Print PDF
Favorite
Email
September 5th I am working on a one dish version and you can see it on facebook at
http://www.facebook.com/album.php?aid=278164&id=736625766&l=8b34cdb5e0
It is trial and error and it will change a LOT before I can include it in the instructable.
I really hoped that someone else would do this and save me the trouble. I might not have time to use it but hopefully the pictures will explain what I am trying to do.
I am 99% sure that it will work well. (If not for me, then for someone with greater technical skill).
A great Austrian humanist called Wolfgang Scheffler thought up a new design for a solar concentrator while daydreaming in university class in Germany. He could not afford to make his design a reality in Germany or Austria so he left for Kenya (and its different labor and price structure) and after about 2 years the design became reality. It is still something they can make cost effectively in Kenya but not in Germany. As soon as he built the first one, he was asked to build another and pretty soon he was asked to help design more in India. So off he went and now there are thousands of Scheffler solar kitchens in developing countries around the world! But very few in rich countries due to subsidized fossil fuels here.
Basically Scheffler solves a problem with seasonal adjustment of parabolic dishes by warping the dish dish a little every day and effectively making a new parabolic dish every day as the sun's path changes with the seasons! His dish is on equatorial mount and turns at 15 degrees per hour (Just like telescopes following the sun).
Basically the task here is to design a parabolic dish that works on equatorial mount but does not need to be a shape changer. If we can do this we can have powerful effective parabolic solar cookers stamped out by the millions for next to nothing by the type of machine that turns a piece of metal into a car body.
http://www.facebook.com/album.php?aid=278164&id=736625766&l=8b34cdb5e0
It is trial and error and it will change a LOT before I can include it in the instructable.
I really hoped that someone else would do this and save me the trouble. I might not have time to use it but hopefully the pictures will explain what I am trying to do.
I am 99% sure that it will work well. (If not for me, then for someone with greater technical skill).
A great Austrian humanist called Wolfgang Scheffler thought up a new design for a solar concentrator while daydreaming in university class in Germany. He could not afford to make his design a reality in Germany or Austria so he left for Kenya (and its different labor and price structure) and after about 2 years the design became reality. It is still something they can make cost effectively in Kenya but not in Germany. As soon as he built the first one, he was asked to build another and pretty soon he was asked to help design more in India. So off he went and now there are thousands of Scheffler solar kitchens in developing countries around the world! But very few in rich countries due to subsidized fossil fuels here.
Basically Scheffler solves a problem with seasonal adjustment of parabolic dishes by warping the dish dish a little every day and effectively making a new parabolic dish every day as the sun's path changes with the seasons! His dish is on equatorial mount and turns at 15 degrees per hour (Just like telescopes following the sun).
Basically the task here is to design a parabolic dish that works on equatorial mount but does not need to be a shape changer. If we can do this we can have powerful effective parabolic solar cookers stamped out by the millions for next to nothing by the type of machine that turns a piece of metal into a car body.
Remove these ads by
Signing UpStep 1Problems
One of the reasons for Schefflers solution is that as the seasons change you have to keep the parabolic dish pointed at the sun AND the focus pointed at the cooking pot or heat collector.
(which must be on the axis of rotation to keep the timing right)
And that is a big problem!
And another big problem is that every time you change your dish you screw up the center of gravity and that makes it harder to move the thing at the exact speed you want.
Also if you make your dish bigger to collect more heat, your poor cook can no longer reach the cooking pot without extremes of posture, etc. Scheffler dishes are 2 sq meters in size and bigger. Most other parabolic solar cookers are 1 or 1.5 sq meters.
How can we get a big fixed shape dish like Scheffler without running into these problems?
(which must be on the axis of rotation to keep the timing right)
And that is a big problem!
And another big problem is that every time you change your dish you screw up the center of gravity and that makes it harder to move the thing at the exact speed you want.
Also if you make your dish bigger to collect more heat, your poor cook can no longer reach the cooking pot without extremes of posture, etc. Scheffler dishes are 2 sq meters in size and bigger. Most other parabolic solar cookers are 1 or 1.5 sq meters.
How can we get a big fixed shape dish like Scheffler without running into these problems?
| « Previous Step | Download PDFView All Steps | Next Step » |
If they were planned into the design from the start, it would have been much more rigid and would focus better too.
Brian
Brian
Cheers, William
The long term object is to have something that slowly rotates to follow the sun, and have the receiver ALWAYS in the one place. So you still probably have to lop off a chunk of the dish, or slices through it to attach it to the equatorial mount because it would get in the way at some parts of the seasons.
My project stalled last September. (My backyard gets little light in winter). And this spring in Victoria has been the coldest wettest since the 1940's. I took it apart and rebuilt part of it recently but now that the sun has showed up, I am insanely busy at work.
Finished at 7.40 today, 9.40 last night and about 8.40 the previous night. (That's burnout schedule for stonemasons!) Anyway, thanks for the comment. Glad someone is still checking the stuff out. Maybe one of you will make it a reality.