Tracking Parabolic Barbecue, the Wave of the Future.

Intro: Tracking Parabolic Barbecue, the Wave of the Future.

This video will hopefully demystify tracking for solar dishes a little.
Please tell me what you think and please also make a better version.
Especially useful would be a 3d version of this video.
Start planning your tracking solar accumulating barbecue today and write the instructable tomorrow!

Comments

[jm1820]

You can have your parabola pointing perfectly at the sun all the time.
1/ Have your axis of rotation pointing north south, and tilted to your latitude (so it is parallel with the earths axis of rotation)
AND
2/ manually tilt the parabola on THAT axis, throughout the year (more horizontal in summer, and more vertical in winter, and parallel at the equinoxes).
AND
3/ As well as the 15° per hour daily rotation.

You are missing step 2

[gaiatechnician]

I think I do have step 2 in the vid too but it is pretty hard to communicate it in 3 dimensions on a sheet of paper. I did this video "on the fly" with no script so I could have missed step 2 or just ran over it. (I get too flustered when reading a script.)
Your comment on how to point the parabola is correct and and well written.
Thanks
I have changed my thinking a bit since the video. I now think a partial dish can be made and counterweighted so that it can work through the summer and the winter.
Brian

[static]

I recall a person who experimented with a catenary arch for reflector. While not theoretically as perfect as a parabola, it was effective, and certainly much easier to lay out than a parabola. So many reflector designs, and other variable, it really does take some study for on the decide what to do at their location. At mine a motorize mount would a an unnecessary piece of machinery , but others essential for their location. Thanks for sharing.

[gaiatechnician]

If you send me your email address, I can email you the interesting curves pdf.
This gives various non motorized options that most people have not seen.
There is winstons compound parabolic trough, the cusp, and several clam shaped troughs to choose from. I found the pdf earlier this year. It is based on research from about 1960 up to about 2000 Tapas Kumar Mallick is the guy who did the pdf and it is related to his work on concentrated pv collectors.
But it is totally useful for thermal collection too.
Brian gaiatechnicianatyahoodotcom

[fishhead455]

Typically in the Northern Hemisphere we who use the sun's energies align our collectors to point South. The angle we use is our latitude plus 15 degrees which gives use the compensation for the earth's wobble between summer and winter months. Perhaps this helps. Great posting. Keep up the good work.

[gaiatechnician]

Thank you. The problem with that approach is that the sun moves too much. 15 degrees per hour means that something pointing at the sun will not be getting full sun for very long. With equatorial mount, and a motor going at 15 degrees per hour it points at it all the time! I hope the instructional members put their thinking caps on and make great tracking devices! Something perhaps with a bimetal strip or something with a car thermostat. Or a telescope tracker modified. There are lots of ways to do it! Some of you will come up with great ones! To make tracking solar accumulating barbecues popular, it is vital that we come up with good switches to let the reflector follow the sun. Hundreds of ways to do it! The world needs both high tech and low tech ways. Post your tracking instructable tomorrow! Brian

[mike7]

They actually meant the tilt of the earth, which is about 15 degrees. That gets added to the latitude. The fifteen degrees per hour movement is a coincidence..

[gaiatechnician]

The tilt of the earth is about 23 degrees. The earth is like a giant gyroscope and when it gets to the other side of the june 22 to dec 22 its tilt in relation to the sun is 46 degrees different. I think the claculation they refer to is a simple optimisation that works for that latitude. brian

[mike7]

You are right, of course.

http://en.wikipedia.org/wiki/Axial_tilt

The confusion may have entered because of information from the same page. I live in Calgary, Alberta (51 degrees North)

=====================================
Example: an observer at 50° latitude (either north or south) will see the Sun 63° 26’ above the horizon at noon on the longest day of the year, but only 16° 34’ the shortest day. The difference is 2ε = 46° 52’, and so ε = 23° 26’.

(90° - 50°) + 23.4394° = 63.4394° when measuring angles from the horizon (90° - 50°) - 23.4394° = 16.5606°
=============================

[arhodes18]

I think this is very good, but a 3D model would be greatly helpful...

[gaiatechnician]

I guess I could do one. It will have to wait for winter though. With a 3 d model, I got to put in the celestial sphere with the sun turning on it above the model. Thats not that easy!

[arhodes18]

ya that is true, but I live in a place with a TON of sun... and it would be nice to make one and use it, instead of for a cooker, for a generator or such...

[GorillazMiko]

Please tell me what you think and please also make a better version.
I think this is great, and that you should post the better version (if you have one).

;-)

[gaiatechnician]

I think this is a better version but it might be too info heavy for people to grasp.
I have diy simple tracking pretty well pinned down now too.
http://www.youtube.com/user/gaiatechnician has all the videos, latest ones are about DIY tracking.
"please tell me what you think and please make a better version" is all about peer review. I can do a million successful experiments (or failures) but if nobody else does the same experiment, it is not science and regardless of my personal success, it is an abject failure. So, you see, your joke is on all of us.
As far as i am concerned I have proved the concepts but of course, it is meaningless.

[gaiatechnician]

I have just started a mould for solar barbecues where I will try to incorperate the ideas from the video. The mould will be made from cob or clay, and the central 1 ft round section or so will detach and be part of the backing and connection for the dish to the axis. I am sorry that the relevent videos are so spread out. I do not think the concepts can be absorbed at one sitting. It took me 6 months to get this far and I am just making the mould now. Brian