Solar collector

In the spirit of recycling, I experimented with a solar collector made from shiny hard disk platters. Here's a picture of it before I had the full set of platters.

When I found out about RepRap, I saw a way to remove the tedium of aligning the individual platters. A computer-modelled base printed by the RepRap, would allow the user to simply attach the platters to pre-aligned facets provided on its surface.

Well that's my two-cents' worth anyway.

Regards
Joseph

Edited 1 time(s). Last edit at 05/10/2008 05:00AM by josegatt.

Hi Joseph

... i tried with plastic-mirrors from our tool-store (can be found in the art/deco or as tiles in bath/kitchen) cut in 4x4mm-squares and glued on the inner surface of a 60cm-satellite-dish - works very good, but with glass-mirrors it's much better!

When i'm comming to this some time again, i want to order some houndred small circular glass-mirrors and recycle an old 120cm-dish (we use as cover for the sandbox of the children), o build a solar-oven or a solar-tracing high-temp-solar-generator ...

Viktor

Wow, that's really a great idea! I guess it's also in the spirit of what many of us are trying to achieve: create sustainable solutions to the world's important problems!

I think you want to print part such that you can easily identify what goes where and precisely have the parabolic shape to obtain the desired focal point. You can probably do this with boolean modeling by subtracting a lathe'd curve from a sparse base. At least that's what I would try in AoI... Haven't worked enough with it to know exactly how I'd do it eventually. Other ways may work better. I would really like it if you published your model files, I have SOOO many CD's laying around and my father has a farm where we have enough space to build a test setup. I think the solar panel needs to move in order to adjust for the 'sun's rotation around the earth' (everything is relative, don't you agree? )

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Regards,

Erik de Bruijn
[Ultimaker.com] - [blog.erikdebruijn.nl]

Hi Eric,

... CD's aren't so good mirrors - when you have a parabolic surface then it's much simpler and more efficient glueing aluminium-foil on it.

With a good finish and using spray-glue it's nearly a perfect mirror for the sun with a spot in the size of 2 to 4 centimetres - this is much more heat then with the suboptimal CD's, which give a spot of 11 cm diameter only and with a poor reflection-efficiency too ...

Viktor

i recommend shiny copper foil for making solar ovens, reflects heat well. also you can model it into needed shape easily. remember its more important to reflect heat than visible light

Last year I built a parabolic solar oven for school. I created it by making 'leafs' of cardboard covered in aluminum foil which I then duct-taped together. Since I needed leeway to correct for my inaccuracies, I made it very bell shaped. It was about 3ft high and 3ft wide at the top, with a focal point 10 cm or so from the base. The goal was to cook one of those tiny bite-size pizzas or a hot-dog, so the focal point was about 3 inches in diameter or so. The advantage of the tall design was that it cooked the food very evenly, because it was cooking from all sides and not just in one spot. As I like to say, the proof is in the puddin', and the cooker was able to cook the pizza faster than a microwave could. It take 4 minutes in the microwave, but only 1.5 minutes in the solar cooker. I am currently designing a collapsible solar cooker which could be carried in a backpack. I am thinking of using a space blanket backed with canvas for strength as the main materials. Here are my sketches.




Edited 1 time(s). Last edit at 05/11/2008 07:53AM by Jay Swift.

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Jay

The Mythbusters on TV did say glass mirrors are the best, but if Viktor is saying it, it must be true

Course, one still has to figure out a good tracker for it to be any good. Again, the Reprap could print brackets and gearwheels.

As for my collector, I think it's up a dead end, because the base is disproportionately heavy. My next attempt will have to be much lighter.

Regards
Joseph

Hi Joseph,

... sorry, i didn't get the point with the Mythbusters and glassmirrors - for me glass-mirrors are the best solution too, especially if you use metall-coated types with the coating on the outside (because glass absorbs some of the energy and 'damps' the sunlight)

But glass is heavy too, so for a portable solar-oven you should use light-weight materials as thin elastic sheets covered with aluminium-foil or such ...

There are some nice solar-ovens made from PVC-foil you can inflate to bring them in the right form - they are transparent on the concave side and the mirror-coating works 'through'.

For your device concerning weight - you should use styropor/styrofoam in 1/2- or 1/4-inch-plates, so you can cut some concentric rings and stack them together to get a parabolic base with no mass ...

Viktor

For concentrated solar applications the usual thought is to make dishes (because of all the solar cookers?)

It's also possible to use a fabbed (read precise) frame to create a Fresnel like mirror structure that can be flat from a macroscopic perspective. I know Fresnel applies to lenses, but the same principle applies to for mirrors. It would contain many smaller flat mirrors (adding up to a little bigger focal point, but that doesn't need tot be a problem). Surfaces curved in two dimensions are at least a bit harder than completely flat ones... so if the it's actually an assembly of flat faces, you evaded this problem.

There's also a good reason to make an elongated profile of a parabolic curve which extends straight (so a paraboloid curve in 1 dimension). You could heat a collector pipe that generates steam. The tracker would then only have to adjust to one angle of the system. Not that the idea is new, I am reminded of some pictures I saw of these, but I think it's possible to build this structure with the aid of fabbing. When the structure gets bigger I think a steel frame is needed but the pieces 'connecting the rods' (not just the dots) is something we already have experience in. Especially if you build a growing production line of repraps to build massive solar collector structures. I'm not sure how fabbed corner brackets would do compared to plain-old welding in terms of total cost (time and material resources)... although we are welding... plastic that is...

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Regards,

Erik de Bruijn
[Ultimaker.com] - [blog.erikdebruijn.nl]

Here is a place that supplies reflective film. I have purchased from them and they supply quality product and very quick service. This is a company I dealt with back in my solar days.

[www.mirrorsheeting.com]

Your mileage will vary.

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Bob Teeter
"What Box?"

Great work! Now if reprap could only print a Stirling engine so we can get reprap running on solar power. This requires the ability to cut or mold metal though... If we could achieve total replication, we might be able to do this: [www.molecularassembler.com]

The key parts of a solar water heater are the solar collectors that grab and concentrate the energy coming from the sun and the storage tank. Such simple setup is usually called passive solar power.Here is a link that might be useful: solar heat information

Glue them to an old satellite dish, and they aim for you: [www.phunguss.com]

happy cooking!