# How to make affordable solar pannels for CubeSat pico-satellites?

Registered Users Posts: 5
How to make affordable solar pannels for CubeSat pico-satellites?
Where can I find the solar cells and how can I assemble them in small panels?

I am currently working on a CubeSat 10x10x10 cm cubical satellite whose total mass must not exceed 1 kg. I mention that this is a school project and it is unlikely the satellite will actually go in orbit. Most probable, once finished, the cubesat will remain in the lab.

What I need is 6 solar arrays 10x10 cm or smaller to cover each side of the cube. The rigid framework of the pico-satellite (the chassis) looks like this:
http://cubesat.ifastnet.com/forum/viewtopic.php?f=1&t=30
Searching on the internet I have found solar arrays, specially designed for these mini cubical satellites, but the prices are huge, more than 2000 \$ for less than 100 square centimeters of photovoltaic cells. I can not afford such costs.
What I need is affordable solar panels that fit the budget of a school project (a few hundred dollars). Can you help me with an advice? I have no experience with solar generated electric power.

The solar arrays distributed around the cubesat have to produce at least 1 W in the most unfavorable position of the cube related to the Sun. I mention that the satellite is supposed to circle the Earth in a Sun-Synchronous Dawn/Dusk orbit which means that the Sun never sets and it always illuminates the cubesat. However the pico-sat spins and some faces of the cube will be always in shadow.
I made some calculations and at 1350 W/m2 solar radiated density of power hitting only one side of the cubesat (supposing all the rest are in shadow) the illuminated panel would generate 1.35 W of electricity at a 10% conversion efficiency. So, in theory, it looks like 1 W should be possible with cheap solar panels.

In case the solar panels surface proves too small, some deployable photovoltaic arrays which fold out, once the satellite reaches orbit, can be added (see: http://cubesat.ifastnet.com/forum/viewtopic.php?f=4&t=32 )
but this is not desirable due to mechanical complications. I would prefer to use only the sides of the cubesat as mounts for a few hundred cm2 of solar cells.

• Solar Expert Posts: 10,300 ✭✭✭✭
Re: How to make affordable solar pannels for CubeSat pico-satellites?

the reasoning for that high cost would be the high efficiency of those arrays and their ruggedness to be able to launch into space and have tiny impacts while in orbit. you could cheapen the modules if you know it won't go into orbit. you need to know the end voltage needed by the satellite as well to determine the number of cells and the current ratings needed for your wattage goal. for terrestrial modules we usually see 36 cells for use on a nominal 12v system with voltage at max power in the area of 17 to 18v. that extra voltage is needed to overcome regulator losses as well as resistive losses we see by long runs of wire to allow about 15v at the battery for flooded lead acid types. other battery/charging arrangements with short thick leads may have a differing vmp output to accommodate these other type systems.
as said, we deal with terrestrial systems here so you could contact amsat to see what they may suggest to you and be prepared to lay out the specs of the system with all of its equipment requirements to them.
http://www.amsat.org/amsat-new/index.php
• Registered Users Posts: 5
Re: How to make affordable solar pannels for CubeSat pico-satellites?

The Size of one assembled panel must be 10x10 cm.
The required voltage is 5 V DC.
The panel should be able to generate at least 200 mA (in direct Sun light) and the voltage must not drop below 5 V DC if a load draws 200 mA or less.
• Registered Users Posts: 5
Re: How to make affordable solar pannels for CubeSat pico-satellites?

Finally I have found some High Efficiency Triangular Solar Cells costing \$250 for a pack of 100 cells (or at least it is claimed so).
Has anybody used them?
• Solar Expert Posts: 157 ✭✭
Re: How to make affordable solar pannels for CubeSat pico-satellites?

Why don't you take a page from NASA's playbook and simply use deployable solar panels? That way you can buy dirt-cheap cells and still have plenty of power for onboard applications.

• Registered Users Posts: 5
Re: How to make affordable solar pannels for CubeSat pico-satellites?
jagec wrote: »
Why don't you take a page from NASA's playbook and simply use deployable solar panels? That way you can buy dirt-cheap cells and still have plenty of power for onboard applications.
As far as I know, solar panels for cubesats run into thousands of dollars. They can be as expensive as a car or even more.
If you have a link to those cheap panels, I would be happy to see it.
You suggest that I can use deployable solar panels covered with cheap, low efficiency solar cells? For instance, instead of using a 10x10 cm2 panel having 30% efficiency solar cells I could utilize three 10x10 cm2 panels covered with cheap 10% efficiency cells? This can work supposing the cubesat can keep its pannels perpendicular to the Sun rays. I have never heard of a cubesat whose panels are able to follow the Sun.
• Solar Expert Posts: 157 ✭✭
Re: How to make affordable solar pannels for CubeSat pico-satellites?
thetis wrote: »
As far as I know, solar panels for cubesats run into thousands of dollars. They can be as expensive as a car or even more.
If you have a link to those cheap panels, I would be happy to see it.
You suggest that I can use deployable solar panels covered with cheap, low efficiency solar cells? For instance, instead of using a 10x10 cm2 panel having 30% efficiency solar cells I could utilize three 10x10 cm2 panels covered with cheap 10% efficiency cells? This can work supposing the cubesat can keep its pannels perpendicular to the Sun rays. I have never heard of a cubesat whose panels are able to follow the Sun.

Ah, if they don't maintain their orientation that does change matters.

How do you keep your instruments facing the earth?
• Registered Users Posts: 5
Re: How to make affordable solar pannels for CubeSat pico-satellites?
jagec wrote: »
How do you keep your instruments facing the earth?

The short answer is that cubesats are not too good in keeping instruments pointing to the earth.
The long answer would be that there are some nanosats, like BeeSat-1, which use experimental reaction wheels that, at least theoretically, should be able to accurately orient the cubesat in a direction of interest.
However, there must be some catches because little 1 kg class satellites with reaction wheels are rare.

There are other systems that control the attitude of cubesats like putting a magnetic bar (or better electromagnets, for more control) inside their body which transform the entire satellite in a kind of compass needle making it to align with the Earth's magnetic field.