ES220208 test WHG

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Wind, Hydro and Geothermal Power Generation AY 2021-22 8th February 2022 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. Consider a three-bladed horizontal axis wind turbine installed on a site with a high roughness factor, resulting in a significant wind speed gradient over the area swept by the blades. Explain the effects on the velocity triangle at the tip, for a blade respectively positioned at the top (vertical up position), middle (horizontal) and bottom (vertical down) of its path during the rotation. What could be the consequences on the turbine operation? (5 points) 2. Explain the methodology for evaluating the primary energy savings and the avoided pollutant emissions for a cogenerative geothermal power plant. With particular reference to CO2 emis- sions, can geothermal plants make a positive contribution? (5 points) 3. Discuss the strategic importance of hydroelectric power plants with respect to the increasing dispatching requirements of the electricity grid. What is the role of different kinds of hydro plants in the electric system? (5 points) 4. Discuss the different types of foundations and mooring systems used for floating offshore wind technology. What are the most promising technologies in your opinion? (5 points) Exercise (10 points) Consider a binary ORC geothermal plant fed by a geothermal brine that provides a flow rate of 700 t/h at a temperature of 175°C. The geothermal plant works with a saturated iso -pentane Rankine cycle described by…