This explains the advantages of compound parabolic dishes for solar cooking. I had to concoct this method because there was no software available. It may prove useful to solar designers everywhere! … Solar grassroots DIY cooking gadget deathray parabolic dish cooker oven
Parabolic is the wrong shape! Compound parabolics explained
Posted by admin | Filed under Cooking Gadgets
Please note that I have just started using a “solar design T-square” to make better reflectors for unattended cooking.
I will not be able to test anything until March. If any of you are interested, please check the latest videos for explanation.
It makes a completely NEW! “clam shell” shape!
Who wants to be the first person in the world to make one?
You can make the T-Square for less than 10 dollars.
Brian
fine great job for a solar kitchen!!!
I have an idea about that too. I believe that if you connect a heat sink that will protrude downwards a bit below the heated cookware, the heat will conduct through the heatsinc to the cookware with negligable losses becauce of its position..
MUDDy
I would like to point out that my idea of spinning the compound parabolid shape to make a dish is not completely correct. (So I still have not designed a 2 hour reflective dish). See the 4 dishes compared and conclusions video. People ARE finally working on the problem though. I hope to put on more video to show the way to the right designs soon. brian
tHIS WAS EXTREMELY HELPFUL AND , NO I HAVENT SEEN ANYTHING LIKE THIS AS FAR AS DEMONSTRATION OF A BETTER SHAPE.
GREAT WORK.
SCOTTY B (THE MUDDMANN)
I do not see how you combined the two parabala’s pleas eadd more info
thanks
Yes, That is what I did. It gives a curve that maintains light on a cooking pot (situated below the focal point), for longer than a parabolic dish would focus light. (But not for the full 2 hours as I had hoped). See the 4 dishes compared video for more details.
Is it correct to assume that you are taking 2 parabolic curves that are focused on the same focal point but are pointed at angles 30° apart, and then you are using the innermost legs of the two parabolas to make your curve?
mylar is 3m’s name for aluminized polyester
I’d like to make a 12 panel oven using a compound parabolic curve.
My question is: how do I draw a 30* to 45* acceptance curve, using a CPC, such that one panel is 24″ high and allows for 12 panel construction?
I have selected what I call “bubble wrap” insulation as the main component because it will stow well and is reflective. My roll is 24″ high.
Doug
Check out my video of a parabola calculator. It may be what you’re looking for. My private email is on the video, and if you want the original spreadsheet, email me for a copy.
Walter (wjj4832)
Oklahoma City
Wow! wow! wow! Good for you. I knew something was wrong with the parabolic method. Again good for you. I will subscribe. Keep up the good work. We could use this the world over!
Gaiatechnician,
Awesome!
Do you have the formula of the parabola for the 45 degree acceptance angle one?
That would be a real help, as I’m currently planning out a Parabolic Solar Collector for a steam powered A/C electricity generation, BUT i don’t have time to work on a complicated tracking method. Thanks
Unfortunately, I did not prove anything. but there are definitely alternatives to a parabolic dish. I think that in the right situation, a hemisphere, or a compound parabolic dish will beat a parabolic dish. Currently I am trying to use software to show this. It all takes time.
Thanks for the comments.
Brian
I was wondering why parabolic collectors weren’t more egg shaped – thanks for proving they could/should be.
It is very helpful,thanks keep sharing,God bless
Thank you. Nice video. The laser is a great tool for checking angles.
Check out my solar grill. It cooks fast using a shallow parabola.
Thank you for the info. I think you should wait a little while before doing anything.
I did my modeling in 2 dimensions and my first dish worked great. BUT I never tested it the math in 3 dimensions because I did not know how!
Others are now interested and they will find and fix any mistakes I made. Then let the pressing begin!
I havent seen any vids yet her on YT, but metalspinning is where you take a flat piece of metal and spin it in a machine, not unlike a metal or wood lathe, and force-press it into the shape of something….like a parabola-shaped wood mold and using like simple wooden or metal tools. The process is fast. I guess the parabola shape has some rigid-strenght to it but I would then weld some extra support onto the back side of it. Not sure if anyone is doing this stuff though, but it would be cheap
I think compound parabolics will also prove useful in a tracking situation. My first cpc had a 45 degree acceptance angle. It accepted 3 hours worth of sunlight. But look at it another way. Plus or minus 22 degrees of error in a tracking mechanism! That means you can have “truly awful tracking” and still catch all the sunlight. The combination of truly awful tracking and CPC is cheap and cheap has great economic merit.
Agreed. CPC’s are the best non-tracking concentrators. When used with a good selective surface and insulation they offer a solar concentrator without the enormous mechanical complication of tracking.
It is not a free lunch, just a lunch that cooks properly without having to watch it all the time. Parabolic has high concentration only if you point them accurately and if you move them a lot. I think concentrating all the heat on the cooking pot for 2 hours is better than concentrating all the heat on one spot for 15 minutes.
CPC’s are clever but there is no free lunch. The greater the aceptance angle, the lower the concentrating power.
Not really, aluminium spreads heat much more quickly. And the surface is much thinner too so the heat is quickly in contact with the food.
Clay and pottery will work, just more slowly than aluminium. You can check heat capacity and heat conduction for different materials on wikipedia and elsewhere. You need to take a whole system approach when designing your solar cookers. A clay pot with the right surface area and volume with the right number of reflectors will work fine.
Oh my, with self drying art clay–that might be pretty easy, really.