parabolic dish sun collector...

[joelutz1]

Dan M. submitted an article about using a satelite dish for collecting sol's rays.  I recently bought an old 10' diameter satelite dish for cheap on ebay.  I will be picking it up soon.  I'm interested in lining the dish with old compact disks (very lightweight, inexpensive, easily replaced, etc.) to reflect the sun.  Anyone know if that will work?  I will also need the controls and motors for tracking the sun.  I am considering a low tech method for doing that, i.e., programming a computer to move the dish horizontally and vertically every ten minutes throughout the day, instead of using electronic sun directional sensors or the like.  Anyone have experience with that?  Any ideas you may have on this project would be most appreciated.  Joe L.

[Dan M]

I'm not sure, but I think the small changes in surface contour on a cd would play havoc with trying to build a reflector.

This is all intuitive, so if it's all wet, somebody please say so.

When you move a cd in the light, you see lots of pretty colors.  This would suggest the there is some sort of primsatic effect going on.  It seems that this would be detrimental to getting a good reflection.

Try bouncing a flashlight beam off one of them and see if it reflects the way a mirror does.

The more I thought about it, the more sense a parabolic trough with a pipe running along the focal line made.

You can point the rotational axis at the north star, and you only need one axis of tracking.  Do a search here for my old postings.  There were some links posted by others for tracking equipment.

Have Fun,

-Dan M

[mlz]

Joe, the CD's may work, IF you only use the prerecorded ones.  I.E. the ones that are silver on the data side.  As to tracking, there are several low cost DIY trackers out there, a computer would cost more to interface than building the tracker, plus your computer would have to basically duplicate the tracker for it to be much use.  

Look for the led heliostat, works good.  You'll also need an couple of actuators, you probably will get one with the dish.  A little digging and I'm sure you can find another on the cheap.

[wooferhound]

OK ,  Plenty of CDs around here ,  lets see . . .

 (putting CD in sunlight to check reflection)

Nope ,  to much defraction to make it work very well

  Not a great amount of reflectivity

    There is a nice hot spot reflection coming off of the thing, but not as bright of a reflection as a mirror, and lots of light coming off at odd angles helping it to be less bright.

I did a quick search of the board and found these stories that are talking about the materials you need to coat your dish with to get the best output.

http://www.fieldlines.com/story/2004/11/1/75954/0065

http://www.fieldlines.com/story/2004/9/29/73248/7777

http://www.fieldlines.com/story/2004/9/2/82718/60523

http://www.fieldlines.com/story/2004/9/10/124321/835

[dalibor]

Yeah, i had a word or two about it with friend of mine. How about using thin aluminium - usually used for baking, keeping food hot, protecting apple pie from tigers :-) etc. just use some glue,it is very nice material for covering any shape. i dont know about reflecting abilitties, i guess they are acceptable.

[BruceDownunder]

I thought about covering my 3 Mtr. dish in those 1 inch square mirror tiles that were popular years back. I'm sure  u can still buy them . Just use a good contact glue/ Silicon. Lay dish horizontal and start from lowest area moving upwards will be easy to stick the tiles on as they will rest edge on to the lower tile.

Just a thought

Bruce

[monte350c]

The dish is a good start - it should have an accurate focus.

There is purpose made material for reflectors ( http://www.cleardomesolar.com/ )

Doesn't seem that expensive, and if you're going to the trouble anyway...

Have fun with your project, and I'd be interested to hear how it comes out.

Ted.

[geoffd]

I have just started along the same path, I am experimenting with a 80 cm dish and 2 cm square mirrors.  I have the dish and the I have ordered the mirrors.  I am also designing a circuit for dual axis light sensor based tracking.  I will probably use 12 volt window wiper motors for moving the disk with a simple gear based on an old bicycle wheel.

Once I get it designed and working I will post up the circuit here, mind you, it will be a month or so before I get it finished.

Cheers

Geoff

[Norm]

   CDs do not work....now is the time to develop your glass cutting skills if you aren't already adept at it why order l inch squares? Just cut them yourself from old mirrors. The beauty of it is that you can even use the little 'oopsies' that didn't quite break square! I guess you would call this fuzzy science...it doesn't have to be perfect...it'll still boil some water just about as quick.

   Scrap mirrors are cheaper than ones you can buy at Lowes or Wallymart!!

               ( :>) Norm.

[dalibor]

when you have that sensor based tracking circuit done, will you put it here on the board? it would be quite useful to all of us :-). thanks!

[geoffd]

No problem, but it will be a while as I have a couple of other projects to finish first.

Cheers

Geoff

[fcfcfc]

ReflecTech, Randy Gee makes a good film product. I have a couple hundred square feet of it for my own never ending 3m dish project.

If you are still looking for a material to cover your dish with, send me your shipping address and I will cut you a square foot or two of the film, and you can "get a feel for it", no charge.

Just go to my website and you will find contact info. there.

www.fitchconsultinginfo.com

.....Bill

[Keyman]

Patriot Sattelite Inc. In Albion Mi. is using a highly reflective finish on several of thier dishes. They can concentrate the energy (heat) and create steam turning salt water to fresh. These are being used by the Navy now as a method to make fresh water on ships. They are also using the parabolic reflective dishes with fiberoptics to pipe light into underground facilities. both great ideas I think.