kick in? The panels ramp up/down linearly over the course of 20% * 416.66s = 83.33s. Starting from 0 kW they will reach 4200kW after 83.33s * 42/60 = 58.33s.

energy to store becomes:
effective output * (length of night + length of dawn * 42/60) = 4200 kW * (41.66s + 58.33s) ~ 420000 kJ

ccumulators needed to keep going:
energy stored / 5000 = 420000 kJ / 5000 = 84 accumulators needed

So 100 solar panels and 84 accumulators allow your factory to consume 4200 kW of power, assuming the consumption is actually flat without any spikes.

[starxplor]

So 100 solar panels and 84 accumulators allow your factory to consume 4200 kW of power, assuming the consumption is actually flat without any spikes.

Yeah, my 100+ lasers going off wont spike demand at al... not one watt.

Thanks everyone for putting these numbers out there.

[Khyron]

We seem to have drifted off topic to a discussion on the ratio of solar panels to accumulators. This has been discussed numerous times elsewhere.

This thread is about the energy cost of making solar panels and the return on investment.

[Marconos]

This thread is about the energy cost of making solar panels and the return on investment.

Once you build a solar panel you have infinite free energy. So infinity / cost == free, not sure what there is to discuss there.

[starxplor]

This thread is about the energy cost of making solar panels and the return on investment.

Once you build a solar panel you have infinite free energy. So infinity / cost == free, not sure what there is to discuss there.

I dont play anything for infinity... I don't expect to live that long.

Also, once you have a dozen oil wells with 0.1/s and filled with speed modules, you have free power for as long as you dont let the biters destroy your infrustructure. That doesnt mean the numbers and ratios are not worth discussing.

[Ethribin]

This thread is about the energy cost of making solar panels and the return on investment.

Once you build a solar panel you have infinite free energy. So infinity / cost == free, not sure what there is to discuss there.

I dont play anything for infinity... I don't expect to live that long.

Also, once you have a dozen oil wells with 0.1/s and filled with speed modules, you have free power for as long as you dont let the biters destroy your infrustructure. That doesnt mean the numbers and ratios are not worth discussing.

I'm still a bit new to the game and don't know the resource costs and numbers by heart...
But for one... I never saw a dozen or more oil fields together, so it will be a pain to transport the oil all together for the solid fuel.
Also, if you use burned energy you will only spawn more biters, which you will have to use more energy against again.

For the resource costs... (that's where I'm not sure about the numbers and all ><) but isn't oil and steam stuff mainly steal and iron, while solar power is mainly copper? (and batteries for accumulators but I don't I'll put this in the same category as the coal/solid fuel and water needed for the burners)

So... in the end it is more a question of what resource you have around you that tells you if the return on investment for solar panels is better then the steam engine. At least in the early or middle game.
In the late game it's totally player preference afterall as basic resources is not really the problem any more as you should have a solid production line at that point.

I personally prefer solar power as I can just plot them down in a safe place and forget about them (if I have accumulators naturally). While with steam engines I have to make sure I don't run out of fuel.
Also, Solar power reduces the evolution speed (I haven't figured out how to best fight aliens yet aside of ever better technologie^^; But that only shows I'm still new)
And finally... for solar panels I only need accumulators to help, or let my factory rest in the night. For Steam engines though I need drills for coal, transport belts, inserters, pipes and pumps. Oh... and I need water of coarse and can't plot it anywhere.

The cost for steam engine power might be lower (I think), iron based or easier then the solar panel, which is copper based, but the steam engine needs a much larger infrastructure around it to work.

[Marconos]

[Also, once you have a dozen oil wells with 0.1/s and filled with speed modules, you have free power for as long as you dont let the biters destroy your infrustructure. That doesnt mean the numbers and ratios are not worth discussing.

To me it comes down to a single salient point ....

Oil --> have to keep pumping, processing, making solid fuel --> cost energy + time + logistics support to move materials
Coal --> have to keep mining, you run out and logistics support to transport, train lines to transport etc.
Solar --> I built it, I'm done, nothing left to do here, ever

Building time isn't really a consideration as they all have to be constructed. The difference is in the long term use potential. It really comes down to how you like to play the game. In my current game I wasn't paying attention and 100% ran out of coal. Having to build a train line beside a biter base and no laser defense, relying totally on my guns was a scary. Then starting it all backup by chopping wood. Was a good challenge.