So, where we live is not exactly on the Equator. We're not blessed with wall-to-wall sunshine all year round. But on occasion, summer does have lots of sunny days. So I thought it would be interesting to build a solar-powered oven.
It is said that these can be used for cooking stews, baking potatoes, and even for baking bread.
There are lots of different designs out there, but I wanted something which was easy to open, without having to buy or make lots of parabolic mirrors. The design I settled on was from a chap on Youtube. This seemed to fit the bill.
In keeping with our philosophy of re-using stuff and buying as little as possible, the size of the oven was determined by the size of panes of glass I had available. These were recovered from the old windows here at La Darnoire Towers when I upgraded to the double-glazing variety several years ago. At the same time, the oven needed to be big enough to fit a couple of LSS's cast-iron pots.
It turned out I had two pieces of glass each measuring 670x340mm. So I sized the oven to suit these, and made the internal height sufficient for the cast-iron pots (with lids of course).
The oven itself consists of a double-walled three-sided box:
The gap between the two wooden walls (made from pallet wood, what else?) is stuffed with rock-wool insulation.
The body needs to fit on a base - again made from pallet wood. To the base is fixed a rock-wool stuffed box, with a piece of sheet metal on top. The inside of the body and the sheet metal on the base were both painted matt black using high-temperature paint.
A mirrored lid is also required in order to increase the heating power. I didn't have a suitable-sized mirror, but I did have some mirror tiles left over from the construction of the solar cooker (made from an old satellite dish) so I used these. If I can find a real mirror at a car boot sale I will install this instead.
The lid itself was made from an offcut of melamine-based plywood given to us by a friend in the village. The hens in the background were very interested!
Once the construction had been completed, everything was given a coat of paint and then assembled.
The purpose of the lid can now be seen. Orient the oven so that it faces the sun, and adjust the angle of the lid to reflect extra sunlight into the heart of the oven. The lid can be set at any angle by tightening the friction hinges which I made by using two M6 coach bolts with knobs.
To put pots or food into the oven, the entire body swings up on rear-mounted hinges. The size of the base is sufficient that, when open, the centre of gravity does not tip the whole thing over. However, I added a length of chain to one side in order to prevent the body from opening too far and causing a disaster.
Here you can see the oven in operation. Nothing was put into the oven at this point as a) I wanted to see if it worked, and b) I didn't have anything to cook.
When the contraption was first set up, the thermometer registered 20°C. Within half an hour, the temperature inside the oven had reached 80°C. Unfortunately at this point, clouds covered the sun for the rest of the day, so the experiment was abandoned. At least for now.
To be continued...