This is the £50,000 winner of a contest to find the world's greenest invention - a solar-powered oven made from cardboard.

[caption id="" align="aligncenter" width="288" caption="The oven costs just R40 and can bake bread cook casseroles and boil water"]The oven costs just R40 and can bake bread and boil water[/caption] It is made from two boxes, one inside the other with an acrylic cover, which lets the sun's power in and traps it. Black paint on the inner box and silver foil on the outer help concentrate the heat while a layer of straw or newspaper between the two provides insulation. It is the brainchild of Kenya-based entrepreneur Jon Bøhmer and his Kenyan wife Neema. They have set up a company called Kyoto Energy. They funded the project with their own money. He has upgraded it by making it out of corrugated plastic, which he says can be mass-produced as cheaply as the cardboard version. This makes a much more robust and longer lasting cooker..... The good that this can do in Africa where so many millions of people live below the poverty line and don't have the means to boil contaminated water to make it safe for drinking and cooking. The saving on wood as a fuel is enormous as well. The Saladmag Blog