Solar Concentrator Mirrors - How to attach?

cdig · 03-08-11, 09:32 AM

Ok, so I've found ~80 some 12" square mirror tiles for my solar concentrator project. I have a 10 ft satellite dish in the back yard that I plan to use as the concentrator once I refit it with new actuators.

I've been thinking for a bit on how to attach the mirrors to the dish, but haven't had that 'Eureeka!' moment yet... any ideas? I'm thinking I will have to glue the mirrors to some sort of base plate for strength, and to give me something to attach anchor bolts to.. but what? plexi-glass maybe? expensive tho... I thought about 1/2" plywood, but that will likely swell as soon as it gets wet. I was thinking about ceramic tile... but I wouldn't be able to drill into it for anchoring to the dish... ARg!

ideas from anyone that has done this? Ideally I want to be able to attach adjusting bolts at 3 of the 4 corners of each mirror tile in order to allow for alignment to the focal point.

Daox · 03-08-11, 12:19 PM

Are the mirror tiles flexible?

Xringer · 03-08-11, 12:36 PM

Maybe some waterproofed plywood? If you are going to make it 8x8 feet or larger,
1/2" is going to get a bit heavy.
It might be better to use a strong frame, with 1/4" plywood over it.?.

Or, maybe just make a 'light' wooden frame, with a strong center section (for the mount),
and use boards (1 x 1/2?) with a 8" to 12" space between them.
Weather-proof all of it, before mounting anything.

How securely you mount the mirrors, depends on your environment.

Do you live in an area where the weather will be a problem?
Like does it snow a lot there, will the mirrors each get a 20 pound ice load?
Or, do you live down south where a hurricane can rip off the mirrors??

cdig · 03-08-11, 01:06 PM

Daox - the mirrors are 1/8" glass mirror tiles, like they used for 'mirror walls' in the 70's!

Xringer - I live in south central Manitoba, Canada. The dish is currently well sheltered from the north wind, which is my biggest concern in these parts. The mirrors could see a bit of snow load, not much problem with ice storms tho.. I want these things solid on the dish so I can brush the snow off them without messing up the alignment.

1/4" plywood may work, covered with a liberal coating of barn paint to seal it?

Xringer - btw, love your Solar Tracker Project thread...

Xringer · 03-08-11, 05:20 PM

If you mount on a flat surface, perhaps the mirrors could be glued on with epoxy.?.

I wonder if one could use a band saw to cut some dense foam (EPS?) into mounting blocks,
with the precise shapes needed to angle the mirrors?
This is starting to sound like a math job!!

Once a mirror was installed, the whole foam mount could be painted with epoxy. (Like a Surfboard).

If the back of the mirrors and the plywood is primed for the epoxy, then
foam mounting blocks (6"x6") should be pretty solid.. Even with a snow load.

This approach means you won't ever need to make any adjustments..
(You would have to saw the foam in the middle, sand it down and re-glue).

You could do a Fit-Check with light duty spay-on glue.

I assume you are going to come up with a fancy X-Y computer controlled mount??

RobertSmalls · 03-08-11, 06:39 PM

Well, Mike Dabrowski did it by gluing thousands of 1" square mirrors to a parabolic dish. If you need the light sharply focused, your 1' square mirrors will be too coarse. I suppose you could break your mirrors into little pieces.

If you don't need the light sharply focused, then my first thought would be to use hardware, e.g. screws and clasps, to hold the glass in place.

cdig · 03-08-11, 10:01 PM

Quote:

Originally Posted by RobertSmalls

Well, Mike Dabrowski did it by gluing thousands of 1" square mirrors to a parabolic dish. If you need the light sharply focused, your 1' square mirrors will be too coarse. I suppose you could break your mirrors into little pieces.

If you don't need the light sharply focused, then my first thought would be to use hardware, e.g. screws and clasps, to hold the glass in place.

Not sure I understand what you mean... you're saying I wont generate enough heat with 75 to 80 mirrors? I'm looking at building a slightly smaller version of this, although I'll be cheating and using the satellite dish as a frame:

A Tracking Solar Concentrator for the home experimenter, Table of Contents and Notices, page_iii,iv, 10/09/99

What do you mean 'sharply focused' ?

Xringer · 03-08-11, 07:53 PM

I wonder if you could use those coarse mirrors, to melt steel etc, by sending the light to a Solar Fresnel Lens ?

YouTube - New Generation of Solar Fresnel Lens

RobertSmalls · 03-08-11, 08:49 PM

No, because a coarse parabolic mirror has already de-parallelized and almost-concentrated the light.

Xringer · 03-08-11, 09:14 PM

Quote:

Originally Posted by RobertSmalls

No, because a coarse parabolic mirror has already de-parallelized and almost-concentrated the light.

If the mirrors are mounted on a flat surface, that wouldn't seem to add
up to being a parabolic reflector.

I found some pics of mirror arrays..

Solar Fire Project - Welcome

03-08-11, 09:32 AM	#1
cdig Helper EcoRenovator Join Date: Sep 2009 Posts: 61 Thanks: 0 Thanked 1 Time in 1 Post	Solar Concentrator Mirrors - How to attach? Ok, so I've found ~80 some 12" square mirror tiles for my solar concentrator project. I have a 10 ft satellite dish in the back yard that I plan to use as the concentrator once I refit it with new actuators. I've been thinking for a bit on how to attach the mirrors to the dish, but haven't had that 'Eureeka!' moment yet... any ideas? I'm thinking I will have to glue the mirrors to some sort of base plate for strength, and to give me something to attach anchor bolts to.. but what? plexi-glass maybe? expensive tho... I thought about 1/2" plywood, but that will likely swell as soon as it gets wet. I was thinking about ceramic tile... but I wouldn't be able to drill into it for anchoring to the dish... ARg! ideas from anyone that has done this? Ideally I want to be able to attach adjusting bolts at 3 of the 4 corners of each mirror tile in order to allow for alignment to the focal point.

03-08-11, 12:19 PM	#2
Daox Administrator Join Date: Aug 2008 Location: Germantown, WI Posts: 5,525 Thanks: 1,162 Thanked 374 Times in 305 Posts	Are the mirror tiles flexible? __________________ Current project - To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. & To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

03-08-11, 05:20 PM	#5
Xringer Lex Parsimoniae Join Date: Feb 2009 Location: Woburn, MA Posts: 4,918 Thanks: 115 Thanked 250 Times in 230 Posts	Permanent Pre-Adjustment If you mount on a flat surface, perhaps the mirrors could be glued on with epoxy.?. I wonder if one could use a band saw to cut some dense foam (EPS?) into mounting blocks, with the precise shapes needed to angle the mirrors? This is starting to sound like a math job!! Once a mirror was installed, the whole foam mount could be painted with epoxy. (Like a Surfboard). If the back of the mirrors and the plywood is primed for the epoxy, then foam mounting blocks (6"x6") should be pretty solid.. Even with a snow load. This approach means you won't ever need to make any adjustments.. (You would have to saw the foam in the middle, sand it down and re-glue). You could do a Fit-Check with light duty spay-on glue. I assume you are going to come up with a fancy X-Y computer controlled mount??

03-08-11, 12:36 PM	#3
Xringer Lex Parsimoniae Join Date: Feb 2009 Location: Woburn, MA Posts: 4,918 Thanks: 115 Thanked 250 Times in 230 Posts	Maybe some waterproofed plywood? If you are going to make it 8x8 feet or larger, 1/2" is going to get a bit heavy. It might be better to use a strong frame, with 1/4" plywood over it.?. Or, maybe just make a 'light' wooden frame, with a strong center section (for the mount), and use boards (1 x 1/2?) with a 8" to 12" space between them. Weather-proof all of it, before mounting anything. How securely you mount the mirrors, depends on your environment. Do you live in an area where the weather will be a problem? Like does it snow a lot there, will the mirrors each get a 20 pound ice load? Or, do you live down south where a hurricane can rip off the mirrors??

03-08-11, 01:06 PM	#4
cdig Helper EcoRenovator Join Date: Sep 2009 Posts: 61 Thanks: 0 Thanked 1 Time in 1 Post	Daox - the mirrors are 1/8" glass mirror tiles, like they used for 'mirror walls' in the 70's! Xringer - I live in south central Manitoba, Canada. The dish is currently well sheltered from the north wind, which is my biggest concern in these parts. The mirrors could see a bit of snow load, not much problem with ice storms tho.. I want these things solid on the dish so I can brush the snow off them without messing up the alignment. 1/4" plywood may work, covered with a liberal coating of barn paint to seal it? Xringer - btw, love your Solar Tracker Project thread...

03-08-11, 06:39 PM	#6
RobertSmalls Journeyman EcoRenovator Join Date: May 2009 Location: Buffalo, NY Posts: 344 Thanks: 3 Thanked 17 Times in 15 Posts	Well, Mike Dabrowski did it by gluing thousands of 1" square mirrors to a parabolic dish. If you need the light sharply focused, your 1' square mirrors will be too coarse. I suppose you could break your mirrors into little pieces. If you don't need the light sharply focused, then my first thought would be to use hardware, e.g. screws and clasps, to hold the glass in place.

03-08-11, 07:53 PM	#8
Xringer Lex Parsimoniae Join Date: Feb 2009 Location: Woburn, MA Posts: 4,918 Thanks: 115 Thanked 250 Times in 230 Posts	I wonder if you could use those coarse mirrors, to melt steel etc, by sending the light to a Solar Fresnel Lens ? YouTube - New Generation of Solar Fresnel Lens

03-08-11, 08:49 PM	#9
RobertSmalls Journeyman EcoRenovator Join Date: May 2009 Location: Buffalo, NY Posts: 344 Thanks: 3 Thanked 17 Times in 15 Posts	No, because a coarse parabolic mirror has already de-parallelized and almost-concentrated the light.