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"designer" to help make exotic reflectors for unattended solar cooking. Answered

I have been thinking about this idea for a while but there are so many options that  I took a while to pick one.  One idea was to have the 2 laser pointers on a turret like a microscope and move the model around underneath.
Before you discount it as rubbish, please look about 5 minutes into this video  And pause it at about 5min 50 to see the "tuba like horns"
http://www.youtube.com/watch?v=TSMzKg6fwJ8    HIs design was done by computer and in my view is way too complicated but I hope it opens peoples eyes to some of the failings of parabolic dishes for unattended solar cooking.
There ARE other options and they do not look anything like what we imagine.
I believe that people can design exotic fairly high efficiency solar cookers (with a range of cooking times)  using the method I show.
If anyone wants to help make the instructable more understandable, I can open it and make a collaboration.
Or I can credit people for their input.    Also, it is community commons so it is no longer my idea,
release and improve it anywhere you want.
I will be improving the instructable myself over the coming weeks but do not expect instant improvement.
The instructable is at https://www.instructables.com/id/Method-for-designing-reflectors-for-unattended-sol/
and I have attach a pic here to get people started (I will improve that picture too).
Brian


Discussions

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gaiatechnician

8 years ago

Just a note that I put 2 videos on youtube to further explain what I am trying to do here.
They are
http://www.youtube.com/watch?v=NFjuoDVU4c8
and
http://www.youtube.com/watch?v=xbiVo12kuKA
It helps to watch the first one before seeing the second one.  (I think).
Brian

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gaiatechniciangaiatechnician

Reply 8 years ago

Thought I would give a progress update
http://solarcooking.wikia.com/wiki/Solar_design_T-Square is the new main page for the project and
http://solardesign.ning.com/photo/albums/solar-design-tsquare has the latest pictures.  I ended up using little mirrors for the models. I stuck them in cob. I did 3 models.  A 1 hour model, and a one shell 2 hour model  and a 2 shell 2 hour model. 2 shell models just  take too long for my patience and I abandoned it got finished.  I only did a half model on the other 2 hour one. (Ran out of little mirrors) and no more available in town!  I have one more model to make and that is it! Maybe someone will follow through.  This got the most response of any of my projects.  A scientist who wrote a book on solar concentrators said I should get students to investigate it.  I have not found too many students interested in low tech stuff in my life.  Do you know of anyone?
Brian

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lemonie

8 years ago

Do you not want one laser on an arc, to represent the movement of the sun?

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gaiatechnicianlemonie

Reply 8 years ago

I think that would be a very good idea.
I am just not sure I could do it myself.
The point of the arc is where the 2 lasers come together in my little diagram.
If I was doing it, I would need some little hinge there.  Someone else with more skills could cut a curved race or path for the laser and just move the laser through the race.
If you do that, you end up having to do the "microscope thing" for focusing the circle center of your arc.
You probably need a little wire to locate it too.
I just  do not have not enough skills to do it that way.
Brian

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lemoniegaiatechnician

Reply 8 years ago

This sort of thing would give you your sun-angles, you'd move the test-piece around under the arc.
?

L

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gaiatechnicianlemonie

Reply 8 years ago

Thank you.  I hope to get a lot more done today.  I have a few protractors.
I will set up both pointers for 75 degrees.  One left one right.

I will label the laser pointer pictures in the forum above a bit better now.
Hopefully I can get them onto the t square and make my first demo model today.
I might have a few problems because the pointers do not stay on when I turn them on.

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lemoniegaiatechnician

Reply 8 years ago

Yea, I have a dodgy-switch on mine.
But you'd want to consider the other angle - as the sun has altitude and azimuth. Unless you're modeling for the equator you don't want an altitude of 90o
But then, if you assume the collector will be angled towards the sun, you're taking that factor out in your test piece.

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gaiatechnicianlemonie

Reply 8 years ago

One of the presumptions I have made is that the  reflector is set up on equatorial mount. 
This has to be the case with the design I have in mind. 
Because otherwise you cannot accurately line up the long axis of it with the path of the sun.
Equatorial mount might take a bit longer to set up but it has quite a few advantages.
I am uploading pictures now which will go some way towards explaining things further.
Thank you Brian

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lemoniegaiatechnician

Reply 8 years ago

Ah yes I see it. You've got a cheap pointer and a more expensive one for attaching to a gun?

L

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gaiatechnicianlemonie

Reply 8 years ago

I have 2 cheap pointers. They are both rubbish. Both lost their tops and I had to tape the battery compartment shut on the second one. They are exactly half inch diameter so I just drill a half inch hole in the wood and they fit really snugly,
The good thing is that clothes pegs are perfect to keep them turned on.
I was going to use  laser levels but they were too heavy. I am removing the laser level pic now.
Thank you for your interest. It kept me going.
I do not know where I will get suitable strips of material to make the reflector model. And I need to think of something to but up against the material to keep it in place too. Maybe tomorrow?
Brian

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lemoniegaiatechnician

Reply 8 years ago

Empty drinks cans may do for a model, as I suggested somewhere else Plasticine or other "modelling-clay" being mouldable may be useful to back-up the reflector on e.g. a wood base?

L

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gaiatechnicianlemonie

Reply 8 years ago

I think the drinks cans do not work.  When you shine the laser on them, the light does not bounce correctly. Perhaps something to do with the way they are made?  I think there are microscopic ridges on the metal. In one direction the bounce is fairly correct but in another, it is totally wrong. It turns into little circles.
No modeling today! I finally went back to work after my illness.

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lemoniegaiatechnician

Reply 8 years ago

Yes I can imagine that. Combine with foil? Might be a bit fiddly to avoid creases though.

L

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lemoniegaiatechnician

Reply 8 years ago

I am thinking of the arc, set at the correct angle. You trace the virtual sun across the day in minutes / seconds - this is the idea of using the lasers isn't it? Big arc, set at an appropriate angle, you can do the development indoors after sunset?

L

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gaiatechnicianlemonie

Reply 8 years ago

I use the lasers so that I can isolate the effects of changes I make to one point at a time. And of course to do the development indoors.
Brian

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gaiatechnician

8 years ago

Well, anyway, I am stuck for the moment. I want to support the strips securely after I adjust them and I have not found a good system yet.  Flowerpots do not do a good  job! 
I guess each one will be supported at 3 or 4 points. 
Lemonie suggested blutac or double sided tape. 
I did not get to try it today. (I still need to get things to put behind the blutac)
Anyway, in the meantime, I found this link on the net. (I was looking for a picture link of Bill Grosses "tuba-like horns" when I found it).
http://en.wikipedia.org/wiki/Holmdel_Horn_Antenna
Has anybody ever done a box cooker with one or 2 ears?
Because the picture looks like a box with one huge ear!
Of course, the dimensions of a horn for collecting solar radiation would be quite different and would change depending on how many hours of light you intended to collect.

Brian

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NachoMahma

8 years ago

.  Your drawing looks a lot like a CNC machine to me. Maybe you can get some ideas by looking in that direction.

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gaiatechnicianNachoMahma

Reply 8 years ago

Thank you.   I am pretty clear on the ideas.
Explaining it to other people does not come easy though.

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gaiatechnician

8 years ago

I made a little track from molding wood and I can hang the lasers on it.
I show it mostly on its side.
It works.
I just have to get it to the right angle for both sides,  attach it to the T square tomorrow and start a model.
Brian

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rimar2000

8 years ago

1) I couldn't view the video (maybe Youtube is temporarily dead)
2) To align my arrangement of mirrors, I use: a) a vertical collimator (which sends a thin beam of light, almost like a laser), b) an horizontal table, c) a strut that holds a piece of plastic in the place where should concentrate the rays.

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gaiatechnicianrimar2000

Reply 8 years ago

http://www.ted.com/talks/bill_gross_on_new_energy.html has basically the same video and if you just jump to 4 minutes 30 or 5 minutes in, you will see the important part.
The idea I show  is a table to design non tracking solar concentrators for unattended use.
For the concept that I show, the concentrator must be alligned with the path of the sun (So it has to be on an equatorial mount). one laser is for the start of the sun's path across the concentrator and the other is for the end of the sun's path across it.  My hope is that if the light bounces and hits the target at the start of the sun's path and at the end of the sun's path, then it will also hit the target at all points between.
Gross's concentrator does not need to be lined up with the sun's path but it may be too complicated to make.
I hope that concentrators designed with this will be a lot simpler. I am guessing they will be more like 2 leaves or 2 flowers that line up with the sun's path.
But this will depend on how far the designer wants to go.
Brian

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rimar2000gaiatechnician

Reply 8 years ago

In the attached photo you can see a previous version of my equatorially mounted solar cooking. It was a success, but I'm making some improvements. The idea is good.

The arrangement of mirrors worked much better than my previous attempts to use film of aluminized mylar or polystyrene.

To maintain focused the "parable" requires only a small electric or spring motor (spring is good for remote locations), I have not yet installed it but it can not be very difficult to achieve. I have not enough time to devote to the project.

IMG_0988.JPG