Solar Concentrator Arrays

[p0lizei]

A while ago I had pondered whether it would be possible to achieve more wattage out of an array of solar panels by focusing more sunlight onto them with mirrors.  This idea was shot down; I had asked if such a thing would be an atrocity against solar panels, the reply was: yes.  

HOWEVER!!1!!oneone  In my reading tonight, I happened upon this little gem: http://nmp.jpl.nasa.gov/ds1/tech/scarlet.html

Granted, I don't know what kind of solar panels they're using, I'm certain they must have some quality to them that would allow them to withstand the extreme conditions of outter space.

But I thought I would post that up there, perhaps somebody has a sacrificial solar panel they would be willing to conduct "research" upon in regards to this upgrade (for lack of a better word).  Or I suppose I could rip apart some old calculators and try it for myself :0p

[dudevato]

Here is my input on your post/link: I'd think mirrors/other types of consintrators would work in outerspace, as there is no heat out there. Also you wouldn't have to worry about oxygen degrading things. 'metor's might be a problem.  It seems to me with all I've read from these 'posting boards' that solar cells are the way to go if you are Way Out of Town and would otherwise need to have powerlines run to your place. If this is the case you'd save money with them.  The other case would be if you want to hobby around and rig up a system to give you pleasure, either from the fact that you are using an alternative energy form, or you like the idea that you are not adding to the polution of the earth/atmosphere.  The benifit of 'enjoying' hobbying around can not be overstated.  Many people spend Alot of time fishing/playing golf/etc. and never making a dime at it, if fact they would all be better off finanically if they were to pay some kid $6 per hour to do it for them.  That having been said I've a couple of those 'garden path' solar lights that I cut up/lengthened/rigged up to be 'bathroom night lights' that I get So Much satisfaction from Each night.  I've also got a solar panel powered attic fan that will be installed soon.  In the mean time I set it out in the sun and watch it spin, while I'm drinking a beer.  

[dalibor]

I do not know what is a kind of NASA panels, but space use is very different from normal conditions around us. The main problem is of course overheating of panels, when you redirect more and more sun beams to their surface. the best results will be probably when you are trying to heat water with that redirecting method.

[p0lizei]

Oh I agree, my understanding has always been that it is more efficient to heat water and generate steam from that concentrated sunlight, the only reason I would consider using solar panels is if a need for mechanical reliability outweighed a need for output.  

That said, I don't see why heat would be such an issue if the solar panels were kept under vacuum and had some form of basic cooling system.  But see now mechanical components are being added on and reliability goes down.

[JW]

uknow been thinking about this lately.

 I have an aluminum(propane) smelter that wiil melt just about anything. Also I have casted 18in diameter 6in thick Alu. disks with this thing(have the steel molds). Currently I am thinking it would be worthwhile to produce about 4 castings with 3/8in high-pressure tubing buried in the castings. I could propably get 120ft of 3/8's tubing in each one. If such a heat-sink was painted black and placed at the focal point of a conventional 8 or 10ft satellite dish for recieving cable, I would bet you could make some steam using that, if the concave part was reflective, and a low pressure 12v pump was circulating water thru the casting. Im going to have to get around to making these castings soon.

JW

[iFred]

Upto now I have seen concentrators from a distance, shooting the reflected light towards the solar panels, at a distance, but this appears different. I have a single cell 3x6 I could sacrifice and a plastic lens that can be bent and will test it tommorow if the sun shines. Will let you know.

[pexring]

Make one of these castings for me -- would be very interesting to experiment with.

Also hoping its sunny tomorrow so I-Fred can run his experiment.

Mark

[Oso]

The comment "concentrators should work well in outer space, as there is no heat out there" deserves some discussion.

There is plenty of heat out there, it just works differently than here in an atmosphere.

Surface temp of an object in space that is exposed to direct sunlight is about 300 degrees C. If the object is not in direct sunlight, the temp is about -267 degrees C.

Most spacecraft require systems to balance the heat distribution within the craft and to disipate excess heat. Some solar arrays are linked to the heat sinks.  The only temp I have seen for an operating solar array in space is for the array on DS1. They listed the "average temp" as 50 degrees C.

[nothing to lose]

"Surface temp of an object in space that is exposed to direct sunlight is about 300 degrees C. If the object is not in direct sunlight, the temp is about -267 degrees C."

Hmm, maybe they should use a pletier instead of solar panels

Obviously if one side is facing directly into the sun the other side is not. I wonder how that would actually balance out then? Would the center of the object be 0 degree C then?

Or if you place a large object in direct sun, then a small object in the shadow?

[p0lizei]

Hey, now THERE is a good idea.  The reason temperature works that way in space is due to its lack of "air."  No air to "store" heat and you'll have some very very sharp temperature differences between objects exposed to sunlight and objects that are not.  Would this work on the same premise here on Earth, where basically you have your hot side exposed to the sun, and the cold side exposed to high vacuum?  

[ghurd]

The goop they make PVs out of is balanced for the conditions it should see.

NASA might sell some PVs of the right goop for mirrors.

Cheaper, dollar per watt, to use PVs made for use on the Earths surface is my bet.

G-

[Jeff7]

A vacuum is more of a heavy-duty insulator. On Earth, convection is often used for cooling, whether it be air or water. Either way, the heat of one object is transferred into a freely-flowing medium, of which there is a great quantity available. In space, you can irradiate heat. That's it. No convection, save for the occasional atom of hydrogen.

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Obviously if one side is facing directly into the sun the other side is not. I wonder how that would actually balance out then? Would the center of the object be 0 degree C then?

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Nope - bear in mind, 200C is not twice as hot as 100C. Celsius is zeroed at the freezing temperature of water, which is kind of abstract. Kelvin however, starts at absolute zero. So 200C translates to 473K, and 100C to 373K. I don't know if the Kelvin scale is linear; if it is though, something twice as hot as 100C would be 746K, or 473C.

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No air to "store" heat and you'll have some very very sharp temperature differences between objects exposed to sunlight and objects that are not.  Would this work on the same premise here on Earth, where basically you have your hot side exposed to the sun, and the cold side exposed to high vacuum?

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There are many things to account for - how fast the material radiates heat into space, and how much mass is available. The entire object might heat up incredibly quickly, unable to radiate enough heat to let one side remain cold. Or it might radiate heat too fast, and thus stay cold. And distance from the sun is also a factor. NASA's Messenger spacecraft, en route to Mercury, has mirrors in front of its solar panels to shield them from the sun, and the entire array is at an angle, to further reduce the risk of overheating. The rest of the probe is protected by a reflective sun shield.

Then there's the Ulysses craft, out around Jupiter. It is at risk of freezing, as it's able to quickly radiate the little bit of heat is is receiving from the sun, and from its own power systems.