Teong Tan, a member of the SolarCooking yahoogroup and owner of the Sunny Cooker website uploaded this design for a Modified CooKit solar cooker. The original CooKit is useful only for cooking when the sun is low in the sky unless additional parts are added so it can be tilted up without the cooking pot tipping over. Teong's modification was that the cooker could be rotated vertically and turned around such that the cooking pot would be placed on a different panel and the overall orientation would be suitable for higher sun angles. But at the same time it would still fold up to a reasonably small size and be easy to make from a single 3 foot by 3 foot piece of cardboard.
Here are photos of the cooker in the two different positions.
Testing the modified CooKit - 1 cup of water
I first tried testing when it was 4C (49F) outdoors. Unfortunately I had my pot in just an oven bag. The temperature in the bag quickly rose to 50C (112F) but wouldn't go higher as the heat losses equaled the heat gains.
I next tried when it was -6C (21F) outdoors. This time I had my pot in a pyrex container and the temperature quickly went up to 100C (212F) in about ten minutes and stayed there. The pot contained 1 cup of water. I left it for around a half hour and when I opened it up the water in the pot was steaming and there was moisture on the inside bottom of the pyrex container, obviously from steam that came out of the hot pot and condensed on the cooler pyrex.
Cooking my Soya Rice Vegetable Concoction in winter
On February 20, 2012 I finally managed to do some cooking here at 45 degrees latitude north (Ottawa, ON, Canada.) I'd tried earlier starting around 2:45pm but the sun really weakened by 3:30pm, probably because it was so low in the sky and had to go through a lot of atmosphere and it couldn't keep up with the below freezing temperatures. But this time I started at 11:30am and by 1:00pm the temperature in the pyrex container was around 260F (125C) and at 2:30pm it was 285F (180C).
Construction of the Modified CooKit
Click here to get the template for the Modified CooKit. It's a pdf file.
Drawing the template onto the cardboard and cutting and folding took only about half an hour. However, I very carefully glued on the aluminum foil, using a separate piece for each panel. This took around an hour or more. It's hard to say since I had to run out for more glue sticks twice, using up four altogether. Many other types of glue can be used (e.g. spray on glue, liquid glue.) Just make sure the glue works for both cardboard and metal.
I used aluminum foil which works well, though over time aluminum will lose some of its reflectivity, probably due to oxidation. Aluminum coated mylar is another option that is far more reflective and will work better.
I took a lot of care to apply glue to the entire area so that the foil would be as wrinkle free as possible. I first tried gluing an entire 12" x 3' area and laying out a 3' length of foil on it but the result was not good; the foil was not stuck to the cardboard everywhere and so would have reflected light in the wrong direction. I ended up doing each panel individually, as you can see in the photos below, and even putting clear tape on the edges so that when it was folded the foil wouldn't lift up off the cardboard.
The following are the steps done during making of this Modified CooKit solar cooker. Click on the images for larger ones.
The following video shows me assembling the modified CooKit and cooking in below freezing weather as well as a bit about the cooking pot and pyrex container and me making the modified CooKit in the first place.
And here's an excellent video by Christine Lilge (), whose son made one of these modified cookit solar cookers for his 4th grade science project. He even used the recipe I made in my video above. This was done on May 13, 2014, at latitude 51 degrees north with an outdoor temperature of 17C (63F). The video can also be found on their YouTube page here.