Design, Construction and Energy efficiency analysis for a collector: the Maputo solar oven system.

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University of Dar es Salaam
Small scale solar thermal systems represent a technology in development, and can be used to serve large amount of energy in cooking, water heating, space cooling, etc. It can also help in reducing biomass, gas, fossil fuels and conventional electricity consumption, thus saving money and the environment. A 4 m2 air-based solar concentrating system, especially for cooking and water heating, has been developed. The reflector consists of six petals, covered with nearly symmetric trapezoidal mirror tiles which together resemble nearly parabolic surface of focal length 915 mm; F/D ratio of 0.315; half angle of 66.50o; half complementary angle of 23.49o; angle of incidence of 33.26o and thickness of the mirror of 3 mm. The present study was aimed at investigating and developing an absorber for the concentrator as the reflector was already made. The experimental focal area (considering a focal length of 920 ± 10 mm) was found by mapping the reflections of the entire reflective surface using a laser beam. From these results, plane and hemispherical shapes were considered to build absorbers of three different diameters (110, 117 and 220 mm). The absorbers were constructed and tested in sunny conditions. To build the absorbers, stainless steel fibres were used. Maximum power and thermal efficiency achieved were 1.28 kW and 39.24%; 871.35W and 25.63%; and 893.29W and 24.67%, for 110, 117 and 220 mm hemispherical absorbers, respectively. The efficiency is very low compared to the theoretical value, which was estimated at 85%. It is expected that if this system was insulated, it could be possible to achieve higher values. Percentage error of temperature measurements were 14.20%, 9.75%, 7.10% and for the 110, 117, 220 mm hemispherical absorbers.
Available in print form, East Africana Collection, Dr. Wilbert Chagula Library, Class mark (THS EAF TJ812.T35)
Solar Collector, Solar cooker, Maputo Solar Oven System
Tamele, B.Z.S.(2014) Design, Construction and Energy efficiency analysis for a collector: the Maputo solar oven system.Master dissertation, University of Dar es Salaam, Dar es Salaam.