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MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329
Posted: 04:41am 05 Jan 2010
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Has anyone had any experience using reflected sunlight on a PV array?
In all my "tracking" solar projects using a concentrating collector (for heat), I always mount the concentrator in a fixed position facing north. I live in California, USA -- latitude + or- 38 degrees. I then track the sun's movements and reflect the light onto my fixed target using a flat-plate mirror (heliostat) (for a number of reasons).
If reflected sunlight gives the same or nearly the same output as direct sunlight, it seems to me using a flat-plate, tracking heliostat would be way easier than moving the 'working end' of things.
Nothing difficult is ever easy!
Perhaps better stated in the words of Morgan Freeman,
"Where there is no struggle, there is no progress!"
Copeville, Texas
Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904
Posted: 03:20pm 05 Jan 2010
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My solar panels (2) come to 2.5m2. This would require a rather big mirror and space to set it all up. It was simpler to get the panels to track on the shed roof mounted tracker.Klaus
GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127
Posted: 10:26pm 05 Jan 2010
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For PV systems, concentrators are not really suitable around a home. Greengoldenergy are still working on concentrators. Have not seen much activity for domestic systems. I played around with mirrors, but there was just more surface to keep clean.
Applications with steam and parabolic reflectors offer more.
I think the moving parabolic trough reflector with a pipe for the working fluid at the focal point is best. Point systems offer high collection gain, but require more control systems.
Parabolic troughs only require a single axis tracking.
Gordon.
become more energy aware
MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329
Posted: 04:40am 08 Jan 2010
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Klaus & Gordon
I should have explained in more detail on my original post maybe. I make my own concentrating solar mirror by bending a 90-degree cone out of sheet metal and lining the inside with reflective mylar glued on. Then I cut out the back of the cone to make it easier to mount. This section has a name, but it eludes me right now. Fustrum? Something like that.
Anyway, the focus (for me) is a single piece of copper tubing bent in the shape of a "U". It extends from the center of the cone at its apex end up through the center of the thing as prescribed by the center of the circle formed at the outer edge of the cone, then back again. Through this litle tube, I pump oil and it gets REALLY hot!
I tried housing the focal axis in a glass tube once, but the tube lasted about an hour and then broke. Got too hot, I guess, eh? Besides that, I think it also reflected some of the incoming rays of sunlight, which was counter-productive.
Hope that clears things up a bit. "I" use the heliostat to facilitate my focal point (line) remaining fixed, but my entire target is less than 3 feet by 3 feet. I meant to share my technique basically for those using a concentrator to achieve gibungas (new word giant + humungous) temperatures.
On a different note:
I received a private message stating a concern about reflected light causing a heat build-up on the surface of their PV panels. I'm posting my reply here, because I think it has some merit and may help someone else. This person wanted me to sign a confidentiality contract before talking further on the subject because he thought his idea was "patentable".
Here's my reply:
Woops! You let slip the magic word: Patent. I'm specifically anti-patent.
I've spent my whole live giving, so you've arrived too late. Should have caught me 50 years ago maybe, eh? In my opinion, I think you'll find most of the folks that post on the 4m feel like I do about patents. They serve to keep information out of people's hands. Patents are greed oriented.
I've invented hundreds of things and let them all go for free. I found out many, many years ago how to garner a 6-figure income working 4 hours a day, so I'm not driven by money. In case you're wondering how I did that, it's easy. I charge a bundle for my services!
Here's a free one for you: It is my understanding that solar PV cells operate on frequency more than intensity. If that's correct, why not cover your array with something like Tyvek or some other sheet material that will transmit the correct frequency range and stop most of the heat?
Nothing difficult is ever easy!
Perhaps better stated in the words of Morgan Freeman,
"Where there is no struggle, there is no progress!"
Copeville, Texas
Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904
Posted: 12:51pm 08 Jan 2010
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Solar PV cells operate on light. Any light. The more intense the better. Sunlight is best .
So, covering the solar panel with anything that restricts the passage of light will be counter productive.Klaus
MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329
Posted: 05:03pm 08 Jan 2010
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Well, you know what they say; you get what you pay for! Apparently, I'm incorrect (note disclaimer in original post).
I'll try harder next time. Nothing difficult is ever easy!
Perhaps better stated in the words of Morgan Freeman,
"Where there is no struggle, there is no progress!"
Copeville, Texas
rgormley Senior Member Joined: 22/02/2006 Location: AustraliaPosts: 245
Posted: 10:57pm 08 Jan 2010
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yea i dont get it how can this "tyvek" be of any benefit...
simply getting more light onto a panel would be beneficial i would have thought. (what spectrum causes heating effect? maybe a film that cuts that spectrum? so as to allow light but not the "heating" part of the light spectrum?
http://en.wikipedia.org/wiki/Tyvek
or am i of in na na land...
MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329
Posted: 02:45am 11 Jan 2010
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rgormly
Tyvek is a building cloth used on a wood-frame, type 5 building in the states. It is applied under the exterior wall covering and acts as a wind barrier for the most part. It is supposed to reduce heating and cooling costs, I think.
I only mentioned the Tyvek, because it's very durable, thin and white. I was interested in passing "white" light, which would include the full visible spectrum, not really knowing if solar cells operated on intensity or frequency.
If you wanted to keep the heat off, I'd block the lower-frequency light, which is to say the red and orange. Remember Roy? That would be ROYGBIV (red, orange, yellow, green, blue, indigo, violet) and the frequency goes from low to high, left to right.
I guess a quick and dirty method might be to cover the cells with a blue- tinted material, which would pass only the higher frequencies of light. I don't really know if this would necessarily block the heat, but it might be worth a try (on a small scale first) to se if it works.Nothing difficult is ever easy!
Perhaps better stated in the words of Morgan Freeman,
"Where there is no struggle, there is no progress!"
Copeville, Texas
neil0mac Senior Member Joined: 26/12/2009 Location: AustraliaPosts: 210
Posted: 03:27am 11 Jan 2010
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From what little I understand it is the higher (UV) frequencies that contribute to the browning of the panels.
Prepared to be proven wrong.
Maybe, we just need a dirty great glass prism to shunt the UV and infrared rays either side of the panels?
MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329
Posted: 04:00am 11 Jan 2010
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Correct me if I'm mistaken, but I think the "browning" of the panels is due to UV degradation of the plastic used in the manufacture of the panels. I don't think UV contributes to heat much.
I could be wrong though; it wouldn't be the first time. Come to think of it, it wouldn't even be the first time TODAY!Nothing difficult is ever easy!
Perhaps better stated in the words of Morgan Freeman,
"Where there is no struggle, there is no progress!"
Copeville, Texas
neil0mac Senior Member Joined: 26/12/2009 Location: AustraliaPosts: 210
Posted: 07:18am 16 Jan 2010
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The debate doesn't seem to have any conclusive evidence either way - at least, not in the public domain.
I've had 'experts' avow that it is an 'excess of light' (UV - or even other?) while others maintain that is just heat absoption by the glass in the panels and even heat absorbed through the back of the panels.
Using a UV filter (or UV Glass) might reduce that part of the problem, but I'm told that it reduces the light transmitted to the cells by 3(?)%. That looks like 'protetion at reduced efficiency - doubtful trade-off.'
The 'scientists'/manufacturers seem to be deathly quiet on the matter.Edited by neil0mac 2010-01-17
neil0mac Senior Member Joined: 26/12/2009 Location: AustraliaPosts: 210
Posted: 07:48am 16 Jan 2010
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To answer your initial post, Mac, have a look at www.pvcool.com.au.
They have a very attractive (and novel) northern European approach to solar PV panels. (OK. They've upgraded their web site thi year! Now offering '145W panels' at $3.80 per Watt, retail. Same principle, slightly different application.)
MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329
Posted: 08:06pm 16 Jan 2010
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neil0mac[b/]
I tried your link and got this:
Forbidden
You don't have permission to access /index.php on this server.
Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.
HostingBay Server at www.pvcool.com.au Port 80
Nothing difficult is ever easy!
Perhaps better stated in the words of Morgan Freeman,
"Where there is no struggle, there is no progress!"
Copeville, Texas
neil0mac Senior Member Joined: 26/12/2009 Location: AustraliaPosts: 210
Posted: 09:25pm 16 Jan 2010
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OK. I went to www.pvcool.com.au and hunted around for links to solar panels to find the URL.
Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.
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