Laminated Aluminum Foil for Solar Cooker

Check out chewing gum wrappers.

Hi rsalaskar,

Yes, there are methods to laminate just about any two thin substrates together. This is usually done on machines that can keep controlled tensions on the rolls of materials. Laminating by hand pretty much sucks. For your application however, have you thought of using a metallized (Aluminum deposition) film? You can get metallizated polyester (PET) and polyethylene. I've worked with PET with enough metal that it was as shiny as a mirror.

Here's a link for hobby sized amounts:

http://www.rplastics.com/metallized-mylar.html

For durability, you may also want to paint a clear coat of some type over the metallized surface (not water-based!).

Good luck,

Mike

Hi Mike,

Yes, I have tried metalized polyster and it is good, but the reflectivity is around 60 to 70% if I am correct. I have also tried vacuum metalized polycarbonate and that is better. I feel Aluminium film would be better option and I want to try out.

I have conical solar cooker developed by a friend. The cooker is 26 inches diameter, and is made of FRP that cost $15 to fabricate and the reflector is anodized aluminium that cost about $1.5 to $2 per square foot. Kitchen Aluminium foil would help to reduce cost drastically. I want to make the cooker affordable(without any subsidy) to a tribal family and should cost less than $20.

Rajesh

Try a mylar balloon and use a spray can of contact type glue. Use a round object, ball; start in the middle and slowly work outward.

Use a contact type adhesive but as you stretch the foil blow compressed air gently under to avoid wrinkles.

I have tried something like that too, some 7-8 years ago. I used some scotch tape in order to strengthen the aluminum foil. Just wanted to obtain a reflective surface. The resulted foil had some wrinkles because I wasn't searching for mirror like surface. Anyway I tried that reflector in the sun and was quite impressive in concentrating heat. Be sure to use a straight surface like a window glass. First stretch the foil and hold it straight, then apply the tape.

good luck

I would personally use 1" thick styrofoam insulation as it bends nicely, and use that special glue for styrofoam to stick the foil on.

Why worry about a few wrinkles? Its more important that no heat passes through and out the other side......

Yes you can do it

There is company in Chennai by name Global Applied Materials they make lamiantion binder.

You can brush that binder or spray it and then dry at 70C and laminate at 90 to 130C

If you need further help in contacting or how to do this let me know and will guide you through

Masyood

That's good news for me. I would like to try it. Please give me details.

I tried the aluminium foil lamination on a double sided tape, would it be similar to what you are suggesting? Any way, I would like to try it

Thanks

Rajesh

No Jajesh

What I am suggesting is to paint it using foam brush or spray it then place another sheet

Apply pressure using steel plate and 90C and the sheet will laminate

If you need more details will provide you contact information so you can get this from him, work with him and in case you need me to discuss I will be more than happy to help you out. This work I have done using two stainless steel plate with 5 Kg load at 90C.

You will be able to do mass production using this glue

Have you tried ironing them together, with a layer of baking paper above and below the laminate to prevent sticking?

mylar is over 90% reflective at least to visible light. Aluminum foil is only around 75%.

Infra red end of the spectrum?

http://www.mirrorsheeting.com/

If the OP did research that's the only way I would see, as I did research and bought some mylar, and it's over 90%. reflective wrapping paper is even cheaper then mylar but it will rip easy. Anyways Mylar will last about a year before the UV rays wrek it.

Please let me know where I can get this data on reflectivity, this will help me to select proper reflector.

Thanks,

Rajesh

you can spend days searching the web or you can go straight to this

http://www.fsec.ucf.edu/en/research/solarthermal/solar_cooker/documents/reflectivematerialsreport.pdf

Explore

Company name Global Applied Materials

Contact name Dr, T. Settu

Cell # 9449834827

You can say my name as Dr. Masyood Akhtar, Managing partner from Custom Nano Adhesive,in United State

If you need further help just ask for it and will try to do the best I can

Some of the newer premium metalized mylar films have 92-93 reflectance values. Apply it to your plastic substrate with spray-on 3M (or other) construction adhesive. I've just completed building some "test" solar troughs using longitudinally cut PVC pipe.

Good luck! Have a great sunny day!!!!

Thanks friends for all the information, should keep me busy on lot of week ends.

I have added image of conical solar cooker I am experimenting with, made by a friend Ravindra Pardeshi. You can get details of this if you search for "Parvati Solar cooker".

The diameter is 26 inches, fabrication cost is approx, $40 that includes about $20 for anodized aluminium reflector normally used in luminaires. I am trying to reduce this cost.

I am trying with vacuum aluminium coated polyster, vacuum aluminium coated Polycarbonate and want to try kitchen aluminium foil, that I feel would be cheapest, but wrinkles badly.

Rajesh

Although it would be really great to have a material that reflects over 90% of the available Sun's energy, surely price, especially in countries where the folk have less money to play with, is more important?

If for example the units reflector needs to be twice the size but only costs a Dollar or so to produce, then surely that is a better alternative.......also the Sun's energy in many 3rd World Developing Countries, is available for far more of the time than say here in Germany!!! Also, at a higher temperature!!!

Cooking different dishes requires different times and temperatures, being able to shield part of an oversize reflector to achieve that may be a huge plus factor......

Its like the "argument" here for solar water heaters, the evacuated glass tube versions are at least twice as efficient as any home made unit from old radiators for example.

But whereas you can put a home radiator panel (single) version together for maybe as little as $20 and a bit of elbow grease, the expensive ones cost $1000 and are very delicate!!!!!!

I would rather build twice as many panels of a cheap material that I can put together and repair myself, than pay $20,000 for a system that will take 20 years to pay for itself and only a specialist can repair!!!!

So go for a cheap, but larger reflector, that is easy to produce and repair/replace.

Best of luck.....

You are right, what matters finally is economics and affordability apart from user friendly attributes.

I got feedback that this cooker capacity needs to be increased by about 2.5 times to suit the families in tribal areas and their food(mainly rice). When I increased the size, apart from cost, the usage is now not so simple, the positioning of cooking vessel has to be positioned correctly.

The better reflectivity also helps in making the cooker more effective in smaller size. When I used cheaper reflective papaer, the efficiency dropped. So I am trying to balance all these factors and trying to keep the making cost to less than about $20.

Incidentally I am also installing evacuated tube solar heating panel for bath water. The capacity would be 125 litres per day and should save me about $20 per month in electricity bills.

We have very good solar energy availability in India but we hardly use it. Even if we use 1% of the available energy, no any other type of energy would be required. Especially, people in villages use firewood for cooking resulting in deofrestation. Solar cooker is a very good proposition. Surprisingly, the progress is very slow. I understand that in Germany, there is good amount of interest and people experiment a lot and there is good progress in terms of usage of alternate energy.

Rajesh

Instead of using convenience items why not employ available materials which can be polished enabling increased reflectivity?

I am not only using available material but also trying out vacuum coating on polyester and polycarbonate for reflector. I feel this would be the most cost effective way for experimental cookers.

Evaporation deposition...?

We are getting there, but slowly......too many companies with too few customers.......

Lots of suggestions- now one more-

Form the "cooker" by a series of parallel vertical supports 3 inches (80 mm) on center made of light weight wood (weather-grade 1/4" (6 mm) or 3/8" (9 mm) thick plywood) with a parabola cut into the frame for the cooker. Mount the uprights on a base of the same material.

Then, form the reflector using HEAVY-DUTY aluminum foil rolled onto another 2" (50 mm) or so diameter spindle so the shiny face is to the spindle and the dull face is exterior and a sheet of corrugated paper cut so the corrugations will go perpendicular to the upright wood supports.

With the corrugated paper laying smoothly on a flat surface, coat the mating surface liberally with rubber cement (or liquid silicone glue), then roll out the aluminum foil into the still wet rubber cement (silicone). You will likely have to use two widths of the aluminum foil, with the joint at the mid-point (bottom / apex) of the ultimate parabola. Larger parabolas will likely need 3 plies, but the overlap can be on the sidewall so long as the overlap is edges on top of the base (apex) thickness.

Let the aluminum foil extend about 1/4" (6 mm) past the paper so it can be bent down to cover the edges of the corrugated paper for water and oil protection. After you have rolled out the aluminum foil, use the spindle to "burnish" it onto the corrugated paper by rolling over it a few times.

Let it dry overnight, then carefully bend it into the parabolic shape and install it in the uprights using silicone glue applied to the "grooves" in the upright supports.

You should end up with a smooth, reflective cooker that is reasonably weather resistant. If you coat the outside (not mating side) of the corrugated paper with silicone and letting it cure overnight prior to installing the foil, the entire assembly will be fully weather tight- and relatively inexpensive.

Part 1 details DIY a parabolic dish, part 2 details applying the mirror finish

http://www.youtube.com/watch?v=FZh-CRneIII&feature=fvw

It seems that he is using the weight of the concrete to form the curve. If so, the curve formed is a catenary and not a parabola. The catenary, which is sometimes referred to as the chain curve, is formed by gravity when a flexible member with uniform density is suspended between to points, i.e. a chain hanging from to points. While the catenary looks very similar to a parabola and the shape in nature was thought to be a parabola form many years, it does not have a focus and therefore would not make a good device for focusing parallel rays of light. Inverted catenary curves make perfect arches for supports.

A spinning liquid on the other hand will flow against gravity based on the square of the radius creating a more accurate parabola.

*It seems that he is using the weight of the concrete to form the curve.

I cannot apprehend the thought used to make this statement a description of the process depicted in the video?? Weight has null to do with the shape.

After watching the video I did not find any reference to how the curve in the bottom of the tank was formed. I am not sure that you can assume that it would be parabolic in nature. Do you know how that curve was formed? As a physics teacher, I have students who are always looking for ways to create parabolic shapes.

The curved bottom of the tank is used as a mold for the concrete

Possibly for a project a mold may need special design though his way seems to work too...

Thanks for the link.

My problem is not parabolic shape. I get the 32" dia parabolic fibreglass shape in 2mm thickness in about $15.

My problem is the reflector on the parabola, I have tried the adhesive metalised polyster and aluminium tapes, these work fine. The best reflector that lasts long is the anodized aluminium normally used as reflectors in lighting fixtures that cost about $ 2 per square foot.

For my conical cooker, I need about 10 sq. ft reflector, an expense of $ 20. Thus the total cost of cooker in the range of about $35 to $40 makes it un affordable. My aim is to make the cooker in about $20 to make it sustainable without any subsidy.

Cheaper reflector like metalised polyster would make the cooker affordable, but the metalized polyster has reflectivity of about 60 to 70%.

I am in the process of procuring polycarbonate film for vacuum coating with aluminium. This makes it excellent reflector. I am not aware of the life of polycarbonate in sunlight. I assume this should last about 1 to 2 years.

Rajesh

The best reflector that lasts long is the anodized aluminium normally used as reflectors in lighting fixtures that cost about $ 2 per square foot.

I doubt this material would retain its reflectivity in the presence of UV and oxygen which rapidly degrades Aluminium.

The one to two year time frame is a good approximate for polycarbonate and do take care not to abrade the reflective side.

I thought the heads on water heater pressure tanks were basically portion of a sphere or ellipsoidal, not parabolic.

The spherical section obtained from the tank head could be polished into a parabolic shape but the one he made wouldn't be.

Even so, the focusing doesn't have to be exact for a solar cooker, so a spherical shape should be good enough.

A wooden mold could be readily turned on a lathe and used to make a fiberglass reflector.

This could be made larger than needed for a perfect reflector and then sprayed with an Aluminium paint. Reflectivity would be no where near as good as polished Al, but the reflector should be able to be made large enough to compensate and be cheap.

In India, the setting time of polyester resin could be a problem due to the temperature. At Mt Isa, we needed to cool the pot if we were using epoxy spray paints so the setting time was delayed enough for it to be used. I imagine polyester would have similar problems.

Wood flour filled polyester may make a satisfactory base for your reflector, without needing the expense of fiberglass. Just make it thicker to compensate for the reduced strength.

This may be able to be sprayed onto your mold and built up in layers until the required thickness is reached.

Just a few ramblings that may be worth your investigating.

Good luck

I have to agree with your ramblings, to my mind the focus should not be good, or you will get "hot-spots", when the whole base of the "pot" should be heated evenly to maximize the cooking effect.

Hot spots will just cause localized burning, not cooking.....

If a slightly diffused beam or slightly out of focus focal point is used it will spread the heat and reduce hot spotting

a) Theres no point wasting time making the dish more accurate than the thing that your trying to cook. Have you considered making the dish shape out of several flat sections of an appropriate shape instead?

(incidentally much early chemistry was done using solar furnaces to get high temperatures within inert atmospheres ... a very high concentration factor dish will simply burn the outside of the food quickly but leave the inside uncooked!)

b)A few wrinkles are unlikely to make much difference (provided the basic sphere shape is ok) as they constitute a small proportion of dish area.

c) kitchen foil is 88% reflective according to google searches so I expect the results to be similar to the things you have already tried..

d) Consider making your dish 20% bigger instead of combating the reflectivity levels. ...Its probably a cheaper and easier