Parabolic is the wrong shape! Compound parabolics explained Captions tell of updates

[pwnageinthemaking]

im to dumb to understand any of this. i just clicked on this video because i saw the word "concoct" in the description and laughed.

[bxxj]

I recently saw a solar pasteurizer that used a automotive thermostat as a flow valve. they work at 140 to 160 degrees. since your "dish" is not dependent on precise angles the heating and cooling effects of a gravity flow water cylinder or possibly a simple water bag controlled by a automotive thermostat just off the focal point might work very well. very low tech and reliable.

[gaiatechnician]

@bxxj The automotive thermostat sounds like an excellent idea.

I thought about it but never got round to doing it. You can have the entry water pipe coiled round the exit water pipe to reuse some of the heat too. It is the obvious way, using an off the shelf automotive part to control the flow. 140 F is 60 centigrade (for me and others). Pasteurization is achieved by a combination of temperature and duration. Engineers should be able to make your device up fairly quickly.

[vossua]

You could make solar pistons from copper pipe and commercially available refrigerant or in absence of this, one could use propane, butane or possibly [with much less efficiency] acetone.

I do not know what is commercially available in your area, but many items can be bought without license or permit in most places which will perform the needed actions. One simply needs skills and determination.

[gaiatechnician]

@vossua So you didn't check? There is no need for pistons and refrigerants. I did a small one with a water clock and 2 paint buckets.

That is a dripper tracker.

I also made one with a clock (wall clock with hands) controlling the process. The clock based tracker.

Just demo's. They worked.

But I have not done a demo of the liquid piston tracker. Just diagrams.

If you make the liquid piston tracker, it can be more reliable and more accurate than your refrigerant thing

and cheaper too.

[vossua]

We in my group are building a precisely calibrated 'clock' tracker based on actual sidereal time, but its going to be for utility scale collectors.

I'm sure the average commercial light sensitive solar tracker is too costly for such an adventure but one person built an expansion based device once which was based on placing bulbs of a gas similar to freon inside dark colored cylinders then arranging them in such a fashion that they were shaded from direct sunlight when properly aimed...

[gaiatechnician]

@vossua Please check out my dripper tracker options. They are here in video form and on solarcooking on their tracking page. (I cannot do the link here). There are 3 to choose from. A guy working at uvic said the liquid piston tracker would be perfect for a student the mecatronics course in UVIC university to design. If I was a business they would have done it. But I am not and rules are rules! Liquid piston would be the most accurate. Time based too! Robust in wind too!

[vossua]

The only problem I see is the inability of the user to think well enough to AIM their mirror!

[gaiatechnician]

@vossua It is a big problem! I have been thinking of "workarounds" for a few years since this video.

The clam shaped solar cooker (last year) is the latest thing and it works. It probably works REALLY well if aimed properly BUT it has to be aimed at the sun and aligned with the PATH of the sun.

Thats hard!

My solar compass is part of an attempt to easily do this.

Seasons make it tough.

The tracking solar accumulator is semi automatic and is a potential solution for parabolic dishes.

[datzfast]

thanks for your response i will check out the T-square

[datzfast]

ok but yea cant make a round compond parabolic or can you

[gaiatechnician]

@datzfast The video is a couple of years old. So it is outdated. It is part of a long term "learning" or design process. I left it up because there are plenty of links to it and it does show the laser in design concept fairly well. By round, do you mean 3 dimensional? like a dish. No, it does not work as round. If you want to see what it develops into, please search solar design t-square and clam shaped solar cookers. With the solar design t-square, you can design custom dishes.

[jcanivan]

Great video. gaiatechnician

So what are theadvantages and disadvangages of a compound parabola.

John

[datzfast]

@canavan advantage, you dont have to reposition often, disadvantage the highest temp possible for the area of collection not achieved.

[artsychic2000]

lol...i got one of those for my husband for christmas. He said it was useless too : p

[gaiatechnician]

@artsychic2000 The best ones here are cheap 15 dollar 9 inch torpedo laser levels. And it is all about the brightness. Wheres the point of the 60 dollar super level if its point disappears in bright sunlight? And one that makes a point usually comes with attachments to make a line anyway. The useless one I used in the video was only useful for that video because even though it is bright, it only makes a line! (which totally wastes the power)

[solarsenthil]

it is very useful but your video explanation requires clarity. thanks

[gaiatechnician]

@solarsenthil Thank you. This video is outdated and some of my conclusions were wrong. (You cannot just revolve a curve to get 2 hours acceptance ) . But I leave it up because it is useful to people as a starter or primer.

The newer stuff is solar design t-square and clam shaped dishes for 1 or 2 hour solar cooking. The t square also use a laser and is much more accurate on the 3d physics. (Not perfect but very very close) and it does a great job in 3 dimensions.

[gaiatechnician]

@solarsenthil Please also note that the solar design t-square could be used to design parabolic dishes too. Even an approximation of one made with mirrors on a flat piece of plywood.

[moryl]

hello Gaia,

I am looking to build a parabolic dish to heat water. THis is for a project in developing country.

My question is how to draw, accurately the compund parabola curve? I did not realy understand how you optain the combined the 2 curves. Do you have a technic?

Thanks .

Leo

[gaiatechnician]

@moryl My video should be called parabolic is the wrong shape for "unattended solar cooking". You might need a winston w curve on a trough. Its probably about the best you can do. if you want a parabolic dish then the mechanical mathematician should work or you can do it mathematicially. But you have to do tracking to keep the dish focused.

So yeah, Winstons W curve was patented but it expired and anyone can use it now. Brian

[PaulArveson]

scotty - Sorry, but you are incorrect. The laser level emits a parallel beam that represents a source at a far distance like the sun. It is not a near source like a light bulb. The experiment is ok.

[scottythefiddler]

gentlemen....there is a genuine error in this test....

a parabola will focus the light as expected if the source of the light is at an infinite distance from the parabola. With the light so close to the parabola in this experiment, this demonstration is showing something known as longitudinal abberation.

[gaiatechnician]

@scottythefiddler Thanks for the comment. I think that in 2 dimensions it is fine but not when you extrapolate it to 3 dimensions.

At the time, (over a year ago) that I added it, I thought that you could just rotate your shape round a centerline and have a dish with great unattended cooking time. This is not so. Please check my solar design t-square and clam shaped solar cooker videos for the updates. I leave this on because it IS useful to people and it is watched a lot.

[gaiatechnician]

Just a note to anybody looking at this, I have moved on. The latest developments are the solar design t-square and clam shaped solar cookers. I have made the tsquare, made models and scaled them up and it works. The models are clam shaped. There is quite a bit of trial and error involved. It is totally new, I am the only person who has ever made and used one. Why are the environmental organizations, and aid organizations not interested? It works. Brian

[ducttaperulestheworl]

clever

[bobWsterguy]

Terrific videos...great wisdom...keep up the good work so we can all learn. Tx. much, Bob

[Cyara248]

Excellent! Never seen this before. Thank you so much.

[darkwrath]

fine great job for a solar kitchen!!!

[gaiatechnician]

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

[muddymuddymuddmann]

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)

[gaiatechnician]

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

[muddymuddymuddmann]

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

[Swazooli]

I do not see how you combined the two parabala's pleas eadd more info

thanks

[macrumpton]

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?

[gaiatechnician]

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.

[circusboy90210]

mylar is 3m's name for aluminized polyester

[capt8ron]

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

[menderfire9]

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!

[ObiWanShinobi1]

I was wondering why parabolic collectors weren't more egg shaped - thanks for proving they could/should be.

[gaiatechnician]

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

[chrisr0207]

It is very helpful,thanks keep sharing,God bless

[bloggycreek]

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.

[trailbuddi]

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

[gaiatechnician]

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!

[pupplesan]

CPC's are clever but there is no free lunch. The greater the aceptance angle, the lower the concentrating power.

[gaiatechnician]

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.

[pupplesan]

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.

[gaiatechnician]

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.

[Marcus711]

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 :)

[wjj4832]

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

[TVParkdale]

I came up with a weird idea.

The romans used to heat their houses with water pipes beneath the floor.

If one took your pump, and some form of solar cooker [really BIG]...

I wonder if it would be possible to use the pump shoot water through a solar cooker style heated pipe and heat a house? Or heat a tank, use the pump to shoot the solar heated hot water through the pipes?

[gaiatechnician]

Aluminium is one of the fastest conductors of heat so aluminium pots spread the heat really well. Clay is more of an insulator, the heat moves slowly through it. I did not shoot water through a house but for a couple of weeks I sent air from one of my pumps down a steel pipe in a chimney and into a room.

The air warmed up the room considerably and continued to warm the room for perhaps an hour after the fire went out. (But the air from the pump has an unpleasant fishy river smell so I stopped).

[TVParkdale]

Eureka:D

So it *is* possible. I knew a fella that surrounded his woodstove with bricks so that when the stove went out, the brick would continue to keep the cabin warm for hours afterwards.

There MUST be a way...you are SO onto *something* with these discoveries!

[TVParkdale]

Would there be a way of using mirrors or glass on a clay dish [since heat spreads through them] to keep the heat consistent?

[gaiatechnician]

I am not sure that I understand your question.

You can certainly stick lots of small mirrors straight onto a clay dish (when the clay is wet) to give an overall parabolic or compound parabolic reflective dish.

Brian

[TVParkdale]

I was thinking as the actual cooking utensil, if clay because it spreads heat through it's surface, would be a more useful cooking "pot" than something else?

[gaiatechnician]

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.

[TVParkdale]

Oh my, with self drying art clay--that might be pretty easy, really.

[TVParkdale]

Thank you for explaining how the "focus" heat moves because I wondered about that...

[micsolaire]

Bravo !

Very useful info.

[echever7]

Thanks a lot!!. Beautiful, easy, useful. How do you make the ray visible?. I use some powder, smoke and so on to trace the ray by scattering. But your ray seems to go at the table level...

[gaiatechnician]

Most laser levels make a dot but they usually come with an attachment for making a line.

Sometimes it is just a little thing you twist or push down on you laser level.

You have to put the line attachment on and have it vertical. Then some of the line shines on the table, and some hits the mylar and bounces off! By the way, if your mylar is thick enough you might not need the plastic strip. You can also stick 2 strips of thin mylar together with a film of water to make them more rigid. Brian

[desertblbuesman]

Another great video! But, I can not see the two parabolas you are combining from the camera angle. You are describing very important information. Please could you do a quicky with a overhead veiw so as to see the two parabolas and how you are combining them. Thanks very much B.

[gaiatechnician]

The 2 parabolas are the same size, the second one is on tracing paper, I rotate the tracing paper on the focal point to the desired acceptance angle and then combine the inner portions of both parabolas.

[desertblbuesman]

Thanks, that clears it up nicely. Great information.

[infinitetease]

Very interesting. I thought about using a laser to test the shape of my parabolic trough, and find its focal line.

[NGYT40]

Realy interesting

[scorpio21x]

Great video, thanks!