High temperature solar … sand bricks.

This started with a fascination with Markus Keyser’s solar sinter. After unsuccessfully trying to get a Fresnel lens cheaply, I gave up on this idea. It also just didn’t seem that easy to do; too much fiddling for a hobbyist. When I sniffed around his website some more, I got the feeling he felt the same way. Compare his more recent 3D glass printing which I think could be done by melting the sand with a solar thermal collector (more on this below), and then interestingly, when I found his thesis defence, his wider logic was particularly impressive.

He talks about “multi-agent communicative entities assembling larger constructs out of simple, unifunctional, ’generic’ materials. ” His thesis focus was to “depart from these uniaxial manufacturing approaches and develop a novel swarm-inspired distributed digital fabrication method capable of printing tailorable multifunctional materials that is also collaborative. ” I really like that. It has a biomimicry feel, a decentralised co-op action that could work for countries like South Africa trying to shift how they manufacture.

Bowl made by Markus Keyser’s solar sinter

My ultimate goal would be to make pretty things from very high solar temperatures. I really love the bowl he made, and that low-poly, or granular look I think could work well for sculptures at a large scale, or things like earrings at a tiny scale. Being made locally with local materials and the sun, that appeals to me. But for starters, I need bricks to build a house with in my new place in Hopefield, and I need a road because all vehicles that tried to enter my place got stuck in the sand.

Inspiration for my house, from https://www.designboom.com/architecture/team-group-sunken-courtyard-bagh-chal-iran-02-18-2020/
 ‘sunken courtyard’ or bagh chal, subsurface house to keep cool in summer.

So the purpose of this post is to research how to make sand bricks, for a start.

The first thing was to look at if this can indeed be done, and how.

From a brief internet search, I found a depressing answer and an inspiring one. On Quora the answer was a brutal “That’s probably the most complicated, tedious and inefficient way anyone has ever devised to make bricks. It would be economically unfeasible.” (Can you believe it. Shitting on innovation like that. The real economically unfeasible thing for any product is transport, and this tries to use local material. And of course it’s going to be expensive at first. And it’s friggin art, who cares about the price. Anyway. #triggered.)

Inspiringly, this mechanical engineering internship thesis from the University of Twente also exists, with the theoretical calculations, and an evaluation of the potential mechanical designs. It tried to replicate Markus’s solar sinter and also uses a Fresnel lens. Before I forget, just throwing the precious plastic global open-source project in, because it could help with the driveway.

The internship thesis and the old grumpy guys made me wonder what other options are there.

  1. Can we add additives to reduce the melting temperature? (Yes, in theory)
  2. What are the pro’s and cons of melting sand to glass vs making something then baking it like ceramics? Is it dependent on the source of material? (I think ceramics need clay rather than sand…) What made people start making ceramics, what is the history of it?

The thesis says “As can be seen, the liquidus temperature of the mixture changes highly with the amount of additives to silicon dioxide. The additives can make a eutectic mixture, where the combined melting point is lower than both of the separate melting points.” The max point to plan for is 1700 degrees C, but could be as low as 1000.

“Current soda lime glass that is found in bottles and windows is a mixture of approximately 74% SiO2, 13% Na2O, 10.5% CaO, and minor fractions of metal oxides. The glass transition temperature is around 560 ° C and the liquidus temperature around 1040°C. This is a relatively low temperature. Commonly the furnace is heated up to 1575°C.”

Next steps to pursue this line of thought is to build something that can reach temperatures of about 1500degreesC, and to do an analysis of the Hopefield sand, which is apparently high in SiO2, but also of ‘random coastal deposit’ origin, so who knows. I wonder how dirty sand (with all the other stuff that’s in dirt) influences the liquidus temperature.

Next is how to do ceramics using solar. So a solar powered kiln. The nice thing about this is that I can use the clay products to build the solar collector.
I could probably make glazed, curved hexagonal pieces in an existing kiln to fit together to make a bigger mirror, if needed (imagine the awe and beauty of a 20m diameter bowl!! )

I think this is what I have in mind, from https://www.cbc.ca/news/canada/newfoundland-labrador/solar-powered-kiln-catalina-1.4235318 using old satellite dishes.

So to pursue this line of thought I need to calculate the size and radians or something of the hexagonal pieces, then make a bunch of them using sourced clay in a conventional kiln and put the lot together. It will be very good to get back into pottery again, either way.

Another thought is if it is possible to make the sand into something that can be baked. Dyllon’s urine bricks come to mind, which doesn’t need baking though…

Other links:

https://en.wikipedia.org/wiki/Solar_thermal_collector#Bowl_collectors
And/or additives that reduce the energy required: https://www.sciencedaily.com/releases/2017/02/170228084222.htm

One Reply to “High temperature solar … sand bricks.”

  1. Ah, so the thing to bind sand together is … a binder! lol. But not always for baking – cement is a binder with sand to create concrete. Apparently the sand in Hopefield is ‘dead sand’, apparently has dolomite, and thus apparently does not bind well to cement. Other binders I guess could be clay, resin … I’d need to do a cost comparison, cost of the material and transport cost (depending on the volume of the additive).
    https://en.wikipedia.org/wiki/Sand_casting

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