To find the obtainable energy in solar cookers, ovens or dehumidifiers the surface, that faces toward the sun, has to be figured out. This surface is called opening surface or surface of aperture. A round shaped parabolic cooker with a diameter of 70 cm has an opening surface of 0.385 square meters, a rectangular cooker with the dimensions 50 x 40 cm an opening surface of 0.2 square meters.
In case a parabolic cooker is in use, the sun rays are beamed to the pot. The air cools it down at the same time by convection (heat flow). Therefore the parabolic cooker must have a certain size. A box cooker traps the heat inside, similar to what you experience when you get into a car which was exposed to sunlight for a while. In such a case the construction does not need to be very voluminous. Mueller Solartechnik offers solar cookers in any construction shapes for a variety of applications.