Cone/funnel solar cooker

My first solar cooker was this cone solar cooker. Some might call it a funnel solar cooker but there seems to be a specific design to most of these on the web that looks quite different so I tend to refer to it as a cone solar cooker. You can find complete videos on the design and construction of this solar cooker here.

My cone solar cooker.

Looking down the cone.

Look at the above photos and you'll see that I specifically chose the width of each cone segment to be around the width of the cooking jar. That way all the light gets directed to the jar and not passed it. Each segment is simply cardboard with aluminium foil glued to it.

The first thing I cooked was long grain brown rice. I put 1/4 cup rice in 1 1/4 cup water. It was 3C (38F) outside. I watched it every 10 minutes up to the first hour. Then I checked it after one and a half hours cooking time and then at two hours. Sometime in between one and a half and two hours of cooking time it had started boiling and became fluffy like in the photo below.

Note the well known trick of leaving a portion of the glass unpainted so you can see inside.

Long grain brown rice - cooked in between 1.5 and 2 hours with no insulation.

Painting the jar using BBQ & Stove paint. Note the masking tape on the jar where I want the window to be.

The end result - a dinner fit for a king!

The design and the assembly of the cone/funnel solar cooker

This cooker started out as a big bowl in a box (see photo below.) I did some testing with that and on a slightly hazey day, after two hours the water got up to only 70C (158F).

Initial testing with just a bowl, a jar with water and a cooking thermometer.

I then decided to add a reflector to get better results. So as a whole, it more evolved than was designed. However, I did have some design criteria such as that it be able to be stored away using very little room and be assembled quickly and simply.

The box with rags for insulation.

I used strings to hold the bowl in place.	The ends of each string was tied on the side.
The whole thing prior to assembly is fairly compact.	Attaching the vertical supports that'll hold the cone in place.

Assembling the cone.

To attach the two end segments of the cone together, the following steps are done at both the top and bottom.

1. Bring the two end segments of the cone close together.	2. Thread the wire through the holes of each end segment.	3. Twist the wire ends together.

As the following photo shows, when the cone was attached to the box and the whole thing was tilted, I found that the sides at the top drooped. My quick and simple fix was to cut two strips of cardboard, attach aluminium tape to them and wedge them at the base of the cone between the insulation and the bowl and sticking up enough to hold the bottoms of the cone in place.

Droopy cones.

Fixed.

I needed some way to position the jar with food in it firmly in the bowl of the solar cooker. I tried fashioning something out of clothes hanger wire, fabricating something using aluminium bars and finally found a simple way of making a table for the jar to sit on that works well using aluminium flashing. This flashing can be found in hardware stores and usually comes in rolls. It's easy to cut with tin snips.

Making sure the solar cooker table is in place.

How the solar cooker table works.

The last step was to aim the solar cooker directly at the sun. For this I attached my homemade sun finder to a top corner of the box. The photo below shows me aiming it.

And remember, you can find complete videos on the design and construction of this solar cooker here.

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