How do I determine my electricity needs?

[Invader Jim]

I launched a science station into Kerbin orbit for a contract. There was plenty of fuel left so I sent it to Minmus. I collected some science and put it in the processing lab but I don't have enough power to run the lab. I have two OX-4W 2x3 Photovoltaic Panels but they can't keep up. How do I know how much I am generating and how much I need?

I turned off all the lights and the SAS but the lab needs a lot more power than I expected.

Edited May 26, 2015 by Invader Jim

[Snark]

Yeah, the science lab is a real bear for electricity when it's researching. Turning off lights won't help you much (their power drain is tiny), nor will SAS (it doesn't use a lot of power unless you're actively spinning around).

Quickest way to determine energy needs is to look it up on the KSP wiki, e.g.:

http://wiki.kerbalspaceprogram.com/wiki/Mobile_Processing_Lab_MPL-LG-2

(5 EC/second researching)

...compared with the energy from the solar panels:

http://wiki.kerbalspaceprogram.com/wiki/OX-4W_3x2_Photovoltaic_Panels

(1.64 EC/second at Kerbin's distance from sun)

...which says you need slightly more than 3 of them to keep up. In reality, you'd want even more than that, because the 1.64 number assumes that they're pointed directly at the Sun, and none of them are shaded at all from any part of your spacecraft. Usually you won't have that ideal unless you do a lot of manual fiddling. So I'd say play it safe and get like 6 of them, it's not like they weigh much.

Also: Any particular reason you're using the 2x3 instead of the 1x6? I almost always use the 1x6, mainly because they're good at putting as much of their area as far away from the main body of the ship as possible, which means that they're less likely to get shaded by their own ship. Plus I can densepack them closer together without having them collide with each other.

[MrDude]

When Building you can right click on the items in the parts menu and it will give Charge units per unit time (sometimes seconds sometimes minutes). Tally up all the draws you plan to have running simultaneously (including probe cores and SAS). Once you have a units per second draw, pick solar panels up to that task with a little more for battery charging. Note that you should only count the panels that can see the sun simultaneously (so single square panels on opposite or 4 sides of the ship - only one counts). Be conservative since based on your positioning the panels may only get a fraction of their power so you want either to have it easy to align your station to the sun, or allow enough light to be caught at all angles.

Then guesstimate (or research how to find) the amount of time your planned orbit will be in darkness. Make sure you have more than that time periods amount of power draw in the batteries. That way when in shadow of the planet and or moon your draws will be fed by battery, then be fed by your panels with a little extra planned in for charging the batteries.

That should do it.

[FancyMouse]

MODULE

{

name = ModuleScienceConverter

scientistBonus = 0.25 //Bonus per scientist star - need at least one! So 0.25x - 2.5x

researchTime = 7 //Larger = slower. Exponential!

scienceMultiplier = 5 //How much science does data turn into?

scienceCap = 500 //How much science can we store before having to transmit?

powerRequirement = 5 //EC/Sec to research

ConverterName = Research

StartActionName = Start Research

StopActionName = Stop Research

}

[cybersol]

You might already know this, but its still worth noting. To monitor actual production and use, you can open the resources panel. Positive numbers inside the parenthesis are net energy drain and negative numbers are net energy gain (both in EC/sec). Also, you can right click panels to monitor their efficiency and power generation individually.

[DarkGravity]

Also remember what you launch might not be what you use. Solar panels tend to break a lot.

[mrklaw]

If it helps, the processing lab will eventually complete the job, it'll nibble away as the solar panels generate electricity.

i have 8 3x2 panels on my lab and 1800 stored electric when full. That still wasn't enough when I had 450 data to process - it ran out at about 70% complete so I had to wait for it to regenerate.

[Murph]

Something that must also be considered is how close the craft will be to the sun on its mission. Panel performance varies with distance to the sun, the nominal output is accurate for a panel near Kerbin's solar altitude and pointed directly at the sun. Output drops off with distance from the sun as well as angle to the sun. In practical terms, you're only rarely getting full output from panels, without actively keeping the panels aligned perfectly (including for rotating panels, as they only rotate on 1 axis).

In orbit around Kerbin, a couple of the Gigantor XL arrays is what you really want for a lab, and I personally prefer 4 of them in a + shape, so that I don't have to worry about the orientation of the lab (with 2, you'll have no output if they are close to perfectly end-on to the sun).

Don't forget to bring enough battery for the long cold dark nights, and eclipses. I like about 5–10k of battery for a Kerbin lab. Minimum is probably about 4k-ish.

So, basically if you're going to Duna or beyond, make sure you have too much panel at Kerbin. And, wherever you're going, too much is just a tiny amount of extra fuel getting there, too little is a major pain or even a failed mission.

[Warzouz]

As I've notice recently beware of ecplises, espectially around Duna. Best thing is having a fuel cell backup.

[Juicy]

I just add lots of batteries these days. Inline when I can get them. Enough that passing through the Muns' shadows with SAS enabled for several hours hardly makes a dent.

[Xannari Ferrows]

EC/s + EC/p = EC(gen) -3EC/s

OR

EC/s + EC/p = EC(stg) + EC(gen)

[match]

Atmosphere also partially blocks the sunlight, so if you do a bench test on Kerbin, you will get much better results once out of the atmosphere.

[luizopiloto]

You generally sum the consumption of all the parts that needs electricity in your craft and then put fuel cells/solar panels/RTGs, to generate the needed amount, and a bit more, of energy...

On critical missions, aways remember to have some kind of backup power generation system on-board...

[juanml82]

There is a mod called fusebox that shows how much the ship can generate and how much it consumes... except that there are many parts (including the mobile lab) which the mod can't get consumption reports from and that it shows generation at Kerbin's orbit only.