Browsing by Author "Craig, Omotoyosi Onalapo"
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- ItemA stand-alone parabolic dish solar cooker for African conditions(Stellenbosch : Stellenbosch University, 2015-12) Craig, Omotoyosi Onalapo; Dobson, Robert Thomas; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.ENGLISH ABSTRACT: The reduction in the availability and the ever-increasing prices of fossil fuels, as well as the expensive and insufficient electricity supply, are some of the reasons explaining why the public awareness of the use of alternative cooking methods has increased in recent years. In most rural areas of Africa, the use of wood is even more preferred for cooking than either fossil fuel or electricity, and this has led to deforestation in many areas. However, the time spent on wood collection by women, who often walk kilometres under scorching hot, sunny conditions, can be utilised better in more productive activities. Most of those lacking access to convenient cooking methods live in places with good solar resources and where solar cookers would thrive if developed. The study presented in this report considered a prototype solar cooking system that is relatively cheap and that can be modified to meet these challenges faced in African communities. A parabolic solar cooker, which uses a parabolic dish as concentrator, was designed and developed. The concentrator used was a television satellite dish of 2 m in diameter, in which the reflecting area was covered with reflective aluminium strips. The dish concentrates radiation from the sun onto a conical cavity receiver placed at its focal point. The system uses heat transfer fluid as its working fluid and a cuboid- shaped storage tank insulated with ceramic wool to enhance the sensible heat storage technique used. A specially modified automotive pump was used to circulate the heat transfer fluid throughout the system, while a cooking head in the form of a flat spiral copper tube put onto the storage tank was used as the cooking section. The cost of manufacturing the system was approximately R9 000, without considering the cost of the tracking system. However, this amount is expected to decrease if the system is mass produced. The solar cooker was tested under winter conditions in South Africa, and each cooking test was done according to international standard procedures for testing solar cooker performance. A utilisation efficiency of 47 % was achieved, the exergy efficiency was 0.05 %, while the average characteristic boiling time was around 13.32 min/kg. The solar cooker can be used indoors, thus eliminating the need for its user to stay in the sun. The reflecting dish was mounted on an automated dual tracking system stand, which eliminated the need for regular adjustment by the user. The cooking section of the system can be modified to be used for other high temperature-based development activities in African communities, such as, among other things, industrial baking.