Here is a video update on the solar turbine project and the open source tractor – plus other fruits of Factor e Farm:
Stay tuned for the next episode. The front-end loader is already on LifeTrac, we connected the Factor e Liberator CEB press to LifeTrac, and we’re in the process of making sample production runs of compressed earth blocks.
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Marcin, have you looked at using air pressure as a way of getting your parabolas in mylar?
Just suck a little of the air out of the box over which the mylar is stretched, and… is that worth a shot?
Vinay
I have considered that briefly. From the first look, this sounds like a technically-advanced proposition to carry out with good accuracy. Our hands-on work with the mylar shows that it’s not a trivial task to tame mylar into a desirable shape. In the case of using air pressure- one has to consider air-tightness, plus the presence of strong winds in a given environment. Another way to look at it – would someone in the third world be able to pull this technology off with basic, available resources?
Can you shape mud (maybe with the Liberator :-)) and glue mylar onto it? You need a real parabola or maybe a set of segments close to a parabola would do? There was somebody’s work with flat mirrors, if only I could find the link. They created a model and intended to copy it many times over.
Can you get scrap glass cheaper than mirrors? If so, you could stretch your mylar across that, producing a sort of jerry rigged mirror. If you can’t use glass, you might be able to use some other material that is transparent at UV and visible spectra. If you wanted a parabola, you could probably approximate it with strips of glass backed by that material.
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What about mylar balloons ? As demonstrated here:
http://www.coolearthsolar.com/technology
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Rasmus –
Very interesting. I’d like to see cost, performance, and longevity data. I suspect that the maintenance costs will be prohibitive, and I am not convinced that successful deployment of this will be cheap in any way. There are no pictures of real implementations that prove feasibility. If there is any more evidence that addresses these points, I would like to know about them. – Marcin
>pictures
put in “cool earth solar” into Goog image search and a few pictures come up.
In terms of longevity, the CoolEarth design calls for replacement of the balloons every six months. Mylar is cheap, so for their design with very large arrays, it’s a minor factor. I have no experience with using mylar film on solar installations. Is it the sunlight that degrades the polymer ? This seems likely. It could also be the heat from the focus point that eventually damages the balloon. Depending on the reason for balloon replacement, one could change the design.
Possible alterations:
1.) If heat is the problem, one could put the mylar surface in front and the balloon in the back. This structure would have the cross-section of a crescent (=trough parabolic mirror).
2.) if sunlight is the reason for degradation, this is a bigger problem. This would mean that a different type of mylar foil would have to be used, one that is resistant to UV degradation. If the metallic surface is facing outside and the polymer underneath, that might solve it.
These mylar balloons have been used in space in the 1960s.
If such an inflatable design is chosen, I still would go with a linear type. A trough-type parabolic design could be extremely simple to build.
A balloon structure would be susceptible to wind, which creates new challenges. Putting it inside a greenhouse would solve that.
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