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In this answer Russel says solar panels are:

a sandwich of glass + bonder + silicon PV cells + bonder + backsheet

This got me wondering how much of those materials are needed to make the solar cells easy to transport and/or install. Assuming (for the sake of this question) that I invent a robot that will 3D-print solar cells directly on to my roof, how could such a machine work, and would it still need all those layers?


EDIT: to clarify, the main thrust of my question is: isn't the backsheet (and its bonder) just needed for ease of transportation? And isn't the glass needed for protection? (e.g. so if I am putting silicon PV cells directly on the roof, and not needing to transport/install big panels, can this glass be much, much thinner, or even done away with completely, and some simple waterproof spray used instead?). I.e. do the backsheet and glass layers do anything beyond make the panels easier to transport and install?


In addition, and especially as this is the Sustainable Living site, how might their overall energy cost compare? E.g. we have solar cars, so a robot crawling over my roof using only solar-power seems reasonable. Assume I have a good source of sand within 1km. Can I just pour sand in to get the silicon, or is making silicon from sand in your own back-yard not reasonable, and is always going to require a big facility?

P.S. I'm not asking how to do the above today. I'm wondering with say 5-20 years of direct R&D effort, what kind of product might be possible. (And I'm thinking not just roofs, but also robots that paint solar panels on top of deserts, or over radioactive areas of Fukushima, etc.)

  • Current technology requires pure silicon which is then doped with tiny amounts of carefully selected impurities. The crystal structure is also important. 3D printing that would have to happen at the atomic level "74 atoms of silicon, then an atom of gallium, 26 atoms of silicon, an atom of tellurium...." and likely have to be done in a vacuum to stop immediate oxidisation and even an inert gas would probably cause enough Brownian motion to be a problem. A much more likely approach is the organic PV systems that can be painted on. – Móż Feb 14 '14 at 1:01
  • Actually, given that level of 3D printing, you'd probably also have Maxwell's demon tech, so you could probably use sand and old computers as the inputs. – Móż Feb 14 '14 at 1:10
  • @Ӎσᶎ Thanks: your comments, together, would be great as an answer. (I found redorbit.com/news/science/1112845619/… but do you have a better reference for organic PV that can be painted on?) – Darren Cook Feb 14 '14 at 4:16
  • As far as I know they're very much a theoretical thing where people have sort of got the parts working in the lab. There's not yet an actual "paint on panel" anywhere, even in a lab. The big challenge is making them amorphous enough to paint on, rather than needing exact microstructures. – Móż Feb 14 '14 at 4:51
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Not reasonable to do. Firstly, what you describe is only the final assembly. I don't see any advantage to doing that on site instead of at a plant. And I see considerable disadvantages.

Paint on PV while demonstrated in the lab, has serious issues with longevity.

Even at the household scale the infra-structure is now more expensive than the PV panels themselves. Supporting frameworks, DC-AC converter, intertie so that if the grid goes down so does your system (otherwise your system can kill a lineworker who thinks that the lines are de-energiesed.

Implementing this on a large scale runs up against system issues -- you need the right sized wires to each panel, you need to aggragate the lines together, you need to keep all the AC in phase.

Doing it by robot on abandoned land? The present state of robot art barely allows vehicles that drive themselves on a road network. Doing this on land that makes service calls impossible is a non-starter. Get it to work in someplace tolerable, like the Sonoran Desert.

DIY is quite practical for solar hot water, especially if you have a use such as a swimming pool that can use large quantities of not very hot water.

  • Thanks for the thoughts. Re: the advantage of on-site, items that are only needed to make the panel strong enough to transport, or easier to install, are no longer needed. Thus saving fuel (and raw material). – Darren Cook Feb 21 '14 at 2:35
  • BTW, do you have any reference for the longevity issue with paint-on-PV? (I would've thought wiring it up would be the big issue, but then I don't really understand how it works :-) – Darren Cook Feb 21 '14 at 2:37

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