Testing Reflective Materials

by Jim La Joie, All Season Solar Cookers
(Bonsall, California)

The All Season Solar Cooker is a work in progress.
Recently I experimented with a new reflective material - radiant barrier.
Radiant barrier looks like a woven poly tarp but it is coated with aluminum on each side. I liked the durability of this material and, since it was relatively shiny, thought it might work for solar cooking.
Radiant barrier does not perform as well as the aluminum foil tape that I have been using - and difference in performance is significant.
For the test I used one liter of water in matching pots. The pots were placed inside the ASSC cookers. One cooker's reflectors were built with aluminum foil tape, the other with radiant barrier. I measured the temperatures every 15 minutes and re-adjusted the cookers when necessary.
Results: The aluminum foil tape brought the liter of water to a boil almost twice as fast as the radiant barrier.
For now, I will stay with the aluminum foil tape.

I have also used aluminized polycarbonate film for my solar cookers. I don't anymore. This reflective film works well at first, but it scratches very easily, cannot be re-polished and the aluminum coating tends to separate from the film after a few months. Whether this separation is due to sunlight or the glue that I use I do not know. But I no longer use the reflective film because it cannot be restored once dulled.

Does anyone know of a very bright, durable, renewable foil? I am still searching for a mirror-like finish.


____________________________________________

Greetings Jim,

Thank you very much for this valuable information, this should be very helpful to those who might be looking at reflective material options and their abilities to perform.

I found it very helpful myself.

I wish I knew where to obtain a foil such as you described, that can be "re-polished".

The material closest to this capability on the market that I have hear of is offered by Derris of Cleardome Solar.
I will say though that the material is not cheap.

For those who may not be aware,on our site we offer an adhesive material that is quite reflective and pretty durable for use on solar reflector panels and such.
Of course there is no perfect "shiny" reflective material, ours is a good economical reflective vinyl

We will continue to search for better and higher quality products for the solar cooker market.

Please share with us any new and innovative information you wish on you solar cookers and solar cooking in general.

Nathan
Admin.

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Jun 27, 2012
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more on reflective materials
by: Jim La Joie

I finally did a side by side test of the aluminum foil tape and the reflective film.
I expected the reflective film to perform best because it is very shiny - like a mirror.
But the aluminum foil tape, which is less expensive, easier to use, more durable and can be re-polished if necessary, beat out the reflective film.
Just thought i would pass this along.

Nov 10, 2011
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Reflective material comparison
by: Nathan

Dana,

The reflectance rate of our silver vinyl on this site is 86% reflectivity and which is slightly above or about that of the reflective tape you indicated.
Ours also comes in rolls allowing for larger sheets or sections to be cut since the width of each roll is 27" inches.

There is reflective material (vinyl) that has a higher reflectance rate (95%) but it costs almost five times more that our material, thus we decided to go with the less expensive material.

Our material seems to do quite well for most people that purchase and use it though.

I hope this is helpful.

Nathan
Admin.

Nov 09, 2011
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Comparison?
by: Dana

I was wondering if anyone has done testing on the reflectivity difference (reflectance rate) between reflective tape and the reflective vinyl sold here. I've been doing some reading on reflectivity ration, but (1) can't make much sense of the data and (2) can't find much specific to the use of reflective materials for solar cooking.

Our mirrors are working great (now that the clouds are finally lessening), but they are so breakable we're looking at other options.

Oct 05, 2011
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Off gassing wood
by: Jim La Joie

You are correct about the off-gassing of the plywood. If you are using an enclosed cooking area, this acts just like a smoker used for smoking foods. Just like a smoker, the gas from the plywood will get into the food.
At the very least you should be cooking in a covered pot.
A better solution is to place your pot inside a cooking bag and leave the door off.
What I do is to line my cooking area with foil or aluminum tape, then place my pot inside a bag or a couple of glass bowls, one inverted over the other. Doing this will change your solar oven into a solar reflector cooker. And it will likely cook a little faster. You can see the glassware on my webpage allseasoncooker.com

Oct 04, 2011
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mirrors on solar oven
by: Dana

We've had great success with our homemade solar cooker, using mirrors bought at a substantial discount at Goodwill and then cut to fit our reflectors. Definitely a HUGE improvement over the taped on aluminum foil we were using at first. We have 4 main, square reflectors and two angled ones between the back reflector and the two sides. We stay about 300 degrees for several hours in the middle of the day (we live in Florida, so the sun still gets pretty high this time of year). Today we cooked an incredibly delicious loaf of bread and then a pot of chicken, and we didn't start cooking until noon.

Our biggest problem is a chemical smell, we think from the plywood lining the box. We've got it covered with a black cotton towel, but the plywood still gets incredibly hot, and we're assuming it's the glues holding it together that stink so much. Kind of nervous about the chemicals in the oven, with the food.

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