230830 theoretical test

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POWER PRODUCTION FROM RENEWABLE ENERGY AY 2022-23 30th August 2023 Prof. Andrea Giostri Time: 1 hour NAME and SURNAME:.................................................................................................................................................. COURSE and CFU:............................................TYPE (Complete or Theory only):................................................. Instructions for the examination: 1) Clearly indicate your name on all the sheets you will deliver. 2) Give a synthetic and clear answer to as many questions as possible. The final score will be normalized according to the average results. 3) Talk with colleagues and / or cheating will cause the cancellation of the exam. OPEN QUESTIONS (points 18) 1. Consider a modern wind turbine (large in size) and draw an ideal Coefficient of Power (Cp)-speed curve highlighting and defining cut -in speed, rated speed and cut -off speed. Describe and explain the “active stall” control strategy. 2a. For Management Engineering students: Consider the collectors of a solar thermal power plant and highlight the differences between Fresnel and parabolic -trough technology. Explain the pros and cons of each solution. 2b. For Mechanical Engineering students : Discuss pros/cons of biogas. Describe qualitatively the process of biogas production reporting the main components of a plant to produce electricity. 2c. For Energy Engineering students: Consider a liquid dominant geothermal source and explain the reasons why the adoption of an ORC cycle can be beneficial. Draw the layout of a single pressure level ORC and report on a T- s diagram the streams conditions and represents the corresponding T-Q chart. Explain how to choose the ORC evaporation pressure and the reinjection temperature of the…