Cooking with solar energy

The sun is the earth's greatest potential energy source and the one that holds the brightest promise for a constant, limitless and non-polluting supply of electrical power.  People have been trying to use its free reservoir of energy since the dawn of history. So what's the next application for solar energy?

It could be that weekend­ institution, the backyard barbecue. On a clear, sunny day — the perfect time for a barbecue — a solar reflector should provide enough heat to bring a kettle to the boil, to cook sausages in a frying pan or, perhaps with a little more difficulty, to grill a steak. The simplest types of solar cooker use a dish-shaped (or parabolic) reflector to concentrate the sun's rays and focus them on a kettle, cooking pot or hot plate. The process is helped if the cooking receptacle is black so as to better absorb heat.

The manufacturers of one solar oven say it offers an efficient and convenient alternative to more conventionally fuelled ovens. Solar rays are converted into heat by trapping them within a double-glazed cover and additional rays are reflected in from the oven's adjustable lid. Temperatures in the cooking chamber may reach 150°C (300°F).

With a few basic skills you can even make your own solar cooker.

• The materials needed (aluminium foil, wood, clay) are simple and readily available.
• The tricky part is shaping the parabolic reflector, and building it within a moveable frame (for example a large wooden box) so that its position can be adjusted every 15 or 20 minutes to follow the sun as it moves across the sky.
• Apart from the reflector and its box, the only other components needed are the cooking vessel and a metal arm to support it at the point where the reflector concentrates the reflected sunlight.