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The encasing of wind turbines in a duct to enhance performance is not new. A ducted wind turbine produces more power than an unducted wind turbine of the same parameters. A number of approaches in studying the effects of diffusers and other wind concentrating devices have been done and have resulted in a number of prototypes produced but without any commercialization. The aim of this paper is to investigate the failure of commercialization of ducted turbines. A technical and economic analysis of a ducted turbine is also presented. The work shows that traditional economic methods used to evaluate ducted wind turbines are erroneous; they do not account for external effects of power generation and individual and community benefits derived from this technology. Failure to penetrate the market is due to negative publicity as a result of the erroneous evaluation undertaken and lack of appropriate engineering techniques to protect ducted wind energy systems in extreme wind conditions.

SUMMARYThe performance of a low-cost compound box-reflector solar cooker designed and constructed by the department of Mechanical Engineering, at the University of Zimbabwe, was investigated and evaluated using a microcontroller-based measurement system over a period of 3 months. Solar radiation and temperature measurements are sent directly to the computer for monitoring and subsequent analysis using a spreadsheet program. The system is connected to the computer through the RS232 port. Temperature was measured by LM335 temperature sensors, whereas solar radiation was measured by a Kipp & Zonen CM3 thermopile-based pyranometer that was initially calibrated against the Eppley Precision Spectral Pyranometer. Peak temperatures of about 901C for the food can be attained in about 5 h on a clear day in Bindura, Zimbabwe (181S, 311E). A standardized cooking power of 11 W and an overall efficiency of 15% were found for this cooker.

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