Browsing by Author "Tewodros, Driba"

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    Small Wind Turbine Blade Optimization for Smooth Starting Performance in Low Wind Speed Regions
    (Addis Ababa University, 2021-02) Tewodros, Driba; Wondwossen, Bogale (Assoc. Prof.)
    Access of electricity in the developing country is a big issue that the government highly concerned. Small wind turbines are one of the alternative the government have in order to address electricity specially in rural areas. Wind turbines are highly dependent on wind speed, hence the areas with low wind speed region can not access the electricity as expected. This is because the turbine works in low wind speed range which gives the annual energy production more less than the desired output.This thesis investigate the way how to get the optimum energy output from small wind turbines by lowering the time at which the wind turbine starts rotating and generating electricity with out decreasing performance of the turbine. The main objectives of the thesis were starting time and coe cient of performance and the parameters used for the optimization processes were chord value, twist value and type of airfoil. Two non optimized blade with single and mixed airfoil section are designed with usual designing procedure by using horizontal axis wind turbine design code credited to Oboe Daniele and Marinoni Andrea. Three optimized blade which have 0.8466m, 0.5m, and 0.5m radius with the rst two blades have SG6043 airfoil section and the third one has SD7062 airfoil section are designed. The optimization is taken by multi objective genetic algorithm and di erent input criteria like airfoil type, blade number, starting wind speed, resistive torque is taken for a better investigation. Beside to analysis of the optimized and non optimized blade, the e ect of weight given to starting, genetic algorithm parameters, limiting the boundary of twist and chord value, airfoil, designing the blade with single and mixed airfoil, blade number, and starting data are well investigated. Non optimized 3-bladed, SD7062 airfoil section blade starts in 16.3sec at 5m s wind speed while the Optimized blade with the same blade speci cation starts at 8.63 second which means there is 88.8% improvement in starting time but the coe cient of performance only decreases from 0.34 to 0.335, which means its percent reduction is 1.49% . From previously conducted research on starting performance with the same input criteria with this thesis by (1) which gets 87% improvement in starting time and 1.6% reduction in coe cient of performance. This research shows improvement by altering airfoil type, chord and twist value. The optimum blade which have lowest starting time and better power performance was manufactured from Australian timber by Computer numerical control machine and experimental testing was conducted. In order to get constant wind speed ow, a controlled moving vehicle was used for the experimentation process. The starting time and coe cient of performance of the blade from the software were 8.63sec and 0.335, while the experimental result gives 9sec and 0.3228. This shows there is a 3.61% and 4.2% error while testing in Cp and starting time respectively. Value of errors comes from rst the generator, since it needs to be excited it makes some delay on recording some seconds as it starts generating electricity.Beside to excitation the generator is used and maintained repeatedly, this makes it to do not perform as it is rst manufactured. There is also some manufacturing and assembling di culties while making parts and assembling the wind turbine which add some contribution on the performance of blade under experimental testing. Finally the manufactured wind turbine produce 19.4W electrical power at 5 m sec which is the frequent available wind speed in low wind speed region(2).