How bright is this planet anyway?

[DaveMcW]

Since the earth-based solar industry prefers to use kWH, we can convert Factorio data to that.

42 kW per solar panel * 24 hours / 9 m^2 = 112 kWH/m^2 per day.

112 * 365 = 40,880 kWH/m^2 per year.

Compare to some earth data:
http://www.pveducation.org/pvcdrom/prop ... -radiation
http://www.greenrhinoenergy.com/solar/r ... idence.php

[MadZuri]

I must say that I love the way this conversation has gone. I started the post as a way to conceptualize the homework I was doing in my energy systems and the environment class in my nuclear engineering curriculum. In real life, solar and wind have a max of about 30% utilization factor. That means you can only use on average about 30% of the installed maximum power that those systems provide, and you still need a baseline power system. You can't really choose when wind kicks in, and solar only works on clear days half the time (pretty close to a sine wave, really). That kWhr unit is an endless source of frustration for me. It is a unit of energy, equal to 3600 kJ. Power for most plants is in MW. You gotta multiply time * power * utilization factor to get the average, but they charge by energy, in kWhr. Long story short, if you want minimal impact on carbon emissions, nuclear is the only way to go. Supplement it up to 15% solar, 15% wind, and that is about it. Energy storage is HARD. Current technology almost exclusively is in the form of pumping large volumes of water into reservoirs for storing energy. We don't have accumulators IRL. Maybe eventually, but now... not so much. Be glad the game is the way it is, and that renewable is a viable form of baseline power production. Real life isn't so kind.

Add to my struggle that I live in the US, and that most things are in units of BTU's, kCals, F, and pounds-feet and you should understand my frustration with the topic.

[Khyron]

...and you still need a baseline power system.

... says conventional wisdom. Challenge the status quo, man. We can do better! Part of the problem here is that we arrive at this need for a baseload power system if we start by assuming a) we will need a ubiquitous power grid and b) power companies will store the power for nighttime use. Apparently nobody told the consumer that because you can get residential solar systems which include an array of 12v lead-acid batteries to power your needs overnight and be fully off-grid.

Alright, so there are problems with that. But we're still at an infancy stage in terms of power storage technologies. There simply hasn't been a mass-market demand for this technolgy until very recently. Look what mobile phones and laptops have done for battery technology in the past 10 years. Fully electric cars will be the next big push. Personally I love the idea of massive banks of flywheels (in a sort of steam-punk kind of imagining) but again that has challenges (some of which are being tackled by materials engineering). But some future technology would be awesome.

We don't have accumulators IRL. Maybe eventually, but now... not so much.

Sure we do. Capacitors. Rechargeable batteries. The problem is a) charging them is a lossy process (put more in that you get back out) and b) they physically degrade over many charge/discharge cycles.

Add to my struggle that I live in the US, and that most things are in units of BTU's, kCals, F, and pounds-feet and you should understand my frustration with the topic.

You started it. Maybe your generation will make the US change to le systeme international d'unites. Eww, French... gross. And upgrade your bloody 110v low efficiency domestic grid, geez...

[cpy]

USA is our medieval fair fun place, where they use old inefficient power grids, use ancient measurement units, they use this illogical nonsense to preserve history for future generations, but i prefer old stuff to be written in books or digital storage, but whatever.

[JimiQ]

I recommend this blog of american physics professor Tom Murphy. It contains lots and lots of calculations about solar and other forms of energy (pretty much every form we know) and multiple forms of energy storage (from pumped air through water reservoirs to lead-acid batteries)

[Psycho0124]

Sorry, but a world that bright would just cook. Even two times brighter will kill all life. Indeed the amount of solar power is limited to a relative small zone around a sun (relative in astronomical measures):
http://en.wikipedia.org/wiki/Circumstel ... table_zone

So the logical conclusion is: The solar panels must be somehow much, much, much more efficient. Which is really possible, cause it is a game.

Yep. Modern cells are really only about 20% efficient. They only absorb a limited spectrum, have huge losses to heat and reflection, suffer from the resistance in the conductors in the cells, allow some photons to pass through, etc. Future solar technology is going to have a vastly different efficiency rating. It may use layers of more than one semiconductor material to absorb more of the electromagnetic spectrum, have built-in heat-> electricity conversion technology, have fancy anti-reflective coatings, etc.. The efficiency variable will ruin any attempt to calculate the brightness of the planet based on the power produced.

http://solarcellcentral.com/limits_page.html
^ Neat read on the limited efficiency of modern solar technologies.

[SteelGiant]

Sorry, but a world that bright would just cook. Even two times brighter will kill all life. Indeed the amount of solar power is limited to a relative small zone around a sun (relative in astronomical measures):
http://en.wikipedia.org/wiki/Circumstel ... table_zone

So the logical conclusion is: The solar panels must be somehow much, much, much more efficient. Which is really possible, cause it is a game.

Yep. Modern cells are really only about 20% efficient. They only absorb a limited spectrum, have huge losses to heat and reflection, suffer from the resistance in the conductors in the cells, allow some photons to pass through, etc. Future solar technology is going to have a vastly different efficiency rating. It may use layers of more than one semiconductor material to absorb more of the electromagnetic spectrum, have built-in heat-> electricity conversion technology, have fancy anti-reflective coatings, etc.. The efficiency variable will ruin any attempt to calculate the brightness of the planet based on the power produced.

http://solarcellcentral.com/limits_page.html
^ Neat read on the limited efficiency of modern solar technologies.

The efficiency thing isn't really so much of a problem: even at 100% efficiency, the Factorio solar cells are generating so much energy that the light intensity over the entire planet is so high that liquid water would be immediately split into hydrogen and oxygen. The fact efficiency will be lower than 100% just makes this effect even worse.

[Koub]

The efficiency thing isn't really so much of a problem: even at 100% efficiency, the Factorio solar cells are generating so much energy that the light intensity over the entire planet is so high that liquid water would be immediately split into hydrogen and oxygen. The fact efficiency will be lower than 100% just makes this effect even worse.

Technically, even on Earth, at sea level, and ambient temperature, an infinitesimal fraction of the water spontaneously breaks into H2 and O2. It's an equilibrium.
Now, under same conditions, if you want to achieve thermolysis for good, you'll need to be around 2700ish°C. I am way too lazy to calculate if Factorio's world reveives enough light to have 2700°C on its surface, but I bet not.

[MadZuri]

I'll do the math for you. A temp of 2700C would have a black body radiation of about 4 million w/m^2, a bit much for our example. If we assume the solar panel efficiency is 50% (damn near a theoretical maximum for converting photons to usable electricity) and surface albedo of 30% (about the same as earth), the ground would need to radiate 6.53kW/m^2 with a surface temperature of about 300C. I took into account the daily average solar panel output being 42kW. I neglected the greenhouse effect, which would raise the surface temperature by a fair bit. So there you go. For factorio's solar panels to produce as much energy as they do, the surface temperature would be at a Minimum 300C. For giggles I'll assume that the solar panels are 100% efficient and surface albedo is 50%, and neglect greenhouse effect again.... That's about 177C.

[Psycho0124]

Hahah.. Alright then. Visible light (photons) only accounts for ~40% of the energy spectrum emitted by our sun though. If we assume we have a high-tech panel that can absorb the entire electromagnetic spectrum, and a star with a vastly different spectral irradiance curve, could we have a reasonable surface temperature?

[MadZuri]

Those calculations are independent of wavelength. As in, I completely neglected if the incoming solar radiation is visible or not. So, technically, most of the radiation could be coming in as UV instead of visible, but the temperature calculations remain the same, as well as the solar power output. I just assumed that you could design solar cells to efficiently turn solar radiation into electricity, whatever wavelength that is.

[Cougarific]

*contented sigh*

The discussions on this board are quite a bit different than the usual fare over on the Steam Discussion boards. *wipes tear*

[lusername]

So our next question is, given the minimum temperatures possible on this planet, what kind of atmospheric pressure are we looking at such that we can still have liquid water?

[DaveMcW]

The temperature of surface water is 15C. An estimate of 177C or 300C is a contradiction.

[MadZuri]

Well, obviously, yes. That is the contradiction that I am pointing out. For solar to work the way it does, I've been crunching numbers. Anyway, to answer the question, you would need an atmospheric pressure of 8587.9 kPa, or about 85 atmospheres.

edit: I suppose I could have just said "Well, solar is just that OP compared to the real thing to make them a viable option for gameplay" but that is boring. I would rather crunch all the numbers to figure out the conditions where it would work like that. So, about 10x brighter, with a surface temperature of over 300C, and 85 times the pressure of earth. Thank you for playing along

[ssilk]

3 And The Map Generator said, “Let there be light,” and there was light. 4 The Map Generator saw that the light was good, and he separated the light from the darkness. 5 The Map Generator called the light “day,” and the darkness he called “night.” And there was evening, and there was morning—the first day.

What I want to say is: I just need to change the world generator and the surface temperature will be 100 degrees and I just need to pump water into a steam engine, without any need to heat it up (cause it is still hot enough), and it will produce energy.

[starholme]

3 And The Map Generator said, “Let there be light,” and there was light. 4 The Map Generator saw that the light was good, and he separated the light from the darkness. 5 The Map Generator called the light “day,” and the darkness he called “night.” And there was evening, and there was morning—the first day.

What I want to say is: I just need to change the world generator and the surface temperature will be 100 degrees and I just need to pump water into a steam engine, without any need to heat it up (cause it is still hot enough), and it will produce energy.

That's fine, other than the 'finding liquid water' to pump! You'd need to condense some from the atmosphere, then pump it into a air to liquid heat exchanger to make it hot again!

Actually, that's an interesting mod idea... Somebody needs to build a dehumidifier, so you can extract water from the air. Perfect for petroleum processing far from water. Probably useless for power generation, cause you need power to extract the moisture from the air.

[DaveMcW]

the surface temperature will be 100 degrees and I just need to pump water into a steam engine, without any need to heat it up (cause it is still hot enough), and it will produce energy.

Now we know how offshore pumps work!