Exam test 2

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Wind, Hydro and Geothermal Power Generation AY 2021-22 Example of Test - 2 Prof. Paolo Silva Time: 90 minutes 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. 1. Draw the power-to-wind speed characteristic curve of a modern large scale wind turbine. Con- sidering the adoption of a frequency converter that doesn't cover the full range of velocity varia- tion requested between the cut-in and the nominal wind speed, qualitatively plot on the same graph the following curves: coefficient of performance, pitch angle, tip-speed-ratio and rotational speed, justifying your answer. (5 points) 2. Consider an Organic Rankine Cycle coupled to a binary geothermal plant. Discuss the oppor- tunity of adopting a regenerative scheme. Under what conditions can it be convenient? (5 points) 3. Please describe the different classifications available for hydroelectric power plants, discussing their different role in the electric system. With reference to a high head, is it possible to have a weir-integrated or a run-of-river hydro plant? (5 points) 4. Explain the concepts of “Energy pay-back time” and “Energy Return On Investment” for a re- newable power plant and identify the main items that have to be considered for their definition. If possible, give some examples of renewable technologies. (5 points) Exercise (10 points) A geothermal source has the following characteristics at the outlet of the well: temperature 185°C, enthalpy 1100 kJ/kg. Consider a single flash direct steam cycle cogenerative plant, based on a…