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Building and Using a Solar Cooker

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Punch holes through the two edges and fasten them together with string or wire. Use a stiff piece of wire bent double as a 'needle'

Punch holes through the two edges and fasten them together with string or wire. Use a stiff piece of wire bent double as a ‘needle’

Article by Joanne Brannan June 2012 Home Farmer

Many solar cookers are either complicated to construct, very expensive to buy, or suitable only for climates far sunnier than ours here in the UK. But there is one simple solar cooker design that costs next to nothing to build and works remarkably well, even here!

When lined up with the sun, the solar funnel cooker focuses solar energy on an area towards the bottom of the funnel reflector, but not on a single spot, so there is no risk of burning – an ever-present danger with the alternative parabolic solar cooker. A preserving jar painted black to absorb the sun’s rays acts as a simple pressure cooker, heating the contents up faster than a simple covered container. A surrounding clear plastic oven bag acts as a ‘greenhouse’ to further enhance the heating effect.

 WHAT YOU NEED TO BUILD YOUR SOLAR FUNNEL COOKER

All the things you need to build this solar cooker are inexpensive and readily available. You may even have most of them in your home already!

*             A large piece of cardboard (the bigger, the better). The side of a large corrugated cardboard box is ideal.

*             High-temperature matt black paint, such as barbeque paint. Check that it is suitable for use on glass.

*             A Kilner (or similar) preserving jar, complete with rubber seal.

*             An oven bag (the sort used to contain a roast chicken), large enough to easily contain the jar, and a wire bag tie. You can use an ordinary plastic bag of the type used for vegetables in supermarkets, but it may melt if it touches the hot black jar.

*             Glue. Ordinary paper glue, or even flour and water paste, is fine.

*             Everyday kitchen aluminium foil.

*             A block of wood on which to rest the Kilner jar during cooking.

*             String or wire to fasten the cardboard funnel edges.

Clean and Paint the Kilner jar matt black. Avoid painting the lip of the jar to avoid tainting the heated water or food when it is poured. You may need to 'cure' the paint before use to set it solidly onto the glass. Follow the manufacturer's instructions.

Clean and Paint the Kilner jar matt black. Avoid painting the lip of the jar to avoid tainting the heated water or food when it is poured. You may need to ‘cure’ the paint before use to set it solidly onto the glass. Follow the manufacturer’s instructions.

 

Draw a semicircle at the bottom of your piece of cardboard, in the centre of the long edge. This should be of the same radius as the diameter of the jar. Use a good old-fashioned compass, or simply a pencil on a piece of strong to trace out the semicircle.

Cut the semicircle out of the cardboard. A finely serrated knitchen knife is effective on corrugated cardboard.

Cut the semicircle out of the cardboard. A finely serrated knitchen knife is effective on corrugated cardboard.

Spread glue over one side of the cardboard and apply strips of aluminium foil as smoothly as possible.

Spread glue over one side of the cardboard and apply strips of aluminium foil as smoothly as possible.

Cut a semicircle out of the foil to match the cardboard shape.

Cut a semicircle out of the foil to match the cardboard shape.

Punch holes through the two edges and fasten them together with string or wire. Use a stiff piece of wire bent double as a 'needle'

Punch holes through the two edges and fasten them together with string or wire. Use a stiff piece of wire bent double as a ‘needle’

Place your black kilner jar on a block of wood inside the oven bag. Fill the bag with air and seal with a wire bag tie. The bag should not touch the jar as it heats to add to the greenhouse heating effect.

Place your black kilner jar on a block of wood inside the oven bag. Fill the bag with air and seal with a wire bag tie. The bag should not touch the jar as it heats to add to the greenhouse heating effect.

Posted in: Renewable Energy

About the Author:

Ruth Tott is the publisher of Home Farmer Magazine, and together with her husband, Paul Melnyczuk, Editor,is founder of the company. But her background is far removed having specialised in Costume History with a Post-Grad diploma in Museum Studies to boot. A far cry from looking after chickens, growing veg and making bread!

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