Design and Construction of a Low Cost Offset Parabolic Solar Concentrator for Solar Cooking in Rural Areas
Abstract
In this paper will be presented the process of design and construction of a low cost solar concentrator for cooking in remote areas and underdeveloped countries. To avoid complexity of design of an specific shaped surface a common offset parabolic antenna is used to make the reflector. This type of antennas are widely used both in developed and underdeveloped countries, are cheap and easy to obtain. The parabolic reflector is placed under the pot almost horizontally, specially at midday when the sun reaches elevations of around 65 degrees. This configuration offers many advantages over most common centered-focus solar cookers, like lower wind resistance and higher stability of the structure because of lower center of gravity. It also produces vertically reflected rays that reach the food pot at the bottom like in conventional stoves. Offset parabolic reflectors are more efficient since objects placed at the focus don't create shadows over the reflecting surface. Different types of reflective surfaces have been tested, like aluminium foil and metalized polypropylene sheets. The paper also describes the prototype construction process and test with a parabolic dish of 80 cm diameter. With offset parabolic reflectors it is possible to combine two reflectors that focus at the same point, a configuration that is not possible with centered focus parabolic reflectors. Also a transparent cover can be placed around the pot except by its base, reducing heat losses. This type of device has a security issue due to vertical incidence of radiation that can cause burns and eye injuries. A proposed solution is to cover the cooking area with a dark surface and protect the focal point with a lid when not in use.