240115 practical test

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POWER PRODUCTION FROM RENEWABLE ENERGY AY 2022-23 15th January 2023 Prof. Andrea Giostri Time: 1.5 hours NAME and SURNAME:.................................................................................................................................................. COURSE and CFU:......................................................................................................................................................... Instructions for the examination: 1) Clearly indicate your name on all the sheets you will deliver. 2) The score refers to exercises done in a comprehensive manner with exact numerical results. Numerical results correct but not accompanied by explanations will not be taken into account. The final score can be normalized according to the average results. 3) Answer briefly and clearly only to the asked questions. Calculations and explanations which do not respond to the questions will not be considered for evaluation even if correct. 4) Talking with colleagues and / or cheating will cause the cancellation of the exam. 5) All the needed data for the resolution of exercises lies on this paper. It is NOT ALLOWED to use material other than this (e.g. books, clipboard etc.). Exercise 1 (15 points) Consider a wind turbine whose rotor occupies an area of 33 00 m², designed for a nominal wind speed of 11 m/s and a tip speed ratio of 6.5. The fluid dynamic efficiency compared to that of Betz is 72% and the mechanical -electrical conversion system efficiency is 9 6%. Calculate the net electrical power generated and the rotational speed under nominal conditions. The turbine is located at sea level with a temperature of 15°C (consider air as an ideal gas with molar mass equal to 28.9 kg/kmol) (points 4). A wind farm is made up of 81 turbines identical…