For several decades various solar oven designs have
typically been used in third world regions where electricity or other
fuel sources are hard to find.  Solar cookers have been used
effectively in sunny African countries like Sudan to not only cook
food, but also for water purification and pasteurization.
And like other solar technologies, there's no reason first world
countries should not promote solar cooking at home to help save energy.
Although cooking may take four times longer than conventional ovens, no
electricity or fuel is used - just the power of the sun.
Over time many solar oven designs have been mastered, but they
generally fall into three main categories: parabolic solar cookers,
panel cookers, and box cookers.
Parabolic Solar Cooker:
A parabolic solar cooker, as the name implies, is made from any
reflective material in a parabolic (bowl like) shape that focuses
sunlight to a single point.  It is the most effective at cooking food
quickly and efficiently, however, it tends to be more expensive and
hard to make by hand.  Furthermore, its fixed shape makes it less
portable and raises some safety concerns.
Panel Cooker:
A panel cooker is any cooker made with a series of flat, reflective panels arranged to direct sunlight to a focal point.
Although not as effective as a parabolic cooker, it is safer, easier
to make, and can be folded up for portability. Panel cookers come  in a
number of innovative designs, the simplest being made from a fold-able,
reflective windshield shade.
Box Cooker:
The third type, a box cooker, operates rather differently to the
parabolic and panel cookers. Instead of reflecting light to a central
point, it absorbs, traps and intensifies the light to create heat.
Essentially the entire box heats up, allowing larger quantities of
food to be made at once. The box cooker is easiest of the three to
make, since it can literally be made from a cardboard box, tin foil,
and sheet of glass or perspex.
What's great about most solar oven designs is that they can be built
from everyday materials in a few short hours. Like a conventional oven
or stove, they can be used to prepare anything - such as roasted meat,
steamed vegetables, rice, fried eggs, and baked bread. And since a
solar cooker is used outside, it will not heat up the kitchen and place
stress on China1 impact wrench your cooling system.
To think that - according to the Residential Energy Consumption
Survey - almost 75% of Americans prepare at least one hot meal at home
per day, 33% prepare two or more, a large amount of electricity can be
saved if more of us try solar oven design at home.
So get started cooking with solar today.  There are a number of
commercially available solar cookers on the market. Alternatively you
can make your own at home by searching online, where a variety of free
solar oven designs with full building instructions are provided.