Wanted: Large Parabolic dish solar collector

Why not use lots of smaller much cheaper reflectors focussed at the point of interest?

It would also be much more portable and easy to get to site etc...

Don't forget the humble umbrella - they are remarkably good parabolic shapes and can easily be lined with reflective foil...?

There you go.... my consultation fee invoice is in the post to you!!

John.

thanks--my imaginary check is in the mail! I've thought of all those things--umberellas, satellite dishes, wedgewood ashtrays, but I'm not building a tower for a target--and I'd like to minimize flyover hazzard as well

The latest way of making a large parabolic mirror is to spin a bowl of water, with silver nano particles floating on top. For such a large collector I would suggest using something a little more viscous to stop waves and vibrations, eg oil as a base liquid. reflectivity would be up to 80%. Sounds like a crass idea, but it is seriously being looked at for zenith telescopes, the surface is that exact

Admittedly the mirror axis has to be vertical, and it really only focuses the sun directly over head, but for heating purposes one could collect from the sun off axis for a couple of hours before and after midday, using a moveable off axis focal heat absorber.

A simelar idea was shown in an issue of popular science a number of years ago, for building your own low cost telescope. The idea was to build a mold (essentially a cylinder), stick it on a record turntable and use a thin epoxy. By changing the speed, you could change the shape of the reflector. Once the epoxy set, you could then clean up the surface and have it coated with a reflective material (mylar comes to mind). Granted you probably arent going to turn a 24 foot dia. mold with a record player, but I'm sure you could find something more appropriate. But, if all you're interested in is solar collection and not optical quality, then I might agree with whats already been suggested - gluing a bunch of mirrors to a frame - as probably the most cost effective means.

Avery Montembeault

Have you considered fiber-reinforced light weight concrete "skins"? Manufacturing location to suit market! Would be happy to discuss more details.Gulmodena

That sounds very interesting--would you recommend a website?

hi,

no idea. am curious how you specked this. what are you wanting to use it for?

depending upon what you are trying to accomplish, there are somethings that are much smaller and give equal performance.

need two 24ft. diameter collectors minimum to run 275kW thermalelectric generator--goal is for distributed utility grid support--four generators + eight to ten collectors = one megawatt for WalMart, HEB, ETC.--or community amenities for Centex, Lennar, ETC.

Hi dear,

Unfortunately, you can not get 275 kW with Stirling engine from 24 ft dia.(7.3 mt).

If you are lucky you can get max 20 kW with that size of dish. You need another technology which is not invented yet. Check Tessera Solar farm with 1080 dishes totallaing up 27 mW.

Good luck

Do you need round to focus to a point or sheet formed to focus light on a pipe?

Anyway here's a link to an interesting method. It's called a stretched membrane.

http://query.nytimes.com/gst/fullpage.html?res=9E0CE6D81230F935A15757C0A964958260

http://www.osti.gov/energycitations/product.biblio.jsp?osti_id=5494221

yes, this right up my alley--problem is they appear to no longer be in business

Help the environment recycle those old obsolete satellite dishes.

Been doing that--too small, even at 8' diameter, plus too heavy

Er, for home-brew, how about sticking smaller pieces of mirror glass, or even aluminium foil shiny-side outwards, onto a parabolic 'something else'? Is there a parabolic satellite dish luring somewhere on eBay? Can the local amateur radio community provide some guidance as to sources of them, perhaps?

Thanks--as a matter of fact I have a reflective film I can use--problem is finding a "low cost" means to fabricate a large dish--they need to be individual dishes with individual targets--"Dish Network" dishes, first-generation satellite dishes are too small and/or too heavy--upper-end needs to be 24 ft. diameter, lower-end needs to be 12+ft.--my "example" dish is 8ft. and I'm thinking of trying to adapt it to create a larger mold, but I'd prefer to find something already available

Is seems you are still "fishing" for a source for a 24 foof parapoloc solar collector. I would like to encourage you to investigate the potential application of advanced "inorganice materials" i.e. cement. We prototyped this material concept - eight foot reflector - eight years ago, when the material science for this material system was in its infancy. Current refinement suggest this material concept for low cost, rugged, solar cells.

Food for thought or action?

Is this the sort of thing you're suggesting?

http://www.freepatentsonline.com/4268332.html

"An improved method of making a high precision trough shaped parabolic reflector apparatus is described. A smooth surfaced sheet of flexible material is bent and formed over a convex mold comprising a number of precision shaped parabolic arcs mounted to a base. Means are provided for clamping the flexible sheet of material and drawing it into close conformity with the convex mold. The backside or convex side of the sheet of material is then cemented to a support framework comprising a number of approximately parabolic, but not necessarily precision formed web or rib members which are joined together by a torsion tube or similar structural stiffening means. The type of cement utilized accurately fills any discontinuities and/or inaccuracies in the arcuate shape of the approximately parabolic ribs so that the ribs and the flexible sheet are bonded rigidly together as a unit without distortion or strain on the sheet. The approximately parabolic, but non-precision ribs and stiffening means thereafter serve to maitain the sheet of flexible material in a highly accurate and precision parabolic contour produced by the precision parabolic mold."

You have to dig deeper. Your findings are generally on the right track but fail to indicate the "optimization" potential of the material properties and processing through available science and know how. I would like to cite just on example of advanced processing and application of "cementitious" materials - Green, disposable fast food packaging! Demonstrating a Green, low cost solution for a demanding and competitive market.

The determination of the validity and suitability of this technology for parabolic dishes depends on a realistic market assessment, which has to include an effective distribution net work.

The elevator is ready to go to the next level!

Well Scotty, the doubletalk generators are on overload! Seriously, I'm looking into "foaming" biological, plant-based epoxy insulation, such as used in the "green" building industry, and scrap wood or metal for structural support--now I need to work out my "wedge" form so I can make squared-off "dishes" of the correct parabola, and just add or remove to get the size(s) I need.

Sounds to me like you may have trouble finding an off the shelf design ... With that said, our company can possibly help you out. Our design group has experience designing and building telescopes among other equipment, and may be interested in breaking into the alternative energy industry.

We have design facilities in Vancouver Canada and have a manufacturing facility in Texas.

please contact me at 604-986-5600 if you are interested in pursuing further.

Regards,

Hans.

You wouldn't by any chance be Oceanworks.com, would you? If so, I see there is a Houston office--perhaps it would be better to contact them? In any event I will seek to contact you this week.

Or you may contact me at clamrod2001@hotmail.com

Indeed, it is OceanWorks. Our Vancouver office is the primary design center where we have about 30 designers and a core group of about engineers. Our engineering manager and one other fellow both have many years of experience with telescope design and fabrication.

please do contact me.

Regards,

Hans.

Try google on "heliostat". There are multiple examples of such instalations around the world.

Benefits: Single (fixed) focal point, portions of mirror can be replaced without taking whole unit out of service, can be "expanded" to provide the various sizes that you require with a common (interchangeable) controller, lightweght (relative to a single large dish and necessary support mechanism) able to track the sun across the sky, able to clean individual mirror portions without taking whole unit out of service.

Disadvantages: Cannot perform as well as "full tracking single mirror" near horizon, multiple devices to "aim" each small mirror.

There's one located in Newcastle (Australia) being used for energy research at CSIRO centre for energy technology.

Great suggestion, mate!

Found this site http://www.heliotrack.com/Parabolic.html

It has heliostats, parabolics, lots of goodies.

Did you ever find what you were looking for? If so do you have any success stories to share because it seems like I am embarking on the same road as you, and the fact the information is so scarce and the idea is such a good one, you have to wonder why info is so scarce. I live up in maine, and we use the most oil to heat our houses, and thought these would be a great "alternative" to cut back on some of the bills. Feel free to email me, and thanks for starting this topic. sbruel@yahoo.com

did you ever find the dish source ?

Never did find dish source, I created one from an 8 foot satellite dish, used acrylic mirrors 4x8 feet, and cut in to triangular pieces, and used locktight in 1 pound tubes from home depot to secure the mirrors in place: 2 problems: something cheap and accurate to track the sun (wanted software, not light diodes, and the wind will destroy this monstrosity now, think of it as an eight foot umbrella in the wind.

hi from downunder,

was looking at same type of collectors as your self but have found some or heaps of results from solar 1 in nevada desert:www.nrel.gov/csp/troughnet made from german aurospace technology.is trough parabola in about 4meter sections the flat trough mirrors are cheaper to make than a complete parabolic reflector(the only cheap way to make that is by sectioning -like an old reflector from a flashgun.)hope this might help but you have the tech people there should have already thought of this anyway.

cheers peter hawkes.

What is going to be at the focus of this reflector? You're concentrating sunlight, to be sure, but what's the target? A heat exchanger? Too much sunlight focussed at your target and you'll destroy it.

Others have mentioned various means including distributed collectors, segmented mirrors or collector arrays. Must your "dish" be a single, monolithic mirror?

It s too big, the problem is how you will controll its direction to point to the sun? it will need a large motor and complex control system.

or you fit it as a side of wall, like a building somewhere in USA, use it for fusion reaction.

Check out Acro Solar Lasers. They have 8 foot solar dishes and 14 foot dishes, as well as a 44 inch dish. All are one piece lightweight fiberglass. They use a reflective mirror film on them. They also sell the tracking and management system. Tiny Low mili amprage motors are used to move them on 2- axis very efficiently. They use optics to track the sun very accurately which is something you will have to do when using a parabolic dish or the reflection won't hit on target. Lots of power to be had there. Simple structural balanced design with a tracking computer that will controll tracking motors, pumps and monitor temperatues. Completely automated. Its the only system of its kind I've seen available to the public and average Joes.

http://www.acrosolarlasers.com/

Don't get the acrosolarlasers dish. They are poorly constructed. The welds on the tracker look like my kid was playing with the welding machine again. The tracker gets off course eaisly when any clouds are present. It is worth looking at though for ideas.

www.tmeink.com will build most custom anything

try www.tmeink.com they will build most anything

We represent a manufacturer of a composite solar parabolic trough and is capable of building them in these large lengths. Our focus now is water heating however we can discuss other opportunities.

Can you tell me more about what you are looking for?

You could use a Fresnel lense instead of a dish. You can get them on Ebay.