Last updated: 8 September 2015
This is my first attempt at a parabolic solar grill. I live in South Africa and this cooker will work best between 10:00 and 14:00. The design is made out of flat mirrors and steel. Minimal testing have been done, with an omelet being the first successfully cooked item by this cooker.
We built this design with the aid of a CNC machine to cut the parabolic curves into the wood. The main structure is made from steel and works like a swing. A metal cable keeps the swing in position. the whole structure needs to be rotated to face the sun, and then the swing needs to be adjusted to reflect the sunlight through the bottom glazing where it strikes the grill. The mirrors are composed of long rectangular strips that are 600mm x 50mm. I used a full parabola with a focal point of 560mm. That worked out to fit a comfortable height for the glazing tabletop. I used Sketchup to draw the curve and imported it into the CNC software. we cut the six wooden forms and fitted it onto the steel frame. The cooker doesn't work well at low solar incidents angles, but because of the pulley system it can be operated relatively easily under low wind conditions. It needs to be adjusted every half an hour or so. The heat generated for cooking in a pot can be improved by insulating the pot around the sides. It is good that the cooker heats from the bottom and can be accessed from the top.
From a safety perspective I wouldn't cook without sunglasses or leave the cooker unattended since this could posed a fire hazard. Also people that use it need to be aware not to look into the cooker at the glass since that could blind them. I suggest placing a shadow stick on the swing in order to better aim the sun to the cooking surface. I would also suggest having the grill totally covered so the heat gets absorbed and doesn't get reflected out. I would even go so far as to suggest making a high temperature oil tray to transport the heat to the food. These options can be used without using a more intricate 3d mirror array. The design is quite heave but can be pushed by one person with the aid of wheels.
- 600mm x 2000mm mirror
- 2 x 5.5m of 25mm x 25mm steel tubing
- 1 x 4m 75mm x 25mm rectangular tubing
- 1 x 2m of 25mm angle iron
- 6 x 1m x 600mm x 20mm wood
- welding rods
- one can high temperature paint
- 5L paint
- 4 wheels and accompanying nuts and rods
- 2 x 500 ml silicone sealant for glueing the glass
- 2 x 12mm x 100mm bolts and nuts for the swing
- 1 x 4m 5mm metal cable for the pulley system.