My mate Dylan and I have been talking about making a solar cooker for a year (or two) now and we finally made some time to put our ideas into action. Rather than stick to a standard design we decided to experiment a bit.
There's basically two types of solar cookers. The box cooker and a parabolic reflectors. The box cooker is an insulated box with a transparent lid and light directed towards it. These are generally slow cookers, usually used for roasting or stewing.
|A low cost wooden box solar cooker. Source: Solar Cookers International|
The parabolic cookers all work on the principle of reflecting light to a concentrated source. These are quick cookers - good for boiling water or a fry pan.
|Gustavo Ramírez, a co-founder of Ecovilla Gaia in Argentina demonstrates a parabolic solar cooker. Photo taken by Richard Telford in 2006|
Dylan, being a glazier, amongst other things was the right man for the job! We found a day to put our ideas into action.
|Making up a double glazed sheet for the lid - 530 x 530 x 23mm high, using 6mm glass|
|Making the box. Glass, silicon and tape - 460 x 460 x 300mm high.|
|A bead of silicon is covered with acetate (silicon does not stick to acetate), and then a sheet of glass placed on top with a weight to create a flat surface and a reasonable seal. Acetate strips were removed when dry.|
|The finished experimental box delivered to Abdallah House.|
|Initial testing. The glass cube cooker with insulated polystyrene / foil lined walls (2 sides) and base with a 260mm dia x 40mm high steel plate for thermal mass.|
|Second Test: Glass cube solar cooker with steel plate for mass, polystyrene with foil for the base (inside) and reflectors directing light / heat on the outside.|
NOTE: These temperatures are not very accurate, and are measured from the bottom of the cube - the top would be considerably hotter.
|Time||Box temp ºC||Water temp ºC|
As a standard box cooker can get to 150ºC (not sure where measured from), these are not very impressive results. We probably need to set up a standard box cooker to compare. If the glass cube was double glazed I think that results would improve somewhat. Our feeling is that once it gets to a certain temperature inside the cube the single glazed glass cannot contain the heat.
|Third Test: Glass cube solar cooker with insulation / foil on the inside and reflectors on top|
|The polstyrene on the south west corner melted, the steel plate made a depression in the polystyrene and the inside sheet of glass on the double glazed unit cracked - so it got pretty hot|
Now we have to put our heads together and find some time for stage two. Maybe in the new year?