Solar Panel Effectiveness

[Brian444444]

There is a short statement in the readme file that came with 1.1.2 that said: "Solar Panels generate electricity based on the distance to the sun."

That makes perfect sense to me but has anyone noticed that it seems like disproportionately low flow out in the Jool system or God forbid Eeloo? I realize you are out there a good way. Maybe its right and my sense of what it "should be" is distorted.

Just curious what others think.

[moogoob]

That happened some time around 1.0 I think. It always differed with distance but linearly, not it's logarithmic.  Long story short - if you use lots of panels (at least a couple of 1x6ers) out past Dres then you can still power a probe core I think, but good luck running ion thrusters out there on solar.

It's one good reason to either pair w/ fuel cells or use an (extremely expensive) RTG when on Jool missions.

[DChurchill]

Haven't been past Duna since I started playing again. I'm working on it.

 

[Alshain]

I feel like it is normal given the scale of the system.  We don't send solar powered probes out to Jupiter or beyond, I assume for this reason.  Pioneer 10 was the first I think, and it had four RTGs.  I'm pretty sure every craft we have sent beyond Mars Ceres was RTG powered.

 

EDIT: Did a little resarch, Dawn is solar powered, and it is in progress.

Edited May 12, 2016 by Alshain

[Enorats]

Th intensity of sunlight drops increasingly fast as you get farther from the sun. Solar power thus decreasing increasingly fast. This is true in the real world too, it's a basic facts of physics.

Craft in the outer systems need LOTS of large panels, or preferably nuclear powered reactors to power them.

[DChurchill]

2 minutes ago, Alshain said:

I feel like it is normal given the scale of the system.  We don't send solar powered probes out to Jupiter or beyond, I assume for this reason.  Pioneer 10 was the first I think, and it had four RTGs.  I'm pretty sure every craft we have sent beyond Mars was RTG powered.

Right. Eeloo is supposed to be a Pluto analog. New Horizons is a piano with an RTG. Cassini has no solar panels. Even the latest Jupiter mission was the first to have solar. I think.

3 minutes ago, Enorats said:

Th intensity of sunlight drops increasingly fast as you get farther from the sun. Solar power thus decreasing increasingly fast. This is true in the real world too, it's a basic facts of physics.

Craft in the outer systems need LOTS of large panels, or preferably nuclear powered reactors to power them.

Sunlight behaves under the inverse square law. Twice as fire away equals a quarter of the light and three times is one ninth.  It doesn't take long to get pretty dim out there.

[Sknow]

Alshain is correct the first solar powered probe (Juno) to Jupiter arrives this July. 

[Guest]

 

1 hour ago, DChurchill said:

Sunlight behaves under the inverse square law. Twice as fire away equals a quarter of the light and three times is one ninth.  It doesn't take long to get pretty dim out there.

^This.  Treat Kerbin's SMA as r = 1 in the equation and just plug in "1" for "I" in the equation.

In other words: E = 1/(orbital SMA/Kerbin SMA)^2.

E at Eve should be about 1/(9,832,684,544/13,599,840,256)^2, or 1.91.  Multiply your panel's EC/time by that amount.

E2: Gaaaah, forgot to square the divisor!

Edited May 12, 2016 by regex
MATH ERROR ALERT

[JWag]

I got bitten by this in my old (dating back to 23.5) save. My Eeloo probe should be fine as I used RTGs, but my crewed ship in Dres orbit can't afford to run its science lab for more than half an orbit because it has a pair of dinky arrays.

[Brian444444]

I appreciate the responses and thanks for the education. I admit my ignorance regarding the inverse square law and having read what you have written it makes perfect sense now. My expectation was a linear loss of flow prior to learning this. That is why my gut was telling me something was off. Now I know why...thanks guys!

[LordFerret]

I don't know if you've any interest in this, but (I believe it was) @GoSlash27 created a table of solar panel effectiveness at various distances a while back. It might still be valid. I tried searching for the original post/link, but could not find it. However, I did save the table created ... I've relied on it for some time now.

 

Quote

Solar Panel Power Output

OX-STAT
Moho: ~1.5
Eve: 0.64
Kerbin: 0.33
Duna: 0.15
Dres: 0.03
Jool: 0.02
Eeloo: 0.01

OX-4L/W
Moho: ~7.5
Eve: 2.99
Kerbin: 1.54
Duna: 0.70
Dres: 0.15
Jool: 0.08
Eeloo: 0.03

Gigantor
Moho: ~110
Eve: 44.37
Kerbin: 22.90
Duna: 10.40
Dres: 2.30
Jool: 1.18
Eeloo: 0.41

 

 

[GoSlash27]

3 hours ago, LordFerret said:

I don't know if you've any interest in this, but (I believe it was) @GoSlash27 created a table of solar panel effectiveness at various distances a while back. It might still be valid. I tried searching for the original post/link, but could not find it. However, I did save the table created ... I've relied on it for some time now.

 

 

LordFerret,

 That looks like a very handy table. Kudos to whoever put the effort into it... but it wasn't me

Best,
-Slashy

[RandomUser]

The solar panels seem to work fine far out.  I mean, they aren't nearly as effective as they are around Kerbin, obviously, but I find that a few panels works well even on Eeloo missions.  Then again, the only mission where I had brought out equipment that needed a lot of electric charge was to Laythe in a Science save I'm working on.  It worked for the most part, but I can see the low input being a problem for the more bulky equipment used for gather science. 

[Geschosskopf]

57 minutes ago, RandomUser said:

The solar panels seem to work fine far out.  I mean, they aren't nearly as effective as they are around Kerbin, obviously, but I find that a few panels works well even on Eeloo missions.  Then again, the only mission where I had brought out equipment that needed a lot of electric charge was to Laythe in a Science save I'm working on.  It worked for the most part, but I can see the low input being a problem for the more bulky equipment used for gather science. 

It depends on what you're using them for.  As the table above shows, solar panels are only half as powerful at Duna as they are at Kerbin, and only 10% as powerful at Dres.

From Jool to Eeloo, you need a Gigantor just to keep a probe core alive and use a bit of SAS now and again.  And beyond Eeloo (like if you're using OPM), solar panels are nothing but dead weight.  RTGs are by far the better option for simple domestic consumption even at Jool.  And to do anything else, you need considerably more power.  If you've got a 1-way science probe that need to transmit boatlloads of data, you either need a huge battery (that solar and RTGs will take days to recharge) for the transmissions, or you need a fuel cell you turn on only when transmitting.  For anything having a long-term and high EC consumption (life support, Kerbalism, drililng, and refining), you need a nuclear reactor.

Note that I didn't mention rovers above.  Even at Kerbin, solar panels are insufficient to keep crewed rovers moving uphill for any significant amount of time, so you're pretty much stuck with fuelcells from the get-go.

[RandomUser]

Just now, Geschosskopf said:

It depends on what you're using them for.  As the table above shows, solar panels are only half as powerful at Duna as they are at Kerbin, and only 10% as powerful at Dres.

From Jool to Eeloo, you need a Gigantor just to keep a probe core alive and use a bit of SAS now and again.  And beyond Eeloo (like if you're using OPM), solar panels are nothing but dead weight.  RTGs are by far the better option for simple domestic consumption even at Jool.  And to do anything else, you need considerably more power.  If you've got a 1-way science probe that need to transmit boatlloads of data, you either need a huge battery (that solar and RTGs will take days to recharge) for the transmissions, or you need a fuel cell you turn on only when transmitting.  For anything having a long-term and high EC consumption (life support, Kerbalism, drililng, and refining), you need a nuclear reactor.

Note that I didn't mention rovers above.  Even at Kerbin, solar panels are insufficient to keep crewed rovers moving uphill for any significant amount of time, so you're pretty much stuck with fuelcells from the get-go.

Hmm.  For a lander on Eeloo, I find that mine is more than capable with the basic solar panels that is has at the moment. however I have yet to see it transit to Eeloo's apoapsis, which very well could leave my two landers dormant. 

[Guest]

A pair of 1x6s or 2x3s is plenty to keep the smaller probes alive, and even actively recharge batteries for reaction wheels (albeit slowly), out at Eeloo's apoapsis.

[Geschosskopf]

9 minutes ago, RandomUser said:

Hmm.  For a lander on Eeloo, I find that mine is more than capable with the basic solar panels that is has at the moment. however I have yet to see it transit to Eeloo's apoapsis, which very well could leave my two landers dormant. 

But what is your EC load?  That's the thing. Whatever makes your EC, it has to produce a bit more EC/sec than your indispensable domestic needs, so it can also recharge the battery you need for periodic high-consumption things like transmitting data.  If your domestic load exceeds what panels can provide, then your stuff will eventually die.

Of course, high warp level causes a violation of conservation of charge (and energy) in the stock game, so it's possible to get by with less EC/sec than you actually need.  But if you don't like relying on that exploit, or you have a mod that keeps you honest, then you really can't rely on solar panels much beyond Duna, MAYBE Dres even for domestic use.  Especially if it's a crewed ship with life support.  Not to mention Kerbalism, which will be sucking lots of power out there just trying to keep your Kerbals warm in the frozen wastes

[RandomUser]

15 minutes ago, Geschosskopf said:

But what is your EC load?  That's the thing. Whatever makes your EC, it has to produce a bit more EC/sec than your indispensable domestic needs, so it can also recharge the battery you need for periodic high-consumption things like transmitting data.  If your domestic load exceeds what panels can provide, then your stuff will eventually die.

Of course, high warp level causes a violation of conservation of charge (and energy) in the stock game, so it's possible to get by with less EC/sec than you actually need.  But if you don't like relying on that exploit, or you have a mod that keeps you honest, then you really can't rely on solar panels much beyond Duna, MAYBE Dres even for domestic use.  Especially if it's a crewed ship with life support.  Not to mention Kerbalism, which will be sucking lots of power out there just trying to keep your Kerbals warm in the frozen wastes

For basic science equipment, I'd say solar panels work up until Jool.  My Laythe lander was able to do all of it's experiments with just solar panels, during sunset.  The equipment was fairly basic, thermometer, goo canister, Science Jr., pressure equipment, etc.  Seems to have worked for me.  As for the EC load, I'm not certain, but pretty small on just that.  Though in and past Jool, I try to keep electric usage to a minimum, no unnecessary SAS, etc. 

[cantab]

You can use solars quite far out, you just need to be prepared to take a lot of them. I took an ion ship out to the Jool system once and while it was Ec-starved I was still able to enter Bop orbit then return to Kerbin. For power per mass the RTG beats solars at Jool, but for power per funds solars are considerably better even at Eeloo, though I suppose the extra mass may impact the cost of lower stages.

[Geschosskopf]

30 minutes ago, RandomUser said:

For basic science equipment, I'd say solar panels work up until Jool.  My Laythe lander was able to do all of it's experiments with just solar panels, during sunset.  The equipment was fairly basic, thermometer, goo canister, Science Jr., pressure equipment, etc.  Seems to have worked for me.  As for the EC load, I'm not certain, but pretty small on just that.  Though in and past Jool, I try to keep electric usage to a minimum, no unnecessary SAS, etc. 

Well sure, for the extremely minimalist needs you've got, you can eke out a modest living on solar panels.  That category includes not only small science probes but also stock crewed missions that have enough fuel to come home.  But if you want or need to refuel, have life support, or anything else that imposes a fairly high domestic electrical load, solar power ceases to be an option at Duna.  Maybe, if you don't mind spamming Gigantors, you can use it at Dres.  But beyond that, you need a reactor.